A nano-encapsulated seven-strain microbial biostimulant for sustainable agriculture: controlled-release performance and soil-specific responses across Mollisol, Alfisol and Entisol soil orders in Kansas

This study reports an integrated, year-long evaluation of a nano-encapsulated, seven-strain microbial biostimulant developed for sustainable, large-scale temperate agriculture. A living consortium (Lactobacillus plantarum, Saccharomyces cerevisiae, Rhodopseudomonas palustris, Pseudomonas putida, Bacillus subtilis, Azotobacter chroococcum and Azospirillum brasilense) was co-encapsulated with targeted cofactors (molybdenum and silicon) and a balanced IAA-zeatin-gibberellin hormone package in chitosan nanoparticles (150 +/- 20 nm, zeta potential +24 mV) produced by ionic gelation with sodium tripolyphosphate. The carrier preserved viability above 1x10^10 CFU/mL for 12 months across 4-40 C, delivered encapsulation efficiencies of 78-91%, and provided sustained, diffusion-controlled release over 30-60 days. The platform was assessed from laboratory characterization through soil microcosms and greenhouse stress assays to replicated randomized field trials across the three principal Kansas soil orders. Field yield gains reached 14% (Mollisol winter wheat), 22% (Alfisol soybean) and 31% (Entisol corn under deficit irrigation), with a 28% improvement in nitrogen-use efficiency and the ability to substitute 25% of mineral fertilizer with no yield penalty. Nitrate and phosphate leaching fell by ~50% in sandy soils, microbial biomass carbon rose 35-145%, soil organic matter increased 0.5-0.6%, and acidic-soil aluminium toxicity was reduced by 48%. Responses were soil-specific: nutrient-use efficiency amplification on Mollisols, biological correction on Alfisols, and water and nutrient retention on Entisols. The results translate into evidence-based, soil-specific deployment strategies for Great Plains agriculture.