Turfgrass Growth, Quality, and Reflective Heat Load in Response to Deficit Irrigation Practices

Abstract

Turfgrass irrigation practices have come under intense scrutiny in recent years due to concerns over increasing population growth and diminishing water availability. Municipal water restrictions have become commonplace and more recently, the U.S. Environmental Protection Agency has developed guidelines that would restrict irrigation and/or amount of turf within the landscape (Watersense Single Family New Home Specification, 2009). Thus, turfgrass managers are increasingly faced with the challenge of maintaining acceptable turfgrass quality using less water. Understanding the minimal irrigation requirements and extent of water stress that a particular turfgrass species can tolerate while exhibiting acceptable quality is therefore highly valuable information for turfgrass managers and homeowners. Deficit irrigation is the practice of intentionally under-irrigating of a plant to below its maximum water demand. This practice has been long used in crop production, where it often culminates in overall reductions in growth, development, and yield. Turfgrass systems are perhaps uniquely adapted for deficit irrigation because reductions in shoot growth are perceived to be beneficial, as long as visual and functional quality are not significantly sacrificed. Deficit irrigation has been practiced across a number of species, although the particular level of irrigation needed to maintain acceptable quality appears to vary among species. Using minilysimeters in the field, DaCosta & Huang (2006) determined that bentgrass species required ≥60% ETa for maintaining acceptable summer quality, but that irrigating at only 40% ETa was sufficient for maintaining acceptable quality during fall months. Qian and Engelke (1999) found that minimal irrigation requirements for grasses grown along a linear gradient of irrigation ranged from 26% to 68% of Class A pan evaporation (Ep) in a study of five turfgrass species along a linear gradient of irrigation. Feldhake et al. (1984) studied deficit irrigation of three turfgrass species grown in lysimeters and determined that irrigation deficits up to ~27% only decreased growth, but greater deficits resulted in significant loss of quality for Kentucky bluegrass and tall fescue. Zoysiagrass is a warm-season (C4) turfgrass native to Southeast Asia, but has become an increasingly popular turfgrass for use on lawns and golf courses throughout the southern half of the United States and many other tropical, subtropical, and temperate regions of the world (Turgeon, 2002). Whereas some turfgrass species are capable of avoiding drought through production of a deep root system, physiological studies indicate that zoysiagrass tolerates drought largely through osmotic adjustment (Qian & Fry, 1997). Very little information is available regarding the minimal irrigation requirements or response of this