Reshaping the rhizosphere microbiome by bio-organic amendment to enhance crop yield in a maize-cabbage rotation system

Characterizing the rhizosphere microbial community composition associated with enhanced crop yield is an important first step towards understanding the role of the microbiota in soil fertility. In the present study, we conducted a two-seasons field experiment in a maize-cabbage cropping system under chemical (CF), organic (OF) and bio-organic (BOF) fertilizer regimes as a model to investigate the combinatory effect of fertilizer treatment and crop type on rhizosphere soil microbiota by targeted sequencing of both the bacterial and fungal communities. The two-seasons sustainable application of bio-organic fertilizer (BOF) containing Trichoderma effectively increased maize and cabbage yields, whereas organic fertilizer (OF) increased but not significant, compared to the application of chemical fertilizer (CF). Both fertilizer treatment and crop type induced a significant effect on soil physiochemical properties and were the major factors that impacted the composition of the rhizosphere soil microbiome. Relative abundances of Trichoderma were significantly enhanced in the BOF treatment, compared to the OF and CF treatments, and exhibited significant positive relationships with crop yield improvement. The application of bio-organic fertilizer may enhance the growth promotion effect of Trichoderma and increase the abundance of potentially beneficial microbial groups such as the genera Cladorrhinum and Massilia, which were found to be highly correlated to increased crop yields. Overall, the influence of bio-organic fertilizer on crop yield is proposed to be through mechanisms by introduction of the target strain NJAU 4742 and stimulation of a potentially beneficial microbial consortia, in combination with alterations in fungal and bacterial composition and abundance, leading to an enhancement in crop yield.