Enhancing maize growth and reducing irrigation needs with extracellular polymeric substances and microbial inoculants

Soil amendments and microbial inoculants can affect plant growth, water retention, and crop resilience. This study investigated the effects of two amendments, extracellular polymeric substances (EPS) and biochar, with and without bacterial inoculation, on maize (Zea mays) growth, irrigation needs, and physiological responses. Maize was cultivated in soil with 2.5 % and 5 % (w/w) of wet EPS (Kaumera®) or biochar and inoculated with a bacterial consortium consisting of Arthrobacter nicotinovorans EAPPA and Rhodococcus sp. EC35. EPS-treated plants exhibited significantly higher shoot biomass, larger stem thickness, while soil plant analysis development (SPAD) values suggest improved nutrient availability and photosynthetic efficiency. In non-inoculated plants, EPS supplementation increased shoot dry biomass by 78 % and stem thickness by 9 % compared to control plants grown without amendments. This enhancement strongly correlated with nutrient uptake, especially in plants supplemented with 5 % of EPS. Particularly, Mg and Ca concentrations increased by 195 % and 73 %, respectively, compared to non-amended controls. Inoculation further amplified these benefits, underscoring its key role in plant development and resilience. In contrast, biochar-treated plants exhibited reduced growth, suggesting stress effects at the tested addition doses. Electrolyte leakage, a key indicator of plant stress, was significantly lower in soils amended with EPS, suggesting that EPS provides a protective effect to the plants. EPS also demonstrated remarkable water retention benefits, reducing irrigation requirements by 30 % with 5 % of EPS application, compared to 9 % reduction with biochar. The use of EPS, combined with microbial inoculants, represents a sustainable agricultural strategy for optimizing maize production in water-limited environments.