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. The treatments included the following: C: control, U: urea, Zn: zinc sulfate, UZn: urea-Zn complex, UZn-DE: urea-Zn-diatomite, UZn-NDE: urea-Zn-nano-diatomite. The slow-release urea-Zn fertilizers (SRUZns) were characterized and then the releasing behavior of these in 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 by UZn-NDE application. 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 with minimal environmental effluence.

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