Soil carbon reserves in Some Bio-climatic regions of India as influenced by global warming.

Abstract

Soil carbon has a global importance since it plays an important role in global carbon cycle and thus influencing the mitigation of atmospheric levels of green house gases with reference to CO2. There is an increasing concern about the soil quality vis-à-vis organic carbon content in soils due to global warming and enhanced CO2 concentration in the atmosphere. This has led to estimate carbon stock in soils at global and regional levels. A number of methods has been used to estimate changes in soil organic carbon stocks at the regional level. The present study was undertaken to evaluate RothC model for estimating total organic carbon (TOC) changes under three long term fertilizer experimental (LTFE) sites representing humid (Mohanpur, West Bengal), sub-humid (Kheri, Madhya Pradesh) and semi-arid (Akola, Maharashtra) climate. Mohanpur site was modelled for 3 layers (0-13, 13-23, and 23-39 cm), Kheri for 5 layers (0-20, 20-40, 40-60, 60-80 and 80-100) and Akola for only the surface layer (0-15 cm). Quantitative analysis was carried out to evaluate and validate the model, following standard statistical methods. The results showed that RothC could simulate changes in TOC in three contrasting eco-sites. Trends in TOC showed an increase in all the treatments in humid site of Mohanpur; whereas manures alone or in combination with fertilizers increased TOC in Kheri. In Akola, however, TOC remained almost similar over years for the control (no fertilizer, no manure) and 50% NPK treatments. RothC therefore followed the trends of experimental set up in terms of different management interventions in these sites. Relations were worked out between global warming and modelled TOC stocks. Generally to estimate such warming effect on TOC held in terrestrial soil, RothC considers top soil with varying depth as a single homogeneous layer. We used three layers of soil for Mohanpur and five layers for Kheri instead and generated datasets for modelled TOC stocks for these two sites. This was compared with the same site TOC stock considering 0-39 for Mohanpur and 0-100 cm for Kheri. The modelled TOC stocks, considering soil as a multilayer component, captures the real scenario of global warming and its related consequences on accelerated organic carbon decomposition and release of CO2 from soil to atmosphere. It seems the application of inorganic fertilizers in combination with organic amendments will arrest the accelerated SOC decomposition better than putting only inorganic fertilizers.