Effects of coated urea amended with inhibitors on improving N use efficiency and its allocation in a soil-maize system

Coating and inhibitors are proposed as means to increase nitrogen (N) use, but their effects are variable. Coating and incorporation of inhibitors could be more effective. This study aimed at investigating the effects of a novel enhanced urea on yield and N use. We also assessed the N release capability of this novel product. The experiment consisted of six treatments: no-urea control (CT), uncoated 15N-urea (U), polymer-coated 15N-urea (PCU), 15N-urea coated of mixed polymer and inhibitors (PICU), 15N-urea with double-layer coating, polymer on the top of inhibitors (PCIU), and 15N-urea with double-layer coating, inhibitors on the top of polymer (PCUI). The results showed that coated urea amended with inhibitors improved fertilizer-N recovery more effectively than regular coated urea. Yields with PICU and PCIU were increased by 13% and 18%, respectively. Their 15N uptake by plant was increased by 57% and 77%, respectively. Clay mineral and microorganism under PICU, PCIU and PCUI fixed 19%~23% of applied N, facilitating nutrient retention. We demonstrated that PCIU could be an effective means to promote N use and retention as well as improve maize yield.