Effect Of Double-season Straw Incorporation On Soil Quality And Grain Yield In Winter Wheat-Summer Maize Rotation System

This field experiment was conducted from October,2016 to October,2018 using land in a winter wheat-summer maize rotation at the Research Station of Shandong Agricultural University,Tai'an,Shandong,China.A widely planted cultivar,Jimai 22 and Zhengdan 958was selected as the experimental material.We set four treatments:No straw incorporation?NS?;Wheat straw incorporation?WS?;Maize straw incorporation?MS?and Double seasons straw incorporation?DS?.And we researched the responses of grain yield and soil quality to different straw incorporation model.Aiming to investigate reasonable approach to increase soil fertility and achieve high annual crop yield in Huang-Huai-Hai Plain.The main results are shown as follow:1.Effects of different straw incorporation model on soil physical condition.Straw incorporation can perfect soil structure.Three straw incorporation mode especially DS treatment effectively reduced the soil bulk density and R-value in 0-30 cm soil layer,and improved the soil porosity,mass ratio of large aggregates and stability of aggregates with different levels compared with the NS treatment.The two years experiments performance is consistent,and shows a certain interannual effect.The soil bulk density which in 0-30 cm soil layers decreased by 5.0%,3.3%,and 2.6%,respectively;the soil porosity in the same place increased by 6.2%,4.3%,and 3.9%,respectively;the R_0.25.25 increased by 11.9%,10.0%and13.8%;the effect of straw incorporation on the distribution of soil aggregates mainly showed that the mass ratio of large aggregates increased and the proportion of microaggregates decreased.But the soil physical conditions among treatments were not significant differently in the 30-40 cm layer.2.Effect of different straw incorporation model on soil nutrient status.All straw incorporation model can increase soil nutrient content to varying degrees compared with non-returning treatment.The soil total nitrogen increased by 26.7%,the available K increased by 19.2%,and the organic carbon increased by 16.2%in 0-20 cm soil layer.Among the three returning modes,the DS treatment showed the most significant result.However,the soil available P content was less affected by straw incorporation,and the difference between the treatments in the two-year experiment was not significant.Compared with before the start of the experiment,the content of total nitrogen,available K and organic carbon in the 0-20 cm soil that was under NS treatment decreased year by year,which was lower than the basic soil fertility value,and the average annual reduction was15.1%,8.3%and 2.6%.Both single-season returning modes can effectively maintain the original level of soil nutrients.The specific performance of MS is better than WS treatment.DS treatment significantly increased the soil nutrient content,and increased the soil total nitrogen by 29.6%,available potassium by 18.1%,and organic carbon by 11.2%.Compared with 2016-2017,the contents of total nitrogen and available potassium in the soil layer of20-40 cm under each treatment showed a decreasing trend.In the 20-30 cm soil layer,the soil organic carbon content under DS and MS treatments was slightly smaller.Improvement;in the 30-40cm soil layer,each treatment can maintain the original level of organic carbon.Correlation analysis showed that SIR was significantly positively correlated with TN,SAK and SOC in the 0-10 cm soil layer.In the 10-20 cm soil layer,the straw returning rate was significantly positively correlated with SAK and SOC,but poorly correlated with soil total nitrogen content.Meanwhile,in 0-20 cm soil layer,SOC was significantly negative correlation with SBD,and a significant positive correlation with TP and MWD.3.Effect of annual straw returning mode on soil carbon pool composition.After two years of straw input,compared to NS treatment,the soil organic carbon storage under straw incorporation was significantly improved.The WS,MS and DS increased14.8%,17.9%and 24.2%respectively in the 10-20 cm and 20-30 cm soil layers.The effect of straw returning on active organic carbon and its components was inconsistent in the two-year experiment.In 2016-2017,Compared with the return of the field,the straw returned to the field significantly increased the active organic carbon content,mainly high-activity organic;in2017-2018,the increase of active organic carbon decreased compared with the first year,but the content of inactive organic carbon was also improved.Among the three active components,MLOC and LLOC also been different levels of improvement.Meanwhile,carbon pool activity and carbon stock management index have also been improved.From the level of soil aggregates,the straw returning treatment increased SOC of all the aggregates in different sizes.The SOC of each aggregate was increased by 6.1%,11.6%,8.8%6.8%,11.2%and 6.0%respectively under WS;MS treatment increased SOC connect of 9.4%,14.8%,14.6%,12.4%,18.1%and 19.6%in average;Under DS treatment,the average increase was 16.7%,16.9%,20.3%,19.5%,23.9%and 25.1%,respectively.The increase of associated organic carbon content in 1-0.5 mm particle size aggregates is the main reason for the evolution of soil carbon pool.4.Effect of annual straw returning mode on winter wheat-summer maize yield.Compared with NS treatment,straw incorporation to the field significantly improved winter wheat grain yield.The rules are no difference under two-year experiment,with an average increase of 11.1%.The main contribution of the increase in yield was from the significant increase in effective spike number?7.2%,P<0.05?and spike grain number?6.4%,P<0.05?.Summer maize yield responded significantly to straw incorporation,the increase of grain number?9.9%,P<0.05?was the main reason for its yield increase.The annual yield of DS treatment was the highest among the three models.WS treatment mainly increased the summer maize yield,MS treatment mainly increased the winter wheat yield.Consequently,straw returning can improve soil nutrient content in surface layer significantly,optimize soil structure and synergistically increase wheat and maize yield.The double-season straw incorporation model is the best measure to improve soil quality and increase crop yield in Huang-huai-hai Plain.