| Nematodes play an important role in soil ecosystems and are regarded as bioindicators of soil ecological functions.Excessive application of chemical fertilizer will lead to the decline of soil biodiversity and serious ecological environment problems.Organic fertilizers can effectively promote soil biodiversity and improve ecological environment by offsetting the drawbacks of chemical fertilizers.Existing studies have confirmed that legume green manure planting and vermicompost application can promote the development of soil biological community,so as to achieve a variety of ecosystem function goals,such as improving soil health,increasing crop yield and quality.Although the respective effects of green manure and vermicompost are well known,the combined effects of legume green manure and vermicompost,have not been reported.Theoretically,vermicompost can improve soil structure,improve nutrient availability and alleviate nutrient limitations during the growth of green manure.The decomposition of green manure is beneficial to the development of soil nematode communities.However,there are few studies on this respect.Based on this,our study was set up with a three-way factorial design(chemical fertilizer× vermicompost × green manure),with two application levels of fertilizer including reduced40% chemical fertilizer or not,two levels of green manure application(without or with green manure),two levels of vermicompost application(without or with vermicompost)to explored whether the reduction of chemical fertilizer,green manure and vermicompost application affected nematode community.The main results are as follows:1)Fertilization was the dominant driver of soil nematode communities.The pairwise interaction of reduced fertilizer,vermicompost and green manure significantly affected the abundance of soil nematode trophic groups.Green manure significantly increased soil nematodes abundance for two consecutive years.Vermicompost could increase the abundance of omnivorous-predators under the condition of total fertilization;Under chemical fertilizer reduction,plant-parasites was increased by green manure.The enrichment index was significantly increased by vermicompost and green manure under chemical fertilizer reduction.Vermicompost significantly increased the Shannon-Wiener diversity index.Green manure significantly decreased the Shannon-Wiener diversity index.2)Application of green manure and vermicompost regulated soil nematode community by affecting soil physicochemical properties and microbial community.In the 1st year of the study,green manure and vermicompost significantly decreased soil bulk density,and increased SOC,DOC and available P under chemical fertilizer reduction.And,soil fungi/bacteria significantly increased.In the 2nd year of the study,vermicompost and green manure significantly decreased soil bulk density and increased SOC,total N and available P under chemical fertilizer reduction.And,the total amount of soil microorganisms,the fungi/bacteria and the Gram-positive /Gram-negative bacteria significantly increased.Under the condition of total fertilizer without vermicompost,green manure could significantly increase soil mineral N content.The correlation analysis showed that soil bulk density,DOC,total N,mineral N,fungi/bacteria,fungi biomass,bacteria biomass and microbial biomass were significantly correlated with soil nematodes abundance,abundance of each trophic group nematodes,enrichment index,structure index and marglef richness index respectively.The results of structural equation modeling showed that green manure can directly stimulate nematode community structure and indirectly regulate nematode community structure by influencing soil bulk density.In the 1st year of fertilization regulation,green manure could affect nematode community structure by affecting soil mineral N content.Vermicomposting can affect the community structure of nematode by influencing the bulk density or directly stimulating the community structure of nematode.In the 2nd year,vermicomposting and chemical fertilizer could indirectly regulate nematode community structure by affecting soil available P content.In conclusion,the application of green manure and vermicompost can significantly improve soil physicochemical properties and soil microbial biomass under the condition of reducing chemical fertilizer,and the improvement of soil physicochemical properties and microbial community properties can significantly affect the composition and the structure of nematode community.Integrative measures of organic substitution can synergically improve soil health,and there is a close relationship between soil nematode communities and soil function,which proves that nematodes can indicate changes in soil health after fertilization measures changes. |
