Vertical distribution of soil organic and inorganic carbon under silvipastoral system in a dry semiarid agro-ecological region, Tamil Nadu, India

Abstract

A detailed soil survey was conducted in a silvipastoral system of a dry semi-arid region of Tamil Nadu, India at 1:10,000 scale to assess the vertical distribution of soil organic carbon (SOC) and inorganic carbon (SIC) and its relation with soil properties. Around 110 soil profiles were studied and horizon-wise samples were collected from 7 representative profiles. The SOC content of the surface soil was ranged from 1.5 to 8.6 g kg^-1 with a mean value of 4.37 g kg^-1 and it irregularly distributed with depth. The SOC content had significant positive correlation with total N (r=0.513*), ex.Ca (r=0.497*) and clay (r=0.430*) (P<0.05) content of the soil. However, the SIC content ranged from 0.3 to 20.1 g kg^-1 and it either increased or irregularly distributed with depth. Correlation analysis revealed that SIC content had intricately significant positive relationship with extractable Ca²⁺ (r=0.573** P<0.01), Mg²⁺ (0.572*), clay (0.612**) and silt (0.595**) (P<0.01). There was a good relationship observed between surface SIC and SOC content (r²=0.752) compared to subsoil (r²=0.525). It might be because of the potential stabilisation of SOC by calcium from SIC in the soils under silvipastoral system of a dry semi-arid agro-ecological region.