Temporal Effects of Conservation Agriculture-Based Rice-Wheat Cropping System on Soil Aggregation and Organic Carbon Dynamics in Northwestern Indo-Gangetic Plains

Conservation agriculture (CA) is widely advocated in northwestern Indo-Gangetic plains (IGPs) as a climate-smart strategy to mitigate the adverse effects of conventional rice-wheat cropping systems. However, on-farm research exploring the effects of different durations of CA on soil organic carbon (SOC) dynamics and soil aggregation in these regions remains scarce. To address this gap, we assessed the impact of CA practiced for 2 (CA2), 4 (CA4), 8 (CA8), and 12 (CA12) years compared to conventional tillage (CT) on SOC dynamics, soil aggregation, and system productivity at the farmers' field of Nilokheri block, Haryana, India. Adopting CA for 8 to 12 years led to a significant increase in total soil organic carbon, with improvements ranging from 28 to 48% in the topsoil (0-5 cm) and 64.2% to 98.7% in the 5-15 cm compared to CT. All the fractions of SOC (very labile, labile, less labile, and non-labile C) were significantly affected due to CA practice. The CA8 and CA12 showed a respective, 34.8 and 53.8% higher carbon management index over CT in the 0-5 cm soil depth. However, long-term CA resulted in a similar to 20-25% reduction in soil inorganic carbon compared to CT. The percentages of macroaggregates and content of aggregate-associated C significantly improved under the CA8 and CA12 scenarios compared to CT. The derived regression coefficients revealed a strong positive relationship between TSOC and both rice equivalent yield and wheat yield. These findings highlight the potential of enhancing TSOC to boost agricultural productivity under CA, thereby fostering sustainable farming. Such improvements are vital for building climate-resilient cropping and supporting the widespread adoption of CA practices. The farmers in northwestern IGPs may consider adopting conservation agriculture practices for 8 years or more to benefit from enhanced SOC sequestration, soil aggregation, and yield sustainability under the climate change scenario.