Effect Of Different Years Straw Returning On Physicochemical And Microorganism Characteristics Of Black Soil

Straw returning is an important measure to improve and fertilize soil.In view of the long-term continuous cropping conditions in the northeastern spring maize area,the black soil degradation caused by thinning of the black soil layer and the reduction of organic matter,the field positioning test method was used to study the effects of deep-returning for many years(8 years,6 years,4 years)on the soil physical and chemical properties and soil microbes,and the eight-year straw returning field as the research object.We discussed the reduction of nitrogen fertilizer,which is reduced by 1/9,2/9,1/3 and 4/4 on soil nutrient,soil microbial,nitrogen uptake and corn yield on the basis of fertilization by ordinary farmers in order to provide theoretical research on fertilizer reduction under long-term fertilization conditions.The main findings are as follows:1.Long-term straw burying and returning to the field(8 years,6 years,4 years),continuous treatment of stalks significantly increased soil water holding capacity,soil porosity and soil bulk density of 0-20 cm depth and all N,all P and Full K content and available nitrogen.,available phosphorus,available potassium content.After 8 years,6 years and 4 years of straw returning,the organic carbon content of soil tillage increased by 9.28%,7.35% and 4.95% respectively before the start of the experiment;on the organic carbon component,soil microbial biomass carbon and the oxidizable carbon content in soil has been significantly improved.2.The straw returning treatment significantly increased the number of bacteria,fungi,actinomycetes,autotrophic nitrogen-fixing bacteria,nitrifying bacteria,cellulose and decomposing bacteria in the rhizosphere soil.The soil microbial community OUT value,chao1 index and Shannon index analysis showed that the abundance of the treated fungi species increased significantly after 8 and 6 years of straw returning,but the bacterial abundance had no significant effect.Straw returning treatment had no significant effect on community diversity,but the soil microbial community structure richness was significantly improved.3.Straw returning significantly affected the relative abundance of bacterial and fungal microbial species in the soil.The abundance of Proteobacteria,Acidobacteria,Ascomycota and Mortierellomycota,which treats bacteria for 8 and 6 years,reduces bacterial actinomycetes soil abundance of(Actinobacteria)and fungi Basidiomycota.4.The straw was continuously returned to the farmland for 8 years.The nitrogen fertilizer was reduced by 4/9 in the fertilization level of ordinary farmers.The total P and total K content of the soil had no significant effect,while the available phosphorus and available potassium were reduced by 2/9 under the condition of nitrogen fertilizer.There was no significant difference with the control,but the nitrogen reduction exceeded 2/9,and there was a significant decrease.Under the condition of maximum nitrogen fertilizer reduction of 4/9,the soil available potassium content was not significantly lower.5.The straw was continuously returned to the field for 8 years,and the nitrogen fertilizer application rate did not exceed 2/9,and had no significant effect on the number of bacterial fungi,actinomycetes,autotrophic nitrogen-fixing bacteria,nitrifying bacteria and microbial communities.There was no significant effect on the number of cellulolytic bacteria communities under the condition that the nitrogen fertilizer application rate did not exceed 4/9.Nitrogen reduction can significantly affect the relative abundance of bacteria and fungal microorganisms,reduce the relative abundance of Actinobacteria,but increase relative abundance of Acidobacteria,Fungalellomycota and Basidiomycota.6.When the straw was continuously returned to the field for 8 years,under the condition of nitrogen fertilizer reduction,with the increase of nitrogen application,the nitrogen concentration in the grain decreased,but did not reach a significant level(P>0.05);There was a significant decrease in the nitrogen concentration in the stem under the reduction of nitrogen fertilizer application rate over 2/9.With the increase of nitrogen application,the total nitrogen uptake in grains and stems decreased,but the grain showed only significant difference under the treatment of 4/9 reduction,while the stalks exceeded the nitrogen application.Significant differences were observed under 2/9 treatment.On the farmland soil with straw returning for eight years,the nitrogen fertilizer was reduced by 1/9 to the maximum reduction of 4/9,and there was no significant difference in the yield of maize with different treatment(P>0.05).There was no significant effect on the 100-grain weight and grain number of kernels in the yield composition.