Assessing the soil organic carbon stability and greenhouse gases mitigation in rice-wheat system: Seventeen-years assessment of tillage and residue management

Abstract

To mitigate greenhouse gas (GHG) emissions from the rice-wheat system (RWS), various management strategies have been explored. Long-term field experiments are particularly effective in directly comparing these strategies. We analyzed a 17-year field experiment focusing on crop establishment, conservation tillage, and residue management (CTRM) in the western Indo-Gangetic plains of India, a region highly impacted by crop residue burning and GHG emissions for its impacts on carbon sequestration, stability, and GHG mitigation in rice-wheat system. These findings have significant implications for sustainable agricultural practices in regions facing similar environmental challenges. The experiment included five scenarios: (a) Sc-1: Puddled transplanted rice (PTR) – conventionally tilled wheat (CTW); (2) Sc-2: Reduced-tillage direct-seeded rice (RTDSR) – reduced-tillage wheat (RTW); (3) Sc-3: RTDSR-RTW with one-third residue incorporation; (4); Sc-4: Zero-tillage direct-seeded rice (ZTDSR) – zero-tillage wheat (ZTW); (5) Sc-5: ZTDSR-ZTW with one-third residue retention (RR). Our analysis showed that CTRM significantly enhanced soil organic carbon (SOC) stock (by 11.41–17.28 %) and carbon sequestration (by 35.12–86.63 %) compared to conventional practice (Sc-1). Among all the scenarios, Sc-5 (ZTDSR-ZTW + RR) achieved the highest carbon management index (CMI: 150.56 and 188.11) across both the soil layers, indicating a reduced need for carbon management due to higher TOC (10.59 and 10.07 g kg⁻¹) compared to Sc-1. The highest net GHG emissions were observed in PTR/CTW (Sc-1), while Sc-5 recorded the lowest emissions, with 84.07 % reduction compared to Sc-1. Carbon footprints decreased progressively with reduction in tillage intensity and residue incorporation. This study highlights that reduced or zero tillage combined with residue retention in RWS holds substantial potential for increasing carbon sequestration, reducing net GHG emissions, and lowering carbon footprints. Additionally, this practice offers an alternative to crop residue burning, a significant contributor to air pollution in the western IGP, particularly in Punjab and Haryana, India.