Sprayable coating with poly(vinyl alcohol) modified metal–phenolic networks for slow‐release urea

Abstract Urea plays a crucial role in agricultural production; however, issues of misuse and low utilization persist. To address this, a poly(vinyl alcohol) (PVA) modified metal–phenolic networks (MPNs) coating was developed to enable the slow release of urea. The coating formulations involved blending tannic acid (TA) and Fe 3+ at different molar ratio, along with varying amount of PVA. The resulting TA‐Fe 3+ ‐PVA coating with a 1:3 molar ratio of TA:Fe 3+ and 1 mg/mL of PVA formulation exhibited stable and dense properties. Urea granules were then coated with this formulation using a fluidized bed technique, leading to reduction in nutrient release rate and increase in longevity. Especially, the nutrient release rate was approximately 10 days in soil. Pot experiments confirmed that the coated urea effectively enhanced cotton yield and quality. Therefore, the newly developed TA‐Fe 3+ ‐PVA coated urea shows promising potential in agriculture for maintaining yield while reducing urea application amounts in the future.