Indo-Gangetic Plains Of South Asia Research Articles

System of wheat intensification (SWI): Effects on lodging resistance, photosynthetic efficiency, soil biomes, and water productivity.

Intense cultivation with narrow row spacing in wheat, a common practice in the Indo-Gangetic plains of South Asia, renders the crop more susceptible to lodging during physiological maturity. This susceptibility, compounded by the use of traditional crop cultivars, has led to a substantial decline in overall crop productivity. In response to these challenges, a two-year field study on the system of wheat intensification (SWI) was conducted. The study involved three different cultivation methods in horizontal plots and four wheat genotypes in vertical plots, organized in a strip plot design. Our results exhibited that adoption of SWI at 20 cm × 20 cm resulted in significantly higher intercellular CO2 concentration (5.9-6.3%), transpiration rate (13.2-15.8%), stomatal conductance (55-59%), net photosynthetic rate (126-160%), and photosynthetically active radiation (PAR) interception (1.6-25.2%) over the existing conventional method (plant geometry 22.5 cm × continuous plant to plant spacing) of wheat cultivation. The lodging resistance capacity of both the lower and upper 3rd nodes was significantly higher in the SWI compared to other cultivation methods. Among different genotypes, HD 2967 demonstrated the highest recorded value for lodging resistance capacity, followed by HD 2851, HD 3086, and HD 2894. In addition, adoption of the SWI at 20 cm × 20 cm enhanced crop grain yield by 36.9-41.6%, and biological yield by 27.5-29.8%. Significantly higher soil dehydrogenase activity (12.06 μg TPF g-1 soil hr-1), arylsulfatase activity (82.8 μg p-nitro phenol g-1 soil hr-1), alkaline phosphatase activity (3.11 n moles ethylene g-1 soil hr-1), total polysaccharides, soil microbial biomass carbon, and soil chlorophyll content were also noted under SWI over conventional method of the production. Further, increased root volumes, surface root density and higher NPK uptake were recorded under SWI at 20×20 cm in comparison to rest of the treatments. Among the tested wheat genotypes, HD-2967 and HD-3086 had demonstrated notable increases in grain and biological yields, as well as improvements in the photosynthetically active radiation (PAR) and chlorophyll content. Therefore, adoption of SWI at 20 cm ×20 cm (square planting) with cultivars HD 2967 might be the best strategy for enhancing crop productivity and resource-use efficiency under the similar wheat growing conditions of India and similar agro-ecotypes of the globe.

Interactive effects of long-term management of crop residue and phosphorus fertilization on wheat productivity and soil health in the rice–wheat

In the context of degradation of soil health, environmental pollution, and yield stagnation in the rice–wheat system in the Indo-Gangetic Plains of South Asia, an experiment was established in split plot design to assess the long-term effect of crop residue management on productivity and phosphorus requirement of wheat in rice–wheat system. The experiment comprised of six crop residue management practices as the main treatment factor with three levels (0, 30 and 60 kg P2O5 ha–1) of phosphorus fertilizer as sub-treatments. Significant improvement in soil aggregation, bulk density, and infiltration rate was observed under residue management (retention/incorporation) treatments compared to residue removal or residue burning. Soil organic carbon (SOC), available nutrient content (N, P, and K), microbial count, and enzyme activities were also significantly higher in conservation tillage and residue-treated plots than without residue/burning treatments. The residue derived from both crops when was either retained/incorporated improved the soil organic carbon (0.80%) and resulted in a significant increase in SOC (73.9%) in the topsoil layer as compared to the conventional practice. The mean effect studies revealed that crop residue management practices and phosphorus levels significantly influenced wheat yield attributes and productivity. The higher grain yield of wheat was recorded in two treatments, i.e. the basal application of 60 kg P2O5 ha–1 without residue incorporation and the other with half the P-fertilizer (30 kg P2O5 ha–1) with rice residue only. The grain yield of wheat where the rice and wheat residue were either retained/incorporated without phosphorus application was at par with 30 and 60 kg P2O5ha–1. Phosphorus levels also significantly affected wheat productivity and available P content in the soil. Therefore, results suggested that crop residue retention following the conservation tillage approach improved the yield of wheat cultivated in the rice–wheat cropping system.

A Decade of Climate-Smart Agriculture in Major Agri-Food Systems: Earthworm Abundance and Soil Physico-Biochemical Properties

Earthworms (EWs) could be a viable indicator of soil biology and agri-food system management. The influence of climate-smart agriculture (CSA)-based sustainable intensification practices (zero tillage, crop rotations, crop residue retention, and precision water and nutrients application) on earthworms’ (EWs) populations and soil physico-biochemical properties of rice-wheat cropping system in the Indo-Gangetic plains of South Asia was investigated. This study investigates the effect of 10-years adoption of various CSA practices on the abundance of earthworms and physical and biochemical properties of the soil and EWs’ casts (EWC). Five scenarios (Sc) were included: conventionally managed rice-wheat system (farmers’ practices, Sc1), CSA-based rice-wheat-mungbean system with flood irrigation (FI) (Sc2) and subsurface drip irrigation (SDI) (Sc3), CSA-based maize-wheat-mungbean system with FI (Sc4), and SDI (Sc5). Results revealed that EWs were absent under Sc1, while the 10-year adoption of CSA-based scenarios (mean of Sc2–5) increased EWs’ density and biomass to be 257.7 no. m−2 and 36.05 g m−2, respectively. CSA-based maize scenarios (Sc4 and Sc5) attained higher EWs’ density and biomass over rice-based CSA scenarios (Sc2 and Sc4). Also, SDI-based scenarios (Sc3 and Sc5) recorded higher EWs’ density and biomass over FI (Sc2 and Sc4). Maize-based CSA with SDI recorded the highest EWs’ density and EWs’ biomass. The higher total organic carbon in EWC (1.91%) than in the bulk soil of CSA-based scenarios (0.98%) and farmers’ practices (0.65%) suggests the shift of crop residue to a stable SOC (in EWC). EWC contained significant amounts of C and available NPK under CSA practices, which were nil under Sc1. All CSA-based scenarios attained higher enzymes activities over Sc1. CSA-based scenarios, in particular, maize-based scenarios using SDI, improved EWs’ proliferation, SOC, and nutrients storage (in soil and EWC) and showed a better choice for the IGP farmers with respect to C sequestration, soil quality, and nutrient availability.

Outburst of pest populations in rice-based cropping systems under conservation agricultural practices in the middle Indo-Gangetic Plains of South Asia

Conservation agriculture (CA), which encompasses minimum soil disturbance, residue retention either through crop residue, or cover crops and crop diversification-based crop management practices can modify the status of pest dynamics and activities under the changing climatic scenarios. CA has been advocated extensively to optimize the use of available resources, maintain the environmental quality, enhance crop productivity, and reduce the climate change impacts. Information related to the impacts of long-term CA-production systems under rice-based cropping systems on pest status is lacking, particularly in middle Indo-Gangetic Plains (MIGP). Under CA, puddling is completely avoided, and rice is directly sown or transplanted to maintain better soil health. Different sets of experimentations including farmers practice, partial CA and full CA (CA) as treatments in rice-based cropping systems, were established from 2009, 2015 and 2016 to understand the long-term impacts of CA on pest dynamics. In this study, direct and indirect effects of tillage (zero, reduced and conventional tillage), residue retention and cropping sequences on abundance and damage by pests were investigated. After 4–5 years of experimentation, populations of oriental armyworm [Mythinma (Leucania) (Pseudaletia) separata (Wlk.)] in wheat, mealybug [Brevennia rehi (Lindinger)] and bandicoot rat [Bandicota bengalensis (Gray)] in rice were found to increase abnormally in CA-based production systems. Conventionally tilled plots had a significant negative effect while residue load in zero-tilled plots had a significant positive effect on larval population build-up of M. separata. Zero tillage had a higher infestation of mealybug (52–91% infested hills) that used grassy weeds (Echinochloa colona, Echinochloa crusgalli, Cynodon dactylon, Leptochloa chinensis and Panicum repense) as alternate hosts. Cropping sequences and no disturbance of soil and grassy weeds had higher live burrow counts (4.2 and 13.7 burrows as compared to 1.47 and 7.53 burrows per 62.5 m2 during 2019–2020 and 2020–2021, respectively) and damaged tillers (3.4%) in CA-based practices. Based on the present study, pest management strategies in CA need to be revisited with respect to tillage, residue retention on soil surface, grassy weeds in field and cropping sequences to deliver the full benefits of CA in MIGP to achieve the sustainable development goals under the climate change scenarios.

Assessment of nutrient management in major cereals: Yield prediction, energy-use efficiency and greenhouse gas emission

Through improved nutrient management, sustainability of cereal production can be achieved by improving crop yield and economic indicators with reduced environmental footprints and energy use. The objectives of this study were to compare the crop yield and economics, and energy and environment related indicators as the measures of sustainability across three nutrient management practices in three major cereals of South Asia. Nutrient Expert (NE) based fertilizer recommendation, government recommendation (GR), and farmers' nutrient management practice (FP) were evaluated in 600 on-farm trials in two eastern Terai districts of Nepal during 2014–2016. The machine learning (Random Forest) approach was used to identify major indicators to predict grain yield variability. The NE-based recommendation had the highest and FP had the lowest grain yield and gross return in all cereals. Farmer's practice had the highest probability of increasing energy-use efficiency (EUE) followed by NE in all cereals. NE had the lowest yield-scaled greenhouse gas emission (greenhouse gas emission intensity; GHGI) in rice and intermediate in maize and wheat compared with GR or FP. Farmers' practice had consistently the highest GHGI in rice and maize while GR had the highest GHGI in wheat. Except for rice in FP, specific energy (SE) followed by EUE were the major predictors of grain yield of all crops in all nutrient management practices. These findings suggest an opportunity for increasing productivity and profitability with lowered GHGI of the major cereals with NE-based fertilizer recommendation and potential for its out-scaling in Nepal and the Eastern Indo-Gangetic Plains of South Asia.

Long-Term Zinc Fertilization in Calcareous Soils Improves Wheat (Triticum aestivum L.) Productivity and Soil Zinc Status in the Rice–Wheat Cropping System

Rice–wheat cropping system (RWCS) is considered as the furthermost vital system in the Indo-Gangetic Plains of South-Asia, including India, Pakistan, Bangladesh, and Nepal. Recently, the deficiency of micronutrients like zinc (Zn) has emerged as one of the prime limitations for the sustainability issues of this RWCS in Zn deficient calcareous soils, particularly in India, as a result of the calcareous typic ustifluvents taxonomic nature of the soils. Therefore, a new Zn fertilization approach for soils is very much needed in the intensive RWCS. Thus, a six-year-long investigation was designed with three different modes of Zn application, viz., the application of Zn only in the first year of study, application in alternative years, and application in every year. Four different rates of Zn applications in a hectare of area for a single year, viz., 2.5, 5.0, 7.5, and 10 kg ha−1 year−1, and times of Zn application, viz., only at first year, alternative years, and in each year. The major aims of the study were to determine Zn concentration in soil; yield; and Zn accumulation by wheat crop under different application methods of Zn. From this study, it was found that a large portion of the applied Zn was present in the residual fraction, and it was also revealed that increasing the frequency of Zn application resulted in the increment in the crystalline fraction. Significant correlation of water-soluble and exchangeable Zn (WS+EX-Zn), complexed Zn (COM-Zn), amorphous Zn (AMO-Zn), organic Zn (ORG-Zn), total Zn (TOT-Zn), grain yield, and grain Zn uptake by wheat indicated that these Zn fractions were dominant forms in the soil to be utilized by plants under rice–wheat rotation. Concerning yield and Zn uptake by wheat, it was noted that the Zn application at 10 kg ha−1 in alternate years was the best Zn application method, while application of Zn at 7.5 kg ha−1 in each year also resulted in comparable yield.

Rice–wheat system in the northwest Indo-Gangetic plains of South Asia: issues and technological interventions for increasing productivity and sustainability

Puddled transplanted rice (Oryza sativa L.) followed by intensively tilled wheat (Triticum aestivum L.) (R–W) is the most predominant cropping system and the lifeline for billions of people in South Asia. The cultivation of R–W system requires high amounts of water, nutrients and energy, resulting in increased production costs and increased emissions of greenhouse gases. There are also increasing concerns of yield stagnation or decline in the R–W system, with increasing environmental footprints. Hence, the sustainability of the R–W system in South Asia, particularly in the northwest Indo-Gangetic Plains (IGPs), has been questioned and heavily debated. Based on the findings from peer-reviewed literature, this review aims to identify unsustainability issues and research gaps in the R–W system and propose possible solutions to mitigate those issues and technological interventions to close the research gaps. Among the unsustainability issues that the review has identified are declining crop, water and land productivity, deterioration of soil health, emissions of greenhouse gases due to intensive tillage and residue burning, deepening of groundwater levels and shift in weed flora and development of herbicidal resistance in crops. Potential solutions or technological interventions to mitigate the unsustainability issues include resource conservation technologies (RCTs) such as rice residue management, reduced tillage, laser land leveling, soil matric potential based irrigation scheduling, delayed rice transplanting, cultivation on permanent raised beds, direct-seeded rice (DSR), mechanical transplanting of rice and crop diversification with legumes. These interventions have the potential to reduce energy, water and carbon (C) footprints from the R–W system. Rice residue retention with Happy Seeder and adoption of zero tillage (ZT) for wheat establishment have significantly lowered the environmental footprints, with increased soil C sequestration due to additions of large amounts of plant-mediated C input. Residue mulching has helped increase root length of wheat by ~25% and root length density by ~40% below 15 cm depth, compared to no mulching. The Happy Seeder saved ~30% of irrigation water due to reduction of soil evaporation by ~42–48 mm through residue mulching. Crop cultivation on permanent raised beds is less energy-intensive and results in ~7.8–22.7% higher water use efficiency yet crop productivity in long run could be affected due to reduced root growth on beds. The puddled transplanted rice (PTR) established under wet tillage, however, can decrease the water percolation losses by 14–16% and crop water demand by ~10–25%, and it forms hard pan in soil plough (7–10 cm) layer due to increased soil bulk density. Water stagnation under continuously flooded PTR is the major source of methane emissions with serious environmental implications. Methane emissions from flooded rice can increase global warming potential by 18.1–27.6% compared to intermittently flooded rice with multiple aerations. The conventional tillage can favor the germination of grassy weeds in wheat, while the broad-leaved weeds increase under zero tillage. Zero tillage with mulch load conserved ~4.0% higher moisture due to ~2.3% lesser soil temperature and evaporated ~27.6% lesser than the conventional tillage. Delayed rice transplanting with short-duration variety has potential of saving of up to ~140 mm of irrigation water in the semiarid areas of NW IGPs. Although the DSR had lower yield potential than the PTR, it saved ~50% irrigation water. The laser land leveling technology saved ~30% irrigation water and ~25% electricity and had a yield advantage of ~4%, compared with PTR on un-leveled fields. The mechanical transplanted rice had higher grain yield and more water saving than the manual transplanting or DSR. The review demonstrates that a single technology may not be applicable everywhere and integrated approaches with the multiple criteria—productivity, economics, energy and environmental sustainability—would be required to address the unsustainability issues of the R–W system of the NW IGPs. There is a need to elucidate and disseminate various site- and context-specific RCTs appropriate for the region to address the unsustainability issues and challenges of the system. Sustainable R–W production technologies with reduced water, energy and C footprints are required for increased water and energy productivity and C sequestration for the NW IGPs of South Asia.

Mapping Brick Kilns to Support Environmental Impact Studies around Delhi Using Sentinel-2

Cities lying in the Indo-Gangetic plains of South Asia have the world’s worst anthropogenic air pollution, which is often attributed to urban growth. Brick kilns, facilities for producing fired clay-bricks for construction are often found at peri-urban region of South Asian cities. Although brick kilns are significant air pollutant emitters, their contribution in under-represented in air pollution emission inventories due to unavailability of their distribution. This research overcomes this gap by proposing publicly available remote sensing dataset based approach for mapping brick-kiln locations using object detection and pixel classification. As brick kiln locations are not permanent, an open-dataset based methodology is advantageous for periodically updating their locations. Brick kilns similar to Bull Trench Kilns were identified using the Sentinel-2 imagery around the state of Delhi in India. The unique geometric and spectral features of brick kilns distinguish them from other classes such as built-up, vegetation and fallow-land even in coarse resolution imagery. For object detection, transfer learning was used to overcome the requirement of huge training datasets, while for pixel-classification random forest algorithm was used. The method achieved a recall of 0.72, precision of 0.99 and F1 score of 0.83. Overall 1564 kilns were detected, which are substantially higher than what was reported in an earlier study over the same region. We find that brick kilns are located outside urban areas in proximity to outwardly expanding built-up areas and tall built structures. Duration of brick kiln operation was also estimated by analyzing the time-series of normalized difference vegetation index (NDVI) over the brick kiln locations. The brick kiln locations can be further used for updating land-use emission inventories to assess particulate matter and black carbon emissions.

Fertigation Effects on Nutrient Use Efficiency, Energy Productivity, and Economics of Coconut (Cocos nucifera L.) Cultivation in the Eastern Indo-Gangetic Plains of South Asia

ABSTRACT Drip fertigation has potential to reduce fertilizer dose in comparison to surface application in coconut (Cocos nucifera L.) by increasing its’ use efficiency in the Eastern Gangetic plains of South Asia. A long-term field experiment (2007–2013) was conducted on Inceptisol to evaluate 100% of the soil test-based recommended fertilizer dose (RDF; N:P2O5:K2O applied at 500:250:750 g palm−1 year−1) in soil with ring basin irrigation as conventional, 100%, 75%, 50%, 25%, and 0% of the RDF through drips. The fertigation level of 75% RDF resulted in 32%, 19%, 39%, and 16% higher copra yield, energy productivity, net return, and benefit-cost ratio, respectively, over conventional. Increasing trend of nutrient use efficiency was observed with decreasing dose of N, P and K. Use efficiencies decreased from 50.4 kg copra kg−1 N, 230.7 kg copra kg−1 P, and 40.5 kg copra kg −1 K (with 25% of the RDF through drip) to 6.1 kg copra kg−1 N, 27.8 kg copra kg−1 P, and 4.9 kg copra kg−1 K (with 100% RDF through ring basin irrigation). Fertigation with 75% RDF in drip had the highest copra yield (3.19 t ha−1), energy output (206082 MJ ha−1), energy productivity (187 g copra MJ−1), net returns (US $ 3073 ha−1), and benefit–cost ratio (2.36) compared to others.

Precision nitrogen management improves grain yield, nitrogen use efficiency and reduces nitrous oxide emission from soil in spring maize

Precision nitrogen (N) management sustains high grain yield with low N optimum dose and thus may help reduce the escape of reactive nitrogen from soils to the atmosphere. Two-year field studies were conducted at two locations in sub-tropical and sub-humid climate in Indo-Gangetic plains of South Asia with the objectives to establish precision N management technology for fertilizer N topdressings in spring maize while quantifying nitrous oxide emission from soil. A significant positive correlation of 0.64 to 0.90 between LCC (Leaf color chart) scores and leaf N concentrations at different growth stages indicated that LCC scores can successfully be used as an index of leaf N content for precision N management in spring maize. A close linear relationship (R2 = 0.75) between chlorophyll meter (SPAD) readings and LCC score showed that like SPAD meter, LCC score can reliably consider leaf greenness as an indicator of leaf N concentration. Cate-Nelson plot of LCC scores verses relative grain yield expressed LCC score 5 as the threshold for sustaining potential yield. Fertilizer N topdressings based on threshold leaf greenness of LCC 5 produced 6 to 10 percent higher grain yield with improved recovery and agronomic efficiencies in comparison to soil-test based N recommendations. Nitrous oxide emission estimated using Cool Farm Tool (CFT); an empirical model specified that application of 120 kg N ha−1 at LCC 5 down turned nitrous oxide emission by 8.0 percent compared to soil test-based N management.

Effect of conservation tillage and rice-based cropping systems on soil aggregation characteristics and carbon dynamics in Eastern Indo-Gangetic Plain

Traditional rice–wheat cropping system, which follows wet puddling in rice and conventional tillage in wheat, is deteriorating soil health resulting yield stagnation in the Indo-Gangetic Plains of South Asia. Conservation agriculture which endorses minimum soil disturbance, residue retention and crop diversification not only improves soil health but also reduces the CO2 concentration in atmosphere. We hypothesized that adoption of conservation agriculture could improve the soil health and soil organic carbon in comparison with conventional practices. A field experiment was conducted during 2012–2015 to observe the effects of different tillage practices and cropping systems on soil aggregation and carbon dynamics. The experiment comprised of three cropping systems, viz. rice–wheat, RW; rice–maize, RM; rice–lentil, RL, practiced in three tillage practices, viz. conventional tillage, CT; reduced tillage, RT; reduced tillage with 30% residue, RT30 in factorial randomized block design. Adoption of RT and RT30 resulted in higher macroaggregate content of 51.7 and 61.2%, respectively, in comparison with CT. Total water stable aggregates and mean weight diameter (MWD) of aggregates were considerably higher in RT and RT30 treatments, and the effect was most pronounced in the upper 0–15 cm soil layer. The rice–maize cropping system registered the highest macroaggregate content, water stable aggregates (WSA) and MWD of 55.6%, 80.0% and 2.28 mm, respectively, in the upper surface soil. The rice–maize cropping systems under RT30 recorded the highest total soil organic carbon (SOC) stock (51.0 Mg ha−1) in comparison with other systems after 3 years of experimentation. Reduced tillage and residue management resulted in positive changes in soil infiltration rate. The effect of tillage operations and cropping systems on different soil properties (aggregate distribution, WSA, MWD and geometric mean diameter of aggregates, SOC stock, Bulk density) was mostly limited to surface layer of soil.

Energy use efficiency of crop residue management for sustainable energy and agriculture conservation in NW India

In the Indo-Gangetic plains of South Asia, the triple challenges of diminishing farm profitability, deteriorating natural resources and energy deficits threaten conventional agricultural sustainability. This threat is intensified by the open field burning of crop residues that not only squander an indirect renewable source of energy but also impair the soil and environment quality. The crop residues can be used as organic manure by retaining the residues as mulch in the field. After a long term (5-yrs) study, it was concluded that crop residues biomass contributed maximum (∼79%) in total input energy (1,68,556 MJ ha−1) in conservation agriculture (CA) based systems, however fertilizer application (non-renewable energy source) contributed maximum (∼50%) to the total energy (40,636 MJ ha−1) in conventional tillage (CT) based maize-wheat cropping system.CA based maize systems recorded higher input energy and energy intensiveness by 23 and 57% respectively, and recorded almost 44% lower energy use efficiency and energy productivity compared to CT based maize systems. On 5 years average basis, Zero tillage based maize-wheat-mungbean with nutrient expert cropping system(ZT/MWMb + NE) utilized 351% more input energy, which resulted in25%higher output energy and 363% higher EI compared to CT/MW (40,636 MJ ha−1, 4,20,197 MJ ha−1, 39.60 MJ USD−1).

Conservation Agriculture-based Sustainable Intensification of Cereal Systems Leads to Energy Conservation, Higher Productivity and Farm Profitability

In the Indo-Gangetic Plains of South Asia, the quadruple challenges of deteriorating soil quality, declining groundwater, energy shortages, and diminishing farm profitability threaten sustainability of conventional till (CT)-based cereal production systems. A 5-year study was conducted to evaluate the effect of conservation agriculture (CA)-based management (tillage, crop establishment, residue management, and system intensification through mungbean integration) on energy budget, water productivity, and economic profitability in cereal (rice-wheat, RW/maize-wheat, MW)-based systems compared with CT-based management. In CA systems, crop residues contributed the maximum (~76%) in total energy input (167,995 MJ ha-1); however, fertilizer application (nonrenewable energy source) contributed the maximum (43%) in total energy input (47,760 MJ ha-1) in CT-based systems. CA-based cereal (rice/maize) systems recorded higher net energy and energy-intensiveness (EI) levels of 251% and 300%, respectively, compared with those of the CT-based rice-wheat system (RW/CT) (295,217 MJ ha-1 and 46.05 MJ USD-1), irrespective of mungbean integration. MWMb/ZT+R utilized 204% more input energy, which resulted in 14% higher net energy and 229% higher EI compared with RW/CT. CA-based RW and MW systems enhanced the crop productivity by 10 and 16%, water productivity by 56 and 33%, and profitability by 34 and 36%, while saving in irrigation water by 38 and 32%, compared with their respective CT-based systems, respectively. CA-based system improved net energy, crop productivity, and profitability; therefore, it should be outscaled to improve the soil and environmental quality in north-west India.

Effects of crop residue retention on soil carbon pools after 6 years of rice–wheat cropping system

Enhancing soil organic carbon (SOC) is an important strategy to sustain and improve the soil quality, mitigate climate change and increase crop productivity under intensive tillage-based rice–wheat (RW) system in the Indo-Gangetic Plains (IGP) of South Asia. Therefore, the effects of tillage, crop establishment, and residue management practices on total as well as different pools of SOC in a sandy loam after 6 years of RW system were studied. The imposed three main plot treatments to the rice plots were: (1) ZTDSR, zero till dry seeded rice; (2) CTDSR, conventional till dry seeded rice; and (3) PTR, conventional puddled transplanted rice, and the three sub-plot treatments in succeeding wheat were (i) CTW − R, conventional tillage (CT) wheat with both rice and wheat residues removed; (ii) ZTW − R, zero tillage (ZT) wheat with both the residues removed and (iii) ZTW + R, ZT wheat with rice residue. Total soil organic content increased by 6.5–12.5% and 3.1–12.9% in different soil layers up to 0–60 cm depth in ZTDSR followed by ZTW + R over PTR followed by CTW − R practices, respectively. The corresponding increase of the oxidizable C was 4.2–28.2% and 8.2–8.5%, respectively. Significant enhancement in all the carbon pools (non-labile, less labile, labile, very labile pools, water soluble and microbial biomass carbon) and glomalin content were also recorded in ZTW + R treatment. The carbon management index was significantly higher in ZTW + R than ZTW − R and CTW − R treatments. In conservation-based agriculture systems, the principal component analysis revealed that passive pools of SOC and microbial biomass carbon were the most promising and reliable indicators for assessing soil quality. This study showed that adoption of ZTDSR followed by ZTW + R was the better crop production strategy for increasing C-sequestration, improving and sustaining the soil quality and crop productivity in the RW system. This practice also provides an opportunity to retain crop residues as an alternative to burning, which causes severe air pollution in the RW system in the IGP of South Asia.

Fertigation Effects on Productivity, and Soil and Plant Nutrition of Coconut (Cocos nucifera L.) in the Eastern Indo-Gangetic Plains of South Asia

ABSTRACTFertigation has the potential to reduce extra chemical load by improving nutrient and water use efficiency of coconut (Cocos nucifera L.), but studies demonstrating the fertilizer reduction through drip irrigation in comparison to conventional ring basin method are rare in the Eastern Indo-Gangetic Plains (IGP) of South Asia. A long-term field experiment was conducted during 2007–2013 in West Bengal, India, to study the effect of fertigation on coconut var. DXT. The experiment was laid out in a randomised complete block design (RCBD) with six treatments (control – no fertilizers and water applied with drip irrigation; 25%, 50%, 75% and 100% of the recommended dose of fertilizer (RDF), each applied with drip irrigation; and 100% of the RDF and water applied with ring basin method of irrigation (i.e., conventional method)). Nuts yield was significantly higher for 75% of RDF (24.44 t ha−1 year−1) followed by 100% of RDF, each drip irrigation (23.79 t ha−1 year−1) compared to control (21.89 t ha−1 year−1). Copra yield was significantly higher for 75% of RDF (3.19 t ha−1) compared to 100% of RDF (3.12 t ha−1) and no fertilizer (1.87 t ha−1). Nitrogen (N), phosphorus (P) and potassium (K) contents of soil increased by 4.9%, 10.4% and 9.4%, respectively, with 75% of RDF applied through drip irrigation. Microbial population showed inverse relationship with amount of fertilizer application. The most water-use efficient fertigation treatment was 75% RDF (13.48 kg copra m−3) followed by 100% RDF (13.18 kg copra m−3) with drip irrigation as compared to conventional way soil application of fertilizers through ring basin method of irrigation (4.23 kg copra m−3). Role of N on yield variability was most prominent by both available soil N status (R2 = 0.49**) and leaf N concentration (R2 = 0.51**). The study indicated that there is a great scope for reducing the N, P and K fertilizers by up to 25% of the present RDFs for coconut when applied through drip irrigation compared to ring basin method of irrigation for its higher productivity and profitability through efficient use of nutrients and water in the Eastern IGP of South Asia.

Short-term effects of tillage and residue management practices on dry matter yield and fate of 15N-urea in a continuous maize cropping system under subtropical conditions

In the Indo-Gangetic plains of south Asia, conventional tillage (CT) and removal of crop residues have been the major cause of declining soil fertility. While zero tillage (ZT) farming combined with retention of crop residues as surface mulch are well known to improve soil quality and crop productivity in different climatic zones, only limited knowledge exists on the performance ZT technology in the Indo-Gangetic plains. A field study was conducted under subtropical arid climate to elucidate short-term effects of different tillage, residue mulch and N fertilizer regimes on the productivity of irrigated maize grown for five cropping seasons. Treatments included CT and ZT; each with mulch (M+) or without mulch (M−), and with N (N+) or without N (N−). Fate of the fertilizer-N applied to the 5th maize crop was also investigated using 15N tracer. After five cropping seasons, soil organic C (SOC) in the arable soil layer was higher under ZT compared to CT (29% increase), under M+ compared to M− (16% increase) and under N+ compared to N− (13% increase). Highest SOC was recorded under ZT-M+-N+ treatment (19.1 Mg ha−1) and the lowest under CT-M−-N− (10.7 Mg ha−1). Nitrogen application increased the grain yield; the increase was higher under ZT than under CT in three cropping seasons. Mulch application reduced the grain yield in four cropping seasons. During all growing seasons, the grain as well as total biomass yields were highest under ZT-M−-N+. Recovery of the fertilizer-N in soil (0–100 cm depth) ranged from 28 to 39% of the applied with lowest recorded under ZT-M−. The fertilizer-N recovery in plant was highest (40%) under ZT-M−, whereas the total fertilizer N recovery in the soil-plant system was not influenced by tillage or mulch regimes. Plant-N derived from soil (Ndfs) was higher under ZT compared to CT (47% increase), and under M+ compared to M− (15% increase); the highest Ndfs was recorded under ZT-M− (31–68% increase). While mulch had no effect on the added-nitrogen-interaction, the latter was significantly higher under CT compared to ZT (65% increase). Results suggested that as compared to other tillage/mulch regimes, ZT without mulch produced similar or higher grain yield and showed highest fertilizer-N use efficiency in continuous maize cropping system under subtropical conditions prevailing in the Central Punjab, Pakistan.

Evaluation of long-term conservation agriculture and crop intensification in rice-wheat rotation of Indo-Gangetic Plains of South Asia: Carbon dynamics and productivity.

In the context of deteriorating soil health, stagnation of yield in rice-wheat cropping system (RWCS) across Indo- Gangetic plains (IGP) and environmental pollution, a long term field experiment was conducted during 2009-2016 taking four crop scenarios with conservation agriculture (CA), crop intensification and diversified cropping as intervening technology aiming to evaluate the sustainability of the systems. Scenario 1 (S1) represented conventional farmers' practice of growing rice and wheat with summer fallow. In scenario 2 (S2) and scenario 3 (S3), legume crop was taken along with rice and wheat with partial CA and full CA, respectively. Conventional RWCS was replaced with rice-potato+maize- cowpea cropping system with partial CA in scenario 4 (S4). The S3 scenario registered highest total organic carbon (TOC) stock of 47.71 Mg C ha-1 and resulted in significant increase of 14.57% over S1 (Farmer's practice) in 0-30cm soil depth after 7 years of field trial. The S4 scenario having intensified cropping systems recorded lowest TOC of 39.33 Mg C ha-1 and resulted in significant depletion of 17.56% in C stock with respect to S3 in 0-30cm soil depth. The TOC enrichment was higher in S2, S3 and S4 scenario in the surface soil (0-10cm) compared to S1. At lower depth (20-30cm), the TOC enrichment was significantly higher in S2 (12.82 Mg C ha-1) and S3 (13.10 Mg C ha-1 soil) over S1 scenario. The S2 and S3 scenario recorded highest increased allocation of TOC (3.55 and 6.13 Mg C ha-1) to passive pool over S1. The S2 (15.72tha-1), S3 (16.08tha-1) and S4 (16.39tha-1) scenarios recorded significantly higher system rice equivalent yield over S1 (10.30tha-1). Among the scenarios, S3 scenario had greater amount of total soil organic carbon, passive pool of carbon and higher system rice equivalent yield, thus, is considered the best cropping management practice to maintain soil health and food security in the middle IGP.

Development of Sugarcane-cum-Potato Planter for Mechanisation of Simultaneous Planting of Sugarcane and Potato

Sugarcane and potato are the two major cash crops cultivated in the Indo-Gangetic plains of South Asia. Growing potato as intercrop with sugarcane has a synergistic effect on sugarcane, resulting in increased economic returns to farmers. In order to mechanise simultaneous planting of sugarcane and potato for intercropping, a new planting machinery named as sugarcane-cum-potato planter was designed and developed at ICAR-Indian Institute of Sugarcane Research, Lucknow, India. It was equipped with furrowers for opening of furrow and ridge making in between furrows, sett cutting unit for cane planting, potato seed tuber metering mechanism for potato planting, covering unit to cover planted sugarcane setts and potato and insecticide application unit. The designed equipment planted two rows of sugarcane in furrows and two rows of potato on ridges simultaneously in single pass. Picking and dropping of seed potato were automatic, whereas sugarcane seed stalk feeding for sett cutting was manual. Field testing of the developed planter was conducted at IISR farm in sandy loam soil. The effective field capacity of planter was 0.127 ha h−1. Average soil cover on sugarcane setts was 45 mm. Average depth of seed potato tuber placement on the ridges was 40 mm, and average tuber to tuber spacing was 192 mm. Developed machine-planted sugarcane at furrow spacing of 750 mm with average overlapping of 68 mm between the setts. The cost of planting operation with developed equipment was rupees 3160 ha−1 as against rupees 13,600 ha−1 in conventional planting. Saving in cost of planting operation was about 76% and labour about 90% with the developed planter as compared to conventional planting. Irrigation water use efficiency, yield attributes and total yield increased significantly in potato–sugarcane intercropping as compared to relay cropping of potato and sugarcane. Benefit/cost ratio in mechanised intercropping of potato and sugarcane with the developed planter was 2.57:1 followed by conventional manual intercropping (2.26:1) and manual potato–sugarcane relay cropping (1.84:1).

Physical and Chemical Properties of a Sandy Loam Soil Under Irrigated Rice-Wheat Sequence in the Indo-Gangetic Plains of South Asia

Resource conservation technologies (RCTs) such as zero tillage (ZT), dry direct seeded rice (DSR) and crop residues as mulch are known to increase productivity and profitability of rice-wheat system (RWS) in South Asia. There are, however, few studies on assessing the effect of RCTs on physical and chemical properties of soil under RWS. A field experiment on a sandy loam soil was conducted on RWS for two years at Modipuram, India involving six treatment combinations of three tillage and crop establishment methods in rice, (i) conventional puddled transplanted rice (CT-PTR), (ii) conventional dry tillage followed by direct seeding of rice (CT-DSR), and (iii) zero tillage followed by direct seeding of rice (ZT-DSR), and two green manuring options (with and without intercropping of Sesbania aculeata, -S or +S). In the succeeding wheat, rice residue (RR) was retained in sesbania green manure treatments and it was removed from no sesbania plots. Wheat was direct sown after ZT (DSW) in all the plots. Substituting PTR/ DSW without crop residues with ZT-DSR/DSW plus residue cycling reduced electrical conductivity from 0.146 dS mA¢Â€Â’1 to 0.128 dS mA¢Â€Â’1 and increased soil organic C from 5.72 g kg-1 to 6.25 g kg-1 in 0-15 cm layer. Similarly, water-stable aggregates (WSAs) >0.25 mm were 28% higher and their mean weight diameter increased by 11.9% in ZT-DSR/ DSW plus residues compared to PTR/DSW without crop residues plots. On average, there was a 23.6% increase in large (4.75-8.00 mm) aggregates and a reduction of 15.8% in finer (0.106A¢Â€Â’0.25 mm) aggregates in residue retention treatments over the no-residue treatments. In plots without puddling (ZT-DSR), the infiltration rates were higher (2.97-3.34 mmh-1) than in the CT-PTR (2.41-2.62 mmh-1). Residue retention compared to residue removal not only increased available K contents from 110.5 to 129.2 kg ha-1 but also showed favorable effects on soil matric potential and soil temperature during the wheat season. These beneficial effects on soil quality in just two years after introducing conservation tillage and residue management practices demonstrate potential to improve the long-term productivity and profitability of the RWS. However, the increased rate of infiltration under ZT with residue retention needs new irrigation techniques to minimize the loss of water through percolation during rice season.

Sustainable crop intensification through surface water irrigation in Bangladesh? A geospatial assessment of landscape-scale production potential

Changing dietary preferences and population growth in South Asia have resulted in increasing demand for wheat and maize, along side high and sustained demand for rice. In the highly productive northwestern Indo-Gangetic Plains of South Asia, farmers utilize groundwater irrigation to assure that at least two of these crops are sequenced on the same field within the same year. Such double cropping has had a significant and positive influence on regional agricultural productivity. But in the risk-prone and food insecure lower Eastern Indo-Gangetic Plains (EIGP), cropping is less intensive. During the dryer winter months, arable land is frequently fallowed or devoted to lower yielding rainfed legumes. Seeing opportunity to boost cereals production, particularly for rice, donors and land use policy makers have consequently reprioritized agricultural development investments in this impoverished region. Tapping groundwater for irrigation and intensified double cropping, however, is unlikely to be economically viable or environmentally sound in the EIGP. Constraints include saline shallow water tables and the prohibitively high installation and energetic extraction costs from deeper freshwater aquifers. The network of largely underutilized rivers and natural canals in the EIGP could conversely be tapped to provide less energetically and economically costly surface water irrigation (SWI). This approach is now championed by the Government of Bangladesh, which has requested USD 500 million from donors to implement land and water use policies to facilitate SWI and double cropping. Precise geospatial assessment of where freshwater flows are most prominent, or where viable fallow or low production intensity cropland is most common, however remains lacking. In response, we used remotely sensed data to identify agricultural land, detect the temporal availability of freshwater in rivers and canals, and assess crop production intensity over a three-year study period in a 33,750km2 case study area in southwestern Bangladesh. We combined these data with georeferenced and temporally explicitly soil and water salinity information, in addition to relative elevation classifications, in order to examine the extent of winter fallows and low productivity rainfed cropland that could be irrigated by small-scale surface water pumps. Applying observations of irrigated crop sowing dates and yields from 510 wheat, 550 maize, and 553 rice farmers, we also modeled crop intensification production scenarios within the case study area. We conservatively estimate that at least 20,800 and 103,000ha of fallow and rainfed cropland, respectively, could be brought into intensified double cropping using SWI. Scenario analysis indicates that if 25%–75% of the fallow or low-intensity land were converted to irrigated maize, national aggregate production could increase by 10–14% or 29–42%, respectively. Conversion to wheat would conversely boost national production by 9–10% or 26–31%. Irrigated rice is however unlikely to contribute >3%. In aggregate, these actions could generate between USD 36–108 million of revenue annually among farmers. Intensification therefore has important land use policy and food and income security implications, helping to rationalizei SWI investments. Crop choice, water resource allocation, and water governance will however remain crucial considerations for irrigation planners.