Water requirements of North Carolina turfgrasses : a guide for irrigation technicians and turfgrass managers

Water Requirements of (0 NORTH CAROLINA TURFGRASSES ■ A Guide for Irrigation Technicians and Turfgrass Managers Water is an essential component for plant growth. In turf grasses it comprises 75 to 90 percent of the fresh weight of the plant , and irrigation is a key cultural practice in turfgrass management. Only 1 percent of the water absorbed is utilized for metabolic activity. Most is used in transpiration, which is the primary' cool¬ ing process of the plant. Water, absorbed by the roots and carrying nutrients, is dispersed to all cells for function and growth. The uptake of water is also crucial for maintaining turgor pressure of plant cells, which results in plant rigidity and cell elongation. Turgor pressure is a critical function in turf resiliency, influenc¬ ing its ability to tolerate wear and recover from traffic damage. By considering the factors that contribute to water loss, turfgrass managers can devise effective irrigation plans for specific sites. Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. North Carolina State Uni¬ versity and North Carolina A&T State University com¬ mit themselves to positive action to secure equal opportunity regardless of race, color, creed, national origin, religion, sex, age, or disability. In addition, the two Universities welcome all persons without regard to sexual orientation. North Carolina State University, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating. EVAPOTRANSPI RATION Evapotranspiration (ET) is the pro¬ cess by which water is transferred to the atmosphere from vegetative surfaces. The two components to this process are evaporation and transpiration. Evapora¬ tion is the physical process whereby water is changed from a liquid to a gas. This occurs on water surfaces, such as ponds, streams, wet soil, or wet vegeta¬ tion. Transpiration is a plant process whereby water is evaporated through a series of openings on the leaf surfaces called stomata. For all practical pur¬ poses, the two processes are considered together on an area of turf, although STATE UNIVERSITY A&T STATE UNIVERSITY COOPERATIVE EXTENSION Helping People Put Knowledge to Work evaporative loss is usually between 1 and 3 percent, meaning that the great majority of moisture is lost through the transpiration process. ET cools turf¬ grass since energy is used in the pro¬ cess and heat is lost. It is similar to the way humans cool off when the skin is moist and the wind is blowing. A number of environmental condi¬ tions affect the rate at which moisture is lost from the turf surface. The most important of these are radiant energy (sunlight), atmospheric vapor pressure (relative humidity), temperature, wind movement, and available soil moisture supply. When using Best Management