Complex microbial consortia improve yield and physiological performance of leafy greens under deficit irrigation

Water scarcity is an increasing constraint on agricultural productivity and demands scalable strategies that improve crop performance under reduced irrigation. As soil microorganisms regulate key processes at the soil-plant interface, microbial inoculants may help sustain plant growth and physiological function during water limitation. Here, we assembled five functionally diverse microbial consortia containing taxa selected to support rhizosphere colonization, soil structural stabilization, and fungal-mediated nutrient and water foraging. These consortia were evaluated in greenhouse trials with lettuce and spinach grown under full irrigation or a 30% deficit irrigation regime (70% of crop water requirement). Crop responses were assessed using yield, harvest delay, root length, wilting incidence, chlorophyll content, and Water Band Index (WBI). Across both crops, microbial consortium treatments improved performance under deficit irrigation relative to untreated water-stressed controls. In lettuce, yield increased by 3-9%, while in spinach yield increased by 4-13%, with several treatments restoring performance to levels not significantly different from the fully irrigated control. Microbial treatments also reduced harvest delay by an average of three to four days, improved root length, lowered wilting incidence, and reduced WBI, indicating reduced plant water stress. In several cases, these physiological responses approached those observed under full irrigation despite 30% lower water input. Higher application rates (500 vs 250 g h-1) generally produced stronger responses, although this trend was not always statistically significant. Together, these results show that complex microbial consortia can buffer the negative effects of deficit irrigation and improve crop performance in leafy greens. These findings support the development of microbial inoculants as biologically based tools to enhance agricultural resilience under increasing water scarcity. TeaserMicrobial soil inoculants help crops maintain yield and harvest synchrony under reduced irrigation.