Temporal variations of soil microbial community under compost addition in black soil of Northeast China

Soil microorganisms play crucial roles in regulating dynamics of organic matter in agroecosystem, and are conspicuously influenced by agricultural practices. To reveal the effect of compost addition on soil microorganisms, we examined the soil properties, soil microbial biomass, activity, diversity and communities at soybean seedling, flowering and mature stage in a 1-year compost addition experiment system in Northeast, China. Soil microbial communities were determined using Biolog EcoPlates T. Structural equation model (SEM) was applied to disentangle the direct and indirect effects of compost on soil microbial properties. The results showed that compost addition significantly enhanced soil organic matter, electrical conductivity, total nitrogen, total phosphorus (P), available P, available N and kalium. Soil microbial biomass, activity and diversity showed significant temporal variations during the cropping season, but unaffected by compost addition. Moreover, highest soil microbial biomass was found in the seedling stage, while soil microbial diversity and activity were lowest at the same time. SEM showed that temporal change exhibited a stronger effect on the soil microbial community composition than compost addition. Although the soil microbial community composition was unaffected by compost addition in the seedling and flowering stage, it was significantly affected in the mature stage. Our findings highlight the significant effect of compost addition on soil nutrient availabilities, and emphasize temporal change to be a stronger determinant than 1-year compost addition in shaping microbial communities in black soil of Northeast China.