Irrigation Among Tips for a Beautiful Lawn


Lawn pathway at UT Gardens, Jackson

​The lawn pathway at the UT Gardens in Jackson is a fine example of how turf management can enhance the beauty of your landscape. Photo by B. Hayes, courtesy UTIA.


Submitted by Dr. Tom Samples, UT Extension Turfgrass Specialist and Professor, UT Department of Plant Sciences

The Irrigation Association designated July as Smart Irrigation month, but smart land owners can benefit from their advice regardless of the month. The association encourages lawn and landscape enthusiasts to follow five strategies to conserve water, save money and get better overall results: 
(1) Plant right; 
(2) Invest in an irrigation system; 
(3) Water wisely; 
(4) Routinely maintain and upgrade the irrigation system; and 
(5) Work with an irrigation professional.

Actively growing turfgrasses usually contain 80 percent or more water by weight. The essential minerals nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, boron, chlorine, copper, iron, manganese, molybdenum, nickel and zinc move in water from soil to roots. Once inside, water transports them, along with several other substances produced by the turfgrass plant to other plant parts. Sugars, carbohydrates, proteins and amino acids are just a few examples of “foods” produced by turfgrasses and translocated throughout the plant.

Most (about 95 percent) of the water that turfgrasses absorb from soils is transpired, moving as vapor back into the atmosphere. A small (about 5 percent) but critically important portion of the absorbed water is directly used to support photosynthesis, the process by which turfgrasses and other chlorophyll-containing plants use sunlight to manufacture energy rich products from carbon dioxide and water, and release oxygen. 

The rate at which a turfgrass transpires water depends on water availability within the soil and plant, and the level of energy necessary to vaporize water.  Most energy supporting transpiration comes directly from the sun. The amount of water transpired plus the amount of water that evaporates from soil and plant surfaces is collectively referred to as evapotranspiration or ET. Evapotranspiration is usually much greater during sunny, hot and windy days than cloudy, cool and humid days. 

The water use rate of a lawn is defined as the total amount of water required for turfgrass growth plus the amount of water lost due to ET. Turfgrass species and varieties often vary in the amount of water used. Although daily water use rates in excess of 0.4 inch occasionally occur, the water use rate of most turfgrasses ranges from 0.1 to 0.3 inch per day. Warm-season turfgrasses such as bermudagrass, centipedegrass and Zoysia generally use less water than cool-season species such as tall fescue or Kentucky bluegrass.

Although the average annual precipitation of the state of Tennessee is 52 inches, lawns benefit from supplemental irrigation. When properly designed, installed and controlled, an automatic sprinkler system delivers water both timely and uniformly. Water sensors can be installed in the lawn to monitor soil moisture levels and activate the system before turfgrasses become drought stressed. A rain sensor will prevent the irrigation system from operating while it is raining. 

A drought-stressed lawn may first appear grayish-blue as plant leaves roll or ‘cup’ before eventually turning yellow or brown. Another early sign of drought stress is ‘footprinting’. Drought-stressed plants do not spring back quickly following foot or wheel traffic, and footprints and wheel paths remain visible for an extended period of time.

A major objective when irrigating a lawn throughout spring, summer and fall is to promote the growth of turfgrasses during favorable weather and to preserve the plant root system when the lawn is experiencing heat and drought stresses. An irrigation system is also a valuable lawn care tool that can be used to apply water to activate a granular, preemergence herbicide or move nutrients from a granular fertilizer through thatch and into soil immediately after application.

The soil’s texture influences how much water it will hold against the force of gravity and the rate at which water infiltrates. The infiltration rate of clayey soils is usually much slower than that of light, porous sandy soils. However, due to the volume of large pore space among sand particles, lawns maintained in sandy soils are generally irrigated more often than lawns growing in clayey soils.    

Early morning watering (for example, beginning as early as 5 a.m.) is most often recommended to limit water loss from evaporation and to prevent turfgrass leaves from remaining too moist, too long following irrigation. Several fungal pathogens move from plant to plant in water on the surfaces of leaves. The entire root zone should be moist after irrigating, but applying an excessive amount of water may result in water moving off the lawn or well below turfgrass roots. Conversely, turfgrasses irrigated lightly and too frequently (for example, one-quarter-inch every other day) may be very shallowly rooted and drought prone.

Through its mission of research, teaching and extension, the University of Tennessee Institute of Agriculture touches lives and provides Real. Life. Solutions. ag.tennessee.edu

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Contact:

Dr. Tom Samples, Professor, UT Department of Plant Sciences, 865-974-7324, tsamples@utk.edu

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