A Nano-encapsulated Seven-strain Microbial Biostimulant improves Nutrient-use Efficiency, Soil Health and Crop Productivity across Contrasting Soil Orders: An Integrated Laboratory, Greenhouse and Multi-site Field Validation

Abstract

Purpose: This study evaluated the agronomic performance, stability, soil-health effects and climate-resilience potential of a nano-encapsulated microbial biostimulant designed to improve fertilizer-use efficiency and reduce nutrient losses. The formulation combined a seven-strain microbial consortium with a chitosan nanocarrier co-loaded with molybdenum, silicon and plant-growth regulators.

Methodology: A fully integrated 12-month laboratory, greenhouse and multi-site field evaluation was conducted. The microbial consortium comprised Lactobacillus plantarum, Saccharomyces cerevisiae, Rhodopseudomonas palustris, Pseudomonas putida, Bacillus subtilis, Azotobacter chroococcum and Azospirillum brasilense at ≥1 × 10⁹ CFU mL⁻¹. Physicochemical characterization, storage-stability testing, freeze–thaw cycling, soil microcosm studies, greenhouse stress assays and replicated randomized field trials across three soil orders were performed. Root-architecture imaging, 16S rRNA profiling, principal component analysis and economic modelling were also used to validate the results.

Findings: The nanoparticles had a mean size of 150 ± 20 nm, a polydispersity index below 0.3 and component encapsulation efficiencies of 78–91%, with diffusion-controlled release over 30–60 days. The formulation maintained 1.2–2.8 × 10⁹ CFU mL⁻¹ across 4–40 °C for 12 months and remained stable during freeze–thaw cycling. Grain yield increased by 14% in winter wheat, 22% in soybean and 31% in corn under deficit irrigation. Nitrogen-use efficiency improved by 28%, while fertilizer application was reduced by 25% without yield loss. Nitrate and phosphate leaching declined by 52% and 47%, respectively, in sandy soils. In acidic soil, pH increased by 0.4 units and exchangeable aluminium decreased by 48%. Microbial biomass carbon increased by 35–145%, while soil organic matter increased by 0.5–0.6% within one growing season. Under drought, heat and salinity stress, plants retained 75–82% of their growth and photosynthetic efficiency.

Unique Contribution to Theory, Practice and Policy (Recommendations): The study demonstrates that combining beneficial microorganisms, micronutrients and plant-growth regulators within a controlled-release chitosan nanocarrier can simultaneously improve crop productivity, nutrient-use efficiency, soil biological activity and tolerance to environmental stress. The findings provide soil-specific deployment pathways for farmers, agricultural industries and extension services. The technology is recommended as a scalable strategy for reducing fertilizer dependence, limiting nutrient pollution, restoring degraded soils and strengthening climate-resilient agricultural production. Field validation across additional crops, soil types and agroecological regions is recommended before large-scale commercialization and policy adoption.