Effects Of Corn Straw Returning And Supporting Measures On Wheat Yield And Soil Properties

Field experiments were used to study the effects of simultaneous application of nitrogen fertilizer and maize straw returning on the wheat yield and soil fertility on the Guanzhong Plain.The experiment was arranged with a split block design,the main treatmentsweremaize straw return(N+S)and the residue-removed(N),and the split plot treatmentswere 5nitrogen fertilizer application levels(N 0,84,168,252 and 336 kg/hm~2).At the meantime,anotherrandomized block design experiment was set up with treatments of?rotary tillage+straw returning(RS),rotary tillage+straw returning+straw decomposition accelerator(RSD),rotary tillage+residue-removed(RN),subsoiling+straw returning(RS),subsoiling+straw returning+straw decomposition accelerator(SSD),Subsoiling+residue-removed(SN)?with the purpose of investigatingthe changes of winter wheat yield and soil fertility after applying straw decomposition accelerator and the different tillage patterns in the area withthe agricultural system of summer maize-winter wheat rotation.Plants and soil weresampledafter the winter wheat harvest in 2018.The effects of different treatments on crop yield and biomass were systematically analyzed.The main results obtained are as follows:1.Seven-year long-term straw returning location experiment found that the average yields of straw returning and residue-removed treatments were 6133 and 6155 kg/hm~2,respectively,and no significant difference was found between them.When the nitrogen application rate is low,the yield of winter wheat after the straw returning decreases compared with that of residue-removed treatment.When the amount of nitrogen application exceeds a certain amount,returning the straw treatment increase the yield of winter wheat.Returning straw treatments reduce wheat yield when nitrogen application rate is low and increases wheat yield when nitrogen application rate is high,compared with treatments with residue removed.2.Compared with residue-removed treatments,straw returning treatment decreased the nitrogen content of grain by 1%on average,decreased the phosphorus content of grain by2.1%,and increased the potassium content of grain by 1.2%on average.Whether straw returning or not,with increasing nitrogen application rate,the nitrogen content of grain increased and then decreased,the phosphorus content of grain showed a decreasing trend,and the grain potassium content showed an increasing trend.With low nitrogen levels in2012,2013,2014,and 2016,the aboveground nitrogen uptake of winter wheat was lower with maize straw returning.In 2016 and 2018,the nitrogen uptake of winter wheat with straw returning treatment was higher than residue-removed treatment.After returning straw to the field in 2012-2015,with thenitrogen application rate increasing,the wheat aboveground phosphorus uptake oftreatments with straw returning were lower than those of residue-removed treatments with low level nitrogen application.However,when the nitrogen application rate exceeded a certain amount,the aboveground phosphorus uptake of treatment the straw returning was higher than residue-removed treatment.The results in 2016 and 2017were exactly the opposite.With low nitrogen application rate,the aboveground straw phosphorus uptake was higher.In 2012,2013,2014,and 2017,the aboveground straw potassium uptake was lower with straw returnning than that of residue-removed treatment with lower theapplication of nitrogen,while the potassium uptake of straw returning treatment was higher than residue-removed treatment.In 2016 and 2018,regardless of the nitrogen application level,the aboveground potassium uptake of straw returning treatment was higher than residue-removed treatment.3.After straw returning to the field,the content of nitrate and available phosphorus in the soilsurface layer(0-20cm)were significantly increased,with an average increment of 7.8%and 5.1%respectively.After straw returning,the potassium content of the soil surface layer(0-20cm)was significantly increased,with an average increment of 14.8%.After returning straw to the field from 2012 to 2018,compared with residue-removed treatment,the soil organic matter increased by an average of 4.4%,6.6%,4.2%,7.0%,6.9%,7.9%and 8.9%,respectively.In 2012,2013,2015,2017,2018,the total soil nitrogen increased by 3.0%,4.7%,6.6%,5.6%,and 3.1%on average,respectively,compared with residue-removed treatments.The nitrogen balance analysis of treatment with returning straw to the field showed that straw returning increases the input of nitrogen nutrients in farmland.As a result,the total nitrogen input was higher than that of the treatment without straw returning.To avoid excessive or unbalanced of nitrogen input,the amount of nitrogen fertilizer should be appropriately reduced after returning straw to the field.4.Experiments with different farming modes showed that:Treatments of RSD increased winter wheat yield and improved soil nutrients contents.Compared with RN of the farmer's conventional farming model,the wheat yield and above-ground biomass increased by 7.39%and 6.15%in the treatment of RSD,the content of nitrate nitrogen and organic matter in the0-20cm soil layer increased by 8.35%and 8.23%,respectively.Therefore,based on the one year result of this experiment,the agricultural mode of"straw returning to the field+rotary tillage+decomposing agent"is most recommended among six modes in the local area.