Long-term effects of recycled wastewater irrigation on soil chemical properties on golf course fairways

The increasing water shortage in the and and semiarid western USA requires use of recycled wastewater (RWW) when possible. Recycled wastewater has become a common water source for irrigating golf courses and urban landscapes, creating the need to study the effects of RWW irrigation on soil chemical properties. We compiled soil test data from fairways of 10 golf courses that were near metropolitan Denver and Fort Collins, CO. Among these courses, five had been irrigated exclusively with domestic RWW [electrical conductivity (EC) = 0.84 dS m(-1)] for 4, 13, 14, 19, and 33 yr, respectively. The other five with similar turf species, age ranges, and soil textures had used surface water (EC = 0.23dS m(-1)) for irrigation. Our results indicated that soils (sampled to 11.4 cm) from fairways with RWW irrigation exhibited 0.3 units of higher pH and 200, 40, and 30% higher concentrations of extractable Na, B, and P, respectively. Compared with sites irrigated with surface water, sites irrigated with RWW exhibited 187% higher EC and 481% higher sodium adsorption ratio (SAR). Comparison of soil chemical properties before and 4 or 5 yr after RWW irrigation on two golf courses also revealed the following findings: (i) 89 to 95% increase in Na content; (ii) 28 to 50% increase in B content; and (iii) 89 to 117% increase in P content at the surface depth. Regular monitoring of site-specific water and soil and appropriate management are needed to mitigate the negative impacts of sodium and salts accumulations.