The Effect Of Chinese Milk Vetch Incorporation On Microbes Microbial Associated Function Microbes Microbial Community Structure In Rice Field

Functional microorganisms related to soil nitrogen cycling are the key to regulating nitrogen cycle in soil-plant systems.As a source of high-quality organic fertilizer for agriculture,Chinese milk vetch green manure has the effect of improving nitrogen utilization,improving ecological environment and promoting crop growth in paddy ecosystems.However,the effect mechanism of Chinese milk vetch green manure management on functional microorganisms related to soil nitrogen cycle in paddy fields is still unclear.In this study,the rice field under nitrogen fertilizer(base nitrogen fertilization)was alternative nitrogen fertilizer by returning Chinese milk vetch to the field in winter,and the winter idle was set up without nitrogen fertilizer(CK)in the rice season.In winter,the nitrogen application rate of rice season was 180kg/hm~2(CF);A total of 7 treatments were treated with conventional base nitrogen fertilizer reduction of 0%,20%,40%,60%and 80%(CMV,MVCF1,MVCF2,MVCF3,MVCF4)in the field of winter Chinese milk vetch,and the number of nitrogen cycle-related microorganisms(ammonia-oxidizing archaea(AOA),ammonia-oxidizing bacteria(AOB)and denitrifying microorganisms(nirK and nirS)in paddy fields was studied by using real-time PCR and high-throughput sequencing and other molecular biology techniques such as real-time PCR and high-throughput sequencing.The effects of diversity and community structure,combined with soil physicochemical factors to evaluate the main environmental factors affecting the structure of rice nitrogen cycling-related microorganisms,the main conclusions are as follows:(1)Incorporation of milk vetch to the field significantly affected the physical and chemical properties of the soil,but it was affected by the sampling time.During the green manure return period,compared with single nitrogen fertilization,soil total carbon and total nitrogen decreased with the increase of Chinese milk vetch substitution.Soluble organic carbon and ammonium nitrogen increased with the increase of milk vetch substitution.Compared with single nitrogen fertilization,different nitrogen substitute nitrogen treatment significantly improved soil total carbon,total nitrogen and ammonium nitrogen compared with single nitrogen fertilization in rice tillering stage.Compared to other alternative treatments,40%,60%,and 80%of Chinese milk vetch can better improve the carbon and nitrogen content of paddy soil.(2)The return of Chinese milk vetch to the field has a significant impact on the number,diversity,and community structure of ammonia oxidizing bacteria(AOA,AOB)in paddy soil.Returning Chinese milk vetch to the field can significantly increase the copy number of AOA and AOB genes during the tillering stage of rice.The copy number of AOA genes is higher than that of AOB,and the copy number of genes is influenced by the sampling period.The copy number of AOA genes during the tillering stage of rice is higher than that during the green fertilizer returning period.The influence of sampling period on the diversity of soil ammonia oxidizing bacterial communities is also affected.The return of Chinese milk vetch significantly changed the diversity of AOA and AOB communities during the green fertilizer return period.Different Chinese milk vetch returns improved the richness and diversity of AOA communities during the rice tillering stage,while in AOB,the 60%Chinese milk vetch substitution treatment was higher than other treatments.In general,the community structure of Nitrifying bacteria did not show a certain regularity with the increase of the replacement rate of astragalus.But specifically,both AOA and AOB communities have a dominant species in MVCF3.Total carbon,total nitrogen,and soil moisture are the main environmental factors affecting the community structure of AOA and AOB in paddy soil.(3)There were significant differences in the number,diversity and community structure of nirS and nirk denitrification bacteria communities in soil among different astragalus sinicus returning treatments.The return of Chinese milk vetch to the field significantly increased the gene copy number of nirS and nirk,and the gene copy number of nirS was significantly higher than that of nirk.And the gene copy number is influenced by the sampling period,and the gene copy number of nirS in rice tillering stage is higher than that in green manure returning stage.Chinese milk vetch returning significantly changed the community diversity of nirS and nirk denitrification bacteria.Specifically,it increased the community richness and diversity of nirS,reduced the nirk gene community richness during green manure returning,but increased the nirk gene community richness at rice tillering stage.In addition,in this study,the nirS genotype denitrification bacteria had higher community richness and diversity than the nirk type denitrification bacteria.In general,the community structure of nirS and nirk genotype denitrification bacteria treated with different amounts of Chinese Chinese milk vetch did not show a certain rule with the increase of substitution rate,but specifically,the community structure of nirS genotype denitrification bacteria was stronger than that of nirk genotype denitrification bacteria,Both nirS and nirk genotype denitrification bacteria have a dominant species in MVCF2.Soluble organic carbon,total carbon,and soil moisture are the main environmental factors affecting the community structure of nirS and nirk genes in paddy soil.To sum up,there are significant differences in soil physical and chemical properties between different treatments of Chinese milk vetch returning to the field,which causes changes in the number,diversity and community structure of nitrogen cycle functional microorganisms in paddy soil,but their community structure does not change regularly with the increase of the gradient of Chinese milk vetch replacement rate.In addition,different sampling periods also have different effects on the number,diversity and community structure of microorganisms with different functions of the nitrogen cycle.Replacing nitrogen fertilizer with 40%,60%,and 80%purple vetch can better improve the carbon and nitrogen content of paddy soil and improve nitrogen utilization efficiency.40%and 60%of Chinese milk vetch replacing nitrogen fertilizer significantly increased the dominant species of nitrification and denitrification related functional microorganisms.The research results can provide scientific basis for regulating the nitrogen conversion process,improving nitrogen utilization efficiency,and improving the agricultural ecological environment of the farmland ecosystem in the region.