| Increase in greenhouse gas emissions resulted by human activities is one of the key reasons for climate change. As a big agricultural country, China's agriculture not only produces food and other commodities, and it is also the main source of N2O emissions. The study of estimation of agricultural N2O emissions in China and its future trends is of great importance for understanding of agriculture's contribution to climate change. This research studied the IPCC Guidelines for National Greeenhouse Gas Inventories and effects of elevated CO2 on N2O emissions from cropland. Applying GAINS model and"Livestock and Crop Production Dynamics model", agricultural N2O emissions and mitigation potential of N2O emissions from cropland were simulated under different scenarios in China. The main conclusions as follows:(1) Through comparative analysis on"1996 IPCC Guidelines","2000 IPCC Guidelines"and"2006 IPCC Guidelines", the new features of"2006 IPCC Guidelines"was summarized as follow. Except emission factors for liquid/slurry and cattle and swine deep bedding, all other emission factors for manure management in"2006 IPCC Guidelines"are lower than those in 1996 and 2000. EF1 for direct N2O emissions from managed soil has changed from 0.0125 to 0.01 kg N2O-N/kg N. EF5 for indirect N2O emissions from N leaching and runoff has changed from 0.025 to 0.0075 kg N2O-N/ (kg N leaching/runoff). Meanwhile based on the importance of sources and the data availability,"2006 IPCC Guidelines"provided a three-tier methodology to estimate N2O emissions. Because of more strictly demand on activity data and country specific emissions factors in the"2006 IPCC Guidelines", further research on agricultural N2O emission factors is needed in China, and it is necessary to establish a statistical data system for national greenhouse gas inventory gradually and add all of the data required by"2006 IPCC Guidelines"into national statistical systems.(2) Elevated CO2 inhibited the N2O emissions from cropland, but the inhibiting effect of elevated CO2 decreased as the N fertilizer increased. The inhibiting effect of elevated CO2 was significant in normal N and zero N treatments, but not significant in low N. There was a decreasing trend of N2O emissions resulted by N fertilizer under elevated CO2, but not significant.(3) Because of the increasing livestock and N fertilizers, there is an increasing trend in agricultural N2O emissions from 2000 to 2030. Total agricultural N2O emissions in 2000 are 1533 kt N2O for INMIC_central, with an increase of 31 percent by 2030. N2O emissions from cropland are 1258 kt N2O in 2030 which account for 80% of total agricultural N2O, with an increase of 37 percent. N2O emissions from manure management only increased 3 percent by 2030. Agricultural N2O emissions mainly come from Shandong, Henan, Sichuan, Hebei, Jiangsu, Hunan, Yunnan and Anhui province.(4) Base on the analysis of the effectiveness, cost and adaptability of mitigation measures in China, the mitigation potential of N2O emissions from cropland was simulated by GAINS model. Through deep or mixed application of nitrogen fertilizer, the use of nitrogen fertilizer can be reduced by 1897 kt in 2030, saving costs of 7.8 billion yuan and reducing 85 kt N2O emissions from cropland. Through the optimized timing of fertilizer application such as long-acting fertilizer or slow fertilizer, it can reduce nitrogen fertilizer more than 1580 kt N, with 6.5 billion yuan saved and 70 kt N2O reductions. However, reducing nitrogen fertilizer and optimized timing of fertilizer application can not change the emission trend. N2O emissions from cropland reach the peak in 2015 by the application of nitrification inhibitors and then decrease, with a mitigation of 320 kt N2O in 2030. Precision farming is the goal of agriculture development, but the input of capital and technology can not be quantitatively evaluated. Total of 140 kt N2O reduction was projected through the adoption of precision farming by 2030.
|
PDF Full Text Request