Effects Of Warming And Straw Return To Rice Growth And Greenhouse Gas Emissions In Northern Rice Fields

Under the background of global climate change,greenhouse gas emissions from rice fields have attracted extensive attention.At the same time,straw returning,as a rice field management measure that can not only improve soil fertility,but also have ecological benefits,has been widely used in northern rice fields.Therefore,to explore the impact of straw returning to the field on rice growth and greenhouse gas emissions in northern paddy fields under the background of warming,and to reveal its change law and mechanism can provide a basis for predicting the impact of future climate change on agricultural production and ecological benefits.In this study,the rice variety"Beijing 2",which is widely planted in Northeast China,was used as the experimental material.Using the field open active warming system,four treatments were set:control（CK）,warming（T）,straw returning（R）and warming returning interaction（TR）.The effects of warming straw returning interaction on rice growth and greenhouse gas emissions in northern paddy fields were studied,and the comprehensive greenhouse effect of warming straw returning interaction was evaluated.The results show that:（1）The decomposition speed of straw treated with TR and R showed a single peak distribution,and the decomposition rate of straw showed a gradual upward trend.Affected by temperature and soil moisture,the decomposition rate was low in the early stage,increased rapidly in the middle stage,increased slowly in the later stage,and reached the maximum in mid and late September.At the same time,the straw can not rot completely.The decomposition rate of straw treated with TR and R shows a downward trend year by year,and the degree of straw decomposition is between 60-75%.（2）After T,R and TR treatments,the dry matter weight of stem sheath,leaf and aerial parts increased to different degrees compared with CK.The overall change trend of dry matter weight of stem sheath,leaf and aerial parts of rice at jointing stage of each treatment at jointing stage was TR>T>R>CK;The overall performance of panicle weight and aboveground dry weight was TR>T>R>CK;the change trend of dry matter weight of stem sheath,leaf,panicle and aboveground part of rice at the mature stage was T>TR>R>CK.（3）T,R and TR treatments all increased rice yield,and the overall yield trend was TR>T>R>CK.From the perspective of yield composition,both T,R and TR treatments can increase the effective panicle number and seed setting rate of rice;T and R treatments generally reduce the number of grains per panicle,but TR treatment increases the number of grains per panicle;T The 1000-grain weight of rice decreased by the treatments,the1000-grain weight of rice was increased by the R treatment,and the 1000-grain weight of the TR treatment was decreased overall compared with the CK.（4）The paddy ecosystem is generally the source of CO₂ and CH₄,showing a multi peak change from June to September.The variation range of CO₂ and CH₄ emission fluxes is0.32～248.92 mg m^-2 h^-1 and 0.05～10.84 mg m^-2 h^-1,respectively.The order of total cumulative emissions of CO₂ and CH₄ from each treatment was TR>R>T>CK.T,R and tr treatments could significantly increase the emissions of CO₂ and CH₄（P<0.05）.The variation range of N₂O emission flux was-3.25～68.20μg m^-2 h^-1.Warming had no significant effect on N₂O emission,and straw returning significantly increased N₂O cumulative emission.Based on the mean value of three-year data,it can be found that compared with CK,T,R and TR treatment increased the total cumulative emission of N₂O by 33.41%,63.00%and 72.60%respectively.（5）Compared with CK,T,R and TR treatments all increased the global warming potential（GWP）of CO₂,CH₄ and N₂O,and the difference between R and TR and CK reached a significant level,while the GWP of N₂O and CK under T treatment had no difference.Significant differences.The GWP of CK and T treatment was mainly contributed by CO₂,and the three-year average contribution rates were 45.51%and 56.39%respectively.The total GWP of R and TR treatment was mainly contributed by CH₄,and the average contribution rates were 48.89%and 50.12%respectively.Compared with CK,the greenhouse gas emission intensity（GHGI）of T,R and TR treatments increased by 10.41%～45.10%,65.10%～129.31%and 77.75%～160.46%,respectively.The difference between R and TR treatments and CK reached a significant level.CK treatments did not differ significantly.