Effects Of Returning Straw And Applying Nitrogen Fertilizer On Soil Nutrient,Microbial Community Structure And Enzyme Activity In Wheat Field

The purpose of this study was to determine the soil nutrient index of wheat field during the wheat growing period in the Guanzhong Plain area of Shaanxi Province,which is the main production area of grain crops in China,soil enzyme activities and microbial community composition,revealing the mechanism of the effects of Straw returning on soil nutrients,soil enzyme activities and soil micro-ecological environment,in order to provide scientific and theoretical basis for Straw returning and nitrogen fertilizer high-efficiency utilization in this area.The main results are as follows:(1)In the 0-20 cm and 20-40 cm soil layers of winter wheat,the average value of soil organic matter increased by 0.88%,3.72%,7.62%,0.59%,5.71%and 11.69%,respectively,compared with the treatment of returning Straw to the field,the soil available P,available K,p H and total N had no significant difference.Under the conditions of 0 kg/hm~2,84 kg/hm~2,168 kg/hm~2,252 kg/hm~2and 336 kg/hm~2,the increase and decrease of wheat yield were-4.63%,-5.26%,8.80%,4.29%and 1.52%,respectively,the rate of increase was the highest at the level of 168 kg/hm~2nitrogen application.The effect curve of Straw return and nitrogen fertilizer showed that when nitrogen application rate was higher than the crossing point 77.29 kg/hm~2,the positive effect of Straw return began to appear,and the wheat yield of Straw return was higher than that of no return.The above-ground biomass of wheat was significantly increased by 12.92%under 168 kg/hm~2nitrogen application compared with no nitrogen application.(2)At different growth stages of wheat,the activities of catalase,alkaline phosphatase and sucrase in soil tended to decrease with the increase of nitrogen hourly rate,no matter whether sorghum stalk would return to paddy field or not.Compared with nitrogen fertilizer alone,the activities of catalase,alkaline phosphatase and element enzyme in paddy field were 1.39%,6.9%,5.17%,7.79%,4.29%,2.77%,5.17%,6.05%,0.19%and 5.27%,respectively.The element enzyme increased steadily with the increase of time and quality,and the growth trend was relatively flat,When the rice straw of three growth stages was put in the field,the alkaline phosphatase and sucrase in the soil were most active when the nitrogen fertilizer was 168 kg/hm~2.(3)Ace index cop index to treat bacteria and bacteria.OTU has no effect.The bacterial community index of belt exchange is clearly lower than the nitrogen conversion rate and the water belt of nitrogen 252 kg/hm~2.At the same nitrogen level,belt exchange does not significantly affect the Shannon index of bacteria and fungi and the OTU number.As a result,the replacement of the aquarium does not lower the bacteria’humidity and has a significant impact on the diversity and OTU number of bacteria and fungal communities.The Shannon Index and Otu of bacteria and fungi were significantly lower than that of 168kg/hm~2under the condition of Straw returning,which indicated that the diversity and Otu of bacteria and fungi were decreased under the condition of 252 kg/hm~2nitrogen.(4)The relative abundance of Thermoleilia increased with the increase of nitrogen application rate,and that of Blastocatellia decreased with the increase of nitrogen application rate.Under the same nitrogen rate,Straw returning had no significant effect on the relative abundance of the fungi Mortierellomycetes,but under the straw returning condition,the relative abundance of Mortierellomycetes was significantly lower than that of168 kg/hm~2under the nitrogen rate of 252 kg/hm~2,which decreased by 50%,there was no significant difference among treatments of other species.The community structure of bacteria and fungi was different at different nitrogen application levels,but when nitrogen application was the same,the community structure of bacteria and fungi had little difference between Straw return and no return.(5)There was a positive correlation between alkaline phosphatase and the difference indicator species of Bryobacteraceae,WWH38,Micropepsaceae,paenibicillaceae,JG30-KF-AS9,Solibacteraceae,Sphingomonadaceae,SC-I-84,Acetoacteraceae,Sucrase and the difference indicator species of Bryobacteraceae and Micropepsaceae,respectively.There were positive correlation between p H and Tubeufiaceae,Psathyrellaceae,positive correlation between Urease and Catalase,negative correlation between Urease and Tubeufiaceae,among these environmental factors.Alkaline phosphatase has a significant effect on both bacterial biomarker and fungal species at the family level.In conclusion,the return of the Straw to the Field Increases organic matter to the soil,When N was 168 kg/hm~2,wheat yield and soil alkaline phosphatase and sucrose activities increased the most.The community structure of bacteria and fungi was different at different nitrogen application levels,but the difference between Straw returning and non-returning was small at the same nitrogen application level.Alkaline phosphatase has important implications for both bacterial biomarker and fungal species at the family level.