Novel Humo-Pectic Hydrogels for Controlled Release of Agroproducts

Sustainable and precision agriculture requires that agroproducts be employed for plants' benefits with maximum efficiency and reduced environmental hazard. Since hydrogels may become efficient vehicles for agroproduct spreading, we prepared novel humo-pectic hydrogels by first blending low methyl-esterified pectin with either humic substances (HS) extracted from different composted biomasses or humic-like substances (HULIS) from depolymerized lignocellulose waste derived by biorefinery activities and, then, by cross-linking with calcium chloride through ionotropic gelation. Hydrogels were characterized by solid-state C-13 NMR spectroscopy, scanning electron microscopy (SEM), magnetic resonance imaging (MRI) and rheological analyses. Their ability to work as controlled-release systems was tested by kinetically monitoring the release of a previously incorporated phloroglucinol. Our results indicated that the hydrogels made with HULIS (HP-HULIS) showed a better controlled-release property than those containing HS (HP-HS). This highly depended on the larger content of oligosaccharides, lesser porosity, and greater cross-linking density of HP-HULIS as compared to HP-HS. Our study suggests that the development of a technology based on such novel humo-pectic hydrogels as carriers of bioactive compounds may represent a promising strategy for the controlled and environmentally safe delivery of agroproducts to crops.