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In water scarce regions of South Asia, diversification of rice with maize is being advocated towards sustainability of cereal-based cropping systems. Adoption of innovative agronomic management practices, i.e., conservation agriculture (CA) and sub-surface drip irrigation (SSDI) are considered as key strategies for much needed interventions to address the challenges of water scarcity under projected climate change. Benefits from CA and SSDI concerning water economy are well-established, however, information about their complementarity and water budgeting in cereal-based systems are lacking. A field study was conducted with process-based model (HYDRUS-2D) to understand water transport, root water uptake and components of soil water balance in maize grown in rotation with wheat after five years of continuous adoption of conservation agriculture. In this study, altogether eight treatments comprising of 6 CA+ treatments (CA coupled with SSDI); permanent beds using sub-surface drip (PB-SSD) with (WR) and without (WOR) crop residue at different N rates, 0, 120 and 150 kg N ha−1 were compared with CA (PB using furrow irrigation-FI with crop residue-120 kg N ha−1) and conventional tillage practices (CT) (CT using FI without crop residue-120 kg N ha−1). Results showed that the model could simulate the daily changes in profile soil water content with reasonable accuracy in all the treatments. Simulated soil water balance indicated higher cumulative root water uptake (CRWU), lower cumulative evaporation (CE) and higher soil water retention in CA+ (PB-SSD+ crop residue at 150 and 120 kg N ha−1) than CA and CT plots. Hydrus-2D model efficiency > 0, RMSE between 0.009–0.026 and R2 value between 0.80–0.92 at P < 0.01 indicates that the model is performing efficiently. The mean evaporation from CA+ treatments was 10 and 36% less than CA and CT treatments, respectively. On average, CRWU under CA+ treatments were 14–48% higher than FI treatments. The mean cumulative deep drainage in CA+ plots was 80–100 mm less than CA and CT plots. In CA+ based plots significantly higher biomass production and radiation use efficiency were observed with reduced water use than CA and CT. Therefore, the study justifies the water-saving nature of CA+, while maintaining higher productivity and meeting the transpiration demand of crops and halting unnecessary evaporation and deep drainage losses. [ABSTRACT FROM AUTHOR]

Cotton–wheat (CW) is the second most important cropping system after rice–wheat in South Asia. Sowing of wheat after cotton is usually delayed due to late pickings coupled with time needed for seedbed preparation, resulting in low wheat yield. Lack of suitable machinery is a major constraint to direct drilling of wheat into the heavy cotton stubbles. An innovative approach with much promise is the ‘2-wheel tractor-based self-propelled relay seeder’ with seed-cum-fertilizer attachment. On-farm trials were conducted at four locations during 2009–2010 and at 10 locations during 2010–2011 to evaluate the following four wheat establishment methods in CW-dominated areas of south-western Punjab, India: (1) zero till seeding in standing cotton using a self-propelled relay seeder, (2) relay seeding in standing cotton with a manual drill without prior tillage (2010 only), (3) relay broadcast seeding in standing cotton following light manual tillage and (4) conventional sowing of wheat after cotton harvest (conventional tillage and sowing with a seed–fertilizer drill). Planting of wheat under conventional practice was delayed by 20–44 days compared with relay seeding. Seed cotton yield was also significantly higher with relay seeding due to opportunity for one additional picking. Yield of wheat sown with the self-propelled relay seeder was 41.2% and 11.8% higher than with conventional practice in 2009–2010 and 2010–2011 respectively. The increase in wheat yield under relay seeding of wheat was primarily due to higher spike density and more grains per spike. The net income from the CW system was 28.2% higher for the self-propelled relay seeder than with conventional sowing. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]