Integrated Use of Plant Growth-Promoting Rhizobacteria and Chemical Fertilizers Improves the Growth and Yield of the Tomato Plant

Microbial biofertilizers offer a sustainable alternative to reduce inorganic fertilizer inputs in intensive vegetable production. While rhizobia are traditionally associated with legumes, their co-inoculation with native rhizobacteria for non-leguminous crops like tomatoes remains under-explored. This study aimed to isolate native rhizobacteria compatible with Bradyrhizobium diazoefficiens NE1-65 and evaluate their combined effect on the tomato plant (var. max F1) under reduced inorganic fertilizer rates. From the initial eighteen isolates screened on nitrogen-free media, and solubilization assays of phosphorus and potassium, three isolates (RM-8, RM-17, RM-18) were found compatible with B. diazoefficiens NE1-65. Isolate RM-17 (tentatively identified as Aureimonas sp. based on 16S rRNA gene sequence) was selected for its high K-solubilizing capacity (KSI = 8.60). Then, a 90-day growth trial compared various fertilizer application rates (0, 25, 50, 75, and 100%) with and without the bacterial consortia. The 75% fertilizer rate plus the consortia significantly outperformed the 100% fertilizer rate alone. Specifically, it increased plant height (11.57%), fruit diameter (9.23%), fruit number (53.90%), and fruit weight (16.15%). These findings demonstrate that the RM-17 and B. diazoefficiens NE1-65 consortia can partially substitute inorganic fertilizers while significantly enhancing tomato growth and yield, highlighting its potential application for sustainable tomato production systems.