Effects Of Rice Cropping Patterns On Greenhouse Gas Emissions And Soil Organic Carbon In Paddy Fields

The problem of global warming caused by greenhouse gas emissions from farmland is attracting more and more attention.Jianghan Plain is an important rice production base in the middle reaches of the Yangtze River and even in China.The rice cultivation patterns in this region are complex and diverse,mainly consisting of traditional medium rice-winter crop pattern and ratooning rice pattern.However,the effects of different rice cultivation patterns on greenhouse gas emissions from paddy fields and soil active organic carbon pool are not well studied.This study set up through the field test of rice-wheat（RW）,rice-rape（RR）,rice-fallow（RF）and ratooning rice（Rr）of 4 kinds of rice planting mode,compared the different rice pattern greenhouse gas emissions rules,farmland soil organic carbon and rice yield components,for low carbon reduction of jianghan plain rice provide theoretical basis for model building.The main results are as follows:（1）Winter crops had different effects on rice yield in rice season,among which RR treatment had the highest rice yield and dry matter accumulation,and the annual crop yield of different rice cropping patterns showed Rr>RR>RW>RF.Compared with RF treatment,C accumulation in RR and RW treatments increased by 16.89%and 14.97%,and N accumulation increased by 0.55%and 6.99%,respectively.The C content of rice plants in Rr first season was 33.22%higher than that in regenerative season,and the N content was 1.59 times higher than that in regenerative season.（2）In non-rice season,the cumulative methane（CH₄）emissions of RW,RR,RF and Rr treatments were 14.09 kg·hm^-2,10.05 kg·hm^-2,16.45 kg·hm^-2 and 4.69 kg·hm^-2,respectively.The cumulative emissions of nitrous oxide（N₂O）were 2.21 kg·hm^-2,1.29kg·hm^-2,0.56 kg·hm^-2 and 0.74 kg·hm^-2,respectively.In rice season,compared with RF treatment,cumulative CH₄ emission of RW,RR and Rr treatments increased by 113.35%,12.65%and 114.26%,respectively（P<0.05）.The cumulative N₂O emission of RW treatment increased by 20.88%（P>0.05）,while RR and Rr treatment decreased by 26.37%and 10.04%,respectively.Compared with RF treatment,the annual global warming potential（GWP）of greenhouse gas emissions in RW,RR and Rr treatments increased by104.94%,10.82%and 84.71%,respectively（P<0.05）.The greenhouse gas emission intensity（GHGI）of RW and Rr treatments increased by 61.54%and 28.21%（P<0.05）,respectively,while the GHGI of RR treatment decreased by 15.38%.（3）Compared with RF treatment,the content of soil organic carbon in RR treatment increased by 6.30%,while the active organic carbon in Rr treatment increased by 57.48%（P<0.05）.RR treatment improved soil carbon pool management index by increasing soil steady state carbon and carbon pool index,Rr treatment improved soil carbon pool management index by increasing soil active organic carbon and carbon pool activity,and the C/N ratio and soil organic carbon storage of RR and Rr treatments were significantly higher than RF and RW treatments（P<0.05）.In conclusion,rice-rape model improves rice yield,is conducive to dry matter and nutrient accumulation in aboveground,and reduces annual greenhouse gas emissions.Meanwhile,rice-rape model has a good fixation effect on farmland soil organic carbon,which is conducive to improving soil organic carbon storage.