Water deficiency is common in the western United States, such as California, Nevada, Arizona, Utah, Colorado, and New Mexico, where climate is arid and semiarid. Approximately 30% to 50% of the potable water is used for outdoor landscape irrigation in these western states (Maupin et al., 2014). Water scarcity and population expansion are the impetuses for many cities and water districts to search for alternative strategies to promote fresh water conservation. One strategy is using treated wastewater (recycled water) for landscape irrigation. Golf courses are the leading urban landscape users of recycled water.
The total area of golf courses in the United States was 608,732 ha in 2007. It is estimated that during 2003 to 2005, 80% of maintained turfgrass on 18-hole golf courses had been irrigated annually with 285 million cubic meters of water (Golf Course Superintendents Association of America, 2009). Recycled water irrigation can significantly reduce fresh water and fertilizer requirements of turfgrass. However, recycled water has greater levels of Na and soluble salts when compared with fresh water (Qian and Mecham, 2005). Therefore, salinity issues related to recycled water irrigation may impose challenges of growing healthy turfgrass on golf courses. Different levels of increase in soil salinity under recycled water irrigation have been reported (Lockett et al., 2008; Mancino and Pepper, 1992; Qian and Mecham, 2005). Researchers typically found that the increase in soil salinity was not detrimental to turfgrass after several years of recycled water irrigation (Mancino and Pepper, 1992). However, salinity stress has been reported with long-term irrigation with recycled water or other saline water (Ganjegunte et al., 2017; Qian and Mecham, 2005).
Researchers have investigated salinity tolerance of C3 and C4 turfgrass species under controlled environments. Marcum and Murdoch (1990) found that shoot Na+ and Cl− concentrations in C4 turfgrass increased with increasing salinity levels in cultural solutions. Bermudagrass (Cynodon dactylon), centipedegrass (Eremochloa ophiuroides), zoysiagrass (Zoysia japonica and Zoysia matrella), seashore paspalum (Paspalum vaginatum), and st. augustinegrass (Stenotaphrum secundatum) salinity tolerance was strongly associated with Na+ and Cl− exclusion in the shoot. Salt tolerance also highly depended on lower ion concentrations retained in the shoot tissue (Gorham et al., 1985; Marcum and Murdoch, 1990). Alshammary et al. (2004) examined salinity tolerance of KBG, tall fescue (Lolium arundinaceum), alkaligrass (Puccinellia distans), and saltgrass (Distichlis spicata) in a greenhouse experiment. KBG was the most sensitive to salinity treatment among these four species, based on criteria of turf quality, shoot and root dry weight, and root to shoot ratio. The more salt resistant species had less shoot Na+ and Cl− accumulation and a greater shoot K+/Na+ ratio than the salt-sensitive grasses. Very limited research information is available regarding the degree of salt accumulation in turfgrass shoots when recycled water is used for irrigation. More research is needed to determine the relationships among soil salinity parameters, KBG turf quality, and shoot mineral concentrations.
The objectives of this research were 1) to evaluate turf quality and shoot mineral concentration of KBG grown on golf courses irrigated with recycled water for different years and 2) to determine the relationships among KBG turf quality, shoot mineral concentrations, and soil salinity parameters.
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