Carbon sequestration strategies in rainfed production systems of India

Abstract

To counter the adverse effects of climate change and global warming is an urgent need especially in view of the targets set by India for the reduction of CO2 emissions of its gross domestic product by 20-25% by 2020, below 2005 levels. In the light of this, the endeavor to enrich soil organic carbon (SOC) stocks by sequestering atmospheric carbon is crucial and so too is the need to understand soil health and crop productivity under different management strategies. Optimum levels of SOC can be managed through the adoption of appropriate crop rotation (Wright and Hons, 2005), fertility management, using inorganic fertilizers and organic amendments (Schuman et al., 2002; Mandal et al., 2007; Majumder et al., 2008) and tillage methods (Lal, 2009). Soils in rain-deficit environments of the tropical, sub-tropical regions are inherently low in SOC, and agronomic yield is related to soil quality. Therefore, reversing the declining trend of SOC stock is essential to enhancing agronomic productivity through balanced application of plant nutrients (i.e., N, P, K, S, Zn, Mo). Crop cultivation adversely affects the distribution and stability of soil aggregates and reduces SOC stock in soils (Kong et al., 2005). The magnitude of reduction in SOC due to cropping, however, varies depending upon the climatic conditions and intensity of cropping (Lal, 2004). The rate of decomposition/ mineralization of SOC stock is generally higher in the tropics than in temperate regions (Jenkinson and Ayanaba, 1977). Nonetheless, crop species also play Soil Carbon Sequestration Strategies in Rainfed Agriculture Ch Srinivasarao, Sumanta Kundu, Vijay Sandeep Jakkula, Sharan Bhoopal Reddy, R. Prakash Naik, V. Rupendra Manideep and K. Veeramani Central Research Institute for Dryland Agriculture, Santoshnagar, Saidabad (P.O.), Hyderabad, 500 059, Andhra Pradesh an important role in maintaining SOC stock through differences in quality and quantity of the residues returned, which determine the mean residence time (MRT) of SOC (Mandal et al., 2007). Once the pathways of carbon sequestration in soils are identified, suitable agricultural strategies may be developed that have the potential to improve SOC stocks and thus attenuate CO2 loading into the atmosphere and curb global warming (Lal, 2009). Most of the research so far on C sequestration in agricultural soils is confined to temperate regions while little information is available from tropical and subtropical countries including India (Velayutham et al., 2000; Lal, 2004). In India, C sequestration was studied only under irrigated conditions till now. There has been no study in semiarid rainfed conditions, where water stress, high temperature and low biomass are common features. Most of the crop management impact studies on soil carbon sequestration are limited to only surface (0.15 m) or root zone (Paustian et al., 1997).