Temporal Changes in Carbon Stocks in Selected Soils of Semi-Arid and Sbhumid Regions of India

Abstract

The soils that sequesters large quantities of carbon play an important role in global carbon cycles. However, the role of the carbonates as a probable source of calcium nutrition in soils is given less attention till recently. In arid, semi-arid and drier part of subhumid agro-ecoregion of tropical India, the carbon exists as inorganic carbonates and occupy much of the soil mass. It has been reported that the climate had changed from humid to semi-arid in rainfed areas of India during the Holocene period. Earlier studies on soils of tropical areas of India viz. Vertisols, alluvial and ferruginous soils, indicated that drier climate is the primary factor responsible for the depletion of Ca2+ ions from the soil solution due to the formation of CaCO3. It has also been reported that intensive agriculture during the green and post-green revolution period of Indian agriculture has resulted in depletion of organic carbon in soils. Later research on temporal data of soil organic carbon (SOC) and soil inorganic carbon (SIC) status indicated that the SOC has not decreased as envisaged though SIC has increased in selected benchmark sites which is considered as a bane to the farmers and the soil environment. Therefore, the present work was undertaken to study the temporal changes in carbon stocks of selected benchmark soils of semi-arid and subhumid areas to investigate whether the hypothesis made above holds good in the present day.

The comparison of data on carbon stock of seven benchmark sites in semi-arid and subhumid region of India indicated that the organic carbon stock increased for the surface soils (0-30 cm) and the increase varied from 1 to 101%. However, for the 0-150 cm soil depth, the results showed both increase as well as decrease in SOC. Whereas, the inorganic carbon stock in the soils for the 150 cm depth decreased in general to the tune of 3 to 93% during the last 30 years. This indicated that better management in terms of integrated nutrient management system and other interventions have helped the soils to be resilient and revert the process of soil degradation towards favourable conditions in terms of increase in organic carbon and decrease in development of inorganic carbon.