Bio-stimulants improve tomato growth by regulating the rhizosphere microbiome involved in phosphorus and nitrogen...

Bio-stimulants are promising environment friendly alternatives to support sustainable agricultural development, capable of boosting crop growth and yield while cutting down excessive dependence on chemical synthetic fertilizers. Nevertheless, the explicit regulatory mechanisms by which bio-stimulants exert the role of growth-promoting functions still remain largely unclear and require further systematic clarification. In this study, we explored the influences of bio-stimulants (rich in humic acid) on tomato growth performance and rhizosphere microbial community assembly via greenhouse trials, and comparatively analyzed the functional differences between foliar spraying and root irrigation application modes. The results demonstrated that bio-stimulants treatment markedly improved tomato aboveground biomass, plant nitrogen and phosphorus accumulation by 17.1%, 27.4% and 22.7%, respectively. Meanwhile, bio-stimulants application effectively raised soil available nitrogen and soil organic matter levels, and further facilitated phosphorus assimilation in tomato plants. Metagenomic sequencing confirmed that bio-stimulants substantially reshaped the overall structure and composition of tomato rhizosphere microbiome. Specifically, they dramatically enriched the relative abundance of core microbial taxa responsible for soil nitrogen fixation and phosphorus solubilization. Collectively, these results clearly elaborate the underlying action mechanism: bio-stimulants optimize rhizosphere micro-ecological environment, enrich functional nutrient-solubilizing microorganisms, improve soil nutrient availability, and ultimately promote nutrient absorption and vegetative growth of tomato plants. This study confirms that bio-stimulants can serve as efficient and reliable regulators to advance green and sustainable crop production.