CORVALLIS, Ore. — Annual precipitation in the Intermountain West does not meet the watering needs of lawns, plain and simple. And although proper irrigation is an important factor to keep a lawn healthy, it is also the most overlooked.
Overwatering a lawn can lead to negative effects such as excess leaf growth, nutrient leaching, shallow rooting and disease, according to Rob Golembiewski, Oregon State University Extension horticulturist. "Under-watering can cause just as many problems, such as loss of color and density, reduced vigor, wear damage and disease," he said.
Golembiewski is one of the authors of an OSU Extension six-page publication, "Efficient lawn irrigation in the Intermountain West," (EC 1638). It can help homeowners decide on an optimum lawn irrigation schedule and is available online at no cost.
"The publication helps you account for the turfgrass species in your lawn, soil characteristics, nearby trees and shrubs that affect sun and shade, mowing height, potential for disease and quantity of water your irrigation system can deliver," he said.
Kentucky bluegrass is the most common lawn turfgrass in the Intermountain West; it is cold tolerant yet performs well in sunny locations and forms a dense stand when properly managed. Also common to the area are fine fescues, perennial ryegrass and tall fescues. The publication recommends seed mixtures for sun and shade that include a combination of two to three grasses.
Soil characteristics help determine how often watering is needed. Sandy soils, for example, can't hold much and require more frequent watering. The Web Soil Survey of the National Resource Conservation Service can help you determine the type and characteristics of your soil.
From June through August, irrigation from one to five times a week provides the right amount of water, avoids runoff and keeps lawns green and lush. "If a dense, vigorous lawn is not your priority, a single watering every week is sufficient to produce a functional lawn with some brown spots," Golembiewski said.
The publication also suggests an alternative to a predetermined irrigation schedule: Observe your lawn, check the soil moisture regularly and alter your watering to meet turfgrass needs. The key to successful efficient irrigation is to apply only as much water as the lawn actually requires.