Author(s):

RK Naresh, RK Gupta, SS Dhaliwal and Vivek

Abstract: World soils possess the largest organic carbon (C) stock in terrestrial ecosystems and small changes in soil organic C (SOC) stabilization can significantly affect atmospheric C concentrations. This review has identified a range of emerging agricultural management practices in croplands and highlighted knowledge gaps and mechanisms with potentials to increase SOC stabilization that may vary with site-specific conditions. The key practices rely on the principles of: (1) Decreasing C output by minimizing disturbance to soils from tillage, and eliminating fallowing, stubble burning; and (2) Increasing C inputs by retaining stubble, adding C-rich amendments, practicing integrated nutrient management and increasing crop diversity. Effects of different land uses and soil management on dynamics of soil organic carbon (SOC) and their stabilization stock changes remains unclear under intensively cultivated rice–wheat soil profile. Results revealed that balanced fertilization and combined use of chemical fertilizers and manure increased the SOC in all the plots except the unfertilized control. Balanced fertilization (NPK) and integrated fertilization (NPK+FYM) resulted in similar increases in particulate organic carbon, carbon mineralization and microbial biomass carbon, whereas particulate organic nitrogen and microbial biomass nitrogen were more in integrated fertilization (NPK+FYM) compared with control treatment. Soil organic C and carbon stabilization stock changed positively across the fertilizer and manure treatments over the control. In the control plot, at 0–15 cm depth the soil carbon was 15.1 Mg ha^-1, respectively which increased to the 19.5 Mg ha^-1 in NPK+FYM. As compared to the initial (13.7 Mg ha^-1), the SOC stock in 0–15 cm depth increased under all the fertilized treatments in the order: NPK+FYM> N+FYM> NPK> FYM> N> control. The rate of increase in SOC (carbon sequestration) due to different land uses alone varied between 57 and 89 kg ha^-1 yr^-1, while for soil management i.e. FYM addition the rate of increase was 61 to138 kg ha^-1 yr^-1 highest being in NPK+FYM.

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