Turf Fertilizers for Hawaii ’ s Landscapes

Published by the College of Tropical Agriculture and Human Resources (CTAHR) and issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Andrew G. Hashimoto, Director/Dean, Cooperative Extension Service/CTAHR, University of Hawaii at Manoa, Honolulu, Hawaii 96822. An Equal Opportunity / Affirmative Action Institution providing programs and services to the people of Hawaii without regard to race, sex, age, religion, color, national origin, ancestry, disability, marital status, arrest and court record, sexual orientation, or veteran status. CTAHR publications can be found on the Web site or ordered by calling 808-956-7046 or sending e-mail to [email protected]. Fertilizer requirements of the various turfgrasses common in Hawaii differ greatly. Hybrid bermudagrasses have the highest fertilizer requirements; zoysiagrasses, St. Augustinegrass, and seashore paspalum are intermediate; centipedegrass needs the least amount of fertilizer. Fertilizer requirements for any given turf also vary greatly depending upon its intended use, the desired level of appearance, soil conditions, the amount of rainfall or irrigation, and other environmental conditions. Poor fertilizer practices including excess or insufficient application and poor fertilizer distribution are responsible for many of the common problems associated with turfgrass maintenance. In Hawaii, where the growing season is year-long, it is necessary to apply fertilizers throughout the year. Failure to follow a regular schedule, especially with the highdemand turfgrasses, will result in uneven appearance and may increase weed, insect, and disease problems. An important factor in developing a fertilizer application schedule is a good knowledge of the type of turfgrass you are working with. Bermudagrass requires and responds to a monthly feeding of 1 pound of nitrogen (N) per 1000 square feet (sq ft, or ft). Applying the same amount to a centipedegrass turf would be a waste of time and money. The main objective of a good turf fertilizer program is to promote good color and vigor of the grass without producing excessive growth. Overfertilizing with N promotes lush growth, which can lead to a number of problems including rapid thatch buildup, higher susceptibility to disease and insect infestation, and higher water requirements. Overfertilized lawns are always the first to show wilting during dry periods in many species of turf, because excess N promotes top growth at the expense of the root system and can eventually lead to a deterioration of the root system. Of course, lush growth also means that the turf will require more frequent mowTurf Fertilizers for Hawaii’s Landscapes