Work

Development of slow-release humic acid fertilizer using starch-based hydrogel

Year: 2025

Type: article

Abstract: The use of humic acids (HAs) has gained increasing attention as a response to the decline in agricultural land productivity, which has been exacerbated by the excessive use of synthetic fertilizers.This work presents a novel HAs-based slow-release fertilizer (SRF-HAs) developed through in-situ radiation-synthesizing starch-grafted polyacrylamide (AM) hydrogels encapsulating HAs. To prevent the highly active phenolic groups in HAs from quenching the free radicals generated by radiation, the surface of HAs particles was firstly coated with stearic acid or wax. The microstructures and performances of the SRF-HAs were characterized using SEM, NMR, FTIR, rheometer, and release rate. Additionally, TGA was utilized to quantify the grafting and conversion rates of AM. The release rate of HAs strongly depends on the microstructures and strength of the starch-based hydrogel, which is governed by both the surface coating and radiation-synthesizing processing. Both FTIR and NMR confirmed the successful grafting polymerization on starch chains. The release periods of HAs from the coated samples extended up to 53 and 60 days, respectively, and the initial bust releases were significantly reduced to about 30%, complying with ISO and ASTM standards. The relationships between the microstructures, properties of the hydrogels, and release rate were discussed and established.

Source: Industrial Crops and Products

DOI: 10.1016/j.indcrop.2025.120648