Effects Of Environmental Factors And Root Exudates On Soil Microorganisms Under Rapeseed Intercropping With Milk Vetch

In order to clarify the effects of environment and root exudates on soil microorganisms in intercropping in dryland red soil.In this study,milk vetch(Astragalus sinicus L.)intercropping with rapeseed(Brassica napus L.)was used to explore the changes in soil pH,temperature,moisture,total carbon,total nitrogen,alkali-hydrolyzable nitrogen,available phosphorus,and available potassium,and analyze the interrelationship between them and soil microbial communities;To clarify the characteristics and differences of root exudates under intercropping,and explore the impact of root exudates on soil microbial communities.The results showed that:(1)During the flowering period in2021,the soil temperature of monoculture rapeseed and milk vetch intercropping with rapeseed was significantly lower than that of monoculture milk vetch,while the soil moisture content of intercropping was higher than that of monocultures.The content of soil total nitrogen and alkali-hydrolyzable nitrogen in intercropping was lower than that in monocultures at seedling stage.Compared with monoculture rapeseed,intercropping increased the total potassium content during the stem elongating and flowering stages in2021.(2)Intercropping and growth stages of crops have changed the structural characteristics of soil microbial communities,the Shannon diversity index in the intercropping and monoculture milk vetch is significantly higher than that in the monoculture rapeseed in 2021.Through two years of data analysis,it was found that,pH,temperature,moisture,total nitrogen had the most significant impact on soil microorganisms.Soil moisture mainly had a negative impact,while soil nitrogen mainly had a positive impact on microorganisms,such as Choloroflexi,Firmicutes,Acidobacteria.(3)The root exudates of milk vetch and rapeseed mainly include monosaccharides,fatty acids,amino acids,amines,and carboxylic acids,with the highest content being monosaccharides.The fatty acid content of monoculture milk vetch was significantly higher than of monoculture rapeseed,and the amine and carboxylic acid content of monoculture rapeseed was significantly higher than that of monoculture milk vetch.(4)The content of total carbon,ammonia nitrogen and nitrate nitrogen in the soil treated with root exudates increased compared to the control treatment.(5)The relative abundance of Proteobacteria and Actinobacteriota in the intercropping exudates treatment than that in the monocropping exudates treatment and control treatment,while the relative abundance of Acidobacteriota was opposite.Compared with other three treatments,the soil treated with root exudates of intercropping significantly enriched with Patescibateria,Saccharimonadia,Catenulisporales,Frankiales,and so on.The Sobs index,Chao index,Ace index,and Coverage index of soil microorganisms treated with root exudates were significantly lower than those of the control treatment.(6)Root exudates have different effects on the production of soil microorganisms.There is a significant positive correlation between monosaccharide and Proteobacteria,Firmicutes,Myxococcota,Nitrospirota,RCP2-54,etc;Fatty acids have a significant negative correlation with Patescibacter,Elusimicrobiota and Dependentiae.It can be seen that soil temperature,moisture,and nitrogen content are the main factors affecting microbial communities in rape intercropping with milk vetch;At the same time,in different planting patterns,root exudates can increase the content of total carbon,ammonia nitrogen and nitrate nitrogen in the soil,and have an impact on the diversity of soil microbial communities.Monosaccharides and fatty acids are significantly correlated with changes in soil microorganisms.