Comparison of Controlled-release Nitrogen Fertilizers on Turfgrass in a Moderate Temperature Area

Abstract

Coating of conventional urea with polymers is designed to improve N availability to crops. A field experiment was conducted from 1993 to 1994 on turfgrass at Ellerslie, Alta., Canada, to determine release rates of coated urea applied on turfgrass thatch surface, and the effect of coated urea application on growth, color, and N uptake of turfgrass. The experiment was established on existing stands of a mixture of `Merion' Kentucky bluegrass (Poa pratensis L.) and `Gennuina' creeping red fescue (Festuca rubra L.) growing on a Black Chernozemic (Typic Cryoboroll) soil. The annual rate of N application was 100 kg·ha-1 in 1993 and 1994. The release rate of urea fertilizers was determined by the weight loss of the fertilizer granules after application in polyvinyl chloride (PVC) cylinders inserted into the turfgrass thatch. Some coated urea fertilizers released most of their N within the growing season (e.g., Sherritt-G, Polyon 4%, and SulfurKote), while others released only half their N (e.g., Esso T-90 and Meister 7), probably because of the cool ambient summer temperature in the area. The growth and color of turfgrass were more uniform in some controlled-release fertilizer treatments (e.g., Esso T-90, Meister 7, Polyon 4%, and SulfurKote) than in noncoated urea and NH4NO3 treatments. Promotion of growth in 1994 as a residual effect of the 1993 controlled-release urea fertilizer application was also noted. The results suggest that the application of some controlled-release urea fertilizers (with 70- to 90-day release rates) can produce the most consistent quality turfgrass.