RESPONSE OF 3 KENTUCKY BLUEGRASS CULTIVARS TO SPRAYABLE NITROGEN-FERTILIZER PROGRAMS

Developing fertilizer programs that match anticipated maintenance leve ls for Kentucky bluegrass (Poa pratensis L.) is important because cult ivars differ in their response to N management. Our objective was to d etermine the response of 'Vantage', 'Park', and 'Majestic' Kentucky bl uegrass to urea, ureaform, methylene urea, and methylol urea applied a t a yearly rate of 1.952 kg N 100 m(-2) in three application programs: heavy spring, balanced, and late fall. Data collected included visual quality, clipping yield, thatch depth, shoot density, and root weight . Quality ratings were generally highest for the heavy spring program. Urea produced quality ratings that were equal to or higher than the o ther N sources. Clipping yields were 20 to 67% lower for Majestic than for Vantage or Park. Thatch development was 23% greater in Majestic t han in Vantage in 1987 and 16% more in 1988. Majestic produced 18% mor e thatch accumulation than Park in 1987 and 26% more thatch in 1988. M ajestic had more total root mass than Vantage or Park in the spring of 1986 and in the spring and fall of 1987. In the fall after a severe d rought (1988), Majestic had 53 and 43% more total root mass than Park and Vantage, respectively. Plots treated with urea produced 6 to 18% m ore clippings than the other N sources each year. Quick-release N sour ces performed better than slow-release types. The late fall program re sulted in 9% more root mass than the balanced program and 8% more than the heavy spring program at the 0- to 5-cm depth in 1987.