Response Mechanism Of Soil Microorganisms Of Spring Wheat To Different Rotation Fallow Mode In The Western Foot Of Daxinganling Mountains

In the farmland ecosystem,the interaction among crops,soil microenvironment and soil microorganism maintains the balance of farmland ecosystem.The results show that reasonable crop rotation and fallow can effectively protect and improve the soil environment and affect the diversity of soil microorganisms;soil microorganisms could affect the growth and development of crops,enhance the effective use of nutrients,resist adversity and improve soil productivity and crop yield.In this dissertation,based on the five rotation fallow modes of spring wheat²⁰¹⁶-spring wheat²⁰¹⁷-spring wheat²⁰¹⁸(WWW),spring wheat²⁰¹⁶-rape²⁰¹⁷-fallow²⁰¹⁸(WRF),spring wheat²⁰¹⁶-potato²⁰¹⁷-fallow²⁰¹⁸(WPF),spring wheat²⁰¹⁶-fallow²⁰¹⁷-rape²⁰¹⁸(WFR),spring wheat²⁰¹⁶-fallow²⁰¹⁷-potato²⁰¹⁸(WFP)which were constructed in 2016.The spring wheat was studied in 2019,the first year of the second cycle of rotation fallow,and the relationship between spring wheat plant indexes,soil indexes and soil bulk rhizosphere microorganisms under different rotation fallow modes were systematically analyzed.The main conclusions are as follows.(1)Compared with continuous cropping mode(WWW),the fresh weight,dry weight,plant height and other agronomic traits,flag leaf net photosynthetic rate,stomatal conductance and other photosynthetic traits and grain yield of spring wheat were significantly increased in rotation fallow mode.Under the rotation fallow mode,the dry weight,fresh weight and plant height of spring wheat increased significantly(P<0.05);the chlorophyll content of flag leaf increased significantly,photosynthesis increased significantly,and the grain yield increased significantly(P<0.05).Comprehensive comparative analysis showed that spring wheat-potato-fallow mode(WPF)and spring wheat-fallow-potato mode(WFP)had better effects.(2)Compared with the continuous cropping mode,the soil physical properties,chemical properties and soil microbiological properties of the rotation and fallow mode have significant differences(P<0.05).Among them,spring wheat-fallow and potato(WFP)mode had the highest soil comprehensive nutrient content,and soil microbial biomass nitrogen and phosphorus contents increased by 47.50%and34.33%,respectively.(3)Compared with the continuous cropping mode,the Alpha diversity index of soil microorganisms in the rotation fallow mode was higher,the species were rich,and the community structure was relatively stable.The abundance of 6 phyla,5 phyla and 1 phyla in BS,RS and ER increased significantly under rotation fallow mode,respectively.At the genus level,the species and abundance of dominant bacteria increased significantly(P<0.05),especially in the WFP mode.The position of root zone is the first factor affecting the change of soil microbial community structure,the rotation fallow mode is the second main factor,and crop rotation sequence can also affect the change of soil microbial community.(4)The soil microbial diversity in spring wheat field is closely related to the plant characters,photosynthetic characteristics indexes,soil physical and chemical properties indexes.Soil microbial diversity in spring wheat field is closely related to two plant indices of fresh weight and stomatal conductance of spring wheat,five soil physicochemical indexes of total nitrogen,total porosity,p H,total phosphorus and total potassium,three soil microbiological properties index of urease,sucrase and hydrogen peroxide.Among these traits,total nitrogen(r=0.499),p H(r=0.455),urease(r=0.430)and sucrase(r=0.373)had the greatest influence.At the phylum level,the beneficial phylum,such as Firmicutes and Actinobacteria,were also have varying degrees of correlation with environmental factors such as spring wheat plant traits,photosynthetic characteristics indexes,and soil physical and chemical traits indexes.In conclusion,rotation fallow measures can improve soil physical and chemical properties,increase the species and abundance of Firmicutes,Actinobacteria and other beneficial bacteria,make soil enzyme activities in the optimal state,promote the efficient use of soil water and nutrients,and promote the growth and development of spring wheat;Meanwhile,spring wheat can promote the growth of microorganisms,maintain the stability of its community structure,and form a virtuous circle of soil-microorganism-spring wheat,so as to realize the sustainable utilization of farmland soil.