Co-application of biochar and microbial inoculants increases soil phosphorus and potassium fertility and improves soil health and tomato growth

Purpose The objective of this study was to investigate the effects of application of biochar and microbial inoculants on the bioavailability of phosphorus and potassium, tomato growth, and the bacterial community in greenhouse soil. Materials and methods The experiment was conducted in a greenhouse with tomato mono-cropped for 21 years at Yongqing County of Hebei Province from November 2018 to June 2019. The treatments included conventional fertilization control (CF), 2 t/ha of biochar application (B, manufactured from apricot shell), 75 L/ha of microbial inoculants application (M, containing effective strains of Bacillus megaterium and Paenibacillus mucilaginosus ), the mixture of microbial inoculants and biochar application (BM). Results The results showed that the application of 75 L/ha microbial inoculants in greenhouse tomato could increase the yields of tomato by 23.41%, vitamin C (Vc) and soluble sugar concentrations by 14.41% and 13.62%, respectively. The microbial inoculants combined with 2 t/ha biochar enhanced the effects of microbial inoculants on the growth promotion of tomatoes. The application of microbial inoculants combined with biochar increased the P and K accumulation in tomato plants by 28.72–57.14% and 19.53–29.03%, respectively, during the whole growing stage. Moreover, the application of microbial inoculants significantly increased the relative abundance of Bacillus , Paenibacillus , and Flavobacterium and decreased the relative abundance of Acidobacterium . Conclusions The application of microbial inoculants improved the bioavailability of phosphorus and potassium and tomato growth by altering the composition of soil bacterial community. These results show the potential of co-application of biochar and microbial inoculants as a potential tool to sustain longer-term production of monoculture vegetable systems in greenhouses.