Guar gum/PVA/graphene oxide environmentally friendly hybrid hydrogels for sustained release of urea fertilizer

Modern agriculture faces several critical challenges related to water scarcity, leaching and fertilizer runoff. To overcome the afore-mentioned challenges, hydrogels being an excellent choice that act as water/nutrient mini-reservoirs in soil and improve water retention capability for healthier plant growth. For this purpose, guar gum (GG), poly(vinyl alcohol) (PVA) and graphene oxide (GO) hydrogels were cross-linked with 3-Glycidyloxypropyl trimethoxysilane (GTMS) to prepare GG/PVA/GO hydrogels for agronomic applications. The FT-IR spectrums confirmed the functional groups related to the hydrogel ingredients and their intermolecular interactions especially siloxane linkages. FE-SEM micrographs revealed the heterogeneous hydrogel surfaces that can be exploited for fertilizer adsorption. The GG/PVA/GO hydrogels became degradable in the sandy soil up to 18 days. The swelling volumes of the hydrogels were maximum at pH 7. The highest swelling percentages were 2661% and 2151% displayed by GGP(cont) and GGP-8 in the distilled water, correspondingly. The hydrogels also demonstrated excellent water retention when 0.2% was mixed with 20 g of sandy soil. Urea release profile from GGP-16 depicted 89.25%, 94.2% and 85.96% release in phosphate buffer saline, distilled and rainwater in 40 days, respectively. In conclusion, the fabricated GG/PVA/GO degradable, the water retentive hydrogel frameworks would be an ideal platform for the urea release in terms of the agricultural applications.