The late planting of wheat strings along with rice–wheat systems. Except for Punjab, 25–35% of the wheat area in the Indian IGP is estimated to be sown late, which markedly dwindles wheat productivity. Terminal heat entails a decrease in wheat yield potential by 1–1.5% per day if planting ensues after 15 November [9]. The delay in the planting of the wheat crop is a consequence of late rice harvesting, which corresponds to both the late establishment of rice, and the long duration of this crop. As a matter of fact, farmers grow fine-quality basmati rice in some parts of the IGP, which requires a longer duration to reach maturity. However, in the eastern IGP, long-duration and short-grain rice varieties are preferred, due to water lodging resulting in late wheat sowing. Other reasons for the late sowing of wheat in this region are long turnaround periods, which often imply intensive tillage operations, inadequate draft and mechanical power for ploughing, soil moisture problems (soil either too wet or too dry), and the urgency to store the harvested rice before preparing the land for wheat cultivation. Surface seeding promotes timely wheat establishment, as sowing wheat crop in a standing rice field greatly minimizes the turnaround time.

Contrasting results are demonstrated regarding wheat productivity, varying froma0.3 to 25% increase [15,16,17,18]. Generally, increased crop yields under SS are attributed to the improved soil properties, including water infiltration rate, higher SOC, soil aggregation, moisture- and nutrient-availability, and microbial activity [12,16,19,20,21,22,23]. However, it is also reported [24] that positive effects of SS on wheat yield under RW systems are predominantly the outcome of: (a) timely sowing, (b) increased input use efficiency, and (c) weed control. Adopting SS helps to increase long-term farm profitability, as it reduces the number of operations and fuel cost. One of the prime merits of SS, which popularizes it among the farming community, is that it reduces input cost and ensures timely sowing, resulting in higher wheat yields.

A number of studies emphasize the adoption of ZT with crop R retention in IGP for the perpetuation of crop yields and system productivity [25,26,27]. Correspondingly, Bangladeshi farms using SS practices register higher yields, with more profitability [28]. In fact, yield levels of the ZT with crop R retention are proportionate to CT in a long-term experiment conducted in central India, although the energy and labor savings are much greater under the former [29]. The gradual adoption of SS practices for wheat sowing in the RWCS has a direct yield advantage in the eastern IGP, and with the improvement in soil quality, the other beneficial effects are expected to eventually burgeon [30].

Water scarcity is becoming a binding constraint to real agriculture in the IGP; fulfilling the domestic and industrial requirements is similar to walking a tightrope in the current poor water-use efficiency scenario [9]. Over-exploitation of below ground aquifers, when combined with poor water management, exacerbates the predicament of water logging and salinity in some areas, and declining water tables in others [8,51]. Depletion of groundwater resources at an alarming rate is major topic of concern. Management practices based on SS utilize residual moisture, reduce pre-sowing irrigation, and present an immense capability to resolve the issue, as it enhances water-use efficiency. This could prove to be advantageous for the IGP, where farmlands are facing acute water shortages, and the lowering of the water table in some of the RW areas as a repercussion of extreme groundwater pumping [12,18,33]. Progress in crop water productivity (CWP) holds the promise of food security, as well as water sustainability in RW cropping systems of the IGP [13,34,50,52]. Crop establishment technologies, with an emphasis on resource conservation, are normally reported to preserve 20–35% of irrigation water in the wheat against conventional practices [9]. A zero-tillage-based rice–wheat–maize system (RWMS) shows enhanced water productivity over a conventional RW system [20]. The irrigation WP under the RW system demonstrates an augmentation of145% under SS compared to farmers’ practice [53]. Moreover, SS can improve soil structure and facilitate buildup of crop debris, which directly correlates with an increase in water retention and better infiltration, along with a decrease in overall water use elsewhere [24]. Additionally, the faster turnaround time effectuated by SS allows for the early planting and harvesting of wheat crops, which, in some regions, potentially eliminates the need for one or more late-season irrigations. The availability of nutrients to the plant is substantially influenced by water availability. Plants absorb nutrients predominantly through transportation and diffusion processes that are governed by water. As a result, high WUE not only saves water, but also improves nutrient availability to plants.

Irrigation boosts agricultural productivity by expanding cultivable land far more than is possible with rain-fed agriculture, and increasing crop yields. Irrigation boosts yields not just by reducing or preventing crop water stress, but also by reaping the additional benefits of combining irrigation with high-yielding cultivars, fertilizer, and herbicides. In developing nations, irrigation is a critical component of agricultural productivity. In the years 1997–1999, irrigated land supplied two-fifths of agricultural yields in developing nations, accounting for around one-fifth of cultivated areas. Irrigated cereal yields out-performed rain-fed yields by 115% in developing nations [54]. Increased food production from irrigated agriculture can provide nutritional benefits to farmers, their families, and the local community. Irrigation allows for multiple cropping, which can help to relieve seasonal food supply gaps, and stimulate the development of crops that contribute to a more diversified and healthy diet. Improved nutrition can improve quality of life, reduce disease, raise labor productivity, and boost children’s academic achievement [55]. Sun et al. [56] report that increased irrigation significantly increases the bulk density (BD) of soil by 5% to 8% in the upper 20 cm, and decreases salt concentrations [57]. Irrigation enhances the nutrients availability to the crop. However, the irrigable water resources are depleted continuously, as a result of environmental pollution and over-exploitation of groundwater resources. Hence, rural communities are eager to adopt such technologies that enhance water productivity and water-use efficiency. However, the adoption of micro-sprinkler and drip irrigation is not so popular among farmers, due to its high cost and maintenance.

In SS, weed problems are identified as a major issue for management [33,50]. In conventional approaches, tillage operations are performed mainly for weed control, firming seedbeds, and uniform germination [58]. However, the matter of weed control under SS is largely dealt with using herbicides. Glyphosate [N-(phosphor no methyl) glycine], a broad-spectrum herbicide, is mainly used in the absence of extensive tillage to manage weed infestation [38,44,49]. In addition to glyphosate, other herbicides, such as 2,4-D (2,4–dichlorophenoxy acetic acid), clodinafop-ethyl, metsulfuron, sulfosulfuron, etc., are applied to control the weeds [18,32]. Indisputably, countries that previously used relatively higher amounts of herbicides are already experiencing retribution, in the form of environmental hazards and the emergence of herbicide-resistant weeds [59]. Therefore, under the SS system, it is duly advised to use the optimum dose of an appropriate herbicides, at the right time, for an efficient weed control [60]. Likewise, repeated herbicide usage under SS sometimes leads to weed shift, a herbicide-resistant weed population [61], and the dominance of a certain weed species as opposed to in conventional farming practices [62]. In an attempt to manage this problem efficiently, devising an integrated weed management approach, including the selection of appropriate cropping systems and cultivars with SS principles’ reinforcement, would be worthwhile [63,64]. In the eastern IGP, SS is mostly practiced in the standing rice crop, and farmers harvest the rice crop generally 7–10 days after sowing. During harvesting, germinated seeds are covered by the rice straw for 4–5 days until it properly dries, and is then collected manually. Thus, the 10 days of straw coverage reduce the germination of many winter weeds. Use of broad-spectrum weedicides, i.e., glyphosate, is not possible in this practice. The reduction in the weed population is observed in SS under puddled rice.

Tillage is usually considered by farmers as a practice in which soil is physically manipulated for the better crop establishment. Keeping this in perspective, the modifications in the soil’s physical properties deliberately affect the soil and ecosystem [67,68]; moreover, extensive tillage operations may eventually ravage the soil health. Farming communities in the IGP zones also practice excessive tillage, which significantly deteriorates the physical properties of soil, such as bulk density (BD), water-holding capacity (WHC), aggregate stability, porosity, etc. [69]. Apropos to this, Alakukku et al. [70] describe the consequent formation of subsurface hardpan after continuous ploughing at the same depth, resulting in reduced nutrient and WUE, as well as root growth. On the flip side, SS aids in inhibiting the deterioration in soil quality due to CT practices, through the revival of soil’s physio–chemo–biological properties. A brief account of the work performed by researchers in the IGP under the RW system clearly demonstrates a reduction in soil bulk density, and increases in mean weight–diameter (MWD), aggregate stability, and infiltration rate in loam to sandy loam soils under SS over CT. Intensive tillage, non-recycling of crop residue to soil systems, and mono-culture systems-mediated degradation of soil structure and aggregation contribute to a decline in the rate of infiltration under intensively irrigated rice–wheat agro-ecosystems. It inversely affects soil hydraulic conductivity and groundwater recharge, resulting in a consequent depletion of groundwater in such instances [13,20,65,71,72]. When sandy loam soils are exposed to SS rather than CT, the infiltration rate is accelerated by ∼50%, owing to the formation of stable aggregates [12,16,73,74]. The higher infiltration rates in the SS-based RW cropping system facilitate speedy water percolation, and reduce the quantity of run-off that might end up as groundwater recharge [44,75].

The major crop growth benefits of SS manifest through reduced soil erosion, crusting, compaction, and moderated soil hydrothermal regimes [15,18,23,33]. This practice leads to a supportive soil physical environment, which not only promotes root growth and nutrient recycling, but also SOC sequestration [2,17,18,76]. Experimental evidence involving SS shows a substantial decrease in BD and penetration resistance (PR) [34], with a significant increase in soil moisture content, water-stable aggregates (WSA) (>0.25 mm), and MWD, mainly in the topsoil (0–15 cm) layer [2]. Furthermore, soil type and climatic conditions implicitly control the quantum of the impact of SS on the soil’s physical properties. Under the semi-arid conditions, sandy loam soil exhibits a higher WSA (16.1–32.5%), with a significantly decreased PR and BD [27]. Singh et al. [77] document similar results in their five year-long study on sandy loam soil; in accordance with which, Somasundaram et al. [2] observe an increase in WSA (10%) and MWD (20%) in clay soil under the hot sub-humid condition compared to CT four years post-experimentation; meanwhile no significant pattern is observed relative to BD in clayey soil during that time period. Multiple reports advocate the combined implementation of R with a ZT system to yield greater benefits concerning soil’s physical properties [2]; contradictorily, Meena et al. [78] report a 12% and 33% higher MWD for ZT + R and NT − R than CT + R and CT − R, respectively, which implies that the effect of ploughing is more prominent over the addition of R.

Evidently, favorable impacts are noticed with the ZT operations, i.e., retention and recycling of crop residues on the soil surface in SS [12,18]; the pH is reduced, and the content of available N, P, K, and micronutrients increases in soil over CT. Additionally, the stratification of nutrients and their accumulation near the root zone are detected under SS [16,39,40,49]. Several researchers gathered evidence regarding increased SOC and total nitrogen (N) stocks with the adoption of SS practices involving ZT and crop residue retention, along with optimum nutrient application [39,75,76]. By increasing the quantity of C, soil C sequestration is enhanced, and/or the rate of soil C loss reduced, which primarily depends on the local soil and climate conditions [79]. Yadav et al. [66], in their work encompassing the north–eastern region of India, report that by employing SS practices, such as ZT + integrated plant nutrient management (IPNM) + 30% R incorporation in RWCS, higher SOC sequestration (427.9 kg ha⁻¹ yr⁻¹) is achieved. The soil nutrient availability is evaluated by Jat et al. [16] under the SS practices in north–west India, where the highest SOC (7.7 g kg⁻¹) is found under SS, compared to that under CT (4.5 g kg⁻¹). At the depth of 0–15 cm, the available N is higher in SS-based RWMS (33%) and SS-based maize–wheat–mungbean (MWM; 68%) than a conventionally grown RW cropping system. With respect to available P, a 25% and 38% higher concentration is detected under SS-based MWM and SS-based RWMS, respectively, relative to the conventional system. A plausible explanation for this could be the higher R retention and moderation of the soil moisture and temperature by water absorption, where R acts as an insulating material to resist the change in heat, which is conducive for growth at or near the soil surface. As crop debris contains high concentrations of total K, it could contribute to a higher available K level in soil [18,40]. Apart from these, in other research work conducted in the north–western IGP, the adoption of ZT proves to be beneficial in terms of SOC accumulation and N uptake [80]. In central India, Hati et al. [81] and Kushwa et al. [82] witness that ZT soils display more SOC and P concentration in the surface layers than at depth, in contrast to those exposed to CT under a soybean–wheat system. Similarly, a comparative study conducted by Mohammad et al. [75] in Pakistan shows a higher SOM, and mineralizable C and N, along with total N, P, K, in a minimum tillage (MT) experiment, as compared to that of CT and deep tillage at 0–30 cm soil depths.

The ZT in combination with R effectively diminishes the oxidation rate of SOC and crop residue, which improves the SOC content. The effect of SS on soil biological properties reveals a significant increase compared to CT with respect to microbial biomass carbon (MBC), and the activity of soil enzymes such as dehydrogenase, alkaline phosphatase, urease, and phytase. The higher SOC leads to higher MBC, and microbial and mineralization quotients that are the biological indicators under the SS-based system. A significantly higher correlation is witnessed by Bera et al. [39], in relation to SOC: MBC (0.93), SOC: BSR (basal soil respiration) (0.84), and SOC: Qm (carbon mineralization quotient) (0.70) in an RW system while employing various tillage management practices in India. Significant improvements in MBC, basal soil respiration, and microbial and mineralization quotients are observed in the ZT plot as opposed to CT [83]. This is presumably due to the limited microbial decomposition of SOC under ZT which, in contrast to CT, results in greater stabilization of micro-and macro-aggregates, and provides a physical barrier between organic matter and decomposers [84]. Surface seeding also provides a suitable environment for microbial proliferation, due to the retention of crop residue compared to the removal of residue or burning [85]. Diverse microbial communities regulate specific functions associated with the decomposition of crop residues. The soil bacteria instigate the process, while later phases of crop residue decomposition is dominated by fungi [86,87]. The agricultural management practices also influence the soil microbial community structure [88]. Indeed, a study conducted in central Mexico documents that ZT practice coupled with crop R retention augments fungal abundance, and significantly affects the bacterial community structure, thereby promoting the abundance of Bacteroidetes, Betaproteobacteria, and Gemmatimonadetes [89]. These microorganisms take part in several biogeochemical processes, such as C and N cycles, alongside their function of being a storehouse of plant nutrients [90]. Intensive tillage negatively impacts the distribution and abundance of soil microbes, by influencing soil moisture and thermal regimes, as well as nutrient dynamics [91]. Moreover, this practice destroys soil structure, which portends alteration in the abundance and diversity of microbes when compared to the SS system [35,92].

The previous literature suggests that a reduction in tillage accompanies enhanced chemical and microbial activity, microbial biomass, and enzymatic actives such as dehydrogenase, alkaline phosphatase, etc. [19,35,44,93]. Parihar et al. [94] report an increase in soil MBC by 45–48.9% under SS-based systems in sandy loam (Typic Haplustept) soil profiles (0–30 cm deep) in the north–western IGP. Concurrently, an SS-based maize–wheat cropping system (MWCS) improves soil MBC (208%), MBN (263%), and dehydrogenase (210%), and alkaline phosphatase activity (48%), when compared with the conventional practice of the RW system [35]. However, the SS-based RW system enhances the soil MBC and MBN up to 40%, as well as the dehydrogenase and alkaline phosphatase activity by up to 15% [12,53]. In cereal systems predicated on SS, a higher micro-arthropod population is witnessed under RW compared to the MW system. Also, an SS-based MW system secures the uppermost soil quality index (SQI) score of 1.45, while with a CA-based RW system, it is 0.58, with the lowermost score of 0.29 comes from the conventional RW system [35].

Surface seeding is a climate-resilient resource-conserving technology (Figure 3). It has the potential to increase cost and yield with a minimal carbon footprint, as it tends to sequester organic carbon in soil, with lesser expenditure of energy and irrigation water, thus, reducing the total global warming potential (GWP). With respect to the comparative GHGs emissions from SS and CT practices, Sapkota et al. [33] detect a 32% reduction in N₂O emissions in ZT and direct seeding. Similarly, Gupta et al. [37] estimate a minute decrease in N₂O emissions (2.2%) under ZT, which equates to a similar extent of reduction in the GWP. However, Kumar et al. [20] evaluate four wheat management strategies, and report that in an attempt to reduce the GWP of wheat, a soil matric potential (SMP) criteria must be used in place of applying irrigation water at certain intervals at critical crop growth stages. Irrespective of CO₂ emission, Nath et al. [19] observe a 17% decline in CO₂–C flux under SS, whereas Gathala et al. [14] note that, under RT, CO₂ equivalent emission is reduced by 8.4% in comparison to farmers’ practices. Along the same lines, evaluation of different tillage rotation practices are performed by Gupta et al. [37], where ZT alone and ZT+R-based wheat display significantly lower GWP and GHGs emissions compared to CT wheat, signifying that the adoption of SS practices could reduce the GWP of the conventional RW system by 44 to 47%, without compromising the yield. Similar findings are documented by Tirol-Padre et al. [22], Kakraliya et al. [34], Kar et al. [93], and Singh et al. [95]. Aryal et al. [96] employ the Cool Farm Tool (CFT) to estimate GHG emission, which utilizes data regarding total production area, productivity, and management input with pedo-climatic conditions, and the results suggest that CO₂ emissions in CT wheat are significantly higher (0.6 Mg of CO₂ eq ha⁻¹ yr⁻¹) in contrast to ZT wheat, where 0.084 Mg of CO₂ eq ha⁻¹ yr⁻¹ is sequestered. When the collective emissions from a ZT-based wheat production system are converted intoaCO₂ equivalent, the resultant produce is nearly carbon-neutral, as N₂O emissions are counterbalanced by C sequestration [93]. As tillage management practices significantly influence soil C stock, variations in GHGs emissions could certainly be attributed to the SS and CT practices. Any reduction in GHG emissions while practicing SS might also result from the restricted disposal of crop debris through burning, which is quite common in conventional practices; moreover, it is worth mentioning that burning each ton of crop residue can emit 40 g of N₂O, which is equivalent to 12.4 kg of CO₂, along with 2.3 kg of CH₄, which equals 48.3 kg of CO₂ [97].