Nitrogen release from urea with different coatings.

BACKGROUND: Coatings or urease inhibitors are designed to reduce losses of ammonia [NH3(g) ] from urea fertilizers. However, nitrogen (N) release and its effects on soil solution have not previously been evaluated under standardized conditions in soils. In this study, the urea fertilizers were incubated in chambers filled with sandy loam soil, adapted for the collection of NH3(g) and soil solution by centrifugation.

RESULTS: In the fast-release N fertilizers, around 93% and 100% of urea-N applied was recovered within the first hours of incubation. In contrast, in the slow-release N fertilizers, less than 40% of urea-N applied, was recovered at 19 days of incubation. The maximum N release from the fertilizers followed the order: UP1 (106%) ≈ UNBPT (102%) ≈ urea (93%) > USP2 (57%) ≈ USP3 (57%) > USP4 (31%) ≈ USP5 (18%). NH3(g) volatilization accounted for only 3% of the applied N in the slow-release fertilizers, which corresponded to about 88% less than the NH3(g) loss from prilled urea.

CONCLUSION: This study demonstrated distinct N release patterns, which changed the N dynamics in the soil. Some coatings effectively delayed urea release from granules and reduced NH3(g) gas losses, while other were not efficient. © 2017 Society of Chemical Industry.