Double Coating as a Novel Technology for Controlling Urea Dissolution in Soil: A Step toward Improving the Sustainability of Nitrogen Fertilization Approaches

Abstract

This research introduces a novel technology for reducing ordinary urea (OU) dissolution by developing double-coated urea (DCU) using phosphate rock (PR) as an outer layer to reduce its hydrolysis and sodium thiosulfate (STS) as an inner layer to inhibit the urease enzyme and nitrification process. Due to the double coating, the nitrogen content of DCU was lower than that of the OU (36.7% vs. 46.5%). The ultramorphological analysis using scanning electron microscopy (SEM) indicated that the controlled coating of urea, resulting from the outer layer of PR, was due to the adhesive effect of urea formaldehyde (UF), which was used as a glue. In addition, the transmission electron microscopy (TEM) analysis of the DCU revealed its high degree of agglomeration. The mechanical hardness of DCU was higher compared to that of OU (1.38 vs. 1.08 kgf). The seven-day dissolution rate test showed that OU reached 100% dissolution on the fifth day. The rate of DCU, however, was significantly lower (32% dissolution in the seventh day). Cumulative NO3− and NH4+ losses from a clay soil sample reached 68.3% and 7.6%, respectively, with OU measuring 40.5% compared to 4.9% for DCU 70 days after application. Field experiments showed a significant improvement in the marketable yield and agronomic nitrogen efficiency (ANE) of maize grains and zucchini fruits fertilized with DCU. Furthermore, the macro and micronutrient concentrations in maize grains and zucchini fruits showed an increase in the plants fertilized with DCU. In summary, double coating can be introduced as a novel technique to control urea dissolution in soil.

Land Degradation, Causes, Implications and Sustainable Management in Arid and Semi Arid Regions: A Case Study of Egypt

“…The physical extent and adversity of nutrient pollution have progressively increased during the last few decades. Agricultural fertilisers are the primary source of nutrients, and their use has expanded dramatically during the last 20 years (El-Ghamry et al, 2021). Another source of pollution in this area is atmospheric deposition, and while determining the amount with any precision is difficult, all studies indicate that it is significant (such as sulphur oxides, nitrogen oxides, heavy metals etc) (Li and Daler, 2004;Amodio et al,2014).…”