Soil Carbon Pools, Mineralization and Fluxes Associated with Land Use Change in Vertisols of Central India

Abstract

Land use affects soil carbon dynamics which influence the global carbon cycle. Understanding the response of soil organic carbon (SOC) dynamics to land-use changes require size and mean residence time (MRT) of measurable SOC pools. We measured soil carbon pool sizes and decay constants of active and slow carbon pools for different land use systems (agriculture, forest and horticulture) of Central India. Long-term incubation study was carried out for quantification of active (Ca) and slow (Cs) carbon pools and MRT. Chemical fractionation technique (acid hydrolysis) was used for quantification of resistant carbon pool (Cr). The non-hydrolysable carbon (Cr) expressed as a percentage of total C varied between 65 and 68 % in the surface soil of different land use system whereas it was 78 % in sub-surface soil. The incubation study revealed that the Ca pool in different land use system ranged between 3.3 and 10 % of the total C and MRT varied from 25 to 67 days with an average value of 46 days. Our results demonstrate that the active SOC is a sensitive indicator for changes in SOC following land use change. MRT of a slow carbon pool of forest land use was 38.5 years. The MRT of slow pool C in the upper soil layer (0–15 cm) did not differ between horticulture and agriculture land use systems and was approximately 4.5 years. In agriculture land use, MRT of a slow pool of C under was only 2.3 years in sub surface plot. However, MRT of slow carbon pool (Cs) under the Farm yard manure (organic plot) increased by fourfold (17.5 years) in comparison to inorganic treatment (recommended dose of fertilizer-RDF) plot. The results clearly depict opportunity of soil carbon buildup in agriculture with good management practices (application of organic manure). The present research work will also help in improving the SOC dynamics predictive capacity of different global bio-geochemical carbon models.