Effects of rice straw and nitrogen fertilization on greenhouse gas emissions and carbon storage in tropical flooded soil planted with rice P. Bhattacharyya a, *, K.S. Roy a , S. Neogi a , T.K. Adhya a , K.S. Rao a , M.C. Manna b a Division of Crop Production, CRRI, Cuttack-753006, India b Soil Biology Division, Indian Institute of Soil Science, Bhopal-462038, Madhya Pradesh, India 1. Introduction Rice paddy contributes toward the emissions of the most important greenhouse gases (GHGs) responsible for global warming: carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O). Soil is one of the important sources and sinks for GHGs that cause global warming and climate change (Janseens et al., 2003). Soil contributes about 20% to the total emission of CO 2 through soil and root respiration, 12% of CH 4 and 60% of anthropogenic N 2 O emissions (IPCC, 2007). Global warming may affect the global carbon cycle, thereby distorting the structure and functions of ecosystems. Organic matter concentration, which is quite low (<1.0%) in tropical soils, would become still lower and climatic change may also affect its quality (Smith et al., 2008). Soil biology and microbial populations are expected to change with changes in climatic conditions (Baker, 2004). Currently, biotic carbon sequestration is being considered a viable option for mitigating carbon emissions in the form of CO 2 and CH 4 to the atmosphere. Agricultural activities have profound short- and long-term influence on soil organic carbon (SOC). Mitigation of CO 2 emission from agriculture can be achieved by increasing carbon sequestra- tion in the soil, which implies storage of carbon as soil organic matter (Lal, 2004). Judicious nutrient management is crucial to SOC sequestration in tropical soils (Bhattacharyya et al., 2007). Adequate supply of nutrients in the soil can enhance biomass production and SOC content (Van Kessel and Hartley, 2000). Attainable carbon sequestration is essentially limited by the quantity of carbon input into the soil system. The estimated potential of agricultural intensification on SOC sequestration in Indian soils ranges between 12.7 and 16.5 Tg carbon year À1 (Lal, 2003). A recent report by Benbi and Chand (2007) describes increased productivity under improved SOC density (SOC content in the 0–15 cm soil volume) in the 0–15 cm soil layer. There is a strong need to increase SOC density to improve the quality of natural resources for sustainable crop productivity and to mitigate global warming. However, with the rapid economic and social development, tropical paddy soils are subject to degradation as characterized by low organic carbon content and low crop productivity. Therefore, it is necessary to investigate soil carbon dioxide (CO 2 ) evolution from paddy soils to better understand the mechanisms that regulate carbon storage and loss in extensively cultivated paddy fields. Furthermore, the effects of nitrogen fertilization and rice growth on variation in CO 2 emission under anaerobic conditions from paddy soils needs to be better understood. Many studies reported that the application of Soil & Tillage Research 124 (2012) 119–130 A R T I C L E I N F O Article history: Received 17 April 2012 Received in revised form 21 May 2012 Accepted 22 May 2012 Keywords: Green house gases Carbon storage Rice soil Soil carbon fractions Soil enzymes and microbial population A B S T R A C T Effects of four years of inorganic and organic nitrogen (N) management on the emission of three major greenhouse gases (GHGs): methane (CH 4 ), carbon dioxide (CO 2 ) and nitrous oxide (N 2 O), and on soil labile carbon fractions such as water-soluble carbon (C, WSC), microbial biomass carbon (MBC), KMnO 4 oxidizable organic carbon (KMnO 4 -C), carbon management index (CMI) and soil carbon storage were investigated in a flooded rice (Oryza sativa L.) field in India. The treatments included an unfertilized control, inorganic nitrogen fertilizer, rice straw + inorganic nitrogen fertilizer and rice straw + green manure. Maximum global warming potential (GWP) (10,188 kg CO 2 equivalent ha À1 ) was determined for the combined application of rice straw and green manure. Total carbon content and carbon storage in the topsoil were significantly increased for the rice straw + inorganic nitrogen fertilizer treatment. The combined application of rice straw and green manure was more effective in increasing WSC, MBC, KMnO 4 -C concentrations and CMI than the inorganic fertilizer treatments, although it increased gaseous carbon emission. The combined application of rice straw and an inorganic fertilizer was most effective in sequestrating soil organic carbon (1.39 Mg ha À1 ), resulting in a higher grain yield. Therefore, it could be the best option for improving productivity and carbon storage in the rice–rice cropping system. ß 2012 Elsevier B.V. All rights reserved. * Corresponding author at: Central Rice Research Institute, Cuttack-753006, Orissa, India. Tel.: +91 0943 8213108; fax: +91 0671 2367663. E-mail address: pratap162001@yahoo.co.in (P. Bhattacharyya). Contents lists available at SciVerse ScienceDirect Soil & Tillage Research jou r nal h o mep age: w ww.els evier .co m/lo c ate/s till 0167-1987/$ – see front matter ß 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.still.2012.05.015