Subsurface-Applied Tailored Water: Combining Nutrient Benefits with Efficient Turfgrass Irrigation

Irrigating turfgrass with treated effluent water has become a common practice in response to shrinking supplies of potable water. Newly developed decentralized water treatment systems produce recycled water containing varying quantities of N on short notice. Using such tailored water to irrigate turf areas would reduce or eliminate the need for additional mineral fertilizers if concentrations of nitrate in the water were raised during the growing season to meet the annual N requirement. On the basis of our estimates, in order for turfgrasses to receive their entire annual N requirements (20 to 25 g N m(-2) yr(-1)) solely from effluent irrigation, nitrogen concentrations in irrigation water would need to range from as low as 11 mg L-1 for arid regions with a 12-mo growing season to more than 50 mg L-1 in areas with only a 6-mo growing season. Furthermore, tailored water should be applied with advanced irrigation systems with high distribution uniformity to minimize nitrate leaching. Subsurface irrigation systems distribute water more efficiently and uniformly and minimize human exposure to treated effluent, which would help dispel negative public perceptions regarding the use of effluent to irrigate public turf areas. As the use of treated effluent for turfgrass irrigation continues to increase, the idea of adjustable nutrient content in irrigation water combined with a subsurface irrigation delivery system could become an important means to sustainably maintain much-needed urban green spaces.