Straw Return Controls Soil Organic Pool And Winter Yield In Dryland

Straw return is an important form of exogenous carbon input,which is essential for maintaining soil carbon stocks and increasing crop yields.Although studies have been conducted on the effects of straw fielding on crop yield and soil organic carbon in different regions,the effects of straw fielding on crop yield and soil organic carbon at the global scale are remain unclear.The assessments from a carbon balance perspective to straw fielding rates in the major wheat regions of China is also lacking.Therefore,we studied the effects of straw returning on the yield of main food crops（wheat,maize and rice）,soil physical and chemical properties and soil organic carbon balance through Meta analysis on global scale,and the wheat straw returning rate was explored the in main wheat areas based on carbon balance.Meanwhile,we identified the effects of straw return on yield,soil organic carbon,and cluster stability of dryland winter wheat through a long-term localization experiment arranged in the dryland of Weibei dry plateau.The main research results are as follows:（1）The effects of straw regranting on grain crop yield and soil organic carbon were studied based on Meta-analysis.At the global scale,straw return to land increased crop yields by 6.6%on average,with wheat,maize and rice yields increasing by 8.6%,5.6%and 5.8%,respectively.In addition,straw return also increased soil organic carbon（SOC）,total N,total P and total K by 11%,10%,5.0%and 4.7%,respectively.Straw returning also improved soil quality and soil physical properties,among which,the content of agglomerates larger than 250μm(R_0.25),mean mass diameter（MWD）and geometric mean diameter（GWD）were increased by 11%,12%and 5%,respectively.Under different management measures,soil properties and climate conditions,straw returning could increase soil carbon sequestration rate by an average of 152%.Management measures were the most important factors affecting soil carbon sequestration rate,in which the relative contribution rates of exogenous carbon and nitrogen input were 18%and 16%,respectively.Scientific management of straw resources is an important way to increase soil organic carbon in grain fields.（2）Estimation of straw return rate in China based on carbon balance of straw carbon input and carbon emission during wheat period.The wheat yield in Northeast China,North China,Northwest China and South China was 2.8-6.6 Mt yr^-1,44-86 Mt yr^-1,17-20 Mt yr^-1 and 33-44 Mt yr^-1,respectively.Straw biomass is 2.3-6.7 Mt yr^-1,38-76 Mt yr^-1,15-17 Mt yr^-1 and 28-38 Mt yr^-1,respectively.The root biomass was0.42-1.3 Mt yr^-1,6.5-10 Mt yr^-1,2.5-3.0 Mt yr^-1 and 4.7-5.6 Mt yr^-1,respectively.The results of life cycle evaluation showed that the carbon emissions in Northeast China,North China,Northwest China and South China were 0.37,18,3.9 and 11 Mg C yr^-1,respectively,and the carbon emissions during the growth period of wheat in China were33 Mg C yr^-1.Nationwide,the carbon input from straw in the soil can theoretically offset the carbon emissions from wheat fertility when the wheat straw return rate is 47%.Northwest and southern rates of 46%and 58%,respectively,can offset carbon emissions from wheat fertility in this wheat region,higher than in northeast（26%）and north China（43%）.Accurate assessment of wheat straw biomass and exploration of appropriate straw return rates are important references for guiding integrated wheat straw utilization in China.（3）To identify the effects of straw return to the field on the yield and soil organic carbon stability of dryland winter wheat based on long-term positioning experiments.From 2021 to 2022,there was no significant effect of straw return to the field on the dryland winter wheat seed yield and its constituent elements in the northern Weibei dry plateau.Straw return significantly increased the SOC content in the 0-20 cm soil layer by 11%.Further analysis of organic carbon fractions showed that soluble organic carbon and particulate organic carbon increased by 19%and 42%,respectively,while easily oxidized organic carbon increased by the lowest 0.90%.Straw return to the field significantly increased the content of soil large agglomerates（>2000μm and 1000-2000μm）by 113%and 83%,respectively.Straw fielding significantly increased the stability of agglomerates,with R_0.25,MWD and GWD increasing by 64%,34%and 25%,respectively,but had no significant effect on the organic carbon and total nitrogen content of each particle size.In conclusion,straw return to the field can effectively improve soil fertility and soil quality,which play a significant role to improve organic carbon sequestration in grain fields and guarantee food security.