New Slow-Release Urea Fertilizer Fortified with Zinc for Improving Zinc Availability and Nitrogen Use Efficiency in...

Improving nitrogen (N) use efficiency (NUE) is necessary to reduce the entry of excess N into the environment and to retain N in the soil. Few studies have been done on dual-purpose slow-release fertilizers using urea and zinc (Zn). In this study, a new Zn-incorporated urea slow-release fertilizer with diatomite (DE) and nano diatomite (NDE) was synthesized by matrix-type formulation. The treatments included the following: C: control, U: urea, Zn: zinc sulfate, UZn: urea-Zn complex, UZn-DE: urea-Zn-diatomite, and UZn-NDE: urea-Zn-nano diatomite. The slow-release urea-Zn fertilizers (SRUZns) were characterized, and then the releasing behavior of these in the soil was monitored. A greenhouse study was carried out to check the agronomic effects of the maize (Zea mays L.). Instrumental analyses approved the binding of the UZn complex into DE and NDE. Usage of SRUZns leads to better retention of NH₄⁺ relative to NO₃^-. The nano diatomite was twice as effective as diatomite in NH₄⁺ retention in soil. The cumulative losses of available Zn in the soil were the lowest upon UZn-NDE application. A pot study revealed that UZn fertilizers boosted crop growth in comparison to urea and zinc sulfate. N uptake increased 44.8% in the application of UZn-NDE compared to the U, and Zn uptake in soils supplied with the same treatment was 34.37% more than the ZnSO₄ application. The NUE increased by about 50% in plants supplied by nano slow-release compared to U. The results showed that the dual-purpose SRUZns with slow-release behavior could be reflected as well-organized N and Zn fertilizers in agricultural and horticultural areas with minimal environmental effluence.