Conservation agriculture influences crop yield, soil carbon content and nutrient availability in the rice-wheat system of north-west India

Context. Tillage-based agriculture has led to soil health deterioration and decline in crop productivity. Recently, zero tillage (ZT) and crop residue management has emerged as an alternative to conventional tillage. Methods. This experiment was done in northwest India over 3 years, with four treatments: (1) conventional transplanted puddle rice (TPR) + conventional tillage wheat (CTW) with 1/3 of wheat residues incorporated (TPR-[CTW.sub.RI/3i]); (2) TPR + CTW (TPR-CTW); (3) ZT direct-seeded rice (ZTDSR) + ZT wheat (ZTW) with 1/3 of wheat residues incorporated (ZTDSR-[ZTW.sub.RI/3i]); and (4) conventional tillage direct-seeded rice (CTDSR) + ZTW with full residues of both rice and wheat crop incorporated (CTDSR-[ZTW.sub.Rfr]). Two rice (CSR 30, CSR 36) and two wheat (HD 2894, KRL 213) varieties were used. Soil samples were collected after harvest at 0-15 to 15-30 cm soil depth. Key results. In rice, yield was significantly higher under conventional tillage, and variety CSR 36 outperformed CSR 30 in various yield attributes. In wheat, the number of grains per spike was significantly higher in TPR-[CTW.sub.RI/3i] than TPRZTW. After rice harvest, there was ~10% and 5% higher available N in TPR-CTW and CTDSR-[ZTW.sub.Rfr] compared to ZTDSR-[ZTW.sub.RI/3i] and TPR-[CTW.sub.RI/3i], respectively (0-15 cm depth). After wheat harvest, highest SOC content (7.5 g [kg.sup.-1]) was found under CTDSR-[ZTW.sub.Rfr] (0-15 cm depth); and highest total water-stable aggregates were observed under CTDSR-[ZTW.sub.Rfr] (37.52%; 0-15 cm depth). Compared to farmers' practise, the total global warming potential of rice-wheat cropping system was reduced by 43% with conservation agriculture-based management practises (ZTDSR-[ZTW.sub.R]l/3i). Conclusions. DSR (in rice) and ZT in wheat with full residue retention best improved soil organic carbon and nutrient availability in soil. Implications. Conservation agriculture systems can be adopted to improve crop productivity, soil health and reduce greenhouse gas emissions. Keywords: aggregate stability, crop varieties, crop yield, GHG emissions, Indo-Gangetic Plains, residue management, water-stable aggregates, zero tillage.
Introduction Rice-wheat (RW) cropping occupies a 13.5 million ha area of the Indo-Gangetic Plains (IGP) and provides food for more than 400 million people of South Asia (Kumar et al. [...]