Soil physical environment and active carbon pool in rice–wheat system of South Asia: Impact of long-term conservation agriculture practices
Rishi Raj, T. K. Das, Debashis Chakraborty, Ranjan Bhattacharyya, Subhash Babu, Prabhu Govindasamy, Vikash Kumar, Utpal Ekka, Suman Sen, Sonaka Ghosh, Arkaprava Roy, Tarun Sharma
Abstract
Soil degradation, carbon depletion, and resource degradation have questioned the sustainability of rice–wheat system (RWS) of South Asia. Therefore, we assessed the changes in soil physical properties and carbon pool in a ten-year old CA system undertaken in a clayey loam soil. Results revealed that a triple zero-tillage (TZT) system with crops residue [i.e., ZT direct-seeded rice (ZTDSR)+mungbean residue (MR) - ZT wheat (ZTW)+rice residue (RR)- ZT mungbean (ZTMB)+wheat residue (WR) (CA5)] resulted in higher soil aggregates than conventional tillage [CT, i.e. puddled transplanted rice (PTR)-conventional tillage wheat(CTW)], double zero-tillage (DZT) [i.e., ZTDSR-ZTW (CA1), ZTDSR+WR-ZTW+RR (CA2), ZTDSR+WR+brown manuring (BM)-ZTW+RR (CA3)] and TZT without residue [(i.e. ZTDSR-ZTW-ZTMB) (CA4)]. The CA5 also led to higher proportion of large macroaggregates (>2 mm), whereas microaggregates were higher under CT. The bulk density of soil at 0-5 cm depth was reduced by 9.9% under CA5 than CT. Soil penetration resistance (PR) was increased by 22.4% at 5-15 cm soil in CT system. Soil infiltration rate (58.4 cm h −1), sorptivity (239.5 cm h –1/2), and saturated hydraulic conductivity (5.3 cm h −1) were significantly higher in CA5 than in CT. Similarly, macroaggregate-associated active carbon pool was 106% higher in 0–5 cm soil under CA5 than in CT. The RWS productivity and net returns were 37.9 and 50.9% higher under CA5 than in CT, respectively. Thus, this study demonstrated that the CA-based rice–wheat–mungbean system (CA5) would be an alternative to conventional PTR-CTW system in the Indo-Gangetic Plains of India and in similar agro-climatic situations of South Asia.