Although the amount of rainfall received in Massachusetts is generally ample, it is not uniformly distributed throughout the year. Thus, it occasionally becomes necessary to provide supplemental irrigation especially during the summer months. Water is lost from the soil by gravitational drainage, evaporation, and plant use. If plant or soil water content becomes limiting, drought stress and/or, turfgrass death may occur.
WHEN IS IRRIGATION NECESSARY?
Many variables influence the amount of water used by turfgrasses. These include: amount of solar radiation, temperature, humidity, grass species, and rate of growth. Rooting depth and soil texture also affect turfgrass water needs. More deeply rooted grasses can extract water from a greater volume of soil and are thus more drought tolerant than shallow rooted species. Finer textured soils hold more water than coarse soils and require less frequent irrigation. Because so many factors interact to determine turfgrass water use, it is difficult to give a general estimate of how often to water a lawn. The best technique for determining when to irrigate is to observe both soil and plant conditions in the lawn and then water when the turf needs water rather than based on the calendar.
TURFGRASS DROUGHT TOLERANCE
The following turfgrass types are listed in order of their tolerance to drought:
DETECTING WILT AND DROUGHT STRESS
In order to maximize water conservation and avoid the detriments of overwatering, lawns should be watered just prior to the development of wilting and drought stress. This may be difficult to determine initially, but a little knowledge and experience will make it easier. Wilting occurs because the plants' internal water content drops so low that the plant cannot remain turgid (stiff), and plant cells begin to shrivel. Turfgrasses undergo a series of visible changes when they begin to wilt. Development of a bluish-green coloration and the rolling or folding of leaf blades are two noticeable changes associated with wilting. If footprints remain visible on the lawn for several minutes after walking on it, the turf is not very turgid and wilting is imminent. These initial symptoms of wilting will not cause permanent injury to the lawn. However, they do indicate that the lawn should be watered soon in order to avoid drought stress and possible turfgrass death.
Cooperative Extension University of Massachusetts L-484
The goal of the University of Massachusetts Turf Integrated Pest Management (PMI )Program is to provide education in the use of environmentally appropriate techniques of horticultural and pest management practices.