Organic matter-derived soil amendments containing humic substances (HS) have a functional role in improving plant growth and soil quality. A recent study assessed the impact of lignite-derived HS on biota growth and evaluated their potential mitigative effects under water deficit stress in bell pepper plants grown in sandy and clay soil previously mixed with HS. Our results showed that HS increased plant root development and soil bacteria population in moderate and no stress conditions (60%, 80% water holding capacity). Physiologically, HS rapidly decreased leaf stomatal conductance and transpiration (reducing water loss) after imposing severe or mild stress (20%, 40%). Due to their capacity to improve plant root growth, soil nutrient cycling, and microbial activity, application of HS may have long-term benefits in agricultural systems. A follow-up HS study using path analysis distinguished abiotic factors that affected the rhizosphere microbial biomass in a bell pepper system. This study can be a reference to establish applied approaches to improve the persistence and benefits from rhizosphere microbial communities.
