Shifts in Soil Bacterial Community Composition of Jujube Orchard Influenced by Organic Fertilizer Amendment

Organic fertilizer application in agricultural land is known to improve soil microbial processes, fertility, and yield. In particular, the changes in soil chemical composition due to multi-year application of organic fertilizers are thought to alter the microbial community. Here, the effects of organic fertilization with oil-cake amendments (OC) on soil bacterial diversity, community profile, and enzyme activity were evaluated and compared to those amended with chemical fertilizer (NPK). Diversity indices show that the application of organic fertilizer potentially increases microbial diversity as well as the number of different microbial groups. The ordination plot distinguished and clustered both treatments, showing the differential effects of soil chemical factors on the microbial communities in each treatment. Proteobacteria, Verrucomicrobia, and Bacteriodetes were significantly more abundant in OC-amended soil than in the NPK soil, indicating alterations in community structure, composition, and diversity, concurrent to the changes in the pH, Ca, and Mg contents of the soil. These shifts in bacterial community structure and composition, partially explained by differences in soil chemical factors, could be observed from the phylum to the genus level in NPK- and OC-amended soils. The OC soil contained a significantly higher abundance of predicted genes corresponding to enzymes related to biogeochemical cycling, decomposition, and plant growth promotion. Collectively, these results support the use of an unconventional organic fertilizer positively altering bacterial populations in jujube orchards. The application of an unconventional organic fertilizer improved microbial diversity and enhanced ecosystem functions related to biogeochemical cycles, mineralization, and plant growth promotion.