PROPER WATERING: Many factors influence lawn water requirements, and no two lawns are identical. A healthy, high quality lawn may need up to 1¾ inches of water per week to keep it growing vigorously under hot, dry, windy summer conditions. This total water requirement includes both rainfall and irrigation. The lawn will require less water when the weather is cool or cloudy. A turf-type tall fescue lawn may require less watering than a Kentucky bluegrass lawn, if it can grow a deep root system. In many cases, however, tall fescue rooting is limited by poor soil conditions and subsequently such lawns require as much watering as Kentucky bluegrass to look good and maintain healthy vigorous growth. Fine fescues are excellent choices for lawns receiving limited or no irrigation. Fine fescues, however, are less tolerant of traffic under drought stress than Kentucky bluegrass, tall fescue and perennial ryegrass.
Shady lawns and areas protected from wind require less water over the growing season than more exposed turf sites. The roots of trees and shrubs, however, also need water. Thus, you may need to water mature landscapes because of the competition for water from the roots of many plants. Healthy turf, encouraged by proper mowing, fertilizing, and cultivation uses water more efficiently and is more drought resistant.
Application of Water
Each time you water the lawn, apply enough water to moisten as much of the root zone as possible. If the soil has a considerable amount of clay, apply 1 to 1½ inches of water to moisten to a 6-inch depth. Sandy soils hold less water therefore you should apply about ½ inch of water to wet the soil to the 6-inch depth. Watering too deeply, especially on sandy soil, wastes water and allows it to percolate past the root zone. Over watering can also drown plants. 25% of the soil is pore space, which provides air so the roots can breathe, over watering can fill up this area, shutting the plant down by drowning and root rot.
Frequency of Watering
Based on the above, turf grown on sandy soil must be watered more often than the same grass grown on clay or loam soils. Watering too often (daily) results in less efficient use of water because of greater loss to evaporation. Excess watering can also increase the amount of weeds that appear in a lawn. Under most lawn situations in New Jersey, a thorough watering of a lawn more than two (2) or three (3) times per week is probably excessive.
Do not apply water too rapidly, otherwise it may runoff from sloped sites, thatchy turf, or turf growing on highly compacted soils. Core cultivation (aeration) can resolve some water infiltration problems by reducing soil compaction and thatch. A healthy durable lawn that withstands minor drought is achieved by watering thoroughly but as infrequently as possible. Allowing some wilt stress to develop in a lawn will not ruin the lawn. As drought stress becomes more severe, however, the lawn becomes more susceptible to insect and disease damage and to weed invasion. A sure sign that turf will benefit from irrigation is a wilted appearance. One initial symptom is “footprinting”, where footprints on the lawn will not disappear within 1 hour. This symptom is soon followed by actual wilt, where the leaves of the turf lose an upright erect appearance and take on a grayish or deep purplish-to-blue cast. Usually, only a few spots will appear wilted in the same general location of the lawn and will serve as good indicator spots for the need to water. You can delay watering the entire lawn for another day or so by watering only the wilted spots. If the weather pattern provides rain, you will have avoided watering the entire lawn by watering only the wilted areas.
What Time of Day Should You Water??
The most efficient time of day to water is early morning (between 4 a.m. and 10 a.m.). It is generally less windy, cooler, and more humid at this time, resulting in less evaporation and a more efficient application of water. Water pressure is usually better during these hours resulting in a more uniform application of water through sprinklers.
Seasonal Need for Watering
Based on historical records of rainfall, established lawns in New Jersey usually need watering to maintain vigorous growth during the months of June, July, and August. In occasional years, watering during the months of May and September may be useful for an established lawn. Watering in May and September should only be done infrequently to compensate for minor drought (for example, watering thoroughly once or twice per month). Sound cultural practices, often referred to as best management practices, are needed if a lawn is to have good drought resistance or survive dormancy. Mowing, fertilization, and cultivation (aeration) are important cultural practices, in addition to irrigation, that affect the health of a lawn and its ability to survive drought.