Assessment of soil carbon mineralization and stock in mineralogically different agricultural soils of India

A study was conducted to assess the influence of different soil types on soil organic carbon (SOC) mineralization, stock and related soil properties in the four major soils of India. The results revealed that both soil type and depth had significant influence on SOC mineralization and SOC stock. At 0-20 cm soil depth, C mineralization, SOC stock, labile C fractions such as, Walkey and Black C (WBC), permanganate oxidizable C (KMnO₄-C), microbial biomass C (MBC), microbial indices and other soil physicochemical properties significantly differed among soil types. At 20--40 cm depth, most of these soil parameters had decreasing trend. At 0-40 cm depth, the amount of SOC stock was found in the order: Mollisol (31.7 Mg ha^-1) > Vertisol (24.4 Mg ha^-1) > Alfisol (20.1 Mg ha^-1) > Inceptisol (17.0 Mg ha^-1). The minimum (1.18 Mg m^-3) and maximum (1.35 Mg m^-3) bulk density (BD) was found in Mollisol and Inceptisol, respectively. Bulk density was found to be negatively related to SOC stock and WBC. Labile C fractions were found to directly influence C mineralization. Pearson correlation coefficients indicated positive and significant (p=0.05) correlation among C fractions, stock and nutrients. Principal component analysis (PCA) depicts high variations in soil properties among different soil types. Biplot clearly showed that most of the C fractions and nutrients were higher under Mollisol. In terms of accumulation of labile C and protection of SOC, Inceptisol and Alfisol behaved similarly probably due to similar soil texture and type of clay as well as lesser input of organic matter.