Effects Of Different Annual Straw Returning Methods On Greenhouse Gas Emission,Organic Carbon Pool,Soil Nutrient And Crop Yield

China,as a large agricultural country,is rich in crop straw resources.Crop straw contains a lot of nutrients,which is a valuable natural resource.Straw returning is a direct and effective straw treatment method to improve farmland quality and increase crop yield.In recent years,China’s grain output has been increasing,the amount of crop straw also increasing fast,so traditional straw returning method can not meet the needs of production.In addition,global warming is a huge challenge facing the world today.Greenhouse gas emissions are the main cause of global warming.Farmland soil is the main source of greenhouse gases.Agricultural management measures have an important impact on greenhouse gas emissions.The results showed that straw returning could increase greenhouse gas emissions.Therefore,it is very important to explore safe,ecological and efficient straw returning methods.This study was carried out in November 2014 to November 2015 in Qinglong Community,Chunhua Town,Jiangning District,Nanjing City,Jiangsu Province,through field plot experiment,set up four kinds of straw returning treatments(i.e.without straw returning,CK;wheat straw concentrated ditch-buried returning and rice straw covered returning,WDRC;wheat straw concentrated ditch-buried returning and rice straw rotated returning,WDRR;wheat straw rotated returning and rice straw covered returning,WRRC;wheat and rice straw rotated returning,WRRR.)The effects of different straw returning methods on greenhouse gas emission,soil carbon pool and yield were studied.The purpose of this paper is to explore a safe,ecological and efficient method of returning straw to field.To provide theoretical and practical basis for the establishment of reasonable straw returning methods.The main results of this study are as follows.1.Annual straw returning could improve soil nutrients and soil carbon pool,two kinds of ditch buried straw returning is the best way to increase soil nutrients and soil carbon pool.Four different straw returning methods can improve the soil nutrient and carbon content in different degrees.Compared with CK,WDRC and WDRR increased content of soil available phosphorus significantly,increased by 42.1%and 23.5%respectively in rice season.WDRC;WDRR;WRRC;WRRR increased content of soil available kalium significantly,increased by47.2%、44.6%、26.2%、25.2%respectively in rice season.WDRC;WDRR;WRRR increased content of soil water soluble organic carbon significantly,increased by 83.0%;50.9%and 57.6%in rice season.WDRC;WRRC;WRRR increased content of soil microbial biomass carbon significantly,increased by 30.9%;25.6%and28.3%in rice season.Compared with CK,WDRC;WDRR;WRRC;WRRR increased content of soil total nitrogen;available phosphorus;available kalium;total organic carbon;readily oxidized organic carbon significantly,increased by 18.5%、25%、16.4%、48.5%,72.4%、73.8%、36.3%、49.9%,27.9%、32.7%、6.7%、18.5%,99.4%、100%、28.4%、59.3%respectively in wheat season.2.In rice season WRRR CH4 and N2O emissions are the lowest.In wheat season WRRC CH4 and N2O emissions are the lowest.Four kinds of straw processing,rice and wheat straw were CH4 N2O rotary tillage withstraw rice season,the lowest cumulative emissions,respectively 61.59kg hm-2,4.89 kg hm-2,compared with no straw returning,rice season global warming potential is reduced by 7.2%,is the lowest in all treatments.In addition,straw returning,rice straw mulching tillage CH4,N2O minimum cumulative emissions.3.Compared with No straw returning,the annual straw returning could increase crop yield.Different ways of anniversary straw returning can increase crop yield,which,compared with no straw returning straw ditch burying straw,rice straw mulching,straw ditch burying straw,rice straw,wheat straw rotary tillage and rotary tillage with straw returning,rice straw mulching,straw,rice straw were also rotary tillage field,rice yield was increased by 5.6%4.3%,5.4%,1.6%.Compared with no straw returning straw ditch burying straw,rice straw mulching,straw ditch burying straw,rice straw,wheat straw rotary tillage and rotary tillage with straw returning,rice straw mulching,straw,rice straw were rotary tillage with straw,wheat yield respectively increased 20.9%,18.2%,21.3%,31.5%,significantly improve the yield of wheat.