Study on Microbial Community Structure and Soil Nitrogen Accumulation in Greenhouse Vegetable Fields with Different Planting Years

Soil microbial communities are an important part of the soil ecosystem in greenhouse vegetable fields, where ammonia-oxidising microorganisms play a key role in nitrogen conversion. The health and stability of the ecological environment of greenhouse vegetable fields are affected by the number of years of continuous cultivation. We used real-time PCR amplification and 16S rRNA gene sequencing to analyse the changes in soil microbial community structure and diversity in different planting years (0, 3, 9, and 13). The content of environmental factors increased with the increase of planting year; the NO3−-N content in the 0–20 cm soil layer showed a cumulative trend, peaking to 1290–1390 mg/kg in year 13. The abundance of operational taxonomic units (OTUs) in the microbial community gradually decreased, and the OTUs of 0–20 cm soil layer in year 13 decreased by 52.2% compared to year 0. The Shannon and Simpson indices indicated a substantial decrease in microbial diversity after year 9. The dominant phyla in the soil microbial community mainly included Firmicutes (23.6%), Actinobacteria (23.2%), Proteobacteria (17.6%), Crenarchaeota (83.4%), and Euryarchaeota (2.7%). Nitrosopumilus and Nitrososphaera in the ammonia-oxidising archaeal (AOA) community and Nitrolancea and Nitrospira in the ammonia-oxidising bacterial (AOB) community dominated the ammonia-oxidising microorganisms. With the increase in planting years in greenhouse vegetable fields, the structure of soil microbial community changed significantly, with soil biomass and diversity significantly decreasing in years 9 and 13. Reasonable fertilization and planting year would improve microbial activity and provide a basis for sustainable utilization and high-quality production in greenhouse vegetable fields