Tuesday, June 17, 2008

Turf and Landscape - Overirrigation

With the recent hot weather, irrigation systems have been running in turf areas and landscapes. However, there is potential for over-irrigation and this can cause many problems. The following is an article on the subject.

One common problem that I routinely see is over-irrigation in the landscape. This occurs with improper use of manual irrigation systems, automated irrigation systems with design flaws such as improper overlaps, and irrigation systems with maintenance problems such as broken sprinkler heads or missing drip emitters. It also occurs where irrigation scheduling is improperly done so that excess water is applied or is applied incorrectly.

Excessive irrigation can lead to many problems. Frequent, light irrigation can lead to shallow rooting, especially in turf, making plants more susceptible to stress. Excessive watering can increase foliar disease pressure in turf and root and crown rots (Phytophthora, Pythium) in susceptible ornamentals such as Taxus (yew), junipers, azaleas, rhododendrons, Japanese hollies, hemlock, dogwood, Camellia japonica, Pieris, deodar cedar, mountain laurel, heather, high-bush blueberries, white pine, leucothoe, boxwood, and others. Many perennials and annuals such as geraniums and chrysanthemums are also susceptible to these root rots in wet conditions. Over-irrigation also results in nitrogen leaching and runoff. Excess water can lead to increased weed pressure from nutsedge, nimblewill, bent grass, crabgrass and moss and will decrease the longevity of preemergence herbicides. Weed growth on top of mulch is encouraged in landscape beds that stay wet. Drainage ways, low areas, shaded areas, and areas with restrictive soil layers are the most at risk for overwatering.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

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