Nitrogen Release of Coated Urea Fertilizers in Different Soils.

There are many management practices that can increase fertilizer use efficiency, such as correct fertilizer type, application time, quantity, placement, and potentially the use of coated urea fertilizers (CUFs). Most nitrogen (N) uptake in row crops occurs during a short time period of maximum growth. In particular, rapid N uptake in corn grown in North Carolina begins at approximately 30 days after planting (Chandler, 1960). Therefore, the timing and extent of N release from CUFs are of interest in agronomic management decisions. The N release from CUFs (Arborite® and ESN®) and traditional N fertilizers (urea [(NH₂)₂CO)] and urea ammonium nitrate (UAN) [(NH₂)₂CO, NH₄NO₃]) in three North Carolina USA soils was measured throughout a 12-week laboratory incubation. Treatments were N source and moisture level (60% and 80% of field capacity). In the study, ESN and Arborite resulted in maximum N release at week 4 in the Candor soil and at week 2 in the Portsmouth soil at 60% of field capacity. Initially less N was in plant available form in the coated urea treatments (Arborite, ESN). Though, by the end of the incubation period (12 weeks), no differences in %N release were found among treatment in the Candor or Cecil soils. These results suggest that the coated ureas release profiles may better match N uptake patterns for crops such as corn, and may have the potential to increase yields and N use efficiency over more traditional N fertilizers. A more detailed study of these coated ureas in crop production systems under prevailing environmental conditions will be required to determine if these products are equally economical with more traditional N fertilizers for production agriculture in places such as North Carolina.