2.1 Study site

The study was conducted at the Bee Research Station, CSKHPKV, Nagrota Bagwan (32.1°N, 76.3°E; elevation ~650 m), located in Kangra district, Himachal Pradesh. The site lies in the lower western Himalayan region and experiences a subtropical to temperate climate, ideal for apiculture and wasp activity.

2.2 Heat balling of wasps

This study examined the response behaviour of A. mellifera against the predatory wasps by heat balling. Three colonies of almost equal strength in the apiary were selected. Wasps were collected alive from the field using insect net and maintained in ventilated containers with sugar solution for 12 hours prior to experimentation to allow acclimation. For attaching the wasp to the temperature meter, beekeeping gloves were used to prevent stinging and injury to the wasp. The adult wasps of three different species: V. auraria, V. basalis and V. tropica were gently attached to the tip of electronic temperature meter using a fine thread loop around the thorax, taking care not to restrict movement or cause injury. The temperature meter with the attached wasp was then carefully kept at the hive entrance to elicit the heat balling response from the bees. The temperature inside the bee ball was recorded after every 15 seconds. The highest temperature recorded inside the ball, the number of bees involved in balling the wasp and the time to make a ball was recorded as per the method of (Tan et al. 2005). This experiment was replicated three times.

2.3 Thermal limits of honey bees and wasps

Ten honey bee workers of both honey bees species, A. mellifera (n=10) and A. cerana (n=10) as well as adult workers of three different species of predatory wasps, V. auraria (n=10), V. basalis (n=10) and V. tropica (n=10) were all placed in separate cages (10x10x10cm). These cages were fitted with fine wire-mesh side panels, allowing enough ventilation for the wasps. These cages were kept in incubator at initial temperature of 43°C. The cage dimensions provided sufficient space for normal movement of the insects during the short-term heat tolerance assays while preventing overcrowding. All thermal tolerance experiments were conducted with three independent biological replicates. The three replicates were conducted on different days using insects collected from different colonies (for honey bees) or different foraging sites (for wasps) to account for natural variation in thermal tolerance.

The temperature in incubator was raised by 1°C after every 20 minutes of exposure until 54°C. These cages were removed after every 20 minutes of exposure to each temperature degree and were given a rest of 5 minutes before exposing to the next temperature level. The same experiment was done by locating the same number of bees and wasps inside cages into the incubator for 5 minutes; however in this case, they were not given the rest of 5 minutes and instead they were directly exposed to the next degree of temperature after the observation. The number of dead bees and wasps after exposure to every degree of temperature was recorded as per the method of (Tan et al. 2005).

Cumulative survival percentages were calculated based on the original cohort at the start of the experiment. For example, if 10 individuals were initially placed and 8 survived after exposure to a specific temperature, the cumulative survival at that temperature level would be 80%. The same wasps or bees that survived at a given temperature were subsequently exposed to the next temperature level. This approach accounts for cumulative mortality across increasing temperatures. The percentage at each temperature level represents the proportion of surviving individuals from the previous temperature level not relative to the initial cohort.

2.4 Agonistic interactions between honey bees and predatory wasps

The A. mellifera colonies selected for conducting the observations on the incidence of predatory wasps were monitored for different agonistic interactions between honey bees and wasps. Observations were conducted at fortnightly intervals from July to November (the active wasp season in the Himalayan region), with a total of 10 observation periods over the five-month study period. Each observation period consisted of 10 minute observation sessions for each parameter, during the peak foraging activity of wasps.

2.5 Number of attacks by wasp/catch of honey bee

The number of attempts by a wasp of the three most prevalent species viz. V. auraria, V. basalis and V. tropica to catch a single honey bee was recorded. The reaction time or the time that a wasp of each species took to capture a bee was also recorded.

2.6 Type of wasp attack

The selected colonies were also observed for the number of wasps of each species associated in a single attack to the colony (Solitary or Group).

2.7 Site of attack

The colonies were observed for the preference of site of attack by the different species of wasp. The number of each species of wasp attacking to the colonies through different sites: hive entrance, ground level and disruption of bee foraging, were recorded.

2.8 Statistical analysis

The experiments were conducted using a completely randomized design (CRD) with three replications for each treatment combination. For the heat balling experiments, one factor analysis were used with three replications. For thermal tolerance assays, a three factorial design (Wasp species × Time interval × Temperature) was used for wasps and a three factorial design (Honey bee species × Time interval × Temperature) was used for bees. For predatory behaviour observations, a one factor analysis was employed.

The statistical analysis of observations recorded was done using the technique of analysis of variance for randomized block design for the interpretation of results as described by (Gomez and Gomez 1984). Analysis of Variance (ANOVA) for Randomized block experimental design (RBD) was performed at 5% level of significance, critical difference between the treatments was computed after the ANOVA for the treatments was found to be statistically significant.

3.1 Average temperature variation in heat balling of predatory wasps by Apis mellifera

The variation of temperature inside bee ball was studied by attaching an adult worker of each of the three wasp species to the tip of thermometer and placing it in front of an A. mellifera hive. This study was conducted to examine the temperature variations and to determine the temperature at which different species of predatory wasps die during heat balling by A. mellifera. The study was conducted on three predatory wasp species: V. auraria, V. basalis, and V. tropica. The results for this experiment are presented in Table 1 which revealed species specific temperature variations during heat balling by honey bees against different predatory wasps, with V. tropica recording the highest temperature (48.53°C) followed by V. auraria recording the maximum temperature of (47.60°C) and V. basalis (45.77°C). These findings suggest that V. tropica is the most heat tolerant among the three species of wasps followed by V. auraria and V. basalis. The temperature inside the bee cluster was found to be lower than that inside the bee ball (42.73°C), suggesting that the bees concentrate their heat around the wasp as a defence behaviour rather than spreading it evenly throughout the cluster. This also shows that A. mellifera continues the balling activity to a level of temperature in which the wasp dies.

Wasp species	Temperature (°C)
V. auraria	47.60
V. basalis	45.77
V. tropica	48.53
Bee cluster	42.73
CD ()	0.37

3.2 Variation in bee numbers during heat balling of predatory wasps over time

During this study, the number of A. mellifera honey bees participating in the heat balling activity against different species of predatory wasps (V. auraria, V. basalis, and V. tropica) during different time intervals was investigated. The findings of this study which are presented in Table 2 revealed that the highest number of bees involved in heat balling of two predatory wasp species viz. V. auraria and V. basalis, was recorded within the first 90 seconds, with (41.33) for V. auraria, and (41.00) for V. basalis. However for V. tropica the most number of bees involved in heat balling was recorded after 120 seconds with (51.67). Beyond this, the number of participating bees in the ball gradually declined, for V. auraria and V. basalis after 120 second, while for V. tropica which maintained a relatively high level of involvement before gradually decreasing to 4.67 at 210 seconds. For V. auraria and V. basalis, the bees successfully killed the wasps within 180 seconds, after which the balling activity ceased. In case of V. tropica, however the activity continued up to 210 seconds before coming to an end. These results suggested that V. tropica had more tolerance towards the heat balling activity of bees compared to the other species, likely due to its general ability to resist high temperatures.

Time intervals (s)	V. auraria	V. basalis	V. tropica	Mean
After 15s	6.67	6.67	12.33	8.56
After 30s	14.33	13.33	22.33	16.67
After 60s	23.33	24.00	39.00	28.78
After 90s	41.33	41.00	48.33	43.56
After 120s	31.67	32.33	51.67	38.56
After 150s	19.00	20.67	42.33	27.33
After 180s	4.67	5.67	20.00	10.11
After 210s	0.00	0.00	4.67	1.56
Mean	17.63	17.96	30.08
Factors	CD ()
S	2.89
T	1.77
S x T	5.01

3.3 Cumulative survival of predatory wasps at different temperatures and exposure durations

Ten adult wasps of each species (V. auraria, V. basalis, and V. tropica) were placed in separate cages of diameter (10 × 10 × 10 cm) and exposed to different temperatures ranging from 43°C to 54°C for two time intervals (5 minutes and 20 minutes). The survival percentage was recorded after exposure to each temperature to determine the heat tolerance of each species (Table 3;Table 4).

In the 5-minute exposure, 100 per cent survival was observed in all of the three species at 43°C. At 44°C V. auraria and V. tropica showed 100 per cent survival, while V. basalis, showed a slight reduction in survival, showing 83.33 per cent survival. With every degree of rise in temperature, the survival was decreased. V. basalis recorded 67.59 per cent survival at 45°C, while the other two species showed no mortality. At 46°C, V. auraria recorded 80.00 per cent and V. basalis 47.62 per cent survival, while V. tropica remained unaffected. At 47°C, 71.03 per cent survival was observed for V. auraria, while V. basalis completely died at this degree of temperature and showed 0% survival, indicating that V. basalis could withstand the highest temperature of 46°C. V. tropica recorded only 93.33 per cent survival at the same temperature. V. auraria showed 65.56 per cent survival at 48°C and 0 percent survival at 49°C, suggesting that V. auraria could not tolerate temperature above 48°C. V. tropica did not survive beyond 50°C indicating stronger resistance to heat compared to other two species.

During 20-minute exposure, survival rates were comparatively lower at the same temperature levels compared to 5 minutes exposure. This temperature and time dependent mortality might be due to the cumulative physiological stress caused by prolonged heat exposure. V. basalis showed 90 per cent survival at 43°C and 69.72 per cent at 44°C, while V. auraria and V. tropica showed complete survival at these temperatures. V. auraria recorded 86.67 per cent survival at 45°C and 77.32 per cent at 46°C. V. basalis did not survive beyond 46°C, while V. tropica was minimally affected at this degree, showing 93.33 per cent survival. V. auraria showed 0 per cent survival at 48°C, suggesting that this species was completely intolerant to this temperature at this timing interval. However, V. tropica showed 61.90 per cent survival at this temperature. V. tropica again showed the highest tolerance towards heat as all of its individuals survived up to 49°C in 5 minutes exposure and up to 48°C in 20 minutes exposure.

Temperature (°C)		Cumulative survival of predatory wasp (%)
		5 mins exposure
	V. auraria	V. basalis	V. tropica	Mean
43	100.00	100.00	100.00	100.00
44	100.00	83.33	100.00	94.44
45	100.00	67.59	100.00	89.20
46	80.00	47.62	100.00	75.87
47	71.03	0.00	93.33	54.79
48	65.56	0.00	71.11	45.56
49	0.00	0.00	55.56	18.52
50	0.00	0.00	0.00	0.00
Factors				CD ()
T				1.79
S				NS
Temp				NS
T x S				NS
T x Temp				5.07
S x T				6.20
T x S x Temp				8.77

Temperature (°C)		Cumulative survival of predatory wasp (%)
		20 mins exposure
	V. auraria	V. basalis	V. tropica	Mean
43	100.00	90.00	100.00	96.67
44	100.00	69.72	100.00	89.91
45	86.67	69.72	100.00	85.46
46	77.32	0.00	93.33	56.88
47	59.52	0.00	75.19	44.90
48	0.00	0.00	61.90	20.63
49	0.00	0.00	0.00	0.00
50	0.00	0.00	0.00	0.00
Factors				CD ()
T				1.79
S				NS
Temp				NS
T x S				NS
T x Temp				5.07
S x T				6.20
T x S x Temp				8.77

3.4 Cumulative survival of honey bees Apis mellifera and A. cerana at different temperatures and exposure periods

In similar experiment, ten bees of each species (A. mellifera and A. cerana) were placed in separate cages of diameter (10 × 10 × 10 cm) and exposed to various temperature degrees inside an incubator from 43°C to 54°C, under two time durations of 5 minutes and 20 minutes. Survival percentage with increase in each temperature and duration was noted to assess thermal tolerance limits of honey bee species (Table 5;Table 6).

At the 5-minute exposure, both of the honey bee species exhibited 100 per cent survival up to 49°C. At 50°C, A. mellifera showed a slight reduction with 93.33 per cent survival while all of A. cerana workers were still alive. A. mellifera, recorded 71.48 per cent survival at 51°C and 44.44 per cent at 52°C. All of the remaining workers of A. mellifera died at 53°C. A. cerana displayed relatively higher heat resistance in early stages, remaining unaffected up to 50°C, while it showed 93.33 per cent and 67.78 per cent survival at 51°C and 52°C respectively, before reaching 36.51% at 53°C. The rest of the remaining workers of this honey bee species died at 54°C, suggesting that A. cerana bees can not tolerate temperatures above 53°C. During the 20-minute exposure, mortality occurred at lower temperatures which might be due to longer exposure period causing exhaustion of the bees. A. mellifera remained unaffected till 48°C but exhibited a slight reduction in survival (93.33%) at 49°C. The survival decreased sharply to 53.71 per cent at 50°C and 33.33% at 51°C, while all of the remaining bee workers died at 52°C. A. cerana showed no mortality up to 51°C while the first reduction in survival was recorded at 50°C (73.33%) and at 51°C (72.02%). There was a 55.71 per cent survival at 52°C before reaching complete mortality at 53°C.

Our results suggest that A. cerana has slightly higher tolerance compared to A. mellifera which might be due to its evolutionary adaptation to the warmer conditions in its native regions in Asia, while A. mellifera which is a native species of Europe is slightly more susceptible.

Temperature (°C)		Cumulative survival of honey bees (%)
	5 minutes
	Apis mellifera	Apis cerana	Mean
49	100.00	100.00	100.00
50	93.33	100.00	96.67
51	71.48	93.33	82.41
52	44.44	67.78	56.11
53	0.00	36.51	18.26
54	0.00	0.00	0.00
Mean	51.54	66.27	58.91
Factor			CD ()
T			NS
HS			NS
Temp			4.57
T x HS			3.73
T × Temp			6.47
S × Temp			6.47
T ×HS × Temp			9.14

Temperature (°C)		Cumulative survival of honey bees (%)
	20 minutes
	Apis mellifera	Apis cerana	Mean
49	93.33	100.00	96.67
50	53.71	73.33	63.52
51	33.33	72.02	52.68
52	0.00	55.71	27.86
53	0.00	0.00	0.00
54	0.00	0.00	0.00
Mean	30.06	50.18	40.12
Factor			CD ()
T			NS
HS			NS
Temp			4.57
T x HS			3.73
T × Temp			6.47
S × Temp			6.47
T ×HS × Temp			9.14

3.5 Quantification of predatory behaviour of different wasp species in Apis mellifera apiary

To study the predatory behaviour of different wasp species, an experiment was conducted to evaluate different predatory behaviour parameters of wasps on A. mellifera apiary. This study analyzed number of attacks by different species, their reaction time to catch a bee, type of attack, whether solitary or group, and preference of different wasp species for the site of attack (Hive entrance, ground level or disruption of foraging). The observations on this aspect were recorded for ten minutes for each parameter. The results of this study that are presented in Table 7 reveal that V. auraria exhibited the highest attack frequency (2.13), followed by V. basalis (0.70) and V. tropica (0.36), suggesting that V. auraria is the most abundant species. The reaction time for attacks varied significantly, with V. auraria being the fastest and most agile among species to react and catch a bee (8.08 seconds). V. basalis was the weakest among species taking (31.04 seconds to capture a bee while V. tropica required comparatively shorter time than V. basalis and longer than V. auraria (24.08 seconds) to capture a bee. These results documented species specific differences in predatory behaviour and abilities of wasp species. Solitary attacks were the dominant mode of predation across wasp species, with V. auraria, V. basalis and V. tropica recording (1.51, 0.70 and 0.36 attacks, respectively. Among species, only V. auraria used to attack the colonies in group while V. basalis and V. tropica preferred attacking solitary. This could also be due to the less abundance of the later two species in the apiary. Assessment of attack on different sites of the colonies revealed that the hive entrance was the preferred location for predation, particularly for V. auraria (1.46 attacks) and V. tropica (0.29 attacks), while V. basalis preferred targeting and catching honeybees at ground level (0.60 attacks). Only V. auraria was observed to disrupt the foraging activity of the bees with (0.35 attacks) catches during foraging of the bees, while the other two species did not show this tendency.

Wasp species			Type of attack			Site of attack
	No. of attacks	Reaction time (s)	Solitary	Group	Hive entrance	Ground level	Disruption of foraging
V. auraria	2.13	8.08	1.51	0.61	1.46	0.31	0.35
V. basalis	0.70	31.04	0.70	0.00	0.10	0.60	0.00
V. tropica	0.36	24.08	0.36	0.00	0.29	0.08	0.00
CD ()	0.27	0.89	0.15	0.21	0.24	0.17	0.23

4.1 Temperature variation inside the bee ball

The study on temperature inside heat ball of honey bees revealed that A. mellifera bees are capable of killing wasps with lethal temperatures. Among the wasp species, V. tropica was the most tolerant of the species, standing temperatures up to (48.53°C), followed by V. auraria and V. basalis. The bee cluster itself recorded a lower temperature as compared to the wasp species, confirming that bees generate higher levels of heat around the wasp during their defence. Our observations of heat balling behaviour in honey bees align with previously documented studies of (Sugahara and Sakamoto 2009) from Japan who found that honey bees utilize the heat balling behaviour to defend against V. mandarinia, with bee balls reaching temperatures around 46°C. Also the present results are strongly supported by the findings of (Tan et al. 2005) who have documented wasp heat ball temperature of 45°C for V. auraria. (Ono, Okada, and Sasaki 1987) have also reported the heat ball temperature as 46°C for V. auraria, while, later work of (Ono et al. 1995) reported a temperature of 47°C, highlighting a notable concordance. Additionally, (Vaziritabar and Esmaeilzade 2019) reported a heat ball temperature of 47°C for V. auraria.

4.2 Number of bees involved in the bee ball

The study on the number of bees involved in heat balling revealed that a greater number of bees participated in balling the adult worker of V. tropica for a longer time period, supporting the idea that this species is more resistant to heat. These results are well aligned with the findings of (Baracchi et al. 2010) who documented that the number worker bees forming the ball around the hornet was strongly correlated with the maximum temperature inside the bee ball. The findings show that bees increase the heat inside the ball to a level where the wasp dies and that some wasps can resist this defensive tactic better than others.

4.3 Cumulative survival of bees and wasps in different temperatures and exposure periods

The cumulative survival data for wasps and bees after their exposure to different degrees of temperature and various exposure timings revealed that the ability of wasps vary in terms of their tolerance towards heat exposure. V. basalis was the least heat tolerant among the species, surviving only up to 46°C in a 5 minute exposure. V. tropica was most resistant, surviving up to 49°C and dying completely at 50°C. In contrast, honey bees, especially A. cerana tolerated higher temperatures than wasps. A. cerana could survive up to 53°C in 5 minutes exposure, while A. mellifera was not able to withstand the heat of 53°C. Longer time exposures increased mortality at lower temperatures with both wasps and bees dying in slightly lower temperatures than they used to die at short time exposure. Our findings on the heat tolerance levels among wasp species and honey bees are supported by (Sugahara and Sakamoto 2009) who reported that A. cerana could withstand slightly higher temperatures than wasps during heat balling.

The higher thermal tolerance observed in A. cerana compared to A. mellifera likely reflects its long evolutionary history in Asia, where it has co-evolved with various predatory wasp species over millions of years (Radloff et al. 2010). This adaptation has likely enhanced thermoregulatory mechanisms in A. cerana, including more efficient heat-shock protein expression, greater mitochondrial density for sustained thermogenesis and superior behavioural coordination during ball formation (King and MacRae 2015; Garrido et al. 2013; Stabentheiner, Kovac, and Brodschneider 2010; Tan et al. 2007). In contrast, A. mellifera, which originated in Europe and Africa, has had substantially less evolutionary exposure to Asian wasp predators, having been introduced to the region only recently (Ruttner 1988). The lower tolerance of A. mellifera may thus reflect its evolutionary history in environments with fewer high-temperature wasp predators.

The differential tolerance between honey bee species may also reflect adaptation to ambient temperatures in their native ranges, with A. cerana naturally inhabiting warmer tropical and subtropical regions where selection for heat tolerance has been stronger (Tan et al. 2007). Future genetic and physiological studies exploring the molecular basis of these differences would provide valuable insights into the mechanisms underlying species-specific thermal adaptations.

The findings are in close agreement with the findings of (Tan et al. 2005) who have also reported mortality of A. mellifera honey bees between 51 to 52°C. Among other similar studies, (Vaziritabar and Esmaeilzade 2019) have reported that wasps were dying at temperatures between 48°C and 49°C while A. mellifera were reported to die at 53–54°C.

4.4 Predatory behaviour of wasp species

The observation on the predatory behaviour of different wasp species showed that V. auraria was the most aggressive and agile wasp across different species, attacking more frequently and also with quick reaction to catch the bees compared to the others. It was the only species which attacked in group, preferred attacking and catching the bees at the hive entrance, and also disrupted the foraging of bees. Only solitary attacks of V. basalis and V. tropica were observed on the colonies and these two species were not as damaging as V. auraria and were slower in capturing bees. The aggressive predatory behaviour of V. auraria observed in our study is consistent with previous findings of (Srivastva et al. 1995) who documented that V. auraria was one of the most aggressive predators of honey bee apiaries, capable of capturing bees rapidly and causing significant damage to the colony. (Motmayen et al. 2024) also reported V. auraria as the most agile and damaging wasp species attacking honey bee colonies followed by V. basalis and V. tropica.

3.1 Optical remote sensing

Optical remote sensing is among the most commonly applied geospatial techniques for monitoring biodiversity and ecosystem dynamics. These systems record reflected solar energy in the visible, near-infrared (NIR), and shortwave infrared (SWIR) regions of the electromagnetic spectrum, making it possible to evaluate vegetation health, productivity, and seasonal behaviour. Various spectral indices generated from optical data, such as the Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), Soil-Adjusted Vegetation Index (SAVI), and Photochemical Reflectance Index (PRI), are widely used as indicators of photosynthetic efficiency, biomass accumulation, vegetation stress, and phenological variation (Pettorelli et al. 2014; Huete et al. 2002). These indicators play an important role in assessing habitat quality, ecosystem processes, vegetation condition, and biodiversity patterns in forests, wetlands, grasslands, and agricultural ecosystems. Long-term satellite missions, particularly NASA’s Landsat series and the European Space Agency’s Sentinel-2 program, have significantly strengthened biodiversity monitoring efforts through the provision of freely available and continuous multi-temporal datasets. These extensive archives support the monitoring of deforestation, habitat fragmentation, vegetation decline, invasive species expansion, and ecological restoration over broad spatial and temporal scales (Wulder et al. 2019; Drusch et al. 2012). Frequent satellite revisit cycles also enable near-real-time observation of environmental disturbances, including droughts, wildfires, floods, and land-use transformations.

Optical remote sensing plays a crucial role in studying vegetation phenology, as seasonal changes in vegetation are closely linked to ecosystem processes and species interactions. Time-series satellite data enable continuous monitoring of key phenological events such as leaf emergence, flowering, senescence, and variations in canopy greenness throughout the year. These observations are valuable for assessing the impacts of climate change on ecosystem dynamics, species distribution shifts, and habitat suitability patterns (Pettorelli et al. 2014). Moreover, multi-seasonal imagery improves the differentiation of vegetation types and habitat classes, thereby strengthening biodiversity evaluation and conservation planning. Recent advances in hyperspectral remote sensing have significantly enhanced vegetation analysis compared to conventional multispectral systems. By capturing hundreds of narrow, continuous spectral bands, hyperspectral sensors provide detailed information on plant biochemical and physiological characteristics, including chlorophyll concentration, water content, nutrient status, lignin–cellulose composition, and stress-related pigments. This rich spectral information facilitates improved discrimination of plant functional types and, in certain cases, enables species-level identification (Rocchini et al. 2016). As a result, hyperspectral data are increasingly utilized in applications such as species diversity mapping, invasive species detection, forest health monitoring, and ecosystem stress assessment.

The development of very high-resolution satellite platforms and unmanned aerial vehicle (UAV)-based optical sensors has further broadened the scope of ecological applications. High spatial resolution imagery allows detailed characterization of fine-scale landscape features such as canopy gaps, microhabitats, riparian zones, and coral reef structures that are often not detectable using coarser datasets. In addition, the integration of optical remote sensing with machine learning and artificial intelligence techniques has substantially improved automated land-cover classification, habitat suitability modelling, biodiversity hotspot detection, and species distribution mapping, offering higher accuracy and operational efficiency (Zhu et al. 2017; Maxwell, Warner, and Fang 2018).Despite these advantages, optical remote sensing is subject to several limitations. Atmospheric interference, cloud cover, terrain-induced shadows, and spectral saturation in dense vegetation can reduce data quality, particularly in tropical and humid regions. Furthermore, many biodiversity applications rely on indirect habitat proxies rather than direct species observations, which may not fully capture actual species richness or abundance patterns (Rocchini et al. 2016). Consequently, there is a growing consensus that integrating optical remote sensing with complementary methods such as field surveys, LiDAR, radar observations, UAV data, and environmental DNA (eDNA) approaches is essential for generating more robust and comprehensive biodiversity assessments.

3.2 Radar and microwave sensing

Radar and microwave remote sensing have become essential tools in biodiversity assessment and ecosystem monitoring due to their capability to collect information under almost all environmental and lighting conditions. Unlike optical sensors that rely on reflected sunlight, radar systems actively transmit microwave signals and record the reflected energy from the Earth’s surface. Because of this active sensing mechanism, radar observations can be obtained during both daytime and nighttime and are minimally affected by cloud cover, fog, smoke, or rainfall. These characteristics make radar-based remote sensing especially valuable in tropical and humid regions where continuous cloud cover often restricts the use of optical imagery. Among microwave technologies, Synthetic Aperture Radar (SAR) is one of the most widely applied systems for ecological and environmental studies. SAR sensors are highly responsive to vegetation structure, canopy texture, moisture levels, and surface roughness, enabling accurate assessment of forest cover, biomass distribution, wetland extent, floodplain dynamics, and habitat fragmentation (Le Toan et al. 2011). Since microwave signals can partially penetrate vegetation canopies, SAR data provide useful information about forest structural complexity, which is closely linked with habitat quality and biodiversity patterns.

The launch of modern satellite missions, particularly the European Space Agency’s Sentinel-1 constellation, has greatly expanded the application of radar remote sensing in ecological research. Sentinel-1 delivers freely accessible, high-frequency C-band SAR observations that support continuous monitoring of forests, wetlands, agricultural landscapes, and coastal ecosystems worldwide (Torres et al. 2012). Its short revisit interval enables rapid detection of environmental changes such as deforestation, habitat degradation, wildfires, floods, and land-use transitions. This capability is particularly important for biodiversity conservation and environmental monitoring in remote and difficult-to-access regions.

Radar remote sensing is widely used for estimating forest biomass and carbon stocks, which serve as key indicators of ecosystem productivity and climate regulation. Variations in Synthetic Aperture Radar (SAR) backscatter, along with interferometric radar approaches, provide valuable insights into canopy height, vegetation density, and forest structural attributes. These measurements enhance the detection of carbon-rich ecosystems and biodiversity-rich regions. In particular, long-wavelength SAR systems such as L-band and P-band offer improved penetration through dense vegetation canopies, making them especially effective for monitoring tropical forests and identifying areas of ecosystem degradation (Saatchi et al. 2011).The integration of radar data with optical remote sensing has significantly advanced habitat characterization and biodiversity assessment. While optical sensors capture spectral information related to vegetation composition and productivity, radar contributes complementary structural and moisture-related information. The fusion of these datasets helps mitigate limitations such as cloud cover, seasonal variability, and sensor-specific constraints, resulting in more reliable land-cover classification, habitat mapping, and ecosystem modelling across diverse environmental settings (Rocchini et al. 2016). Consequently, multi-sensor approaches are increasingly applied in studies focusing on forest fragmentation, wetland dynamics, wildlife habitat evaluation, and ecosystem restoration.

Advancements in radar technology, cloud-based geospatial processing, and artificial intelligence have further expanded the ecological applications of SAR data.Machine learning and deep learning techniques are increasingly employed to process large-scale radar datasets for automated forest change detection, habitat classification, and ecological monitoring with improved accuracy and efficiency (C. Zhang et al. 2018). In addition, the integration of SAR with LiDAR data, UAV-based imagery, and field observations has strengthened multi-scale analyses of habitat structure and biodiversity distribution.Despite these advantages, radar remote sensing has inherent limitations. SAR backscatter is influenced by multiple interacting factors such as vegetation structure, soil and canopy moisture, terrain conditions, and sensor wavelength, making interpretation complex. The presence of speckle noise and geometric distortions can further affect data quality and complicate analysis. Moreover, radar data processing often requires advanced computational resources and technical expertise. Therefore, the combined use of radar with optical imagery, ground-based surveys, and ecological modelling approaches is increasingly recommended to obtain more accurate and comprehensive biodiversity assessments.

3.3 LiDAR (Light Detection and Ranging)

Light Detection and Ranging (LiDAR) has become an important remote sensing technology for ecological studies and biodiversity assessment because of its capability to generate accurate three-dimensional information about vegetation and terrain structure. LiDAR systems function by transmitting laser pulses toward the Earth’s surface and calculating the time required for the reflected signals to return to the sensor. Using these measurements, highly detailed models of land elevation, forest canopy structure, and vegetation architecture can be produced. In contrast to passive optical sensors that mainly record reflected light, LiDAR directly captures vertical structural properties of ecosystems, making it highly effective for analysing habitat complexity and species–environment interactions (Dubayah et al. 2020; Guo et al. 2020).Several structural characteristics derived from LiDAR data, including canopy height, vertical layering, crown arrangement, gap fraction, foliage density, and understorey structure, are strongly linked to habitat heterogeneity, which plays a major role in shaping biodiversity distribution. Many organisms rely on distinct vertical habitat zones for feeding, nesting, movement, and protection; therefore, LiDAR-derived structural information provides valuable insights into habitat suitability and ecological niche availability in forested and heterogeneous landscapes. This technology is particularly useful in dense forests where traditional optical imagery often fails to capture detailed beneath-canopy structural variations (Ehbrecht et al. 2017).

Airborne LiDAR has been extensively utilized for characterizing forest structure, estimating aboveground biomass, quantifying carbon storage, and assessing habitat quality. A wide range of ecological studies has demonstrated strong relationships between LiDAR-derived measures of structural complexity and species diversity, particularly among forest-dependent taxa such as birds, mammals, insects, and arboreal organisms (Davies and Asner 2014). Forest ecosystems exhibiting higher vertical stratification and canopy complexity tend to support greater biodiversity, as they provide diverse ecological niches and microhabitats. In addition, LiDAR-based structural indicators have enhanced understanding of forest dynamics, vegetation regeneration, and ecosystem processes across environmental gradients (Coops et al. 2021).

Recent advancements in terrestrial LiDAR, UAV-mounted laser scanning systems, and spaceborne LiDAR missions have significantly expanded the application of this technology in ecological research. Satellite missions such as NASA’s Global Ecosystem Dynamics Investigation (GEDI) and ICESat-2 deliver large-scale observations of forest structure, biomass distribution, and ecosystem dynamics, enabling analyses at regional to global scales (Dubayah et al. 2020). These datasets are increasingly applied in monitoring forest degradation, habitat fragmentation, and ecological responses to climate change. At finer scales, drone-based LiDAR systems provide high-resolution structural information with greater operational flexibility, enhancing local ecosystem assessments (Seidaliyeva et al. 2025).The integration of LiDAR with complementary geospatial technologies, including optical and hyperspectral remote sensing, Synthetic Aperture Radar (SAR), and Geographic Information Systems (GIS), has substantially improved biodiversity assessment and habitat modelling. While optical and hyperspectral data provide insights into vegetation composition and physiological status, LiDAR contributes precise three-dimensional structural information. The fusion of these datasets enables more robust habitat classification, ecosystem characterization, and species distribution modelling across varied environmental conditions (Rocchini et al. 2016).

The application of artificial intelligence and machine learning techniques has further advanced the ecological use of LiDAR data. Modern algorithms are capable of efficiently processing large-scale three-dimensional point cloud datasets to classify vegetation types, estimate biomass, identify habitat features, and model biodiversity patterns with high accuracy (Lopatin et al. 2016). Deep learning frameworks and cloud-based geospatial platforms are increasingly facilitating automated ecosystem mapping, habitat monitoring, and conservation planning using LiDAR-derived products (Guo et al. 2020).Despite its strengths, LiDAR technology is associated with certain limitations. Airborne LiDAR surveys are often costly and require specialized equipment as well as technical expertise for both data acquisition and processing. The substantial volume of generated data also demands high computational resources and advanced analytical capabilities. Moreover, factors such as dense canopy cover, complex terrain, and sensor configuration can influence data accuracy and interpretation. Nevertheless, due to its ability to capture detailed vertical structural information, LiDAR remains one of the most powerful tools for biodiversity monitoring and ecological analysis.

3.4 Unmanned Aerial Vehicles (UAVs)

Unmanned Aerial Vehicles (UAVs), commonly known as drones, have become important tools in biodiversity monitoring and ecological research because they provide ultra-high-resolution imagery with high spatial and temporal flexibility. Unlike conventional satellite systems, UAVs operate at low altitudes and can capture detailed ecological information that is often difficult to detect using coarse-resolution satellite imagery. Their rapid deployment and flexible flight operations make them highly suitable for repeated monitoring of ecosystems and environmental changes over short time intervals (Anderson and Gaston 2013). UAV-based remote sensing is widely used in biodiversity assessment, habitat mapping, wildlife monitoring, and ecosystem management. Drones are frequently applied to map canopy gaps, monitor forest regeneration, assess wetlands and coral reefs, and validate satellite-derived environmental data. In wildlife studies, UAVs are useful for detecting and counting birds, mammals, marine organisms, nests, and burrows while causing minimal disturbance to natural habitats (Christie et al. 2016). Their ability to access remote and difficult terrain has further increased their importance in ecological surveys and conservation programs. Recent improvements in UAV sensor technologies have significantly expanded their applications in biodiversity research. Modern drones can carry different types of sensors, including RGB cameras, multispectral sensors, hyperspectral imagers, thermal cameras, and LiDAR systems. These sensors provide detailed information on vegetation condition, species composition, habitat structure, and moisture status. Thermal imaging technology is increasingly used for detecting wildlife populations, monitoring nocturnal animals, and identifying organisms hidden beneath dense vegetation (Barnas et al. 2018).

The integration of unmanned aerial vehicles (UAVs) with artificial intelligence, machine learning, and computer vision has significantly enhanced the efficiency and precision of ecological monitoring. Automated image analysis systems are now capable of detecting, classifying, and enumerating wildlife from high-resolution drone imagery and video datasets, thereby substantially reducing manual processing efforts (Willi et al. 2019). In parallel, deep learning frameworks are increasingly being applied for habitat mapping, invasive species detection, species identification, and the analysis of ecosystem change dynamics. These developments have strengthened the application of UAVs in rapid biodiversity assessments, conservation planning, and long-term ecological monitoring. UAVs also play an important role in ecosystem restoration and environmental management. High-resolution aerial imagery acquired from drones is widely used to assess habitat degradation, track reforestation and afforestation initiatives, monitor coastal erosion processes, and detect environmental disturbances such as wildfires, floods, and unauthorized land-use changes. Within agricultural landscapes, UAVs support precision agriculture and agroecological research by enabling monitoring of crop health, pollinator dynamics, and biodiversity patterns within farmlands (Tang and Shao 2015).

Technological enhancements in autonomous flight control, power efficiency, cloud computing, and real-time analytics have increased the ecological relevance of UAV platforms, and their coupling with satellite datasets, GIS, LiDAR, and ground-based measurements has strengthened biodiversity assessment and habitat modelling frameworks (Manfreda et al. 2018).Such integrative approaches provide a more holistic understanding of ecological processes and species–environment interactions.Despite these advantages, UAV-based biodiversity monitoring is associated with certain limitations. Operational constraints include sensitivity to weather conditions, limited flight endurance due to battery capacity, regulatory restrictions, and relatively restricted spatial coverage compared to satellite-based systems. Moreover, the processing and interpretation of high-resolution UAV data require considerable computational resources and technical expertise. In addition, UAV operations may cause disturbance to wildlife in ecologically sensitive areas due to noise and proximity effects. Nevertheless, owing to their high spatial resolution, flexibility, and declining operational costs, UAVs are increasingly recognized as a highly valuable tool for contemporary biodiversity monitoring and conservation applications.

3.5 Environmental DNA (eDNA) and molecular geospatial data

Environmental DNA (eDNA) has become an important and innovative tool for biodiversity assessment and ecological monitoring. eDNA consists of genetic material released by organisms into the environment through sources such as skin cells, mucus, feces, urine, saliva, pollen, spores, and decaying tissues. These traces of DNA can be collected from environmental samples including water, soil, sediment, snow, and even air, enabling scientists to identify species without directly observing or capturing them (Deiner et al. 2017). Due to its non-invasive and highly sensitive nature, eDNA techniques are particularly effective for detecting rare, endangered, invasive, or difficult-to-observe species that may not be easily identified through conventional survey methods. A major advantage of eDNA-based monitoring is its ability to evaluate biodiversity rapidly across extensive geographic regions while causing minimal disturbance to natural ecosystems. In aquatic environments, eDNA has been widely used to monitor fish, amphibians, molluscs, plankton, and marine organisms. Terrestrial applications are also expanding and now include the study of soil microorganisms, insects, mammals, birds, and airborne biological particles such as pollen and fungal spores (Taberlet et al. 2018). The development of high-throughput sequencing and metabarcoding technologies has further improved eDNA analysis by enabling simultaneous identification of multiple species from a single environmental sample, thereby increasing the efficiency of biodiversity surveys.

When environmental DNA samples are linked with geographic coordinates and incorporated into Geographic Information Systems (GIS), they generate spatially detailed biodiversity information that complements traditional ecological field observations and remote sensing data. The combination of eDNA with remotely sensed environmental variables has substantially enhanced species distribution modelling, habitat suitability analysis, and landscape level biodiversity assessment. Environmental characteristics derived from remote sensing platforms such as vegetation cover, canopy structure, land use patterns, temperature, moisture conditions, and hydrological features can be integrated with molecular species detections to better understand ecological relationships and species environment interactions (Ruppert, Kline, and Rahman 2019). This combined approach improves the accuracy of biodiversity mapping and ecological prediction across diverse landscapes.

Ongoing advancements in satellite remote sensing, hyperspectral imaging, LiDAR, and UAV-based observations have enhanced the role of eDNA in ecology by integrating large-scale environmental monitoring with detailed species detection, supporting conservation planning, invasive species monitoring, and ecosystem analysis (Bush et al. 2019). For instance, integrating eDNA results with remotely sensed temperature and hydrological data has improved the monitoring of freshwater ecosystems and the identification of environmentally sensitive habitats.The growing use of artificial intelligence (AI), machine learning, and advanced bioinformatics has also improved the processing and interpretation of complex genomic and environmental datasets. These computational tools help enhance species identification, biodiversity hotspot mapping, ecological forecasting, and environmental monitoring. As a result, integrated eDNA and remote sensing approaches are increasingly being applied in ecosystem restoration projects, protected area management, and early-warning systems for invasive or threatened species (Cordier et al. 2021).

Despite its considerable potential, eDNA monitoring still faces several scientific and technical limitations. Environmental factors such as temperature, ultraviolet radiation, pH, salinity, and microbial activity can influence DNA degradation and affect detection reliability. In addition, contamination risks, incomplete reference databases, and uncertainties related to estimating species abundance remain major challenges (Deiner et al. 2017). Moreover, eDNA methods generally provide limited information regarding population structure, behaviour, or demographic characteristics. Therefore, researchers increasingly recommend integrating eDNA analysis with remote sensing technologies, ecological field surveys, conventional taxonomy, and ecological modelling approaches to develop more accurate and reliable biodiversity monitoring systems.

3.6 In situ sensor networks

In situ sensor networks - including acoustic recorders, camera traps, microclimate sensors and GPS-enabled animal tags - generate continuous, fine-scale observations of species presence, behaviour and environmental conditions. Acoustic sensors enable the monitoring of vocal species such as birds, amphibians and insects, while camera traps provide critical data on terrestrial mammals and elusive species (Kays et al. 2015).

When integrated with geospatial datasets, these sensor networks create hybrid monitoring systems that combine organism-level observations with landscape-level environmental context. Such integrative approaches allow more robust analyses of species-environment relationships and support scalable, long-term biodiversity monitoring frameworks (Jetz et al. 2019).

A wide range of geospatial technologies has been adopted for biodiversity monitoring and ecological assessment, with each approach providing distinct advantages and constraints in relation to data acquisition, spatial resolution, analytical capability, and environmental application. Table 1 presents a comparative overview of the major geospatial technologies used in biodiversity monitoring, emphasizing their principal applications, methodological strengths, limitations, and recent advancements.

4.1 Convolutional Neural Networks (CNNs)

The automatic classification of habitats, plant types, and individual animals in remotely sensed pictures is now mostly dependent on Convolutional Neural Networks (CNNs), a class of deep learning models especially ideally adapted for image analysis. From high-resolution aerial and satellite data, CNN-based methods have proven to be highly accurate in recognizing tree species, detecting canopy gaps, and classifying land-cover categories, significantly minimizing the need for human interpretation (Zhu et al. 2017; Maxwell, Warner, and Fang 2018). Deep learning models have been effectively used in wildlife monitoring to identify and categorize large animals in camera-trap and aerial picture datasets, increasing survey reproducibility and efficiency (Willi et al. 2019).

4.2 Embedded AI driven image analysis

AI-driven analysis of camera trap images and embedded vision cameras are revolutionary new methods in wildlife conservation that allow for effective, scalable species surveillance without continuous human supervision. They overcome the human picture review barrier that traditionally overwhelmed ecologists by combining machine learning and hardware developments to handle large image collections in real-time or nearly real-time.

With integrated CPUs (such as those from NVIDIA Jetson or Intel Movidius) housed in small, waterproof cases, embedded vision cameras enable on-device AI inference without requiring cloud access. In remote locations, this configuration saves battery life and bandwidth by capturing motion-triggered photos or video, running detection algorithms instantaneously, and flagging pertinent wildlife events. These work in perfect harmony with conventional camera traps, which are frequently infrared-enabled for night vision.

4.3 Ensemble machine learning methods

In addition to deep learning, habitat suitability evaluations and species distribution modeling (SDM) frequently employ ensemble machine learning techniques including Random Forests, Gradient Boosting, and Boosted Regression Trees. When incorporating heterogeneous predictor variables as spectral indices, topographic metrics, and vegetation structural characteristics, these models perform very well. Particularly in data-rich situations, ensemble ML techniques consistently outperform classic regression-based SDMs by accounting for non-linear responses and interactions among predictors (Elith, Leathwick, and Hastie 2008; Cutler et al. 2007).

4.4 Data fusion

By combining data from many geospatial sensors and environmental data sources, data fusion is a complementary analytical development that improves biodiversity modeling. The simultaneous assessment of vegetation composition, structure, and moisture conditions is made possible by combining optical, radar, and LiDAR information. The addition of meteorological and hydrological variables further contextualizes the relationships between species and their environments. In habitat mapping and biodiversity assessments, multi-sensor data fusion has been demonstrated to lower model uncertainty and increase predictive accuracy, especially in structurally complex and heterogeneous ecosystems like mangroves, coral reefs, and mountainous forests (Rocchini et al. 2016; Fassnacht et al. 2016).

The computational demands of AI-driven and data-fusion approaches have been greatly alleviated by the emergence of cloud-based geospatial platforms. Environments such as Google Earth Engine and the European Space Agency’s cloud infrastructures enable rapid access to global-scale, multi-temporal remote sensing archives and support parallel processing of large datasets. These platforms allow computation-intensive machine learning workflows to be implemented at regional to continental scales, facilitating reproducible biodiversity analyses and near-real-time ecological monitoring (Gorelick et al. 2017). Collectively, advances in AI, machine learning and data fusion are enabling a paradigm shift in biodiversity science-from static, site-based analyses toward scalable, integrative and predictive ecological modelling frameworks.

5.1 Kriging for interpolation

Kriging is a geostatistical technique that takes spatial covariance into account while creating continuous surfaces from point data. It is ideal for predicting values like species richness across unsampled locations from sparse biodiversity data. It minimizes prediction error through best linear unbiased prediction (BLUP) by using a variogram model to give closer observations more weight. While universal kriging takes into account trends like elevation gradients in species richness mapping, ordinary kriging assumes a constant mean. (Stein 2012)

An innovative Bayesian spatial statistical method for interpolating sparsely measured two-dimensional geospatial data using Sparse Representation Kriging (SR-Kriging) is presented in the work by Miao and Wang (2026). By explicitly including statistical uncertainty of covariance parameters in the kriging framework-a factor that is frequently overlooked in traditional kriging techniques-the research significantly advances spatial statistics. The suggested method offers a more objective and dependable interpolation solution for sparse geographical datasets by eschewing detrending and semi variogram fitting. The combination of Gibbs sampling and hierarchical Bayesian modeling improves prediction reliability and uncertainty quantification. The method is very useful for applications in environmental statistics, geostatistics, agriculture, and spatial prediction studies since simulation and real-data analyses show that it successfully reconstructs geographical variability while offering realistic confidence intervals.

Kriging treats the data as a regionalized variable, consisting of both spatially linked random fluctuation and deterministic trend, in order to estimate continuous surfaces from scattered point observations. In contrast to more straightforward techniques like inverse distance weighting (IDW), it uses a variogram to represent how similarity diminishes with distance in order to extract optimal weights from the empirical spatial structure of the data. This produces variance estimates (kriging standard error), which measure uncertainty at each site and are essential for conservation mapping where sample gaps are frequent.

In biodiversity contexts, kriging interpolates sparse eDNA samples or field surveys to estimate richness across forests, aiding hotspot delineation. Cross-validation assesses accuracy through metrics like mean squared error (MSE).

In conservation, kriging creates heatmaps for hotspots in fragmented ecosystems like Kerala’s Western Ghats by filling in gaps in GBIF occurrence data or drone-sampled richness. It outperforms splines in heterogeneous terrains by interpolating soil nutrients or canopy height that affect plant variety. It optimizes habitats in rice fields by mapping pollinator concentrations using trap counts for precision agriculture ties.

5.2 Moran’s I for clustering detection

In order to determine whether similar values (high species richness) cluster together, Moran’s I evaluates global spatial autocorrelation:

where,

• is the number of spatial units indexed by and ;
• is the variable of interest;
• is the mean of ;
• are the elements of a matrix of spatial weights with zeroes on the diagonal (i.e., );
• and is the sum of all , i.e.,

Positive I (>0) indicates clustering (e.g., high richness in biodiversity hotspots); negative suggests dispersion; I=0 implies randomness. A z-score and p-value test significance via Monte Carlo permutations.

Apply to raster cells or polygons for species richness; clustered patterns show environmental factors such as soil fertility, which are frequently seen in plant population studies where Moran’s I performs better than other indices.

Local Moran’s I (LISA) identifies hotspots (high-high clusters) and coldspots, visualized in cluster maps for targeted conservation.

5.3 Moran’s eigenvector maps for anisotropy

MEMs capture patterns at various sizes by breaking down spatial correlations from a distance matrix into orthogonal eigenvectors. Negative eigenvalues deal with discontinuities, while positive eigenvalues model clustering. They explicitly represent anisotropy from irregular landscapes such as Kerala’s Western Ghats by regressing against response variables (such as richness) as predictors in GLMs (Dray, Royer-Carenzi, and Calenge 2010).

Using stream diatoms as model organisms, Leboucher et al. (2020) presented a unique metacommunity-based methodology for identifying species impacted by mass effect in freshwater environments. In order to differentiate mass effect from dispersion limitation and species generalism, the study included asymmetric eigenvector mapping (AEM), species co-occurrence analysis, and niche breadth estimation. The results showed those species impacted by the mass effect had comparatively small ecological niches, weak negative co-occurrence patterns, and substantial spatial dependence. The scientists also noted that a number of these species are included in widely used diatom-based bioassessment indexes, suggesting that the bulk effect may distort assessments of water quality and mask local environmental conditions. The study makes a significant addition to the knowledge of dispersal-driven community assembly processes in river ecosystems and to the improvement of ecological monitoring.

Significant MEMs are found using forward selection (fine-scale for local variation, broad-scale for regional trends). By eigen-decomposing connection graphs (e.g., Gabriel, relative neighborhood), this performs better than ordinary coordinates.

MEMs link spatial autocorrelation to habitat diversity in agro-biodiversity by revealing structuring in crop-edge-oak transitions.

2.1 Study location and experimental conditions

The present study was conducted at the Clonal Propagation and Research Development Centre of The Sirpur Paper Mills Ltd. (a unit of JK Paper Ltd.), located in Telangana, India. The experimental site falls under a semi arid tropical climatic zone, characterized by hot summers, mild winters, and moderate but seasonal rainfall. The region receives an average annual rainfall of 850–900 mm, most of which occurs during the southwest monsoon period between June and September. The mean maximum temperature during peak summer months reaches approximately 38 °C, whereas the mean minimum temperature during winter months falls to approximately 12 °C. These climatic conditions are representative of major pulpwood-growing regions in southern India, making the site suitable for evaluating clonal propagation performance under operational nursery conditions.

All experiments were conducted in a naturally ventilated polyhouse designed for vegetative propagation. The polyhouse was equipped with automated misting and adjustable shading systems to maintain optimal conditions for rooting and early growth of Eucalyptus mini cuttings (Joshi, Negi, and Rawat 2016). The misting system ensured uniform moisture availability by regulating air humidity and reducing transpiration losses during the critical rooting phase. Shading arrangements were used to regulate light intensity and prevent heat stress during peak daytime temperatures. Environmental parameters, including air temperature, relative humidity, and light intensity, were monitored regularly using digital sensors to ensure consistency throughout the experimental period. Any deviations from the desired range were corrected through adjustments in misting frequency or shading intensity, thereby minimizing environmental variability across treatments.

2.2 Vegetative multiplication garden

Mother plants originating from TCP and CCP were established as clonal hedges in a vegetative multiplication garden following standardized protocols for Eucalyptus clonal propagation (Ferreira, Xavier, and Wendling 2004). The objective of maintaining a dedicated multiplication garden was to ensure a continuous and uniform supply of physiologically juvenile shoots suitable for mini cutting production. The hedges were established in raised cement brick lined sand beds to provide adequate drainage, prevent waterlogging, and facilitate root aeration. Beds were filled with clean river sand to create an inert growing medium that minimized pathogen buildup and allowed precise control of nutrient inputs.

Plant spacing within the sand beds was maintained uniformly at 10 × 10 cm to promote consistent shoot emergence and ease of cultural operations such as irrigation, fertilization, and harvesting. Manual irrigation practices was adopted to ensure adequate moisture availability without excessive wetting of the foliage. Fertilization was carried out using a standardized nutrient solution prepared based on the nutritional requirements of Eucalyptus hedges. The nutrient solution was adjusted to the appropriate pH and applied daily to the rooting zone using a hand operated sprayer to promote vigorous shoot growth and maintain hedge productivity. Nutrient concentrations were carefully monitored and regulated to avoid deficiencies or toxicities, ensuring continuous production of healthy, disease free shoots.

The first harvest of mini cuttings was carried out approximately one month after hedge establishment, once the plants had acclimatized and produced sufficient new growth. Subsequent harvests were conducted on a weekly basis as new shoots reached a harvestable length of 6–10 cm. During the entire production cycle, adequate moisture levels were maintained using a tap-water sprinkler system to prevent desiccation, particularly during high temperature periods. Regular monitoring of pest and disease incidence and sanitation practices like removal of senescent leaves were followed to maintain the physiological health and productivity of the mother plants.

2.3 Planting material and mini cuttings preparation

Apical shoots measuring approximately 6–10 cm in length were initially excised from the clonal hedges maintained in the sand beds. These shoots were further trimmed to include 2–4 nodes and were referred to as mini cuttings. Only young, actively growing lateral shoots were selected to ensure high rooting potential and uniform physiological status. Shoots were harvested using clean, sterilized scissors to minimize mechanical damage and reduce the risk of pathogen contamination. Immediately after harvest, the cut shoots were placed in a thermocol box lined with moist material to prevent dehydration and maintain turgidity during transport to the processing area.

In the processing area, the mini cuttings were further standardized by trimming them to a uniform size consisting of two nodes and one internode. This standardization was essential to reduce variability among cuttings and to ensure consistent exposure to rooting conditions. All leaf trimming and cutting operations were performed carefully to avoid excessive tissue damage. Prepared mini cuttings were inserted into root trainers containing the rooting substrate within 15 minutes of preparation to minimize moisture loss and physiological stress.

The rooting substrate used for the experiment consisted of coir pith and carbonized rice husk mixed in a ratio of 70:30 (%). This substrate was selected due to its constructive physical properties, including adequate aeration, good moisture retention, low bulk density, and inert nature. Root trainer technology was employed for rooting of Eucalyptus mini cuttings, as it facilitates proper root architecture development, prevents root coiling, and improves transplant success (Alfenas et al. 1997; Rawat and Dhiman 2002). Root trainers were selected with appropriate dimensions to support optimal root growth while maintaining sufficient moisture without water stagnation. The rooting medium was maintained as lightweight and well drained to prevent excess moisture, root rot, and fungal infections.

Mini cuttings were maintained in the mist chamber under controlled conditions, with an average relative humidity of 85% and a temperature of approximately 38 °C for about two weeks. These conditions were maintained to promote callus formation and adventitious root initiation. Once rooting was observed, the plantlets were transferred to a shade house for acclimatization for a period of three days under 50% light intensity. This gradual acclimatization helped reduce transplant shock and improved survival. Following this period, the rooted plantlets were exposed to full sunlight to harden them for further nursery growth and eventual field planting.

2.4 Rooting conditions

Root trainers containing the mini cuttings were maintained under controlled environmental conditions at 38 ± 2 °C and relative humidity ranging between 80 and 85%. Misting was scheduled at regular intervals of every 20 minutes for a duration of 60 seconds to maintain optimal moisture levels on the cutting surfaces and surrounding air. A photoperiod of 9 hours was maintained to simulate operational nursery conditions and support physiological activity during rooting.

2.5 Experimental design

The experiment was conducted using a single Eucalyptus hybrid clone (EU × EG), with two sources of mother plants: TCP and CCP. The experimental layout followed a randomized block design to minimize the effects of environmental heterogeneity within the polyhouse. Each treatment consisted of three replications, with 500 mini cuttings per replication, resulting in a robust sample size for statistical analysis. All cultural practices were kept uniform across treatments to ensure that any observed differences in rooting and growth parameters could be attributed solely to the origin of the mother plants.

2.6 Data collection and statistical analysis

Data collection was carried out at 45 days after planting, a stage considered appropriate for evaluating rooting success and early growth performance of Eucalyptus mini cuttings (Schwambach et al. 2008). Observations were recorded on shoot length, root length, number of new leaves, root volume, and root shoot ratio. Rooting success was assessed using 30 randomly selected cuttings per treatment to provide a representative estimate of rooting performance (Joshi, Negi, and Rawat 2016; Naickar et al. 2024).

All collected data were subjected to statistical analysis using IBM SPSS v29.0 software. Results were expressed as means ± standard error (SE). Analysis of variance (ANOVA) was employed to test for statistically significant differences between treatments at p≤0.05. Where applicable, appropriate post hoc comparisons were conducted to further interpret treatment effects. This analytical approach ensured rigorous evaluation of the influence of mother plant origin on rooting efficiency and early growth parameters of Eucalyptus hybrid mini-cuttings.

3.1 Survival and rooting efficiency

TCP demonstrated a markedly higher survival percentage of 94.73% during the acclimatization phase compared to CCP, which recorded a survival rate of only 75%. Root initiation in TCP cuttings occurred within 6–8 days, which was noticeably faster than that observed in CCP cuttings Figure 1.

3.2 Early growth performance

Quantitative assessment of early growth parameters revealed significant differences between TCP and CCP derived cuttings. TCP cuttings produced significantly longer shoots (28.20 ± 0.92 cm) and roots (16.40 ± 0.84 cm) compared to CCP cuttings, which recorded shoot and root lengths of 20.50 ± 0.81 cm and 11.00 ± 0.64 cm, respectively. Leaf initiation followed a similar trend, with TCP cuttings producing a greater number of new leaves (6.0 ± 0.32) than CCP cuttings (4.6 ± 0.28) (Table 1; Table 2).

3.3 Root system development

Root system characteristics differed significantly between TCP and CCP derived cuttings (Figure 2; Figure 3). TCP cuttings exhibited greater root length and higher root volume, reflecting more vigorous root initiation and elongation. In contrast, CCP cuttings produced finer and more fibrous root systems, with overall lower root volume and elongation.

3.4 Leaf initiation and vigour

TCP cuttings demonstrated a significantly higher rate of leaf initiation and overall vegetative vigour compared to CCP cuttings (Figure 4). Additionally, TCP cuttings exhibited more uniform growth patterns across replicates, whereas CCP cuttings were associated with greater variability and increased mortality rates, particularly during the mist chamber stage.

1.1 Methodolgy of literature review

This study adopts a systematic narrative review approach to synthesize existing knowledge on tillage systems and their implications for soil and water conservation. A structured literature search was conducted across major scientific databases, including Web of Science, Scopus, ScienceDirect, and Google Scholar, covering publications from 1990 to 2025. The search utilized combinations of keywords such as “conventional tillage,” “zero tillage,” “conservation agriculture,” “soil carbon,” “water conservation,” “residue management,” and “Indo-Gangetic Plains.” The inclusion criteria comprised peer-reviewed journal articles, review papers, and reports focusing on tillage impacts on soil, water, yield, or sustainability, particularly in major agroecological regions with emphasis on South Asia. Exclusion criteria included non-peerreviewed sources lacking scientific validation, studies without clear methodological descriptions, and regionally irrelevant or redundant datasets. In total, approximately 120 relevant studies were screened, of which around 70 high-quality sources were selected for synthesis. The analysis emphasizes comparative evaluation, trend identification, and critical interpretation rather than purely descriptive reporting.

2.1 Conventional tillage framework

Conventional Tillage (CT) is structured as a sequential two-stage system consisting of primary and secondary tillage interventions, each aimed at achieving specific yet interconnected soil conditioning goals (Kladivko 2001). Moldboard plows, disc plows, or heavy rotary tillers are used for primary tillage to turn the soil over to depths of 15 to 30 cm. This causes a lot of soil movement and aggregate disruption (Kladivko 2001). This process of inversion breaks up compacted horizons, covers up surface residues and weed biomass, and makes it easier to mix fertilizers and soil amendments into the plow layer. However, the extensive disturbance speeds up the oxidation of soil organic matter, breaks up the continuity of macropores, and makes the structure more likely to break down.

Secondary tillage comes after primary inversion and is done with tools like tandem harrows, disc harrows, spike-tooth harrows, or field cultivators. This breaks up soil clods even more, makes the size distribution of aggregates more even, and creates a flat, uniform seedbed that is best for mechanized planting (Kladivko 2001). These repeated passes break up the soil more and make it easier to work with in the short term, but they also use more fuel, require more workers, and make it more likely that a crust will form on the surface. From a residue management point of view, CT systems usually keep less than 15% of the surface cover after planting because most of the crop residues are buried or mixed in during inversion (Chivenge et al. 2007). This low residue retention exposes the soil surface to direct raindrop impact and wind shear forces, which greatly increases the risk of water and aeolian erosion, nutrient runoff, and long-term damage to the soil’s physical integrity.

2.2 Reduced and minimum tillage systems

Reduced or minimum tillage (RT/MT) systems are a group of different ways to manage soil that are designed to reduce the amount, depth, and frequency of mechanical disturbance compared to traditional inversion-based methods (Kladivko 2001). These systems usually get rid of one or more field operations, like fall plowing, or replace high-disturbance tools with lower-impact ones. This cuts down on the total amount of soil that is moved and the amount of fuel that is used (Franzluebbers 2004). RT/MT frameworks are made to keep about 15–30% of the soil surface residue cover after planting, which protects against erosion while still getting some of the benefits of seedbed preparation (Chivenge et al. 2007).

This classification includes a number of different technical methods. Mulch tillage uses tools like chisel plows, sweeps, or field cultivators that don’t turn the soil over but do disturb the whole surface. These tools also keep at least 30% of the crop residue cover, which is the minimum amount of cover that is usually required for conservation tillage systems (Chivenge et al. 2007). This system keeps the soil temperature from changing too much, stops moisture from evaporating, and makes it easier for water to get into the soil while still allowing for mechanical weed control (Jayaraman et al. 2021).

Strip tillage is a type of disturbance model that only affects narrow bands, usually 15 to 20 cm wide, that will be future crop rows. The areas between the rows stay undisturbed and covered in residue (Kladivko 2001). This zonal soil conditioning method makes a seedbed that is thermally and structurally optimized right below the planting line. This helps roots grow and take in nutrients more quickly in the early season, while also protecting the soil between rows with residue.

Ridge tillage, on the other hand, is when soil ridges are built up and kept up during the growing season so that crops can be planted on them (Franzluebbers 2004). When planting, residues are moved mechanically from the ridge crest to the furrows next to it. This makes it easier for seeds to come into contact with the soil in a specific area, while keeping the residue in the inter-ridge areas to help prevent erosion and keep moisture in. RT/MT systems are a middle ground between agronomic operability and better soil conservation results (Kladivko 2001).

2.3 Zero tillage and direct seeding

Zero tillage (ZT), also known as no-till or direct drilling, is the most intensive type of soil management that is good for the environment. It involves completely stopping mechanical soil disturbance between cropping cycles (Derpsch et al. 2010). In this system, the soil profile stays structurally sound from one harvest to the next. The only time it gets disturbed is during planting, when a narrow slit or slot is made to put seed and, if needed, basal fertilizer at the right depth (Franzluebbers 2004). This localized disturbance is usually done with special seeding machines that have disc openers, inverted-T openers, or heavy-duty tine-based drills that can get through thick surface residue layers and soil of different strengths while keeping a precise depth control and seed-soil contact (Kladivko 2001).

ZT systems keep 50% to 100% of the soil surface covered by crop residue, which is much more than the minimum conservation level (Figure 2). This makes them the best protection against raindrop impact, surface sealing, and wind erosion (Chivenge et al. 2007). The layer of residue that is kept acts as a biophysical buffer, keeping the temperature of the soil stable, lowering the amount of moisture that evaporates, speeding up the rate at which water enters the soil, and keeping the soil stable by adding organic matter over time. Also, not having an inversion stops the oxidation of soil organic carbon and keeps the macropores open, which helps the soil structure get better and the carbon stay in the ground for a long time. However, to make ZT work, weed management strategies must be integrated, often using chemical or cover-crop-based methods to make up for the lack of mechanical weed control (Franzluebbers 2004). Zero tillage is a change in the way crops are planted that focuses on soil integrity and system resilience instead of short-term changes to the way the soil is tilled (Derpsch et al. 2010).

2.4 Soil Tillage Intensity Rating (STIR)

The Soil Tillage Intensity Rating (STIR) was created by the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) to make it possible to compare different tillage systems quantitatively. It is a standardized, operation-based metric for measuring cumulative soil disturbance over a full cropping cycle (Claassen et al. 2018). The STIR framework includes all field operations that happen between harvests, so it gives a system-level assessment instead of a single-pass assessment. It takes into account several mechanistic factors, such as the type of implement, the depth of tillage, the speed of operation, and the percentage of soil surface area disturbed during each operation. This lets you make a weighted guess about how intense the disturbance is.

STIR takes into account both the physical features of tillage equipment and the changing conditions in the field where work is done. It then turns qualitative management practices into a continuous numerical index that shows how much soil has been disturbed overall. Higher STIR values mean that the soil is disturbed more, which is usually the case with inversion-based conventional systems. On the other hand, reduced and zero-tillage systems have lower STIR scores because they don’t disturb the soil as much in terms of depth, frequency, and surface disruption (Claassen et al. 2018). So, the index is an important tool for decision-making and benchmarking in conservation planning. It lets agronomists and policymakers check if they are following soil conservation rules, compare management strategies across agroecological zones, and look at the long-term effects of tillage intensity on soil structure, erosion risk, and sustainability outcomes.

As summarized in Table 1, zero tillage systems are characterized by high residue retention (50–100%) and low STIR values (<20), distinguishing them clearly from conventional tillage practices that involve intensive soil disturbance and minimal surface cover (Kladivko 2001).

Note: Values compiled from multiple studies across agroecological regions; variability dependson soil type, climate, and management practices.

3.1 Soil structure and aggregate stability

Soil aggregation is one of the most sensitive and all-encompassing signs of changes in soil quality caused by tillage. This is because the movement of aggregates shows the balance between mechanical disruption and biological stabilization processes. Soil aggregates are the basic building blocks of the pedosphere. They are made up of mineral particles that are held together by organic “glues” like polysaccharides, microbial metabolites, fungal hyphae, and root-derived exudates. These materials work together to make the soil more cohesive and stable (Charles et al. 2024). These aggregates control the structure of pores, how much water they hold, how well they aerate, and how well they protect soil organic matter within microaggregates. This affects how well carbon is stabilized and how well nutrients are cycled.

Intensive conventional tillage breaks up macroaggregates mechanically by using repeated inversion and shearing forces. This breaks up fungal networks and root structures that help make aggregates. This physical breakdown makes organic substrates that were previously hidden more accessible to microbes and aerobic decomposition, speeding up mineralization processes and making structures less stable over time. Long-term studies in the real world, like those done at the Kellogg Biological Station (KBS), have shown that zero tillage systems gradually improve soil aggregation. After about ten years of continuous use, the stability of the aggregates has improved significantly (Charles et al. 2024). On the other hand, even one inversion tillage event on soil that has been managed with no-till for a long time can undo a lot of the structural gains that have been made, making the aggregate stability drop to levels that are similar to those of systems that have been tilled in the traditional way for decades. These results show that tillage affects soil structure in a nonlinear and cumulative way. They also show that aggregate stability is both a diagnostic metric and a mechanistic pathway that connects management practices to long-term soil health outcomes.

3.2 Soil Organic Carbon (SOC) and carbon sequestration

Conservation Agriculture (CA) systems are widely recognized for their potential to enhance soil carbon dynamics and increase soil organic carbon (SOC) stocks, thereby contributing to atmospheric carbon mitigation (Rathika et al. 2025). Zero tillage (ZT) systems minimize soil disturbance, reduce aggregate breakdown, and limit the exposure of physically protected organic carbon to microbial oxidation, particularly when combined with crop residue retention (Xing and Wang 2024). Long-term conservation agriculture experiments have demonstrated that SOC can increase at rates of approximately 0.2-0.4 Mg C ha⁻¹ yr⁻¹ under zero tillage with residue retention, particularly in the upper soil layers (0-15 cm), due to enhanced microaggregate formation and continuous organic matter inputs.

Evidence from long-term trials in the Indo-Gangetic Plains indicates that ZT-based systems not only improve surface SOC stocks but also enhance carbon use efficiency and net carbon balance compared to conventional tillage systems (Chaudhary et al. 2025; A. Kumar et al. 2025). These improvements are attributed to increased biomass production, reduced fuel consumption, and lower fossil energy inputs. However, several studies report that SOC accumulation is often stratified near the surface, with limited changes observed in deeper soil layers (>30cm), raising questions about the long-term stability and whole-profile carbon sequestration potential. Despite these uncertainties, meta-analytical studies consistently show that CA systems improve overall carbon sustainability indices by integrating enhanced carbon retention with reduced external energy dependence (Jayaraman et al. 2021). Therefore, SOC management under reduced disturbance systems represents a critical pathway linking tillage practices with climate-resilient and resource-efficient agricultural systems.

3.3 Soil biological community and ecosystem services

Soil is a living ecosystem that changes over time and is home to many different types of microbes and animals, such as bacteria, fungi, actinomycetes, earthworms, and micro-invertebrates. These organisms work together to control nutrient cycling, change organic matter, and keep the structure of the soil (Mandal et al. 2025). These organisms create complex trophic and symbiotic networks that support important ecosystem services like decomposition, nitrogen fixation, carbon stabilization, and keeping soil-borne pathogens from spreading. By breaking up fungal hyphal networks, collapsing earthworm burrows, and changing the continuity of habitats, conventional tillage mechanically breaks these biological links. This makes microbial biomass less stable and ecosystems less connected (Kladivko 2001). Repeated disturbances like these can reduce the variety of functions and make the soil less resilient over time.

Conservation agriculture systems, especially zero tillage (ZT), on the other hand, promote biological stability by keeping soil disturbance to a minimum and maintaining a constant cover of surface residue. This serves as both a protective habitat and a steady source of substrate for decomposer organisms (Jayaraman et al. 2021). The residue layer keeps the temperature and moisture levels in the microclimate stable, which makes it easier for microbes to grow and enzymes to work better. Because of this, soils managed by ZT often have better microbial efficiency in recycling nutrients, faster decomposition of residues under stable conditions, and better timing of nutrient release with crop needs (Bhan and Behera 2014). These biological improvements make the soil more fertile, help plants use nutrients more efficiently, and make the agroecosystem more productive. Thus, tillage intensity serves as a principal factor influencing soil biodiversity patterns and related ecosystem services, with reduced-disturbance systems typically promoting more intricate and functionally integrated soil biological communities.

The trends summarized in table Table 2 are derived from a synthesis of experimental and review studies examining the impacts of conventional, reduced, and zero tillage on soil structure, organic carbon dynamics, microbial activity, and moisture retention across diverse agroecological conditions (Bhan and Behera 2014; King and Holcomb 1985; A. Kumar et al. 2025).

4.1 Infiltration and runoff dynamics

The intensity of tillage has a direct effect on how water moves through the soil and how it is divided on the surface, especially by changing the structure of the surface and the continuity of the pores. In conventional tillage (CT) systems, the lack of protective residue cover leaves bare soil open to the kinetic energy of rain, which breaks down aggregates and creates surface crusts or structural “seals” during rain events (Charles et al. 2024). This crusting effect makes the surface less porous, slows down the flow of water through the soil, and stops water from moving down into the soil profile. As the ability of the soil to absorb water decreases, extra rainwater is moved to the surface as runoff. This makes it more likely that topsoil will erode, nutrients will be lost, and water will be lost through sediment (Jayaraman et al. 2021). The combination of less infiltration and more runoff can make it harder for soil to hold moisture, recharge groundwater, and improve the quality of water downstream.

In contrast, zero tillage (ZT) systems keep a constant layer of surface residue cover, which acts as a protective mulch layer that absorbs the energy of raindrops and keeps aggregates from breaking apart (Jayaraman et al. 2021). This residue barrier keeps the soil’s structure intact and keeps macropore networks alive. These networks are made up of root channels and soil fauna, like earthworm burrows, that create pathways for water to flow from the surface to deeper layers. Taking care of these biopores speeds up infiltration, lowers surface sealing, and redistributes water better within the profile (Jayaraman et al. 2021). Long-term real-world observations show that infiltration performance in well-established no-till systems can get close to levels seen in natural ecosystems that have been disturbed very little, like forest soils, where stable structure and constant organic inputs support high hydraulic conductivity (Charles et al. 2024). All of these changes to the water cycle that happen under ZT lead to better use of rainfall, less risk of erosion, and a stronger system when it rains in different ways (Figure 3).

Field studies from the United States, Australia, Africa, and Europe demonstrate substantial reductions in runoff and soil loss under zero tillage and conservation agriculture systems, with soil erosion reductions reaching up to 99% in some cases (Table 3) (Jayaraman et al. 2021).

Note: Values compiled from multiple studies across agroecological regions; variability dependson soil type, climate, and management practices.

4.2 Water-holding capacity and drought resilience

Zero Tillage (ZT) systems increase the soil’s ability to hold water by improving the accumulation of soil organic carbon (SOC) and the stability of the soil structure. Both of these things affect the size of the pores and the moisture retention of aggregates (Jayaraman et al. 2021). More SOC leads to a larger specific surface area and better formation of stable microaggregates. Together, these things make the soil better at holding water that plants can use in the root zone. Also, better soil structure from long-term low-disturbance management encourages a balanced pore network, which makes it easier for macropores to let water in and micropores to hold water. These changes to the structure and carbon content of the soil make it better able to handle short-term precipitation shortages and keep crops watered during dry spells.

Keeping surface residue on the ground helps plants survive droughts by acting as a thermal and evaporative regulator. The mulch layer creates a physical barrier between the soil surface and the atmosphere, which reduces direct exposure to sunlight, keeps the soil temperature from changing too much during the day, and stops water from evaporating (Derpsch et al. 2010). This dual thermal–hydrological buffering effect keeps soil moisture available for longer, which is especially important when there is a drought or high temperatures (Bhan and Behera 2014).

In the Indian agroecological context, zero-tillage wheat systems have shown to be more resistant to terminal heat stress, especially during the grain-filling phase, when high temperatures can greatly lower yield potential (Bhan and Behera 2014). Better soil moisture availability under ZT helps transpiration continue, which cools the canopy through evaporation and reduces physiological stress caused by heat. The combination of improved SOC, stable soil structure, and microclimatic regulation through residue under ZT makes crops more resistant to drought, helps them use water more efficiently, and keeps yields stable even when the weather changes.

4.3 Challenges: nutrient leaching and cold soils

Zero tillage (ZT) can help soil hold more water and stay stable, but the changes it makes to the water cycle may create problems for farming and the environment in certain situations. In high-latitude and cool-temperate areas, a lot of surface residue can stay on the ground, which can lower the temperature of the soil surface by blocking solar radiation and changing the way heat flows, especially in early spring (Derpsch et al. 2010). The soil will be cooler and wetter as a result, which could make it take longer for the soil to dry out, slow down the germination process, and delay planting. This could make it harder for crops to grow and establish themselves early in the season. This kind of thermal moderation can help keep moisture, but it can also slow down degree-day accumulation and change the timing of crop growth in places where the temperature is limited.

Conservation agriculture (CA) systems generally reduce surface runoff and the loss of nutrients that comes with it. This makes it less likely for nitrate and phosphorus to get into surface water bodies and lowers the risk of eutrophication (Jayaraman et al. 2021). The maintenance of soil structure and improved infiltration in zero tillage (ZT) reduces nutrient displacement caused by erosion, which leads to better surface water quality. However, in some types of soil and hydrogeological conditions, especially coarse-textured soils with high permeability, the increased continuity of macropores and preferential flow pathways may help soluble nutrients, especially nitrates, move vertically beyond the root zone. This improved transport through infiltration can increase the risk of nitrate leaching into groundwater systems when there is too much rain or nitrogen is not managed well.

Because of this, ZT and CA systems have a lot of hydrological and environmental benefits, but they only work well in certain places. To balance the benefits of saving water with the risks of leaching, farmers need to use integrated nutrient management strategies and regionally adapted agronomic practices.

5.1 Benefits of residue mulching

Within conservation tillage frameworks, a minimum threshold of approximately 30% surface residue cover is commonly used as an operational criterion for classifying a system as “conservation tillage,” reflecting its capacity to deliver measurable soil protection benefits (Kladivko 2001). Residue mulching provides multiple synergistic agronomic and ecological functions that collectively enhance soil system stability.

Erosion protection is one of the primary benefits, as the residue layer dissipates the kinetic energy of wind and rainfall, reducing soil particle detachment, surface sealing, and runoff generation (Kladivko 2001). By shielding the soil surface, mulch minimizes both aeolian and water-driven erosion processes, thereby conserving topsoil and associated nutrients.

Thermal regulation represents another critical function, as surface residues moderate soil temperature fluctuations by reducing direct solar radiation exposure and altering heat exchange dynamics between the soil and atmosphere (Chaudhary et al. 2025). This buffering effect decreases extreme diurnal temperature variations, promoting more stable conditions for seed germination, root development, and microbial activity.

Weed suppression occurs through both physical and biochemical mechanisms. The residue layer limits light penetration, thereby inhibiting photodependent weed seed germination and early seedling establishment. Additionally, certain decomposing residues may release allelopathic compounds that further suppress weed growth, reducing reliance on chemical herbicides in integrated systems (Carr, Gramig, and Liebig 2013).

Finally, residues serve as a biological substrate, supplying continuous organic inputs that fuel microbial metabolism and support soil faunal communities (Kladivko 2001). This sustained carbon source enhances nutrient cycling, promotes soil organic matter formation, and strengthens overall soil biological activity, thereby reinforcing ecosystem functionality within conservation-based management systems.

5.2 Nitrogen immobilization and the C:N ratio

A major technical challenge in high-residue conservation systems is nitrogen (N) immobilization, which results from the biochemical processes involved in breaking down residue, especially when using carbon-rich crop biomass like wheat and rice straw, which has a high carbon-to-nitrogen (C:N) ratio (Derpsch et al. 2010). Microbial communities in soil need enough nitrogen to make the proteins and enzymes that cells need to break down complex organic carbon substrates. When residues have high C:N ratios, microbial decomposers may not have enough nitrogen, so they take in inorganic nitrogen from the soil around them to meet their metabolic needs. This process, called nitrogen immobilization, temporarily lowers the amount of nitrogen that plants can use in the root zone. This could slow down the growth and health of crops in the early stages.

From a nutrient management point of view, this temporary immobilization phase often requires strategic actions, such as applying slightly more nitrogen fertilizer at the beginning to make up for the microbes’ needs or adding leguminous crops to rotation systems to fix nitrogen from the air and make it more available at the system level (Derpsch et al. 2010). These kinds of integrated nutrient management strategies help balance carbon inputs from residues with nitrogen supply that is in sync with them.

Over long periods of time, usually 4 to 5 years under stable conservation management, the soil system may reach a new biogeochemical equilibrium. This is marked by more organic matter building up in the soil and better nutrient cycling efficiency (Derpsch et al. 2010). As organic matter pools stabilize and microbial turnover continues, nitrogen that was previously stored can slowly turn into minerals. This can help recycle nutrients inside the body, which could mean less fertilizer needs to be added from outside in the long term. Consequently, efficient residue-based conservation systems necessitate adaptive nitrogen management strategies that consider temporal variations in carbon-nitrogen interactions within developing soil ecosystems.

6.1 North America: The United States and Canada

Conservation tillage has become widely used in North America, especially in the United States, for major commodity crops. This is due to both agronomic and economic reasons. Conservation tillage is used on a large part of the land where wheat (67%), corn (65%), and soybeans (70%) are grown, which shows that it is in line with large-scale mechanized agriculture. No-till systems make up about 45% of wheat acreage and 40% of soybean acreage within this larger group. This shows that zero-disturbance technologies are having a big impact on staple crop production (Claassen et al. 2018). The main reasons people use this technology are to reduce the risk of soil erosion, especially in areas that are prone to it, and to lower operational costs, especially fuel and labor costs that come with doing the same thing over and over again (Farooq and Siddique 2014). These economic and environmental benefits have made it more likely that reduced-disturbance frameworks will work in U.S. production systems for a long time.

In Canada, adoption patterns, especially in the Prairie Provinces, show an even bigger structural change. The use of no-till farming grew a lot, from about 5% in 1991 to 45% in 2006. At the same time, the use of conventional tillage fell from 65% to 25% (Agriculture and Agri-Food Canada 2014). This quick change shows how flexible Canadian grain systems are when it comes to policy incentives that promote conservation, new technology, and the need to protect soil. The Canadian experience also shows how no-till systems can be flexible in their operations. For example, farmers can use strategic or discretionary tillage when certain environmental conditions are present, like severe surface rutting or too much moisture in the soil during unusually wet seasons. Adaptive interventions stress that conservation systems work along a management continuum instead of as strict rules. This allows for context-sensitive changes while still meeting overall soil conservation goals.

6.2 South America: Argentina and Brazil

One of the most important places in the world for conservation agriculture (CA) adoption is South America. The Pampas region of Argentina and the Cerrado biome of Brazil have especially high rates of CA adoption (Farooq and Siddique 2014). These agroecological zones are known for their heavy use of machines to grow grains, their large changes in rainfall from season to season, and their soil types, which are naturally prone to structural degradation and erosion when subjected to repeated inversion tillage. In these conditions, controlling erosion became an urgent priority for both agriculture and the environment, speeding up the move toward systems with no disturbance.

The widespread use of no-till in these areas was made possible by the coming together of different technological advances. The widespread availability of broad-spectrum herbicides, especially glyphosate, made it possible to manage weeds chemically without disturbing the soil mechanically, which meant that farmers didn’t have to plow the field over and over again (Farooq and Siddique 2014). At the same time, the creation and spread of heavy-duty direct seeding equipment that could work in fields with a lot of residue and different soil types made it possible to place seeds reliably without having to invert the soil first. All of these improvements made it possible to change the way we farm from conventional tillage to no-till-based production models across the board.

As a result, no-till soybean and maize farming now takes up a lot of land in these areas. This is because land management philosophy has changed to focus on soil conservation, residue retention, and long-term sustainability (Farooq and Siddique 2014). The experience in South America shows how technological progress, environmental need, and market-driven commodity production can all work together to quickly and widely adopt conservation-oriented tillage systems.

6.3 Sub-Saharan Africa: Restoration of degraded soils

In Sub-Saharan Africa, conservation agriculture (CA) is becoming more popular as a way to fix damaged soils. This is especially true in places like Northern Ghana, where long-term intensive hand-hoeing or repeated moldboard plowing has caused the soil to lose its structure, organic matter, and fertility (Naab et al. 2017). In these situations, CA-based methods try to restore soil health by reducing mechanical disturbance, keeping residue, and improving nutrient cycling. This solves both biophysical degradation and production limits.

Short- to medium-term empirical evaluations (about four years) show that CA systems may sometimes have lower yields at first compared to conventional tillage. This is especially true during transitional phases when soil biological and structural equilibria are being re-established. Even though there may be some variation in early yields, economic studies show that no-till systems can lower the cost of growing crops like maize and soybeans by about 20–29%. This is mostly because they save a lot of money on labor and don’t need to do the same field work over and over again (Naab et al. 2017). These cost savings are especially important in farming systems where there aren’t enough workers, mechanization isn’t available, and manual labor is a big part of the cost of production.

Over time, as the amount of organic matter in the soil, the way it clumps together, and the efficiency of nutrient cycling all get better, CA systems could make yields more stable and profitable. This would be a win-win situation for the environment and the economy (Naab et al. 2017). This long-term trend shows how important it is to think about time when judging conservation systems. The initial costs of switching may be worth it in the long run because they lead to more fertile, resilient, and efficient use of resources.

6.4 Critical synthesis and research gaps

Despite extensive global evidence supporting conservation tillage, findings are not universally consistent. Yield advantages under zero tillage vary significantly depending on soil texture, rainfall patterns, and duration of adoption. For instance, coarse-textured soils often show faster hydrological benefits, whereas fine-textured soils may experience delayed structural improvements.

Conflicting evidence also exists regarding soil organic carbon sequestration, with some studies reporting surface accumulation without significant changes in deeper layers. Similarly, while reduced runoff is widely documented, the magnitude of improvement varies across climatic zones.

Key research gaps include:

• Limited long-term experimental data from smallholder systems
• Insufficient integration of socio-economic and biophysical analyses
• Lack of standardized methodologies for comparing tillage systems

Future research should focus on multi-location long-term trials and meta-analytical synthesis to resolve inconsistencies.

7.1 The stubble burning crisis and environmental health

In the Indo-Gangetic Plains (IGP), rice harvesting is done mostly by machines, especially combine harvesters. This leaves a lot of rice leftovers in the field after the harvest. Because there isn’t much time between when rice is harvested and when wheat is planted, and because regular seed drills don’t work well in high-residue conditions, about 2.5 million farmers in northwestern India use residue burning as a quick way to clear land so that wheat can be planted on time (Saifuddin et al. 2025). This practice comes about because of logistical problems in the Rice–Wheat Cropping System, not because it is the best agronomic choice.

The amount of residue burned is important for the environment. States like Punjab and Haryana burn about 11.3 million tons of crop waste every year. This releases a lot of fine particulate matter (PM2.5), carbon monoxide (CO), carbon dioxide (CO₂), and nitrogen oxides (NO₂) (Saifuddin et al. 2025). These emissions cause serious air pollution problems in northern India, which makes breathing and heart problems worse and makes the air quality in the region worse (Chaudhary et al. 2025). The sporadic occurrence of stubble burning, especially in post-monsoon periods, exacerbates atmospheric stagnation, increasing pollutant concentration levels.

Burning waste not only affects the quality of the air, but it also causes important nutrient losses in the soil. Burning changes organic carbon and nitrogen that are useful to living things into gases or unstable ash residues. This messes up the way nutrients move through the soil and makes it less fertile over time. Burning organic matter repeatedly removes it from the soil, which lowers the potential for soil organic matter to build up and weakens the structure of the soil. This limits productivity in intensive cropping systems (Saifuddin et al. 2025). Stubble burning is an environmental health emergency and a challenge to soil sustainability. This shows that conservation agriculture frameworks need integrated residue management solutions.

7.2 Technological Solutions: Happy Seeder and Zero-Till Wheat

The use of the “Turbo Happy Seeder” to set up zero-tillage wheat systems is a key technological solution to the problems of managing residue in the Indo-Gangetic Plains. This system lets farmers plant wheat directly into standing rice residues without having to till the land or burn the residues first (Chaudhary et al. 2025). This mechanized solution combines handling of residue and placement of seeds into one process, so that the machine’s cutting and seeding assemblies can work well even when there is a lot of biomass. The system supports timely wheat establishment, preserves soil structure, and keeps surface residue cover (Figure 4), all of which are in line with conservation agriculture (CA) principles (Gorain et al. 2025). This is because it doesn’t require field preparation through inversion or residue removal.

Compared with residue-burning-based conventional wheat, Happy Seeder-enabled zero-tillage systems demonstrate higher yields, lower production costs, significant irrigation savings, and over 50% reduction in global warming potential (Table 4).

Note: Values compiled from multiple studies across agroecological regions; variability dependson soil type, climate, and management practices.

The Happy Seeder has several operational benefits, such as better residue retention, less soil disturbance, less fuel use, and less damage to the environment caused by burning stubble (Chaudhary et al. 2025). The system also helps keep moisture in the soil better and improves soil health over time when used consistently within CA frameworks. Even though these benefits for farming and the environment are great, widespread use is limited by economic and infrastructure problems. It costs a lot of money to buy machinery, and the equipment usually needs tractors with at least 45 horsepower or more, which makes it hard for farmers who don’t have a lot of money to get (Gorain et al. 2025).

To get around these problems, Custom Hiring Centres (CHCs) have come up as a useful new idea for institutions that lets people rent CA machinery without having to own it. By letting small and marginal farmers use zero-till equipment on a service basis, CHCs lower the cost of entry for farmers, help spread new technologies, and make it easier for farmers to adopt conservation-based wheat establishment practices on a larger scale (Hobbs et al. 2019). This service-oriented model makes things more inclusive and helps the Rice-Wheat Cropping System make the switch to more sustainable residue management.

7.3 System-wide transitions: DSR and Double Zero-Till

The long-term goal of the Indo-Gangetic Plains (IGP) is to set up a “Double Zero-Till” system, which means that both rice and wheat phases can be grown without disturbing the soil with machines (Figure 5). This will replace the traditional puddled transplanted rice (PTR) system with direct-seeded rice (DSR) followed by zero-tillage wheat (ZTW) (Chaudhary et al. 2025). The goal of this change is to redesign the Rice–Wheat Cropping System so that it doesn’t have to do the same tillage operations over and over again, uses less water for puddling, and uses resources more efficiently throughout the cropping cycle. By using DSR instead of saturated-field management, soil structure degradation caused by puddling is reduced, and subsurface compaction layers that block root growth and change how water moves through the soil are less likely to form.

When combined with zero-till wheat (DSR–ZTW), the system makes a continuous production model based on conservation that has less soil disturbance, keeps more residue, and uses less energy. Long-term real-world tests show that the DSR–ZTW configuration uses less fuel, requires less labor, and has fewer mechanized field operations than the traditional PTR–conventional tillage wheat (PTR–CTW) system (Chaudhary et al. 2025). This means that it has better energy performance. Also, life-cycle assessments show that this double zero-till system cuts down on greenhouse gas emissions from methane production in puddled rice, carbon dioxide emissions from burning fuel, and nitrous oxide emissions from heavy soil disturbance.

Together, the DSR–ZTW system is a scalable way to achieve climate-smart intensification in the IGP. It does this by optimizing energy efficiency, lowering greenhouse gas emissions, and improving the long-term resilience of the soil (Chaudhary et al. 2025).

8.1 Cost-Benefit analysis: private vs. social gains

When looking at the costs and benefits of zero tillage (ZT) systems, it’s clear that there are differences between the benefits for individual farms and the benefits for society as a whole. This shows how important it is to have a full cost-benefit framework when judging conservation technologies. From a private profitability standpoint, the primary motivation for adopting ZT is the significant decrease in operational costs. In the US, studies show that ZT can cut fuel costs by about 66%, maintenance costs by 54%, and machinery depreciation costs by 43%. This is mostly because it eliminates repeated tillage operations and reduces tractor use (Farooq and Siddique 2014). These savings directly boost net farm income by making farms less reliant on inputs and more energy-efficient.

In India, especially since the Happy Seeder technology was adopted, studies on farms show that operational costs went down by 11.7% and yields went up by 6.8%. This is a big economic benefit for people who use the technology (Gorain et al. 2025). The fact that conservation-based wheat establishment within the Rice–Wheat Cropping System saves money and increases productivity makes it more appealing financially in the short term.

Social Cost–Benefit Analysis (SCBA) looks at more than just how much money a single farm makes. It also looks at how the farm affects the environment and public health. An SCBA done in India’s Trans-Gangetic Plain found that the Happy Seeder had a social benefit-cost ratio (BCR) of 2.10, which means that for every unit of money spent, the society gets 2.1 units of benefit (Gorain et al. 2025). Some of these benefits are less damage to the environment from burning stubble, fewer health problems caused by air pollution, better soil quality, and better ecosystem services. Thus, although private incentives facilitate adoption by lowering costs and increasing yields, the comprehensive rationale for conservation technologies is most apparent when social and environmental returns are incorporated into economic assessments.

8.2 Socio-economic barriers and labor dynamics

Socio-cultural norms, labor market dynamics, and institutional frameworks that affect farmer decision-making in ways other than just agronomic ones have a big impact on how quickly conservation tillage technologies spread. In many places, traditional farming practices include conventional tillage. A well-tilled, residue-free “clean” field is often seen as a sign of good farming and higher social status (Farooq and Siddique 2014). People may not want to use residue-retaining systems like zero tillage (ZT) because they think that standing stubble or surface mulch means that the land is not being cared for properly. These social and cultural beliefs are strong but hard to see barriers to changing behavior, which slows down the adoption of new technologies even when they are clearly beneficial to the economy.

On the other hand, changes in the structure of rural labor markets have made it easier for some people to adopt mechanized conservation practices. People moving from the country to the city has made it harder to find farm workers, which has raised wages and made it harder to find seasonal workers during important times like land preparation and harvesting. In addition, social welfare programs like the Mahatma Gandhi National Rural Employment Guarantee Act (MGNREGA) in India have changed the way rural labor is supplied by giving people other ways to make money. This has made farm work more expensive in terms of opportunity costs (Saifuddin et al. 2025). In these situations, traditional tillage that requires a lot of labor and manual residue management become less cost-effective, making mechanized zero tillage look better by comparison.

So, even though socio-cultural traditions may make it hard to adopt at first, changing labor economics and the need for mechanization can help make conservation-oriented changes happen. The interaction of cultural norms, labor availability, and economic incentives highlights the complex nature of ZT adoption, where technological feasibility must correspond with social acceptance and the changing structures of rural livelihoods.

9.1 Herbicide reliance and resistance

Zero tillage (ZT) systems are inherently more dependent on chemical weed control, particularly broad-spectrum herbicides such as glyphosate and paraquat for pre-sowing “burn-down” operations in the absence of mechanical soil disturbance (Derpsch et al. 2010). While these herbicides provide efficient short-term suppression of diverse weed flora, sustained and repetitive use has accelerated the evolution of herbicide-resistant biotypes globally. In the Indian rice–wheat production system, the grassy weed Phalaris minor (little seed canary grass) has developed resistance to multiple herbicide classes, including ACCase and ALS inhibitors, posing a significant threat to wheat productivity and the long-term sustainability of conservation agriculture (Shekhawat et al. 2022).

The emergence of resistance underscores the urgent need for Integrated Weed Management (IWM), which combines chemical control with ecological and agronomic strategies to reduce selection pressure and diversify weed suppression mechanisms. Key components include:

● Stale seedbed technique: Pre-sowing irrigation is applied to stimulate early weed germination, followed by non-selective herbicide application or shallow control measures prior to crop establishment, thereby reducing the initial weed seedbank pressure (Norsworthy et al. 2012).

● Crop rotation: Alternating cereal crops with broadleaf species such as mustard or pulses disrupts the life cycle of cereal-specific weeds, alters herbicide regimes, and reduces the dominance of problematic species like Phalaris minor (V. Kumar et al. 2013).

● Heavy mulching: Retention of 6–10 t ha⁻¹ of rice residue on the soil surface can suppress light-dependent germination and physically impede weed emergence. Empirical evidence indicates that adequate residue cover can reduce Phalaris minor emergence by over 80%, substantially lowering herbicide dependence (V. Kumar et al. 2013).

Collectively, these measures shift ZT systems from herbicide-centric management toward diversified, resilience-oriented weed control frameworks essential for sustaining long-term agroecosystem stability.

9.2 Pest and disease shifts

Keeping residue in conservation agriculture (CA) changes the microclimatic and ecological conditions of the agroecosystem, which in turn changes how pests and diseases behave. Surface residues can act as a “green bridge” for some pathogens and insect pests that live in the soil, allowing them to survive between growing seasons. For example, pests like sawflies and some fungal pathogens may be more common in CA systems because the straw that is kept provides shelter, keeps moisture in, and gives them places to spend the winter (Chivenge et al. 2007). If not managed carefully, these changed habitat conditions can lead to more pests or more early-season inoculum.

But the ecological changes that come with zero tillage (ZT) can also make biological regulation better. Less disturbance of the soil keeps soil arthropod communities alive and makes habitats more complex. This helps natural enemies like spiders and ground beetles, which are generalist predators of crop pests (Kladivko 2001). More predators often lead to better biological control, which may help balance out some of the risks that come with keeping residues.

Empirical evidence from the rice–wheat system indicates that pest dynamics under zero tillage are complex rather than consistently detrimental. Research shows that stemborer larvae were more common in ZT wheat stubble during the early stages of the crop. However, higher predation rates and winter mortality kept the population from growing, so there was no significant net increase in stemborer pressure for the next rice crop (Hobbs et al. 2019).

These results show that the effects of pests and diseases in systems without tillage depend on the situation, how the residue is managed, the weather, and how different species interact with each other. To make CA work well, it needs integrated pest management (IPM) strategies that take advantage of increased natural enemy activity while keeping an eye on risks from residues to keep the system stable over time.

10.1 Sub-Mission on Agricultural Mechanization (SMAM)

The Sub-Mission on Agricultural Mechanization (SMAM), implemented by the Government of India under the Ministry of Agriculture and Farmers’ Welfare, serves as the principal policy instrument for accelerating the adoption of conservation agriculture (CA) machinery across states (Amuthasaravanan 2025). Revised guidelines issued in 2024 further strengthened its role in promoting residue management and zero tillage technologies, particularly in the rice–wheat systems of northern India.

10.2 Crop Residue Management (CRM) scheme

The Government of India started the Crop Residue Management (CRM) Scheme to stop stubble burning in the rice–wheat belt, especially in the states of Punjab, Haryana, and Uttar Pradesh. Since it started in 2018, the program has given out more than ₹3,600 crore to support technologies for managing crop residue on-site and to improve the ability of institutions to handle crop residue in a way that is good for the environment (Bethi and Deshmukh 2023).

The CRM framework works with SMAM’s mechanization subsidies to focus on lowering open-field burning, which has serious effects on air quality, soil health, and greenhouse gas emissions in the region. Financial help is given to buy machines like Happy Seeders, Super Straw Management Systems (Super-SMS), and balers. There is also help for awareness campaigns and ways to keep track of things.

The 2024–25 action plan for Punjab stresses the use of data to guide the implementation of plans. This includes geo-mapping and tracking of more than 138,000 residue management machines that are already in use to make sure they are used to their fullest potential and not underused (P. Kumar and Joshi 2013). Authorities have also found “hotspot” villages where burning of waste is still going on. This allows for targeted interventions through better access to machinery, stricter enforcement, and outreach programs for farmers.

The CRM scheme is a focused policy response that links the adoption of conservation tillage with broader environmental governance goals, especially in northern India where it aims to reduce air pollution and climate change. It does this by using financial incentives, spatial monitoring, and localized enforcement.

Thus, policy interventions promoting conservation agriculture have shown measurable impacts on adoption rates, resource-use efficiency, and environmental outcomes. For instance, governmentsupported initiatives such as subsidies for zero-tillage machinery (e.g., Happy Seeder) and awareness programs in the Indo-Gangetic Plains have significantly increased the adoption of residue management technologies. These interventions have been associated with reduced residue burning, leading to improvements in air quality and reductions in greenhouse gas emissions. In addition, adoption of zero tillage practices has contributed to measurable economic benefits, including reduced input costs (fuel, labor, and irrigation) and improved profitability for farmers. However, the effectiveness of such policies varies across regions due to differences in institutional capacity, access to machinery, and farmer awareness. Therefore, linking policy support with measurable indicators such as adoption rates, cost savings, and environmental benefits is essential for evaluating the long-term success and scalability of conservation agriculture systems.

11.1 Precision nutrient and water management

Over-fertilizing with nitrogen (N) is still a major cause of greenhouse gas (GHG) emissions in the Indo-Gangetic Plains (IGP), especially through nitrous oxide (N₂O) fluxes that happen when nitrogen is not used efficiently (NUE) (Pratap et al. 2025). In traditional rice-wheat systems, blanket fertilizer recommendations often lead to over-application, which raises costs and harms the environment. Incorporating precision nutrient management tools into zero tillage (ZT) systems is a way to get the most out of nitrogen inputs while still keeping productivity high.

Technologies that use optical sensors, like the GreenSeeker, can measure crop health in real time using normalized difference vegetation index (NDVI) measurements. These sensors make it possible to apply nitrogen at different rates based on crop needs instead of set schedules. The Leaf Color Chart (LCC) is another low-cost decision-support tool that helps farmers figure out when to split their nitrogen applications by letting them see how green the leaves are, which is a good way to tell how much nitrogen is in the soil (Pratap et al. 2025). Both tools have shown that they can improve NUE and lower N₂O emissions by matching the supply of fertilizer to the way plants take it up.

Along with nutrient optimization, improvements in precision water management are also happening at the same time. Soil-moisture sensors and decision-support irrigation scheduling models are being used more and more with ZT systems to take advantage of better soil structure and water retention through residue. Farmers can reduce water extraction while maintaining yield by using real-time soil moisture thresholds instead of fixed intervals for irrigation.

Precision nutrient and water management strategies work together to make conservation agriculture better for the environment by lowering greenhouse gas emissions, making better use of resources, and making agroecosystems that are heavily farmed more resilient to climate change (Pratap et al. 2025).

11.2 AI, Robotics, and the Internet of Things (IoT)

Emerging digital technologies (Figure 7)-including artificial intelligence (AI), robotics, and Internet of Things (IoT) architectures-are increasingly positioned to address structural limitations in zero tillage (ZT) systems, particularly those related to weed management, labor scarcity, and spatial variability (Sadiq et al. 2025). By embedding sensor-driven intelligence into conservation agriculture (CA), these tools enable adaptive, data-centric farm management.

3.1 Vegetative growth and canopy architecture

A rootstock is mainly influential by controlling vegetative vigor, which defines the size of trees, the development of shoots, and canopy structures (Ling et al. 2025). Dwarfing rootstocks inhibit the profligate development of vegetative growth by inhibiting the movement of water and nutrients, as well as the flux of hormones, especially auxins and cytokinins (Khan and N 2018). This creates a reduction in the size of canopies and will have shorter internodes as well as even better distribution in the branches. Vigorous rootstocks, on the contrary, encourage more massive shoot growth and bigger canopies, which can be beneficial in both low-density and stress-prone soil conditions but can cause shading and less fruitful performance when not carefully handled (Pal et al. 2017).

Canopy architecture only has a significant effect on light interception and distribution, which affect photosynthesis, flower bud differentiation, and the quality of fruit. Rootstock promoting moderate vigor supplies a good balance between vegetative growth and light penetration, hence overall orchard productivity (Montesinos et al. 2021).

3.2 Precocity and early bearing

Rootstocks influence the initiation of reproductive development or precocity, as it is often known. Dwarf and semi-dwarf rootstocks have been largely linked with early flowering and fruiting as opposed to vigorous seedling rootstocks (Zhou et al. 2022). Such early flowering is explained by the slowed vegetation growth, increased carbohydrate supply to the organs of reproduction, and positive hormonal signals. The elevation of cytokinin levels, which are carried by the rootstock to the scion, is thought to facilitate floral budding and fruit set (Aloni et al. 2010). The ability to bear precociously is a preferred practice in commercial orchards as it gives a quicker payoff in terms of economic value. Excessive precocity damages the tree structure and long-term productivity if early fruit loads are not handled properly by using supervised thinning and pruning techniques (Hayat et al. 2022).

3.3 Yield efficiency and alternate bearing

Rootstocks affect total yield as well as yield efficiency, which is often reported in terms of yield per unit of trunk cross-sectional area or canopy volume (Scalisi et al. 2024). Dwarfing rootstocks tend to have improved yield efficiency, as they are more effective in light use, less vegetative competition, and better assimilate partitioning to fruit (Chu et al. 2025). Rootstocks that facilitate moderate growth and stable carbohydrate reserves tend to suppress alternate bearing severity by facilitating steady flower bud development and fruit establishment across seasons (Vittal et al. 2023). Conversely, highly vigorous rootstocks can cause an increase in the alternate bearing by promoting vegetative growth at the expense of reproductive growth (Milyaev et al. 2021).

3.4 Longevity of the orchard

Rootstocks do not just influence the initial productive endeavors but also the sustainability and longevity of orchards as well. Good anchorage, disease resistance, and stress tolerance of rootstocks help to increase longevity of tree health and stable yields in the long term (Ali 2025). Dwarfing rootstocks provide some benefits, such as early and efficient production; however, they might need intensive management and support mechanisms to guarantee endurance in the long term. Vigorous rootstocks, which take time to bear, can normally increase orchard life in less-than-ideal environments. Rootstocks are, in general, important in influencing the patterns of tree growth, the behavior of bearing, and orchard longevity (Manzoor, Safyan, and Manzoor 2020). Proper rootstock choice is therefore one of the key factors in the attainment of a balance between early productivity, stability under low yield, and the long-term performance of the orchard (Vahdati et al. 2021).

4.1 Fruit size, weight, and soluble solids

Rootstock vigor and its uptake efficiency have a significant impact on the fruit size and weight. Medium to large uniform fruits are known to be produced by dwarfing and semi-dwarfing rootstocks because restricted vegetative growth causes increased assimilates going to fruits (Biasuz and Kalcsits 2023). Under certain conditions, vigorous rootstocks can yield larger fruit, yet with a greater range because of intense competition between vegetative growth and reproductive sinks (Falchi et al. 2020). Rootstocks also influence TSS, an important index of sweetness and flavor, in the same manner (Lordan et al. 2020). There are literature trends in several crops (Table 2) that demonstrate the overall application of dwarfing and semi-dwarfing rootstocks to increase the TSS levels in the apple, citrus, and mango crops, and that vigorous rootstocks could lead to slightly reduced sugar accumulation. The rootstock selection also regulates acidity, as it affects consumer preference and taste balance.

4.2 Color development, texture, and shelf life

The color of the fruits is closely related to the canopy structure and light interception, which are under the control of vigor brought about by the rootstocks (Lan 2021). Rootstocks that favor optimal canopy density support increased sun access to plants, resulting in high pigment plants and skin color. Rootstocks also affect the texture and firmness of fruits, which affects the shelf life and transportability (Gong et al. 2022). Semi-dwarfing rootstocks can lead to firmer fruit with a better storage life, and a vigorous rootstock can even give softer fruit should vegetative growth become dominant (Lawrence et al. 2025).

4.3 Nutritional quality

Rootstocks may influence vitamin, phenolic, and antioxidant concentration in fruits by adjusting the uptake of nutrients and resiliency under stress. Mango and apple are examples of clonal rootstock that have been linked with increased vitamin C and phenolic concentrations, which improve the nutritional and functional value of fruits (Oustric et al. 2021). A clear comparative summary of fruit quality characteristics of various rootstocks of apple, citrus, grape, and mango is provided in (Table 2). The table reveals trends that include increased TSS in dwarfing or semi- dwarfing rootstock, extended size of the fruit under vigorous rootstock, and acidic differences in different species (Tietel et al. 2020). This table summary will help readers to easily comprehend crop-specific rootstock impacts and make certain selections to apply them in practical horticultural practices.The combination of the table and radar chart will allow readers to quantify changes and evaluate multi-trait patterns orally, making the review even more understandable and effective.

5.1 Water relations and hydraulic conductivity

Control of plant water relations is among the main ways through which rootstocks affect the performance of scions. Rootstocks vary greatly in root system structure, xylem structure, and hydraulic conductivity, and such differing traits directly influence water intake and conveyance into the scion (Casagrande-Biasuz and Kalcsits 2021). Rootstocks that are more hydraulically conductive tend to promote higher transpiration rates, stronger stomatal conductance, and greater vegetative development. Dwarfing or semi-dwarfing rootstocks, in their turn, tend to create hydraulic constraints limiting the flow of water, which leads to the low activity of scions (H. Xu and Ediger 2021). Hydraulic resistance can further adjust the transport of water at the graft union. Continuity changes in the water column could be affected by differences in vessel diameter, vessel density, and xylem connectivity between scion and rootstock (Rossdeutsch et al. 2021). In water-limited environments, scion drought resistance is improved similarly by rootstocks that efficiently use water and have a conservative water-use behavior, which preserves the water potential to the leaf and minimizes unnecessary transpiration. These abiotic stress-related changes are essential in supporting fruit development and quality mediated by this rootstock (Villalobos-Soublett et al. 2022).

5.2 Mineral nutrition uptake and translocation

Rootstocks have high levels of control in the acquisition and translocation of mineral nutrients to the scion. Root morphology variability, root surface area, and membrane transporters are known to affect the uptake of important macro and micronutrients like nitrogen, potassium, calcium, magnesium, and iron (Lynch et al. 2021). Rootstocks that are suited to the specific soil conditions (e.g., calcareous soils or saline soils) may enhance the nutrient levels and avert physiological diseases in the scion. When absorbed, the nutrients should be actively carried to the tissues above the ground (Biniam, Kebede, and Derbew 2021). Rootstocks also affect xylem loading, phloem load, and nutrient partitioning between vegetative and reproductive organs. As an example, the better calcium translocation into developing fruits is related to lower cases of bitter pit and fruit firmness (Larocca, Baldi, and Toselli 2025). In the same way, the availability of nitrogen and potassium regulates fruit size, sugar accumulation, and acidity. In this way, the selection of rootstock receives the direct implication on fruit composition and postharvest quality (Wang and Gao 2025).

5.3 Hormonal signaling between rootstock and scion

Scion-rootstock interactions occur via hormonal signaling, a key biochemical process. Various phytohormones are synthesized and exported by the roots, containing cytokinins, gibberellins, abscisic acid (ABA), and auxins, transported acropetally to the scion via the xylem (Habibi et al. 2022). These hormones coordinate the growth of the shoot, the expansion of leaves, flowering, fruit set, and stress.

The cytokinins synthesized in the rootstock stimulate the division of cells, retard the senescence of leaves, and increase sink strength in growing fruits. Dwarfing rootstocks are frequently linked to lower cytokinin flux, resulting in compact canopy construction and reproductive precocity (Verma et al. 2024). Gibberellins affect the internode growth and growth of fruits, and auxins affect the vascular differentiation and apical dominance at the graft union (Jahed and Hirst 2023). ABA is also a major stress signal molecule, especially during drought. ABA produced by the rootstock can control stomatal closure in the scion, leading to less water loss and increased tolerance to stress (Jiao et al. 2023). These hormones and their interaction with each other are vital in determining scion development patterns and fruit development patterns.

5.4 Gene expression and long-distance signaling

In addition to classical physiological mechanisms, recent reports have shown the role of long-range molecular signaling in the interactions between scions and rootstocks. Small fragments of RNA (mobile RNAs), proteins, and peptides have the ability to cross the graft union and affect the expression of genes in distant tissues (Jeynes-Cupper and Catoni 2023). These signals potentially control developmental processes, stress response, and metabolic pathways in the scion. Rootstocks have the capability of causing alterations in the expression of scion gene concerning the production of hormones, transportation of nutrients, and stress-related responses (Kapazoglou et al. 2021). This is an emerging field, but it is becoming clear that transcriptional reprogramming induced by rootstock can add to long-term phenotypic stability and the capacity to adapt new environments in grafted plants (Harris et al. 2023). The integrated physiological and biochemical map of scion-rootstock interactions is depicted in (Figure 1). The rootstock processes the interaction of the soil environment, taking in water and nutrients, synthesizing, and sending hormonal signals to the scion, producing systemic signals that control fruit development (Gautier et al. 2021). The processes come all together at the scion level, where growth vigor, yield, and fruit quality characteristics like size, firmness, and stress resistance are determined (Bu et al. 2025).

6.1 Drought and salinity tolerance

One of the key limitations to horticulture production is drought and salinity. Deep-rooted or extensive rootstock enhances the process of water acquisition and sustains hydraulic conductivity when water is insufficient (Kumar 2024). Rootstocks that are salt-tolerant inhibit sodium intake or isolate the ions in vacuoles, shielding the scion against osmotic and ionic pressure. These adaptations assure photosynthetic characterization, flowering, and fruit set (Shao et al. 2021). The (Table 3) provides a summary of biotic and abiotic-tolerant rootstocks in the major crops, and they are examples of such rootstocks. Drastic temperature changes may have devastating effects on the plant metabolism and growth. Cold-tolerant rootstocks increase frost resistance through stabilizing cell membranes and facilitating the accumulation of osmoprotectants (Lee et al. 2023). High heat levels enhance rootstocks that tolerate heat as they maintain transpiration and enzymatic functions in the presence of higher temperatures. The effects of these rootstocks have the benefit of sustaining scion growth and fruit development under unfavorable thermal environments, as schematically depicted in the stress buffering (Hashem et al. 2023). Rootstocks are used as an initial line of resistance to soil-borne pathogens and nematodes. The resistant rootstocks may restrict the invasion of the pathogen or evoke the systemic acquired resistance of the scion, eliminating the disease and avoiding vascular blockage (Chen et al. 2024). Rootstocks that are resistant to nematodes preserve nutrient and water movement, as root galling is inhibited, which preserves the scion vigor (Thies and Panthee 2023).

6.2 Indirect effects on fruit quality under stress

Stress-tolerant rootstocks, in addition to survival and growth, result in the reliability of fruit quality during stress (Feng et al. 2023). Their stabilization of water and nutrient supply also maintains sugar accumulation, acidity, and secondary metabolite profiles (Abdulaziz et al. 2017). This buffering capacity reduces fruit size, fruit firmness, and fruit flavor variability, which guarantees predictable marketable quality (Musacchi and Serra 2018). In the (Figure 2) illustrates the general process of stress mitigation by rootstock buffering, where all manners of abiotic and biotic stresses are mitigated to make scion performance stable. Environmental stressors, including drought, salinity, cold stress, heat stress, disease and pest pressure, and nematodes, impose physiological and biotic constraints on grafted plants. Tolerant rootstocks mitigate these stresses through enhanced water and nutrient uptake, selective ion exclusion (e.g., Na⁺ and Cl⁻), and activation of stress tolerance and disease resistance signaling pathways. These buffering mechanisms improve resource acquisition and reduce stress-induced damage, thereby supporting sustained vegetative growth, stable yield, and scion.

7.1 Graft incompatibility: anatomical and physiological aspects

Graft incompatibility can be described as being either anatomical or physiological. Anatomical incompatibility occurs when there is a failure of alignment of the vascular tissues of the scion and rootstock, resulting in a poor union, bark incompatibility, and a structurally weak graft (Loupit and Cookson 2020). Physiological incompatibility, on the other hand, is not as easy to observe. Even if a successful graft union has been achieved, physiological incompatibility may result in a reduction in the performance of the grafted plant (Moghadam et al. 2022).

7.2 Symptoms and etiology

The symptoms appear gradually. Initial symptoms may be swelling, cracking, or discoloring of tissue at the graft union, slow growth, chlorosis of leaves, and irregular development of the tree canopy (McCann 2020). Later, symptoms may appear as dieback of branches, reduction in fruiting, and sudden failure of structural integrity during stress (Tipu et al. 2021). Etiology involves genetic incompatibility, environmental stress, virus infection, and poor grafting techniques.

7.3 Long-term yield decline

Even well-established grafts may experience long-term decline if there is incompatibility. Poor vascular connections compromise water and nutrient transport, resulting in reduced vigor and fruiting of the scion (Frey et al. 2021). Eventually, this may result in a reduction in yield, fruit size, and increased susceptibility to environmental stresses and diseases. Early recognition of compatibility issues is important for effective management (Manik et al. 2019).

7.4 Importance of compatibility screening

Compatibility screening is a vital component of rootstock and scion combination selection. Assays, trials, and anatomical studies can be employed to assess compatibility in a controlled environment, as opposed to a commercial setting (Thompson et al. 2017). Such a process reduces potential financial loss, facilitates uniform establishment, and optimizes long-term productivity (Aydın et al. 2025). The (Figure 3) demonstrates a clear visual differentiation of a graft union. The visual on the left shows a compatible union, as demonstrated by continuous vascular tissues, aligned cambium, and free water/nutrient transport. Conversely, the visual on the right shows an incompatible union, as demonstrated by disrupted vascular tissues, non-aligned cambium, and potential cracks in the interface. Such a visual representation demonstrates a direct correlation between anatomical alignment and physiological performance, thus emphasizing the significance of rootstock selection (Çoban and Öztürk 2020).

2.1 Soil salinity and sodicity parameters

Salt-affected soils are typically characterized using several key parameters. Electrical conductivity of the saturation extract (ECe) serves as the primary measure of soil salinity, with values greater than 4 dS/m indicating saline conditions. Sodicity is commonly assessed through exchangeable sodium percentage (ESP) or sodium adsorption ratio (SAR), with ESP values exceeding 15% indicative of sodic conditions. According to the US Salinity Laboratory classification system, soils are categorized as: (1) saline soils (ECe > 4 dS/m, ESP < 15%, pH < 8.5), (2) sodic soils (ECe < 4 dS/m, ESP > 15%, pH > 8.5), and (3) saline-sodic soils (ECe > 4 dS/m, ESP > 15%, pH < 8.5) (Foronda 2022).

The high salt content, pH value, and sodium concentration in salt-affected soils lead to multiple adverse effects. Excessive salinity results in osmotic stress, limiting water availability to plants despite adequate soil moisture. High sodium content causes clay dispersion and soil structure deterioration, significantly impacting permeability coefficient, water infiltration capacity, and soil porosity. This impedes soil water conductivity and air permeability while causing decomposition of soil structure, loss of organic matter, and nutrient deficiency, ultimately leading to reduced soil fertility (Tian et al. 2023).

3.1 Gypsum applications

Gypsum (CaSO₄·2H₂O) remains the most recognized and widely applied chemical amendment for sodic and saline-sodic soil reclamation. The mechanism of gypsum application involves substituting Na⁺ from clay particles with Ca²⁺, thus promoting better soil structure while decreasing sodicity (Yang et al. 2021; Elmeknassi et al. 2024). The process delivers numerous advantages to soil physical properties and enhances the ratio of Ca²⁺ to Na⁺, providing sulphur needed for amino acid production and protein synthesis.

Recent field experiments have demonstrated the effectiveness of gypsum in reducing soil pH, ECe, and SAR while improving soil quality and boosting agricultural production. In saline-sodic soils from Egypt, application of phosphogypsum and standard gypsum based on gypsum requirement equations significantly reduced ESP from initial values of 29.8 to acceptable levels (Kotb et al. 2000). The efficiency of gypsum reclamation varies with soil texture, with sandy clay loam soils responding more favorably than clay loam soils (Murtaza et al. 2017).

However, calcium input must be carefully controlled to avoid exceeding optimal amounts. Excessive gypsum application may lead to increased soil salinity and counterproductive results (Mao et al. 2016). Recent research has revealed that the traditional view of Na⁺ as harmful and Ca²⁺ as beneficial does not always apply in multi-cationic soil solutions. Initially, adding Ca²⁺ promotes Na⁺ leaching and reduces salinity, but excess Ca²⁺ becomes counterproductive. As Na⁺ leaches, the soil cation composition shifts from Ca²⁺ - Na⁺ - Mg²⁺ to Ca²⁺ - K⁺ - Mg²⁺, and Ca²⁺ function changes, potentially causing opposite effects.

3.2 Elemental sulphur and other chemical amendments

Elemental sulphur represents another effective chemical amendment for saline-sodic soil reclamation. When applied to soil, elemental sulphur undergoes microbial oxidation to produce sulphuric acid, which lowers soil pH and enhances the dissolution of native soil calcium carbonate. This released Ca²⁺ then replaces exchangeable Na⁺ on soil exchange sites. Recent studies by (Rezapour et al. 2023) demonstrated that combined treatments of elemental sulphur with organic amendments achieved substantial improvements in soil health indices, with increases of 116% compared to control treatments.

Other chemical amendments investigated include aluminum sulfate, which also contributes to soil acidification and Na⁺ displacement. A study on calcareous sodic soils found that the combination of walnut-shell biochar with a mixture of gypsum and aluminum sulfate provided optimal results in reducing soil pH and SAR while enhancing soil EC and nutrient availability (Rezapour et al. 2021). Flue gas desulphurization gypsum, a by-product of industrial processes, has also shown promise in soil reclamation while addressing waste valorization in a circular economy approach (Chen et al. 2015).

4.1 Biochar applications

Biochar, a carbon-rich material produced through pyrolysis of organic waste, has emerged as a primary organic amendment under investigation for saline-sodic soil reclamation due to its numerous benefits including nutrient enrichment, improved availability, and non-destructive properties (Santos et al. 2021; Hafez, Popov, and Rashad 2021; Malik, Mor, and Tokas 2023). The effectiveness of biochar in reclaiming salt-affected soils depends on its specific chemical and physical characteristics, which vary based on feedstock sources such as crop residues, wood, and manure materials.

According to (Amini et al. 2017), effective reclamation of salt-affected soils with biochar requires careful consideration of soil properties such as texture, nutrient content, and native carbon, as well as biochar characteristics including pH and feedstock source. In saline soils, biochar may increase or decrease EC depending on its nature, while enhancing soil organic carbon stocks and improving plant growth and yield. In saline-sodic soils, biochar can raise SOC, alter pH and SAR based on its properties, and improve water-holding capacity and hydraulic conductivity.

Recent field studies have demonstrated significant improvements with biochar application. In a study on saline-sodic soil from the High Valley of Cochabamba, Bolivia, biochar at 2% application rate effectively reduced ECe below 4 dS/m and contributed to ESP reduction, though cattle manure proved superior in overall soil reclamation (Foronda 2022). The porous structure and extensive surface area of biochar provide favorable habitat and protection for soil microorganisms, while biochar can release dissolved organic matter into the surrounding environment, enhancing cation exchange capacity and hydrophilicity attributes, positively influencing soil organic carbon content and nutrient availability (Song et al. 2023).

4.2 Vermicompost and humic substances

Vermicompost and humic substances represent valuable organic amendments that contribute to both chemical and biological improvement of saline-sodic soils. Vermicompost, produced through earthworm-mediated decomposition of organic materials, is rich in plant nutrients, beneficial microorganisms, and growth-promoting substances. Recent research has demonstrated remarkable synergistic effects when vermicompost is combined with chemical amendments for soil reclamation.

(Rezapour et al. 2023) investigated the synergistic impact of gypsum, elemental sulphur, vermicompost, biochar, and microbial inoculation on calcareous saline-sodic soils. The combined inoculated treatments of gypsum plus vermicompost and elemental sulphur plus vermicompost achieved substantial improvements in nonlinear soil health indices, with increases of 134% and 116% respectively compared to control. The overall soil health index ranged between 12% to 134% improvement across different treatments. Notably, microbial inoculation further enhanced the impact of treatments on soil health, and the derived soil health properties explained 29% to 87% of the variance in wheat growth.

Humic substances have been shown to stimulate root growth through indole acetic acid production, resulting in enhanced root surface area and enabling plants to access nutrients more effectively, thereby boosting yield. In quinoa cultivation experiments on saline-sodic soils, the combination of biochar, humic substances, and gypsum resulted in significant increases in root biomass of 206% and 176% in two different genotypes, while seed yield doubled in several treatments (Alcívar et al. 2018).

4.3 Cattle manure and other organic materials

Cattle manure has demonstrated superior efficacy in reclaiming saline-sodic soils due to its contributions of organic matter, Ca²⁺, and Mg²⁺, which improve soil aggregation and leaching efficiency. In comparative studies, cattle manure at 2% application rate was most effective in reducing soil ESP from 66.6% to 27.6%, surpassing biochar and peat treatments (Foronda 2022). All three amendments were efficient in lowering ECe below 4 dS/m, indicating their potential for reclaiming saline-sodic soils when combined with appropriate leaching practices.

The superiority of cattle manure can be explained by improvements in soil aggregation and leaching efficiency through its organic matter and divalent cation contributions. However, the choice of organic amendment should consider local availability, cost-effectiveness, and specific soil conditions. Rice straw, green waste compost, and biosolids have also shown promise in various reclamation scenarios, particularly when combined with chemical amendments and appropriate leaching regimes.

6.1 Microbial inoculation for soil health

Microbial inoculation represents a promising biological approach to enhance saline-sodic soil reclamation. Salt-tolerant microorganisms can contribute to soil improvement through multiple mechanisms including bioaccumulation of salt ions, production of exopolysaccharides that improve soil structure, secretion of growth-promoting substances, and enhancement of nutrient cycling processes.

Under salt stress, halophilic microbes can absorb salt ions through bioaccumulation processes (Zhang et al. 2023). According to Xing et al. (Xing et al. 2024), the application of inoculated microbes can decrease Na⁺ ions in soil by stimulating the abundance of microorganisms harboring Na⁺/H⁺ transport proteins, Na⁺/Ca²⁺ transport proteins, and Na⁺/K⁺ transport proteins. This microbially-mediated ion exchange contributes significantly to salinity reduction.

Research on combined chemical and organic amendments with microbial inoculation has revealed substantial enhancements in treatment efficacy. Rezapour et al. (Rezapour et al. 2023) found that microbial inoculation further enhanced the impact of chemical and organic treatments on soil health, with soil health properties explaining 29% to 87% of variance in wheat growth. The study found negative correlations between sodium-containing soil and microbial biomass carbon, indicating that salt-affected soils reduce microbial activity and biomass, which can be ameliorated through appropriate amendment strategies.

6.2 Plant-microbe interactions in saline conditions

Plant-microbe relationships, particularly with synergistic bacteria and arbuscular mycorrhizal fungi (AMF), have been recommended as potential solutions to mitigate salinity and sodicity stress in both halophytes and glycophytes. Nitrogen-fixing bacteria collections can increase salt and sodicity tolerance by creating specific enzymes and hormones, fixing atmospheric N₂, and converting water-insoluble phosphates to bioavailable forms.

Recent research on microbial network-driven remediation has revealed that salt-tolerant plants enrich beneficial bacteria in soil by releasing organic acids and enzymes that promote plant growth under saline stress (Zahra et al. 2024). Jerusalem artichoke, for instance, enhances microbial diversity in saline-alkali soils through root exudates (Shao et al. 2019). Different salt-tolerant plant species release varying organic compounds, which attract beneficial rhizosphere bacteria under saline stress, thereby aiding host plants in mitigating salt-induced damage (Xiong et al. 2020).

Network analysis has provided insights into the role of keystone taxa in saline soil remediation. These taxa, serving as central components of the core microbiome, play critical roles in facilitating plant-soil interactions and enhancing soil improvement (Trivedi et al. 2020; Liu et al. 2023). Partial least squares path modeling has shown that soil quality improvements are primarily driven by shifts in bacterial composition, offering a novel mechanistic framework for understanding microbial contributions to soil restoration.

7.1 Mechanisms and principles of halophyte-based phytoremediation

Phytoremediation using salt-tolerant plants (halophytes) has emerged as a sustainable and effective approach for reclaiming saline-sodic soils. Halophytes, representing approximately 1% of world flora, can survive, grow, and reproduce at salt concentrations exceeding 20 dS/m. These plants possess unique anatomical and morphological features including succulence, osmotic adjustment, ion compartmentalization, selective uptake and transport mechanisms, enhanced antioxidant systems, and salt inclusion or discharge capabilities (Flowers and Colmer 2008).

Halophytes are classified into three main groups based on salt tolerance mechanisms: (1) Excluders, which possess root ultra-filtration mechanisms preventing salt uptake; (2) Accumulators, which sequester salts in vacuoles within above-ground biomass; and (3) Excretors (recretohalophytes), which possess specialized salt glands allowing accumulated salt to be excreted onto leaf surfaces and dispersed via wind through haloconduction processes. The potential of halophytic plants to accumulate enormous salt quantities depends primarily on the capacity of their above-ground biomass, with hyperaccumulating plants showing particular promise.

During phytoremediation, CO₂ released by plant roots during respiration produces H₂CO₃, which increases solubility of CaCO₃ in deeper soil layers. This process releases Ca²⁺, which replaces Na⁺ and other salts from soil exchange sites, thereby reducing sodicity (Robbins 1986). Comparative studies have shown that phytoremediation can reduce sodicity by 52% compared to 62% reduction using gypsum, demonstrating its effectiveness as an alternative or complementary approach to chemical amendments (Qadir and Oster 2007).

7.2 Effective halophyte species for soil reclamation

Numerous halophyte species have been evaluated for their phytoremediation potential. In studies from the bed of Urmia Lake, Iran, Salicornia europaea and Halocnemum strobilaceum proved most effective in salinity-remediation, achieving significant reductions in electrical conductivity and exchangeable sodium percentage (Ghorbanpour et al. 2022). These species demonstrated high concentrations of Fe²⁺ (511.85 mg/kg), Zn²⁺ (99.97 mg/kg), and Na⁺ (25.65 mg/kg) in shoots, with maximum dry matter (38%), protein (16%), and oil percentage (3.5%) found in Salicornia.

Research on Haloxylon recurvum, Suaeda nudiflora, and Salsola baryosma demonstrated sodium removal capacities of 17, 15.6, and 9 g per plant respectively during three-month growth periods. Pennisetum giganteum has emerged as a promising salt-accumulating and salt-tolerant non-conventional crop for sustainable saline agriculture and simultaneous phytoremediation (Hayat et al. 2020). This species effectively reduces soil salinity by 30% within 30 days when grown in saline soil, and when co-cultivated with barley, wheat, and tomato, it reduces negative salt effects on sensitive crops.

Salt-tolerant legumes such as Glycine soja and Sesbania cannabina have successfully rehabilitated saline soils by reducing soil electrical conductivity and accumulating carbon and nitrogen, while enriching microbial communities at different soil depths (Zheng et al. 2023). Atriplex species, particularly Atriplex halimus and Atriplex hortensis, have shown considerable promise for reclamation while providing economic benefits as forage crops. Recent field studies confirmed that Atriplex hortensis maintains relatively stable water potential and high relative water content under saline stress, indicating physiological resilience suitable for salt-affected agroecosystems.

7.3 Microbial network-driven phytoremediation

Recent advances in network analysis have revealed the critical role of microbial communities in halophyte-mediated soil reclamation. Salt-tolerant plants enhance the complexity of both bacterial and fungal networks in rhizosphere soils. Network analysis showed that planting salt-tolerant plants increases the number of nodes, average path length, and modularity of fungal communities, indicating enhanced network complexity (Liu et al. 2023). The presence of generalists (connectors and module hubs) in saline-alkali soils under phytoremediation supports improved stability and efficiency of fungal communities.

Keystone taxa, identified through within-module connectivity and among-module connectivity analysis, play significant impacts on soil enzyme activity and nutrient cycling (Wen et al. 2024). Phytoremediation has been shown to strengthen cooperative interactions among fungi while diminishing competitive dynamics, as evidenced by higher ratios of positive correlations within fungal networks following salt-tolerant plant establishment. Salt-tolerant plants increase rhizosphere ecosystem multifunctionality by reducing soil salinity, with planting halophytes enriching microbial diversity and network complexity (Hu et al. 2024).

8.1 Nanotechnology applications

Nanotechnology represents an emerging frontier in saline-sodic soil reclamation, offering innovative solutions through the unique properties of nanomaterials. Nanoparticles have demonstrated promising results in alleviating salt stress, improving soil properties, and enhancing plant performance in salt-affected soils. The application of zinc oxide nanoparticles combined with soil amendments has been shown to improve wheat yield, physiological attributes, and soil properties in saline-sodic soils (El-Sharkawy et al. 2022).

Different types of nanoparticles exhibit varied mechanisms of action in salt stress mitigation. Magnesium oxide nanoparticles alleviate stress by modulating photosynthetic function, nutrient uptake, and antioxidant potential. Silicon nanoparticle-based biochar has demonstrated effectiveness in improving wheat growth, enhancing antioxidant systems, and optimizing nutrient concentrations under salinity stress (Gill et al. 2024). Biosynthesized zinc oxide nanoparticles have been shown to modulate phytoremediation potential and influence rhizocompartment-associated microbial community structure (Li et al. 2024).

Recent research by Ahmed et al. (Ahmed et al. 2023) demonstrated differential responses of nano zinc sulfate compared to conventional zinc sources in mitigating salinity stress in rice grown on saline-sodic soil. The study revealed that nano-formulations enhanced zinc bioavailability and uptake efficiency, leading to improved plant growth and stress tolerance. Nanomaterials also show promise in enhancing the efficiency of phytoremediation through improved nutrient delivery and stress mitigation mechanisms.

However, the application of nanotechnology in soil management faces several challenges. Concerns about potential ecotoxicity, environmental persistence, and long-term impacts on soil biota require careful evaluation. The development of smart nanomaterials with surface functionality or coatings that resist suppression by biomacromolecules and tolerate climate and environmental triggers remains a formidable challenge. Nevertheless, nanotechnology holds significant potential for improving soil quality through innovative approaches including nano-fertilizers, nano-enabled remediation strategies, and enhanced delivery systems.

8.2 Advanced genetic and biotechnological approaches

Advanced plant breeding and biotechnological approaches offer promising avenues for developing salt-tolerant crop varieties. Recent identification of the Alkali Tolerance 1 locus in sorghum, which regulates aquaporin phosphorylation for hydrogen peroxide transport to alleviate oxidative stress, represents a significant breakthrough. The loss-of-function of this gene in sorghum, millet, rice, and maize improves field performance in sodic land (Wang et al. 2024).

Novel biotechnologies including CRISPR/Cas gene editing, marker-assisted breeding, and double haploid production hold great potential to accelerate breeding processes and cultivate crops with enhanced salt tolerance. However, certain limitations remain, including advanced technology dependence, lengthy processes, unexpected genetic gains, and complex genotype-environment correlations. Despite considerable progress in understanding salinity tolerance mechanisms, obstacles remain in transferring molecular knowledge into practical plant breeding activities.

9.1 Physical and chemical transformation processes

The reclamation of saline-sodic soils involves complex physical and chemical transformation processes. Chemical amendments primarily work through cation exchange mechanisms, where Ca²⁺ from gypsum or other calcium sources replaces Na⁺ on soil exchange sites. This displacement is significantly influenced by soil cation exchange capacity and water movement within the soil profile. The process of reclamation is further influenced by soil texture, with ion replacement occurring more readily in coarser-textured soils (Ahmad et al. 2016).

Organic amendments enhance physical properties through multiple mechanisms. Biochar increases soil porosity and water retention capacity while providing surfaces for microbial colonization. The porous structure creates favorable microhabitats that protect microorganisms from environmental stresses. Furthermore, biochar releases dissolved organic matter that enhances cation exchange capacity and influences soil pH, thereby affecting nutrient availability and microbial activity (Li et al. 2022).

The presence of CaSO₄ contributes to decreasing water-soluble Na⁺ content through both chemical replacement and enhanced leaching. Recent studies showed that proper amendment application resulted in reduced soil ESP and pH by 14.64% and 7.42% respectively. The dissolution of native soil carbonates, enhanced by increased CO₂ partial pressure from organic amendment decomposition, further contributes to Ca²⁺ availability for Na⁺ exchange.

9.2 Microbial-mediated carbon and nitrogen cycles

Microbial communities play crucial roles in carbon and nitrogen cycling within reclaimed soils. The carbon cycle represents a fundamental biogeochemical process regulating soil material dynamics and gas exchange between soil and atmosphere (Meloni et al. 2003). Microbes can decrease salt ion concentrations through bioaccumulation and can utilize CO₃²⁻ or HCO₃⁻ as carbon sources, contributing to salinity reduction (Zhao and Tian 2021).

Phytoremediation using salt-tolerant plants significantly alters soil microbial composition. The relative abundance of Acidobacteria, which decompose plant residues and enhance soil carbon cycling, increases following phytoremediation, suggesting effective pH reduction and improved saline-alkali conditions. Proteobacteria, including various nitrogen-fixing bacteria, remain dominant and play vital roles in nitrogen cycling processes (Kim et al. 2021; Jiang et al. 2024).

Network analysis reveals that soil microbes tend to cooperate more than compete under nutrient-limiting conditions, often establishing symbiotic relationships to obtain essential nutrients and mitigate salt stress. The strengthening of cooperative interactions among microbial communities following amendment application contributes to enhanced ecosystem stability and improved nutrient cycling efficiency.

9.3 Soil enzyme activities and nutrient dynamics

Soil enzyme activities serve as sensitive indicators of soil health and recovery following reclamation efforts. The combination of chemical and organic amendments significantly enhances activities of key enzymes including urease and phosphatase. These enzymes exert positive influences on soil organic matter content by facilitating transformation and cycling of nitrogen and phosphorus. Urease increases soil nitrogen content by promoting nitrogen transformation, while phosphatase enhances phosphorus availability, jointly contributing to organic matter formation and accumulation.

Amendment applications significantly improve nutrient availability in reclaimed soils. Organic and combined approaches significantly increase available phosphorus and potassium, as well as bioavailable iron, manganese, and zinc concentrations. These improvements in nutritional quality directly correlate with enhanced crop growth and productivity. Studies have shown that amendments can increase soil organic matter content substantially, with combined treatments of gypsum and organic materials demonstrating synergistic effects on both enzyme activities and nutrient availability.

10.1 Crop yield and quality improvements

Effective reclamation of saline-sodic soils translates directly into improved crop performance and productivity. Recent field studies have demonstrated substantial yield improvements following integrated amendment strategies. In wheat cultivation on reclaimed saline-sodic soils, derived soil health indices explained 29% to 87% of variance in wheat growth, demonstrating strong linkages between soil improvement and crop performance (Rezapour et al. 2023). The combined application of gypsum and organic amendments significantly increased wheat biomass accumulation and grain yields.

Quinoa cultivation studies have revealed significant improvements in both yield and quality parameters following amendment applications. Seed yield doubled in treatments involving gypsum and humic substances, while all amended soils showed significant increases in stomatal conductance and SPAD index compared to controls (Alcívar et al. 2018). Seed protein content was positively affected by biochar and humic substance applications, indicating improvements not only in quantity but also in nutritional quality.

The increase in crop biomass primarily depends on photosynthetic function enhancement. Applications of gypsum and organic amendments significantly boost net photosynthetic rates, with improvements of 50.7%, 25.3%, and 143.6% observed at different growth stages in maize cultivation. These photosynthetic enhancements directly correlate with dry matter accumulation and final yields, attributed to improved soil properties including lower pH, higher nutrient content, and enhanced organic matter (Wang et al. 2024).

10.2 Root development and plant physiology

Root system development represents a critical factor in plant adaptation to saline-sodic conditions and response to soil reclamation efforts. Combined amendments significantly enhance root biomass, with increases of 206% and 176% reported in quinoa genotypes treated with biochar, humic substances, and gypsum (Alcívar et al. 2018). Enhanced root development provides plants with greater access to water and nutrients, improving overall stress tolerance and productivity.

Plant physiological responses to reclamation include maintenance of water relations, enhanced photosynthetic capacity, and improved ion homeostasis. Halophytes maintain relatively stable water potential and high relative water content under saline stress, indicating efficient osmotic adjustment and sustained cellular hydration. These physiological adaptations, combined with improved soil conditions from amendments, enable sustained growth and productivity under saline conditions.

10.3 Economic viability and sustainability

The economic viability of reclamation strategies represents a critical consideration for adoption by farmers. While chemical amendments like gypsum have historically been cost-effective, increases in industrial demand and reductions in government subsidies have made amendment costs prohibitive in several developing countries. This economic reality has driven interest toward biological approaches including phytoremediation and microbial interventions, which offer lower-cost alternatives with additional environmental benefits.

Phytoremediation using halophytes offers multiple economic advantages. Beyond soil improvement, many halophyte species provide valuable products including forage, biofuel feedstock, essential oils, and food crops. Salicornia bigelovii, for instance, represents a potential oilseed crop for coastal and saline lands. The integration of salt-tolerant forage species into livestock production systems can enhance ecosystem resilience while generating income during the reclamation period.

Sustainable reclamation approaches emphasize waste valorization in circular economy frameworks. The use of biosolids, green waste compost, rice straw, and industrial by-products like flue gas desulphurization gypsum transforms waste materials into valuable soil amendments. This approach reduces disposal costs while providing affordable amendment options for farmers. However, comprehensive life-cycle assessments considering energy inputs, transportation costs, and long-term maintenance requirements remain necessary for informed decision-making.

11.1 Technical and practical constraints

Despite significant advances, several technical and practical constraints limit widespread implementation of soil reclamation strategies. The efficiency of amendments varies considerably with soil texture, salinity levels, and sodicity conditions, requiring site-specific optimization. The relationship between amendment rates and soil response is not always linear, with excessive applications potentially causing counterproductive results. For instance, excessive gypsum can increase soil salinity, while improper organic matter addition may temporarily decrease oxygen availability during decomposition.

Water availability represents a critical limitation for many reclamation approaches. Both chemical leaching and phytoremediation require adequate water supplies, which may be limited in arid regions where saline soils predominate. The quality of irrigation water also significantly affects reclamation outcomes, with moderately saline water potentially suitable for leaching when combined with appropriate amendments, but requiring careful management to prevent secondary salinization.

Time requirements for effective reclamation vary widely among approaches. Chemical amendments combined with leaching can achieve rapid initial improvements, while biological approaches including phytoremediation and microbial interventions typically require multiple growing seasons for substantial effects. This temporal aspect affects economic feasibility and farmer adoption, particularly where immediate productivity improvements are necessary for farm viability.

11.2 Knowledge gaps and research needs

Several critical knowledge gaps require addressing for advancing saline-sodic soil reclamation. The long-term sustainability of various reclamation approaches remains incompletely understood, particularly regarding maintenance requirements and potential for re-salinization. While short-term studies demonstrate effectiveness, multi-decadal assessments of soil quality, productivity, and ecosystem functioning are scarce.

The interactions between different amendment types, rates, and timing require systematic investigation across diverse soil types and climatic conditions. Current understanding of optimal amendment combinations derives primarily from controlled experiments and limited field trials. Scaling these findings to farm-level implementation under variable environmental conditions necessitates additional research. Furthermore, the role of climate variability and extreme weather events on reclamation outcomes requires attention given accelerating climate change.

Microbial community dynamics during reclamation remain incompletely characterized. While recent network analysis has revealed the importance of keystone taxa and cooperative interactions, predictive frameworks for managing microbial communities toward desired outcomes are lacking. The stability and resilience of engineered microbial communities under field conditions, particularly during stress periods, requires investigation. Additionally, the potential for developing designer microbial consortia optimized for specific soil conditions represents an emerging research frontier.

11.3 Environmental and ecological considerations

Environmental impacts of reclamation practices require careful consideration. While improving soil quality, amendment applications may have unintended consequences. Excess nutrient leaching from organic amendments could contribute to groundwater contamination or eutrophication of adjacent water bodies. The carbon footprint associated with amendment production, transportation, and application should be evaluated within comprehensive sustainability frameworks.

Nanotechnology applications, while promising, raise concerns about environmental persistence and ecotoxicity. The fate and transport of engineered nanoparticles in soil ecosystems, their interactions with soil biota, and potential accumulation in food chains require thorough investigation before widespread implementation. Regulatory frameworks for nanomaterial use in agriculture remain under development, reflecting ongoing uncertainty regarding risk assessment and management.

Biodiversity impacts of reclamation efforts deserve attention. While improving conditions for agricultural production, intensive reclamation may affect native halophytic vegetation and associated fauna. Balancing agricultural productivity with ecosystem conservation requires landscape-level planning that maintains habitat corridors and preserves representative areas of natural saline ecosystems. The role of reclaimed lands in regional hydrology and their effects on groundwater recharge and quality warrant consideration in integrated watershed management.

12.1 Integrated management strategies

The future of saline-sodic soil reclamation lies in integrated management strategies that combine traditional practices with innovative technologies. Comprehensive management approaches should integrate physical methods (drainage, tillage), chemical amendments, organic materials, biological interventions, and genetic improvements in crop salt tolerance. These integrated systems must be tailored to local conditions, considering soil properties, climate, water availability, crop preferences, and economic constraints.

Precision agriculture technologies offer opportunities for optimizing amendment applications and monitoring reclamation progress. Remote sensing, soil sensors, and geographic information systems enable site-specific management at field scales, improving efficiency and reducing costs. Digital agriculture platforms integrating real-time data with predictive models could guide adaptive management decisions, adjusting strategies based on response monitoring and changing conditions.

12.2 Climate change adaptation and mitigation

Climate change will likely exacerbate salinization problems through altered precipitation patterns, increased evapotranspiration, and sea-level rise affecting coastal areas. Reclamation strategies must account for these changing conditions, emphasizing approaches that enhance soil resilience and adaptive capacity. Halophyte-based systems may play increasingly important roles, providing both reclamation and climate adaptation benefits while supporting biodiversity conservation.

Carbon sequestration potential of reclamation practices deserves greater emphasis. Biochar applications and establishment of perennial halophyte vegetation can contribute significantly to soil carbon stocks while improving soil quality. Quantifying these carbon benefits within climate mitigation frameworks could provide additional economic incentives for reclamation through carbon credit markets. Life-cycle assessments incorporating greenhouse gas emissions and carbon sequestration across different reclamation approaches would inform climate-smart land management decisions.

12.3 Biotechnology and genetic engineering

Advances in plant biotechnology offer promising avenues for developing superior salt-tolerant crop varieties. CRISPR/Cas9 gene editing enables precise modifications of salt tolerance genes, potentially accelerating development of crops suitable for saline conditions. Understanding complex regulatory networks controlling salt tolerance responses will facilitate multi-gene engineering approaches addressing various aspects of salt stress simultaneously.

Synthetic biology approaches could enable design of microbial consortia optimized for saline soil improvement. Engineering microorganisms with enhanced salt tolerance, exopolysaccharide production, or nutrient cycling capabilities could improve bioremediation efficiency. However, careful risk assessment and regulatory oversight are essential for environmental release of genetically modified organisms.

12.4 Policy and institutional frameworks

Effective policy and institutional frameworks are crucial for widespread implementation of soil reclamation strategies. Government policies should provide incentives for sustainable land management, including subsidies for amendments, technical assistance programs, and research support. Land tenure security encourages long-term investments in soil improvement. Collaborative approaches involving researchers, extension services, farmers, and policymakers facilitate knowledge transfer and adaptive management.

International cooperation is essential given the global scale of salinization problems. Sharing best practices, technologies, and genetic resources across countries accelerates progress. Investment in agricultural research and development focused on salt-affected soils must increase, particularly in developing countries where impacts are most severe. Capacity building programs training farmers and extension workers in reclamation techniques ensure practical implementation of research advances.

2.1 Innovative techniques derived from TILLING

Several mutation detection methods have evolved from the original TILLING platform by exploiting structural differences between homoduplex and heteroduplex DNA. These include Single-Strand Conformation Polymorphism (SSCP), Denaturing Gradient Gel Electrophoresis (DGGE), Conformation-Sensitive Gel Electrophoresis (CSGE), Temperature Gradient Capillary Electrophoresis (TGCE), Denaturing High-Performance Liquid Chromatography (dHPLC), and High-Resolution Melting (HRM) analysis (Till et al. 2007; Szurman-Zubrzycka et al. 2017; Selvakumar, Jat, and Manjunathagowda 2023).

Among these, HRM has gained prominence for its rapid detection of sequence variation based on the differential melting behavior of PCR amplicons. Unlike nuclease-based approaches, HRM eliminates enzymatic cleavage steps and enables scalable, high-throughput screening (Selvakumar, Jat, and Manjunathagowda 2023). It has been successfully applied in crops such as tomato, pepper, potato, and broccoli (Mohan et al. 2016).

The integration of next-generation sequencing (NGS) has fundamentally reshaped TILLING workflows, transitioning the approach from gel-dependent mutation detection to scalable genomic platforms. In NGS-assisted TILLING, pooled PCR amplicons or targeted genomic regions are directly sequenced, enabling digital identification of induced nucleotide variants at single-base resolution (Fanelli et al. 2021; Jiang et al. 2022). Compared with enzymatic mismatch cleavage and fragment analysis methods (Till, Comai, and Henikoff 2007), sequencing-based platforms enhance sensitivity, support multiplexed screening of multiple loci within large mutant populations, and reduce reliance on capillary or gel-based systems.

Reference-guided amplicon sequencing platforms have demonstrated improved mutation discovery efficiency and reduced manual processing in crops such as barley and sunflower (Fanelli et al. 2021; Jiang et al. 2022). Beyond targeted amplicon sequencing, targeted resequencing and exome-capture approaches allow simultaneous interrogation of broader gene sets, particularly in species with available reference genomes. Although initial sequencing infrastructure may require higher investment, per-sample costs decrease substantially at scale, making NGS-assisted TILLING increasingly cost-effective for large breeding programs. Moreover, digital variant datasets facilitate allele frequency estimation, precise validation, and integration with genomic databases, thereby improving data interpretation and traceability. Collectively, these advances position sequencing-assisted TILLING as a central component of contemporary reverse genetics and crop improvement strategies.

TILLING has evolved from a basic chemical mutagenesis approach into a versatile platform adapted to a wide range of crop species and breeding systems. Its modern variants support both functional genomics research and applied crop improvement across diverse agricultural contexts. Table 2 provides a comparative overview of key TILLING approaches, highlighting their applications, advantages, and limitations in contemporary breeding strategies.

1.1 Effect of sowing time on the growth of wheat

Sowing time significantly influences the growth, development, yield and quality of wheat cultivation in India, as evidenced by recent research spanning diverse agro-climatic zones and wheat genotypes. Early to mid-November sowing is widely reported as optimal, promoting favorable growth stages such as enhanced tillering, young spike differentiation and dry matter accumulation, thereby harmonizing individual plant traits and community structure to optimize spike number, kernel count per spike and 1000-kernel weight, ultimately achieving high yields of quality wheat (Pei et al. 2008). Studies focusing on specific genotypes, like “AK 58” in mid Henan, show that later sowing combined with lower seedling density maximizes dry matter in individual stems, yet earlier sowing ensures the largest effective population, highlighting the complex interplay between sowing time of the season and plant density (Jiang et al. 2011 raniconsistently observed), with yield declining approximately by 58 kg ha^-1 for each one-day delay post-optimal sowing, though grain filling rate may increase under later sowing (A. Kumar et al. 2024). Research in the Indo-Gangetic Plains notes that weed infestation, particularly by Phalaris minor, varies with sowing dates; early sowing suppresses weed growth, although it sometimes results in lower yields, while delayed sowing enhances yield despite greater weed biomass, with organic mulching emerging as a sustainable weed management strategy (M. K. Singh et al. 2019). Investigations involving plant growth regulators indicate that normal or timely sowing combined with sprays of substances like salicylic acid at key growth stages significantly improve wheat seed quality, germination rates and seedling vigor compared to late sowing (Kumawat et al. 2023). Site-specific studies in subtropical foothills such as Jammu reveal that sowing dates markedly affect plant height, dry matter accumulation and crop growth rate, with early sowing promoting better growth attributes across varieties (Nikzad et al. 2024). Climate adaptation research in Punjab delineates shifting optimal sowing windows due to rising temperatures, underscoring the critical need for dynamic adjustment of sowing calendars to mitigate heat stress impacts and sustain productivity (Sandhu et al. 2020). Moreover, zero tillage technology adoption in regions like Bihar demonstrates how advancing sowing time without intensive soil preparation boosts yield, resource use efficiency and environmental sustainability, reflecting modern planting practice improvements complementing traditional sowing date optimization (Gupta et al. 2019). Hence, strategic interventions encompassing precise sowing schedules, sustainable weed management, growth regulator application, genotype selection and innovative practices like zero tillage are essential for enhancing wheat productivity and resilience under changing climatic scenarios in India. This synthesis of recent research underscores sowing time as a critical agronomic lever influencing wheat growth dynamics and yield potential, vital for the long-term sustenance of wheat cultivation in India’s diverse agro-ecological landscapes.

1.2 Effect of seed variety selection on the growth of wheat

Seed variety selection is crucial in determining the growth, yield and overall productivity of wheat cultivation in India, influencing factors such as plant height, tiller number, leaf area, disease resistance and adaptability to diverse agro-climatic conditions. Recent research indicates that different wheat varieties exhibit significant variation in growth parameters; for instance, the variety Yuanfeng 998 demonstrated superior plant height and leaf area compared to older varieties, illustrating the advancement achieved through varietal improvement (Ji, Li, and Li 2007). Seed size, an inherent characteristic of varieties, also affects early growth stages, with larger seeds generally promoting taller seedlings and more tillers, which are critical for higher biomass and yield potential (Todorović, Protić, and Protić 2010). Regional variations further complicate seed size distributions, genotypic factors combined with environmental interactions lead to varied seed size proportions across different locations, implying that selecting varieties suited to specific environments is vital for optimizing seed quality and production outcomes (Protić et al. 2010). Growth attributes and yield performance also depend on sowing methods and planting patterns tailored to varieties; for example, sowing with turbo seeders and retaining crop residues enhanced growth and yield of varieties like HD 3086 in Haryana, highlighting the synergy between variety selection and agronomic practices (Malik et al. 2021). Planting density and seed rate adjustments have demonstrated significant impacts on growth and yield; studies reveal that seed rates around 120-150 kg ha^-1 optimize tillers per meter, spike length, grain number per spike and biomass in varieties such as DBW 187, underlining the importance of matching seed rates to varietal and regional conditions for maximizing output (Laghari et al. 2011). Furthermore, seed priming techniques have emerged as promising methods to eenhance germination, seedling vigor and yield attributes in popular Indian wheat varieties such as HD-2967 and PBW 752, with chemical priming agents like potassium nitrate and CaCl₂ significantly improving growth parameters under adverse conditions, indicating integrated management possibilities (R. K. Singh et al. 2016; J. Singh, Aulakh, and Singh 2023). Salinity stress studies on varieties such as Imam and PBW-154 reveal that seed size effects on early growth under such abiotic stresses vary, with larger seed sizes (83%) generally performing better, yet germination responses differ across varieties, emphasizing varietal-specific management for stress-prone regions (El Dessougi and El Sheikh 2020). Multi-environment trials and participatory variety selection approaches further facilitate farmers’ access to diverse high-yielding, resilient varieties like BAW1008 and Shatabdi, which have led to significant varietal diversification and increased wheat productivity in South Asian agro-ecosystems (Pandit et al. 2007). This integrated approach enhances plant establishment, vigor and tolerance to biotic and abiotic stresses, ensuring sustainable wheat production amidst regional variability and changing climatic conditions.

1.3 Effect of planting density on the growth of wheat

The effect of planting density on wheat growth in India has been extensively studied, revealing that optimal planting density plays a critical role in enhancing wheat yield, biomass and quality. Recent research highlights that the ideal planting density often ranges between 300 to 420 plants per square meter, as this balance optimizes spike number and grain weight, thus improving overall yield and protein content. One study conducted under randomized block design revealed that nitrogen application coupled with appropriate planting density increased grain protein and plant height, showing that the interaction of these factors significantly improves both growth and flour quality through enhanced glutenin content in wheat genotypes (Mashiqa et al. 2022). Another investigation focusing on early sowing found that a planting density of 240 × 10⁴ plants per hectare combined with a 20 cm row spacing created the best environment for photosynthetic activity, leaf chlorophyll content and dry matter accumulation, contributing to higher yields (Chen et al. 2015). In agroforestry systems, the spatial arrangement of trees influences wheat growth, where wider spacing under certain tree species like Melia azedarach led to significantly higher dry biomass and grain yield, emphasizing the importance of optimal spacing in intercropping scenarios (Satyawali et al. 2018). Hybrid wheat studies demonstrate that medium planting density (~300 plants m⁻²) maximizes grain yield by balancing population growth parameters such as leaf area index and crop growth rate, indicating that overly high densities may suppress individual plant growth while low densities reduce population vigor (Zhang et al. 2008). Research on the interaction between nitrogen rate and planting density shows that nitrogen efficiency and grain yield reach peak levels at moderate densities and nitrogen input should be adjusted according to density to enhance nitrogen use efficiency and reduce costs (Fang et al. 2015). Physiological traits such as leaf area index, chlorophyll content and chlorophyll fluorescence parameters decrease with excessive planting density, which correlates with decreased yield beyond an optimum density, as shown in cultivars like Wanmai 52 and Yannong 19 (Yanjun et al. 2018). Research on nitrogen uptake reveals that planting density influences nitrogen distribution, with optimum densities enhancing nitrogen uptake efficiency and grain nitrogen concentration, supporting sustainable nutrient management in wheat cultivation. In sum, these recent studies by multiple researchers across different regions and wheat varieties in India consistently demonstrate that an optimal planting density, usually between 300 to 420 plants per m² depending on wheat genotype, environmental conditions, nitrogen management and planting date, is essential for maximizing wheat growth, yield and quality. Adjusting planting density in coordination with nitrogen fertilization and sowing time enhances photosynthesis, biomass accumulation, population quality and grain characteristics, which are key to improving wheat productivity sustainably under diverse Indian agro-climatic conditions (Satyawali et al. 2018). This integrated understanding of planting density effects informs best management practices critical to increasing wheat production and quality in Indian agriculture.

1.4 Effect of soil and land preparation on the growth of wheat

Soil and land preparation play a critical role in determining wheat growth and yield, with recent research highlighting various innovative practices and amendments that enhance wheat cultivation in India. Studies demonstrate that biofertilizers, especially cyanobacteria such as Anabaena cylindrica, significantly improve soil fertility and wheat growth by providing bioactive compounds including nitrogen, phosphorus, potassium and phytohormones, leading to enhanced biochemical and physiological wheat plant responses (Hakkoum et al. 2025). The use of biochar, particularly when combined with mycorrhizal fungi, improves wheat performance in challenging calcareous soils by increasing nutrient uptake, plant height, protein content and root length, indicating biochar’s potential as an effective soil amendment (Khdir and Rahman 2024). Similarly, the application of biochar from organic wastes positively modulates soil physicochemical properties such as pH, electrical conductivity, total carbon, nitrogen, phosphorus and potassium, which collectively promote wheat biomass and microbial soil communities (Aziz et al. 2020). Land preparation techniques like conservation agriculture and zero tillage (ZT) have shown remarkable advantages over conventional methods; zero tillage allows earlier sowing of wheat post-rice harvest, reduces cultivation costs and labor, saves fuel, minimizes environmental pollution and improves water-use efficiency, thus supporting both sustainability and higher income for farmers in regions like Bihar and Haryana (Aziz et al. 2020). Conservation agriculture combined with organic soil amendments notably enhances soil moisture retention, lowers soil bulk density and fosters vegetative growth, ultimately elevating wheat yields (Gupta et al. 2019; Mehala et al. 2016). Comparative studies suggest that deep tillage increases soil infiltration, reduces subsurface bulk density and boosts root proliferation, translating into yield gains, while no-tillage improves soil aggregation and microbial biomass, signaling better soil health (Pandey, Agrawal, and Bohra 2015; Kahlon and Khurana 2017). Moreover, in acidified or sodic soils often seen in some Indian agro-ecosystems, amendments like lime, limestone powder and especially biochar effectively elevate soil pH and nutrient availability, with biochar outperforming lime in boosting potassium content and overall wheat nutrient absorption, which correlates with enhanced grain weight and yield (Huang et al. 2024; Srivastava et al. 2016). More holistic impacts of reduced or no-tillage systems include lower soil erosion risks, better soil structure and maintenance of organic carbon levels without compromising wheat yield, making them suitable for sustainable wheat farming in India. Planting practices include ridge-furrow planting with plastic mulching, combined with optimal planting densities and complementary irrigation, further improve source-sink relationships within the wheat crop, enhancing grain filling and overall yield compared to traditional flat planting and rainfed conditions (Dai et al. 2024). Collectively, these findings underscore the importance of integrating improved soil amendments, appropriate land preparation methods and sustainable tillage practices to optimize wheat growth, yield and quality in India’s diverse agro-climatic zones. Such integrated management approaches contribute not only to elevating productivity but also to preserving soil health and environmental sustainability, addressing critical challenges faced by the wheat sector in India.

In terms of yield performance, biofertilizer and cyanobacteria application increased wheat grain yield by 10-22%, with reported yields ranging from 4.6 to 5.4 Mg ha^-1 under improved soil biological activity (Hakkoum et al. 2025). Biochar application, particularly when integrated with mycorrhizal inoculation, resulted in wheat grain yields between 4.8 and 5.6 Mg ha^-1 in calcareous and degraded soils, reflecting yield gains of 15–28% over untreated controls (Khdir and Rahman 2024; Aziz et al. 2020). Conservation agriculture and zero-tillage-based land preparation systems recorded wheat yields of 4.7–5.3 Mg ha^-1, along with reduced production costs and enhanced water productivity compared to conventional tillage (Gupta et al. 2019; Mehala et al. 2016). Deep tillage practices improved wheat yield by 8–14%, whereas no-tillage systems maintained comparable yields of 4.5–5.0 Mg ha^-1 while significantly enhancing soil health indicators (Pandey, Agrawal, and Bohra 2015; Kahlon and Khurana 2017). Ridge-furrow planting combined with mulching further increased wheat grain yield to above 5.5 Mg ha^-1 by improving grain filling efficiency and soil moisture conservation (Dai et al. 2024).

1.5 Effect of irrigation practices on the growth of wheat

Irrigation practices play a crucial role in determining the growth and productivity of wheat cultivation in India, optimized irrigation scheduling, particularly the application of three irrigations at critical growth stages such as crown root initiation (CRI), flowering and milking, has consistently been shown to enhance key growth parameters of wheat, including plant height, leaf area index (LAI), tiller count and dry matter accumulation, leading to higher yields (Mandal et al. 2024; Verma et al. 2024). Studies indicate that irrigation levels tailored to specific crop water requirements, such as irrigation water to cumulative pan evaporation (IW: CPE) ratios close to 1.0, optimize physiological growth parameters and yield attributes. For instance, an IW:CPE ratio of 1.0 provided significant improvement in grain yield and plant growth, such as in Madhya Pradesh, where wheat was sown under this irrigation regime with appropriate variety selection yielded up to 4,735 kg ha^-1 (Lanjhewar et al. 2022; Gajbhiye et al. 2023). The use of irrigation scheduling based on plant stress indices (PSI), particularly the 0.5 PSI threshold, has proven highly effective in water-scarce regions like Punjab, enabling substantial grain yield improvements while saving water compared to farmer practice irrigation (Kaur et al. 2024). Moreover, adoption of micro-irrigation techniques including drip and sprinkler systems in various Indian states has significantly increased water use efficiency, leaf area development and crop health, thereby improving wheat yield and economic returns. Such methods ensure precise water delivery, often resulting in better physiological responses of the crop and improving resource sustainability (Sagar and Naresh 2019). Crop establishment techniques such as raised bed planting combined with suitable irrigation scheduling also contribute to improved plant growth metrics by enhancing root development and plant height, although soil nutrient status after harvest may remain unaltered (Sagar and Naresh 2019). Additionally, integration of irrigation with nutrient management practices, including the application of organic amendments like farmyard manure and vermicompost, synergistically enhances wheat growth by improving soil moisture retention and nutrient availability, further driving yield increments (Namdeo et al. 2023). The application of silicon foliar sprays under deficit irrigation conditions has also been shown to mitigate drought stress effects, thereby boosting growth and water use efficiency in wheat cultivation under semi-arid tropical climates. However, the timing of irrigation in relation to sowing date is critical; earlier sowing combined with optimal irrigation scheduling enhances physiological growth traits and yield, whereas delayed sowing diminishes these benefits (Gajbhiye et al. 2023). Economic analyses underscore that irrigation scheduling not only elevates wheat productivity but also improves benefit-cost ratios and net income for farmers, reinforcing the practical value of irrigation interventions in wheat cultivation systems. Despite progress, challenges such as resource limitations, climatic variability and the need for mechanized and site-specific irrigation management persist, suggesting ongoing research and adoption of innovative irrigation technologies such as IoT-based smart irrigation systems is essential for sustainable wheat farming in India (Prem et al. 2024; Namdeo et al. 2023). Overall, recent studies affirm that precise, stage-specific irrigation combined with appropriate planting and nutrient management practices markedly impacts wheat growth, yield and water use efficiency, forming a vital component of sustainable wheat cultivation strategies across diverse agro-climatic zones in India.

In terms of yield response, scheduling three irrigations at CRI, flowering and milking stages resulted in wheat grain yields ranging from 4.6 to 5.2 Mg ha^-1, representing yield advantages of 18–30% over limited or poorly timed irrigation regimes (Mandal et al. 2024; Verma et al. 2024). Irrigation scheduling based on IW:CPE ratios of 0.9-1.0 consistently produced wheat yields between 4.5 and 4.9 Mg ha^-1 across central and northern Indian conditions, confirming optimal water-use efficiency at these ratios (Lanjhewar et al. 2022; Gajbhiye et al. 2023). PSI-based irrigation at the 0.5 threshold increased wheat grain yield by 12–20% while saving 15–25% irrigation water compared to conventional farmer practices (Kaur et al. 2024). Micro-irrigation systems recorded wheat yields of 4.8-5.4 Mg ha^-1, accompanied by higher net returns and improved benefit-cost ratios, demonstrating their economic and agronomic superiority under water-limited environments (Sagar and Naresh 2019). Integration of irrigation with organic nutrient sources further enhanced wheat yield by 10–16%, achieving grain yields above 5.0 Mg ha^-1 under optimized soil moisture and nutrient availability (Namdeo et al. 2023).

1.6 Effect of fertilizer management on the growth of wheat

Recent research has extensively explored the combined impact of fertilizer management and planting practices on wheat cultivation in India, highlighting significant advancements and sustainable approaches in enhancing wheat growth and productivity. Studies emphasize the integration of recommended dose of chemical fertilizers 120 kg N, 40-60 kg P₂O₅, and 30-40 kg K₂O per hectare with novel inputs such as nano fertilizers, biochar-coated slow-release nitrogen fertilizers and organic amendments, which together improve nutrient use efficiency, crop biomass and yield under diverse Indian agro-climatic conditions. For example, the foliar application of nano fertilizer alongside 100% recommended NPK doses in Madhya Pradesh has demonstrated improved growth traits and economic return, indicating a synergistic effect of traditional and innovative fertilizer strategies tailored to soil conditions (Sekwadiya et al. 2025). Similarly, biochar-based slow-release nitrogen fertilizers (BCN) in the Indo-Gangetic Plains showed up to a 16.7% increase in crop biomass and better nitrogen uptake compared to conventional neem-coated urea, suggesting the potential for reduced environmental impact without yield compromise (N. T. M. Kumar et al. 2024). Precision nutrient management guided by models such as Nutrient Expert and chlorophyll meter (SPAD) based nitrogen applications further optimize fertilizer doses and timing, leading to significant gains in wheat yield and nitrogen use efficiency, while reducing fertilizer input and associated costs (Phulara et al. 2023; Ghosh et al. 2018). The adoption of site-specific nutrient management practices in eastern Indo-Gangetic Plains, combined with improved crop establishment methods like wet-seeding for rice and zero-till (ZT) drilling for wheat, has resulted in system productivity increases of up to 44% and profitability boosts of over 150%, demonstrating strong interactions between fertilizer management and planting methods (Sahu et al. 2023). Such integrated approaches balance nutrient supply with crop demand and soil health, sometimes incorporating organic sources like farmyard manure (FYM), poultry litter, or sewage sludge with reduced chemical fertilizer doses, enhancing soil fertility and sustainability while maintaining yield levels (Mohammed, Ali, and Marif 2023; P. Singh et al. 2022; Prakash et al. 2024). Fertilizer management also interacts critically with planting density and timing; optimized nitrogen application coupled with suitable planting densities (e.g., 3.3 million plants per hectare) improves canopy structure, leaf area index and light interception, thereby maximizing yield components (Shi et al. 2025). Investigations into mechanization and labor efficiency in regions like North Karnataka stress the role of advanced planting and fertilizer practices in reducing cultivation costs and enhancing economic returns, reinforcing the multifaceted benefits of coordinated fertilizer and planting management (Udhayan, Naik, and Hiremath 2023). Approaches like integrating growth regulators with optimal fertilizer levels also contribute to improved nutrient balance and crop performance under Indian conditions (Kumbhare et al. 2023). This comprehensive strategy not only improves nutrient use efficiency and economic returns but also supports soil health, resource conservation and environmental safety, aligning with the goals of sustainable intensification in Indian wheat production systems.

1.7 Effect of crop rotation and intercropping on the growth of wheat

Crop rotation and intercropping are key planting practices that significantly influence wheat growth and productivity in India, crop rotation, especially when integrated with conservation tillage and residue retention, has proven effective in enhancing wheat growth indices such as plant height, tiller number, biomass and ultimately grain yield. Experiments under zero-tillage with residue retention combined with integrated weed management achieved superior weed control efficiency, which translated into higher wheat growth indices and grain yield, outperforming conventional tillage methods. For instance, wheat grown under zero-tillage with residue retention by employing herbicide rotation and hand weeding recorded plant heights exceeding 100 cm, tiller densities reaching about 548 no. m^-2 and grain yields nearing 4700 kg ha^-1, highlighting the agronomic benefits of conservation agriculture-based crop rotation systems. Moreover, sensor-based nitrogen application within rotation practices demonstrated significant enhancements in wheat plant height and tiller density when compared with conventional fertilizer treatments, indicating that precision nutrient management synchronized with rotation systems optimizes growth parameters (N. Kumar et al. 2023; Patel et al. 2024). Intercropping, particularly with legumes such as chickpea, lentil and mustard, consistently improves wheat growth parameters by enhancing nitrogen availability and utilization, promoting better resource use efficiency and increasing system productivity. Field trials in different Indian agro-ecologies established that intercropping wheat with legumes in strategic row ratios enhances critical growth attributes including effective tillers per square meter, grain count per spike and 1000-grain weight. A wheat-chickpea (2:1) intercropping system yielded an average wheat grain production of over 5mg ha^-1, surpassing sole wheat systems, while improving Land Equivalent Ratio (LER) and water-use efficiency, thereby reflecting enhanced overall productivity and resource conservation (Roy and Singh 2023; M. K. Singh et al. 2019). Further, intercropping impacts nitrogen dynamics positively; wheat plants grown in intercropping systems registered a nitrogen content increase of 17% to 22% across various growth stages compared to monocropped wheat, leading to improved nitrogen uptake and accumulation, essential for vigorous plant development (Zhao et al. 2010). Intercropping also modifies growth rhythms, as demonstrated in wheat-alfalfa systems, where wheat’s linear growth phase is extended but growth rate moderately reduced, implying a shift in growth dynamics due to interspecific competition and resource allocation (Qiong et al. 2022). Some studies reveal that planting configurations within intercropping systems notably influence growth outcomes. For example, wheat-lentil intercropping performed better at 3:1 row ratio for growth parameters, while wheat-chickpea at balanced 2:2 rows maximized total dry matter accumulation, crop growth rate and relative growth rate, indicating the importance of precise spatial arrangements to optimize crop interactions and individual crop performance (Das, Khaliq, and Haider 2011). Furthermore, application of bio-stimulants like seaweed in wheat-chickpea intercropping under North Indian conditions increased nitrogen content and agronomic efficiency, resulting in improved yield and nutrient quality, emphasizing integrative management for maximizing wheat growth in intercropped systems (Rani, Kaushik, and Kapoor 2024).

In addition, crop rotation-based conservation agriculture practices consistently recorded wheat grain yields ranging from 4.5 to 5.2 Mg ha^-1, reflecting yield advantages of 12-25% over conventional tillage-based monocropping systems. Sensor-based nitrogen management within crop rotation further enhanced wheat yield by 8-15%, with reported grain yields exceeding 5.0 Mg ha^-1 under optimized nutrient synchronization (N. Kumar et al. 2023; Patel et al. 2024). Intercropping systems also showed notable yield benefits, with wheat-equivalent yields ranging between 5.3 and 6.1 Mg ha^-1 in wheat-legume combinations, supported by higher LER values (>1.2), indicating superior land-use efficiency compared to sole wheat cultivation (Roy and Singh 2023; M. K. Singh et al. 2019).