Combining soil carbon storage and crop productivity in partial conservation agriculture of rice-based cropping systems in the Indo-Gangetic Plains

Conservation agriculture (CA) is an approach to achieve the ‘Sustainable Intensification’ of the rice-wheat cropping system of South Asia. However, difficulties in adoption of the full CA principles (zero tillage, soil cover, crop diversification) have been a concern in South Asia and the Indo-Gangetic Plains region. Eventually, partial CA which comprises at least one crop with zero tillage (ZT) with or without crop residues, is being adopted in the rice-wheat system in South Asia. However, long-term impact of partial CA in diversified crop rotations on soil organic carbon (SOC) storage and crop productivity is not elaborately studied in comparison to the conventional tillage (CT) without residues in rice-wheat (conventional practice in the region). The present study concerned a 9-year experiment with a split-split-plot design testing three factors, soil tillage (main plot), crop residue management (sub-plot), and crop rotations (sub-sub-plot), respectively with permanent tillage or tillage only on rice, without or with all crop residues and rice-wheat, rice-chickpea and rice-chickpea-mungbean (six years) and rice-wheat-mungbean (three years). Soil was sampled from 0–15 cm depth for SOC storage estimation in present study. Partial CA (post-rice ZT with residues in rice-chickpea-mungbean and rice-wheat-mungbean rotations) increased the SOC concentration and carbon management index by 39% and 42% at 0–15 cm soil depth over conventional practice within nine years, respectively. Specifically, post-rice ZT resulted in 23% higher (P