The addition of molybdenum to urea changes its characteristics and can react with N-(n-butyl) thiophosphoric triamide

ABSTRACT The development or blending of new products represents a common practice of improvement for the efficiency of existing commercialized fertilizers. The physicochemical characteristics of new formulations differ from those of raw materials. These characteristics directly influence the quality of the fertilizer, as they can alter the storage and application requirements. It is hypothesized that molybdenum (Mo) can be added to urea without affecting urea characteristics and N-(n-butyl) thiophosphoric triamide (NBPT) efficacy. The objective of this study was to characterize the addition of Mo sources and rates to urea treated or not with NBPT at 530 mg per kg of urea. A total of 30 fertilizers were formulated by combining three factors: three types of urea (untreated urea, NBPT-coated urea, and NBPT-incorporated urea), two sources of Mo (ammonium molybdate and Mo trioxide), and five rates of Mo (0, 1.5, 3.0, 6.0 and 12.0 g kg–1 N). Unless the degradation rate of NBPT was not measured, the granules were evaluated in terms of nutrient content salinity, hardness, hygroscopicity, and angle of repose. The physical quality of the fertilizer was affected at Mo rates exceeding 6 g kg–1 N, particularly with soluble Mo sources, resulting in the formation granules with lower hardness and higher hygroscopicity. The addition of ammonium molybdate (Am) was observed to exert a lesser impact on the characteristics of the granules, particularly at Mo rates below 6 g kg–1 N. The interaction between Mo and NBPT remains unclear, and further research is necessary to elucidate the underlying mechanism and the stability of the inhibitor.