Nitrogen Release from Sulfur‐Coated Urea, as Affected by Coating Weight, Placement and Temperature1

Abstract

AbstractGreenhouse and laboratory studies were conducted to measure the factors controlling release of N from sulfurcoated urea (SCU). Results of two greenhouse pot experiments with common bermudagrass (Cynodon dactylon) and a third with uncropped soil in controlled environment regimes showed that the rate of dissolution of SCU increased greatly with higher temperatures of cropping or incubation. Dissolution rates of SCU granules were decreased by heavier coating with S, by inclusion of 0.5% coal tar oil microbicide in the coating, and by surface application, as compared to mixing with the soil. Satisfactorily coated urea (SCU) or split applications of uncoated ammonium nitrate (AN) or urea both resulted in more uniform distribution of forage production and N uptake than did a single application of urea or AN at time of seeding. Greater yields of forage were obtained from single applications of some SCU products than from urea or AN. Apparent volatilization losses of surface‐applied urea were severe, particularly at higher growth or incubation temepratures. Losses of N were reduced, but not entirely eliminated by S‐coating.