Drought Avoidance Aspects and Crop Coefficients of Kentucky Bluegrass and Tall Fescue Turfs in the Semiarid West
- Erik H. Ervin and
- Anthony J. Koski
Increasing demand for the scarce water resources of the semiarid western USA, coupled with the highly visible practice of landscape irrigation, has fostered concern regarding turfgrass water conservation. Our objectives were (i) to assess some of the physiological responses and morphological factors which contribute lo the drought avoidance capabilities of Kentucky bluegrass (KBG, Poa pratensis L.) and tall frescue (Festuca arundinacea Schreber) turfs subjected to increasing levels of drought through the use of a line-source irrigation system (LSIS), and (it) to develop water-conserving crop coefficients (Kc) to be used with Penman equation estimates of al falfa (Medicago sativa L.) reference evapotranspiration (ET,), while maintaining these turfs at an acceptable level of quality. The effects of turfgrass species and irrigation level on root dry weight, leaf firing, canopy temperatures, gravimetric soil moisture content, and quality were investigated ai Fort Collins, CO on a Nunn clay loam (fine, monimorillonitic, mesic Aridic Argiustoll). Irrigation treatments were delivered with a LSIS. In 1993, turf-type tall fescue (TF) had 65% more root dry weight from 31 to 90 cm than KBG. In 1994, tall fescue had 45% more total root dry weight from 31 to 90 cm than KBG. Consequently, tall fescue gravimetric soil moisture contains at the two deeper sample depths (31–60 and 61–90 cm) were generally lower than those of KGB. Tall fescue's capacity to exploit deep soil moisture when surface inputs became limiting were reflected in significantly higher quality ratings, lower leaf-firing ratings, and lower canopy temperatures relative 1o KBG. Our conclusion is that, in Colorado, water can be conserved while maintaining acceptable turfgrass quality by irrigating these two turfs every 3 d by adjusting ET, with a KBG coefficient of 0.70 and a TF coefficient of 0.60, provided that soil conditions are such that tall rescue can produce a deep root system.
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