Soil Organic Carbon in Relation to Nutrient Regimes and Crop Rotation Under Rice-Based Cropping System.

A field study was conducted during 2009–2012 on a soil that had been under organic farming practice since 2003. The treatment comprised three nutrient regimes, i.e., organic farming (OF), integrated nutrient management (INM), and recommended dose of chemical fertilizers (CF) under rice-based (Oryza sativaL.) cropping system with wheat (Triticum aestivumL) and vegetable crops for three consecutive years. The experiment was conducted using a split-plot design with three replications. The effect of fertilization practices and crop rotation was evaluated on changes in soil organic matter, soil organic carbon, and its different fractions as well as on crop yield. The highest total organic carbon (CT), oxidizable carbon (Cox), microbial biomass carbon (CMB), and labile carbon (CL) content after three years of crop cultivation were 27.26 mg g−1, 13.00 mg g−1, 0.72 mg g−1, and 7.48 mg g−1, respectively, in soil receiving no chemical fertilization. The percent microbial biomass carbon in total soil organic carbon varied from 1.88–2.20 under CF, from 2.09–2.18 under INM, and from 2.5–2.57 under OF. Organically fertilized soil had much higher carbon management index (147–161) compared with chemically fertilized soil (63–82). INM-based fertilization increased the yield of wheat, broccoli (Brassica oleracea Botrytis cymosa), and cabbage (Brassica oleraceavar.capitata), by 10.2%, 4.9%, and 3.8%, respectively, compared with chemically fertilized soil. However, organic fertilization improved the yield of rice and carrot (Daucus carota) by 8.3% and 4.5%, respectively. INM practice was more economical than organic practices but the latter was more beneficial when produce was sold at a premium price. [ABSTRACT FROM PUBLISHER]