Effects Of Different Agronomic Measures On Soil Physical And Chemical Properties And Crop Yield In Wheat-maize Rotation Area

With a high proportion of low-yielding field areas and superior natural conditions,the Huaibei Plain has a high potential for yield increase and a promising agricultural development.To achieve the purpose of enhancing soil fertility and improving crop yield,straw return treatment was used on the basis of wheat-maize crop rotation,and in addition,N application percentages of 70-30-0、60-30-10 and 50-30-20 were set in the wheat season（maize season）for the basal stage-tiller stage-spike stage（basal stage-seedling stage-large trumpet stage）,and three N fertilizer transport methods,and three different soil tillage depths（10,20,and 30 cm）,for a total of three agronomic measures.Through the cracked area experiment,the best N fertilizer transport and tillage depth under straw return to the field were investigated to provide theoretical basis for the nutrient management and tillage methods in the farmland of maize and wheat cultivation in Huaibei area.The research results are organized as follows:（1）Soil water content and soil fertility increased and soil p H decreased after straw was returned to the field under the three N fertilizer delivery methods.Soil water content increased by 2.3%to 12.3%and 3.0%to 9.1%in wheat and corn seasons,respectively;soil porosity increased by 7.5%to 9.2%and 2.4%to 14.5%;soil organic matter content increased by 6.7%to 11.0%（P<0.05）and 9.5%to 11.5%（P<0.05）,respectively,under the three N fertilization methods;Soil fast-acting potassium content increased by 18.9%to46.3%（P<0.05）and 22.4%to 33.7%（P<0.05）,respectively;soil effective phosphorus content increased by 10.9%to 43.0%（P<0.05）and-12.9%to 9.5%,respectively;soil p H decreased by 0.10 to 0.19 and 0.38 to 0.49（P<0.05）units;and soil bulk weight decreased by 4.4%to 11.9%and 3.1%to 11.0%（P<0.05）.（2）Under the appropriate N fertilizer regimen,straw return to the field significantly increased the yield of wheat and corn as well as the N,P and K nutrient contents in straw and kernels.Under the three N fertilizer regimes,wheat yield increased and decreased between 0.6%and 2.4%after straw return,and wheat yield increased by 1.2%,1.9%,1.4%and 2.4%after N_50-30-20treatment.The highest yield;maize significantly increased by11.8%to 12.7%（P<0.05）,maize plant height,row grain number,100 grain weight and yield increased by 6.5%,9.2%,7.3%and 12.7%（P<0.05）respectively after straw return in N_60-30-10treatment,and maize yield was highest in S+N_60-30-10treatment.Under N_50-30-20treatment in wheat season,phosphorus and potassium contents in wheat straw were significantly increased by 29.2%and 14.7%（P<0.05）,respectively,and phosphorus content in seeds was significantly increased by 27.3%;under N_60-30-10treatment in corn season,nitrogen,phosphorus and potassium contents in corn seeds were significantly increased by 7.1%,13.7%and 18.2%,respectively,after straw return（P<0.05）.（3）With increasing tillage depth,soil p H,organic matter,fast-acting potassium,and effective phosphorus content increased and then decreased with the highest content under MT treatment,while soil water content,porosity,and alkaline nitrogen content increased with increasing tillage depth.Soil organic matter and fast-acting potassium content increased significantly by 7.7%and 6.0%（P<0.05）in the wheat season and 8.0%（P<0.05）in the maize season,respectively,compared to the LT treatment;soil water content and alkaline nitrogen content increased by 12.5%（P<0.05）,8.7%and 14.5%（P<0.05）,respectively,in the wheat and maize seasons under the DT treatment compared to the LT treatment.（P<0.05）,4.7%.At the three tillage depths,soil fertility increased and soil p H and bulk weight decreased after straw return.Under the three tillage depths,soil organic matter content increased by 6.8%to 11.7%and 17.6%to 27.1%（P<0.05）in wheat and corn seasons,respectively,and soil fast-acting potassium content increased by 16.5%to30.9%and 6.5%to 29.4%（P<0.05）in wheat and corn seasons,respectively,compared with the straw-returned control,and soil effective phosphorus content increased significantly by 19.0%to 24.8%（P<0.05）in wheat season.The soil bulk weight decreased by 1.3%to 8.8%and 3.6%to 4.8%in wheat and corn seasons,respectively.（4）Wheat and maize yields increased with increasing tillage depth,and both wheat and maize yields increased after straw return.wheat and maize yields increased significantly by5.8%and 5.3%（P<0.05）in the DT treatment compared to the shallower tillage LT treatment;wheat and maize yields increased by 1.8%to 4.5%and 8.2%to 10.5%（P<0.05）after straw return and S+MT treatment had the highest yield of wheat and S+DT treatment had the highest yield of maize.At the appropriate tillage depth,straw returned to the field significantly increased the nitrogen,phosphorus and potassium nutrient content of wheat and maize straw and kernels.nitrogen content of maize straw increased significantly by 15.9%（P<0.05）and 21.0%（P<0.05）under the LT and DT treatments,respectively;Under MT treatment,the phosphorus content of wheat and maize seeds increased significantly by 15.7%（P<0.05）and 14.2%（P<0.05）,respectively,and the potassium content of wheat seeds increased significantly by 12.5%（P<0.05）under MT treatment.In summary,under straw returning,the nitrogen application percentage of wheat season-tillering stage-heading stage was 50-30-20,and the nitrogen application percentage of maize season-seedling stage-large bell stage was 60-30-10,which effectively improved the fertility level of lime concretion black soil and increased crop yield and nutrient content.Increasing tillage depth under straw returning can effectively improve soil fertility and increase crop yield.Considering human and material resources,20 cm tillage and straw returning can improve soil,increase crop yield and achieve optimal treatment.