CLINOPTILOLITE ZEOLITE INFLUENCE ON NITRATE LEACHING AND NITROGEN USEEFFICIENCY IN SIMULATED SAND BASED GOLF GREENS

The trend in golf greens construction during the past three decades ha s been towards putting greens with at least 90% sand and limited amoun ts of silt, clay, or organic matter. High sand based systems typically have low cation-exchange capacity (CEC) and large saturated hydraulic conductivities (>30 cm h(-1)), thus, are prone to NO3- leaching and p ossibly contribute to ground or surface water contamination. Clinoptil olite zeolite (CZ) has a high CEC (160 cmol kg(-1)), a large affinity for NH4+ ions and water molecules that may reduce N leaching on sand b ased putting greens. The impact of CZ amendment of sand putting greens on N leaching and N uptake by creeping bentgrass (Agrostis stolonifer a L.) was determined. The lysimeter method was used for growing creepi ng bentgrass in the greenhouse to determine NO3- and NH4+ leaching pot ential and fertilizer N use efficiency. Four N levels (0, 98, 196, and 293 kg NH4+-N ha(-1)) and two media, sand-CZ mix (9:1, w/w), and unam ended sand, were included as treatments. Sand plus CZ had a lowered co ncentration of NO3- and NH4+ in leachate while doubling the water rete ntion capacity and increasing CEC 200 fold. The greatest reduction of N leaching was found from lysimeters amended with CZ at the highest N rate. Nitrate and NH4+ leaching was 86 and 99% lower, respectively, th an the unamended sand lysimeters. The N fertilizer use efficiency was improved by 16 to 22% with the addition of CZ to sand, depending on N application rate. Amendment of sandy rooting media with clinoptilolite promoted better fertilizer N uptake efficiency and reduced N leaching from a highly leachable soil.