A novel microbial fertilizer derived from Pennisetum giganteum juice for drip-fertigation of solanaceous fruit vegetables

Jujuncao (Pennisetum giganteum Z. X. Lin) can be used as a substitute for wood in board production, but large amount of juice generated by this process urgently needs to be utilized. Herein, a novel microbial fertilizer was constructed by using P. giganteum juice as main medium to ferment three functional Bacillus spp. strains. Firstly, the strains FJAT-41480, FJAT-41479, and FJAT-41481 were mixed with different ratios and the optimal volume ratio of 1:2:1 was determined based on bacterial contents and the effects on the growth of solanaceous fruit vegetables. Then, the mixed strains were fermented in P. giganteum juice with exogenous nutrients to prepare the herb juice-based microbial fertilizer (HJMF). Furthermore, the preservatives potassium sorbate, sodium dehydroacetate and sodium diacetate were mixed and added into HJMF with the optimal dosage (via orthogonal experiment design with three factors and three levels) of 0.5, 0.5, and 0.01 g mL⁻¹, respectively. Pot experiments showed that HJMF could significantly increase the growth of tomato, chili and eggplant by 300, 500, and 800-fold, respectively. Field experiments showed that HJMF led to a notable decline in disease incidence (DI) of tomato bacterial wilt (TBW) by 76.38–81.50 % in Huian, and by 84.46–94.36 % in Yanping. Moreover, HJMF could significantly increase tomato yield by 87.87 and 58.95 % in Huian and Yanping, respectively, and significantly increase the concentrations of soil organic carbon, total nitrogen and total phosphorus. The rhizobacterial communities for HJMF treatment and non-HJMF control were compared by using high-throughout sequencing, and the results showed that HJMF could enrich soil beneficial bacteria Bacillus, Saccharimonadales, Bauldia and BIRII41, and suppress the growth of pathogenic bacteria Ralstonia and Pseudomonas. Overall, a novel microbial fertilizer was developed, demonstrating the ability to effectively promote the growth of solanaceous fruit vegetables, reduce DI of TBW, and regulate the microecological environments of rhizosphere soils.