Soil Organic Carbon Dynamics in a Chhattisgarh Vertisol after Use of a Rice–Wheat System for 16 Years

Long‐term impact of fertilizers and manure on fractions of soil organic C pools. The critical reasons to find out declined crop productivity. The remedies for arresting C decline and sustain productivity and soil fertility. Identification of factors responsible for poor crop yield. A comprehensive knowledge of total organic carbon (TOC) dynamics in the soil as affected by cropping system and fertilizer application is imperative for maintaining soil health. We investigated the effect of long‐term (16‐yr) use of farmyard manure (FYM), crop residues, green manure (GM) and inorganic fertilizers in rice–wheat rotation on TOC pools, and crop yields with the objective to establish an interrelationship among these parameters under long‐term rice–wheat cropping system. The study was initiated in 1999 under AICRP on a Long‐Term Fertilizer Experiment conducted at Raipur, India, with eight fertilizer treatments, that is, 100% NPK, 150% NPK, 100% NPK + ZnSO4, 100% N, 100% NP, 100% NPK + FYM, 50% NPK + GM and control (no fertilizer and manure). Results revealed that the manure addition increased the sensitive fractions of TOC such as water soluble C, acid hydrolyzable carbohydrates, soil microbial biomass carbon (SMBC). However, the percent increase was relatively lower in chemical fertilizer treatments compared to integrated use of fertilizers and manure. The particulate organic matter carbon (POMC) appeared to be the most affected one. Higher content of POMC was noticed in macro‐aggregates than micro‐aggregates and declined substantially in the aggregates of 100% N‐ and 100% NP‐treated plots leading to lower nutrient supplying capacity of the soils. Humic acid C fractions, that is, a passive pool of TOC was significantly higher in FYM in combination with balanced fertilizer treatments. These results emphasized that the integrated nutrient supply strategy is necessary to sustain the long‐term TOC storage and productivity.