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.
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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
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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