Optimization of the composition of biopolymer matrices for encapsulating liquid biostimulants

Abstract

Modern agriculture demands increasingly higher fertilizer doses to sustain crop productivity, raising concerns about nutrient loss and environmental impact. To address this challenge, this study explores the potential of biopolymer-based matrices for the controlled release of liquid fertilizers. The research focused on optimizing the matrix composition to minimize nutrient exchange and achieve a slower, sustained release of the encapsulated hydrolyzate. Using response surface methodology (RSM), the optimal concentrations of sodium alginate (4% m/m), bentonite (6% m/m), and starch (2% m/m) were determined, ensuring a gradual hydrolyzate release with an absorbance reduction from 0.148 to 0.034 over time. The optimized matrix was evaluated under simulated agricultural conditions, where swelling capacity reached 69.41% of the initial dry mass after 48 h, and the biopolymer structures exhibited 52% biodegradation within 4 weeks. Leaching experiments revealed that the highest nutrient release occurred within the first 15–60 min, followed by a linear release trend up to 168 h, ensuring sustained fertilization. In vivo tests confirmed the effectiveness of the hydrogel matrix in early-stage plant development, showing an increase in stem length by up to 29% and fresh biomass by 46% compared to the control. The encapsulated hydrolyzate enabled the application of up to a 200% fertilizer dose without phytotoxic effects, a significant improvement over direct hydrolyzate application, which previously inhibited germination at doses as low as 20%. Elemental analysis demonstrated improved nutrient retention, with potassium and sulfur concentrations following a linear uptake trend in soil. This study aims to develop a sustainable, biopolymer-based fertilization system that enhances nutrient efficiency, prevents over-fertilization, and improves crop productivity. The findings provide a foundation for precision agriculture, offering a scalable solution for optimizing nutrient release and plant growth while reducing environmental impact.