Medicago sativa and soil microbiome responses to Trichoderma as a biofertilizer in alkaline-saline soils

The use of Trichoderma biofertilizer (BOF) has been proposed to observably elevate plant growth and crop productivity. In addition, mowing can greatly accelerate plant shoot regrowth to increase aboveground biomass and nutrient contents. We aimed to measure the effects of Trichoderma BOF on Medicago sativa growth in saline-alkali soils, especially the effects on the underlying microbial ecological mechanisms, under non-mowed and mowed conditions. We thus carried out a pot experiment to investigate the growth of M. sativa under different fertilization regimes and utilization conditions, and the corresponding responses of soil physicochemical variables and the soil microbiome were also explored. Fertilization, mowing and their interaction had significant (P = 0.000) effects on M. sativa shoot dry weight, while only fertilization had a significant (P = 0.000) effect on M. sativa root dry weight. Compared with nonamended fertilizer (CK) and organic fertilizer (OF) treatments, Trichoderma BOF treatment significantly (P < 0.05) increased the biomass of M. sativa. High bacterial HShannon and SChao1 values in mowed system and high fungal HShannon and SChao1 values in the non-mowed system were significantly (P < 0.05) correlated with a high M. sativa biomass. Mantel test results showed that soil microbial community composition was significantly (P = 0.001) correlated with M. sativa biomass in both the mowed and non-mowed systems. In addition, variance partitioning analysis (VPA) revealed that soil properties were the main factor explaining the variation of soil microbial community composition, accounting for 14.1% for bacteria and 16.5% for fungi. In conclusion, Trichoderma BOF can effectively alter soil properties and the soil microbial diversity and community, resulting in increased M. sativa biomass in alkaline-saline soils in both mowed and non-mowed systems.