Effect of urease inhibitors and cationic materials on growth response and ammonia volatilization following fertilization of Kentucky bluegrass (Poa pratensis L.) with urea

Urea is a major source of nitrogen (N) fertilizer for the turf industry. Fertilization with urea in both liquid and dry forms involves the risk of considerable N loss to the atmosphere as gaseous ammonia (NH[subscript]3). This NH[subscript]3 volatilization is a major N loss mechanism of surface-applied urea. Among the methods that have been proposed to reduce this N loss are the application of urea with urease inhibitors and the combinations of urea with cationic materials. Studies on the effects of urease inhibitors and cationic materials on growth response and NH[subscript]3 volatilization were conducted from 1983 through 1987 in both the field and laboratory. The purpose of the work reported in this dissertation was to evaluate the urease inhibitors phenylphosphorodiamidate (PPD), N -(n -butyl) thiophosphoric triamide (NBPT), and ammonium thiosulfate (ATS), and the cations potassium (K[superscript]+) and magnesium (Mg[superscript]++) as fertilizer amendments for increasing urea-N efficiency by measuring the effect of these compounds on growth response and NH[subscript]3 volatilization following application of urea to Kentucky bluegrass (Poa pratensis L.) turf. The results indicate that the urease inhibitors NBPT and PPD have potential for increasing N use efficiency of urea-N applied as a liquid fertilizer to Kentucky bluegrass by reducing NH[subscript]3 volatilization. It is concluded that NBPT is the most effective of the materials tested and that both NBPT and PPD deserve further evaluations as fertilizer amendments for the turfgrass industry