The nitrogen slow-release fertilizer based on urea incorporating chitosan and poly(vinyl alcohol) blend

For mitigating environmental pollution caused by excess usage of urea fertilizer, this paper reports a new fertilizer formulation, based on urea incorporating chitosan (CS) and poly (vinyl alcohol) (PVA) blend, for the slow release of urea. The urea/CS/PVA formulations were prepared by cross-linking CS and PVA blend in the presence of urea with glutaraldehyde as a cross-linker. The results indicated an interaction between urea and the functional groups of CS and PVA through hydrogen bonding, which has significant effects on the thermal properties of urea/CS/PVA formulation. The surface morphology of urea/CS/PVA formulations showed that the quantity of urea crystals anchored on the surface increased with the contents of urea and the cross-linking agent. Urea/CS/PVA formulations with a high degree of cross-linking had low water absorbency in the early stage. Meanwhile, they improved hydrolytic stability in the latter stage upon being immersed in water. The sustained release of urea from urea/CS/PVA formulations was prolonged to 10 days. The amount of urea released from urea/CS/PVA formulation with low urea contents followed the first order and Hixson-Crowell models. In contrast, urea/CS/PVA formulation with high urea contents fitted well to the Higuchi and Korsmeyer-Peppas models. This study provides a simple process to produce urea/CS/PVA formulation, a potential slow-release fertilizer used in agriculture to minimize adverse environmental and economic impacts. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study presents a new fertilizer formulation based on urea, chitosan, and poly (vinyl alcohol) for slow release of urea, with improved hydrolytic stability and sustained release effects. The interaction between urea and functional groups of chitosan and PVA significantly affects the thermal properties of the formulation. The formulation shows potential as a slow-release fertilizer to reduce adverse environmental and economic impacts in agriculture.