Study on Carbon Footprint Under Different Cropping Patterns of Paddy Fields in the Lower Reaches of the Yangtze River
Reducing carbon emissions while ensuring grain security is currently an urgent problem that needs to be solved for optimizing agricultural planting structure.This study analyzed the influence of different cropping patterns on greenhouse gas emissions and carbon footprint of paddy fields in the lower reaches of the Yangtze River.Four treatments were considered including one single-cropping pattern(i.e.,winter fallow-rice)and three double-cropping patterns(i.e.,Chinese milk vetch-rice,winter rapeseed-rice and winter wheat-rice).Methane(CH4)and nitrous oxide(N2O)emissions were simultaneously measured by static chamber and gas chromatography methods for two consecutive years.The life cycle assessment method was used to estimate the direct and indirect greenhouse gas emissions caused by field production process and agricultural inputs.The carbon footprint was then accordingly calculated.The results showed that:(1)Double-cropping patterns significantly increased the annual CH4 and N2O emissions by 17.5％～64.5％and 60.7％～139.8％,and the annual soil organic carbon sequestrations by 17.3％～37.2％,respectively.(2)The soil organic carbon sequestrations under different cropping patters could offset 26.6％～35.6％of greenhouse gas emissions.When soil organic carbon sequestrations were taken into account,the average annual net carbon footprint per unit area for winter wheat-rice,winter rapeseed-rice,and Chinese milk vetch-rice was 13.79,11.83,and 9.07 t CO2-eq·hm-2,respectively,which was 80.6％,55.0％,and 18.8％greater than that for winter fallow-rice(7.63 t CO2-eq·hm-2).(3)Soil CH4 emissions were the most important contributor to the carbon footprint of paddy fields(61.8％～67.4％),followed by nitrogen fertilizer application(18.3％～23.9％),N2O emissions(3.3％～5.2％)and diesel combustion(2.2％～2.8％).(4)Double-cropping patterns could increase the annual grain yields and economic outputs compared with those of single-cropping pattern,while planting grain and oil crops in non-rice season significantly improved the annual net incomes.However,no significant differences in the carbon footprint per grain yield and the carbon footprint per economic output were observed between the four cropping patterns.Therefore,winter fallow-rice was a relatively low carbon cropping pattern for paddy fields in the lower reaches of the Yangtze River.Considering the carbon emission,grain security and economic output,winter wheat-rice and winter rapeseed-rice were superior to winter fallow-rice.Development of effective strategies for CH4 and nitrogen fertilizer reduction should be considered as a priority for reducing the carbon footprint of paddy fields.
carbon footprintgrain securitycropping patterngreenhouse gassoil organic carbon sequestra-tionthe lower reaches of Yangtze River
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NSTL
万方数据
