Soil Carbon and Biochemical Indicators of Soil Quality as Affected by Different Conservation Agricultural and Weed Management Options

Burning of agricultural residues, cultivation of single crop varieties such as rice (Oryza sativa L.) and wheat (Triticum aestivum L.), and traditional soil tillage practices collectively contribute to the degradation of environmental quality, water systems, and soil resources. To address these issues, conservation agriculture (CA)-based crop management practice has emerged as one of the viable options. The current study was conducted with the aim to evaluate the effect of CA and weed management (WM) practices on carbon dynamics and biochemical properties of soil. The experiment included two factors, viz., CA and WM practices. The CA levels vary from conventional agriculture to partial CA (pCA1, pCA2, and pCA3) and full CA, while WM had three levels consisting of chemical control, integrated weed management, and weedy check. The results demonstrated that soil organic carbon (SOC) under the full CA treatment, was 30.6, 23.5, and 20.6 percent higher than conventional agriculture (T1), partial CA1, and partial CA2 practices, respectively. Similarly, labile fractions of carbon, KMnO4-C MBC, WSOC, and POC, in full CA increased by 46.3, 52.3, 152.4, and 15.6 percent, respectively, over conventional agriculture. Nonetheless, the total organic carbon exhibited no significant impact. The highest SOC stock was sequestered under full CA treatment, which was higher by 26.5 to 40.6 per cent than the rest of the CA treatments. Among biological properties, full CA resulted in 104.3 and 40.6 percent higher dehydrogenase and alkaline phosphatase activity than conventional agriculture. The impact of weed management practices was significant for KMnO4-C, with very labile carbon and alkaline phosphatase activity only in the surface soil layer. Soil quality index (SQI) followed the decreasing order as full CA (0.94) > partial CA3 (0.88) > partial CA2 (0.78) partial CA1 (0.77) > conventional agriculture (0.67) under different CA treatments, whereas WM followed herbicide (0.82) > weedy check (0.81) > IWM (0.80). The current study offered incredible information on soil carbon and biological indicators to monitor soil quality changes in rice–wheat cropping systems in response to conservation agriculture practices.