Carbon and Nitrogen Mineralization Kinetics in Soil Under Differential Nutrient Management Regimes in Inceptisols of Coastal India

Abstract

ABSTRACT In intensive cropping systems, nutrient, and residue management techniques have a tendency to change the soil’s carbon (C) and nitrogen (N) cycle and, consequently, its potential for sequestration and loss. To understand the carbon and nitrogen mineralization kinetics, laboratory incubation studies were conducted with soils at variable depths from a long-term nutrient management experiment on cereal-vegetable-pulse cropping system. The experiment was laid out completely randomized design with 10 treatments replicated thrice. Long-term integrated application of inorganics with organics, biofertilizers, and amendment along with crop residues showed higher carbon and nitrogen mineralization potential and lower potential was observed in soils where crops were raised without application of any nutrient inputs (control) and uncultivated fallow. It was calculated that the potential for higher levels of carbon and nitrogen mineralization existed in the surface (0–15 cm) and subsurface (15–30 cm) layers, respectively, and was negligible in the deeper layer (30–45 cm). The mineralization rate was initially faster up to 42 days of incubation, indicating proper utilization of readily decomposable soil organic matter in the labile pools and thereafter found to slow down. Addition of lime along with the integrated use of organics and inorganics has found to raise the pH to a level that provides a suitable soil environment which affects the carbon and nitrogen mineralization kinetics resulting in buildup of total organic carbon and total nitrogen in the soils. The first-order kinetic model was the best fit in explaining the kinetic parameters of C and N mineralization. Soils under integrated nutrient management (INM) with farmyard manure (FYM) along with biofertilizers, amendment, and inorganic nutrients exhibited better carbon dynamics higher C mineralization (Cmin), potentially mineralizable C (C0), rate of C mineralization (dCmin/dt), and C mineralization quotient (qM), whereas soils applied with similar combinations with vermicompost was found effective for better nitrogen dynamics in terms of enhanced N mineralization (Nmin), potentially mineralizable N (N0), rate of N mineralization (dNmin/dt) and active N fraction over control and fallow soils. Integrated application of inorganic and organic inputs with crop residues over the years has shown beneficial impacts on soil carbon and nitrogen mineralization processes and their kinetics.