Effects Of Different Organic Materials Application On Greenhouse Gases Emission From Cropland In Guanzhong Area

The global warming and ecological environment change caused by greenhouse gases emission is one current international focus.The main cause of global warming is the increasingofgreenhouse gases emission influenced by human activities,and thecropland ecosystem is mostly influenced in the terrestrial ecosystems.Straw returningcould change the basical physiochemical properties of soils,inevitably would affect the greenhouse gases emission.Biochar could improve soil fertility and increase field water capacity whichmightaffect greenhouse gases emission.Maize-wheat rotation is one of the major cropping systems in Guanzhong Area,in this study,farmland ecosystem of maize-wheat rotation in this region was taken as the research object,we designed 4 treatments(conventional fertilization?N?,conventional fertilization+4 t·hm^-2straw returning?NS??conventional fertilization+4 t·hm^-2biochar(NBC_low)?conventional fertilization+8 t·hm^-2biochar(NBC_high)),no fertilization and organic material application as control?CK?.The static chamber and gas chromatography method were used to monitor the seasonal dynamics of greenhouse gases emission for one year during the crop growing seasons.Our objectives are to clarify the effects of different organic materials application on greenhouse gases emission,and analyze the difference and factors of greenhouse gases emission,and further analyze NGWPand carbon footprint values resulted from greenhouse gases emission of cropland.The final goal is to provide scientific basis for cropland carbon sequestration and emission reduction in Guanzhong region.The main conclusions are as follows:?1?In the soil level,straw reurning and biochar application had different degree impacts on greenhouse gases emission,crop yield,soil organic carbon content and NGWP.Compared with N treatment,NS treatment had no significant influence on annualN₂O emission,biochar application reduced annualN₂O emission,and annual N₂O emissionof NBC_hightreatment was significantly lower than NBC_lowtreatment.The soil in the study area showedabsorbingCH₄,straw returning and biochar application both decreased CH₄ absorption.The straw returning couldincrease annual CO₂ emission,but NBC_high treatment significantly decreased annual CO₂ emission,and NBC_low treatment had no significant influence on annual CO₂emission.Compared with N treatment,the yield of maize and wheatincreased13.73%,20.37%and 7.56%,respectively,but annual yield of NBC_high treatment reduced 10.64%compared to NBC_lowtreatment.Compared with N treatment,NS treatment had no significant impacts on soil organic carbon content?SOC?,but biochar application significantly increased SOC.Meanwhile,straw returning and biochar application both decreased the NGWP and NGWP of unit yield,and NBC_hightreatment was significantly lower thanNBC_lowtreatment.?2?In the wheatfarmland ecosystem level,straw reurning and biochar application also had different degree impacts on greenhouse gases emission,winter wheatyield and the value of carbon footprint.Compared with N treatment,straw returning and biochar applictionboth decreased annual N₂O emission,and NBC_high treatmentwassignificantly lower than NBC_low treatment.Straw returning increased annual CO₂ emission,but biochar applicationshad no significant influence.Meanwhile,straw returning and biochar applications coulddecrease annual CH₄absorption.Compared with N treatment,the winter wheat yieldof NS?NBC_low andNBC_highincreasedby 34.71%?71.91%and 37.62%and 8 t·hm^-2,respectively.All the treatments in our study showed carbon net absorption,straw returning increased the value of carbon footprint compared with N treatment,but biochar applicationdecreased the value of carbon footprint,and NBC_low treatmenthadthe lowest value of carbon footprint among all the treatments of straw returning and biochar application.Comprehensive considering greenhouse gases emission and crop yield,fertilization with4 t·hm^-2straw returing and the fertilization with 4 t·hm^-2 biochar application are better management measurements for cropland carbon sequestration and emission reduction in Guanzhong region.However,our study results need further long-term monitoring.Our results have certain reference value and practical significance for scientific management of farmland in Guanzhong region,Shaanxi Province.