Clipping contributions to nitrate leaching from creeping bentgrass under varying irrigation and N rates

The effect of clipping management on nitrate (NO3) leaching beneath creeping bentgrass (Agrostis stolonifera L.) has received little attention. The objective of this experiment was to examine the effects of returning grass clippings to creeping bentgrass in combination with N fertilization and irrigation on NO3 leaching. A 30-week long experiment was conducted using fairway-height creeping bentgrass in large, undisturbed soil columns (20.3-cm diam. x 60.9-cm length) under controlled greenhouse conditions. Treatments were four rates of N fertilization (equivalent to 0, 98, 196, and 392 kg N ha-1 year-1) and two levels of irrigation [standard (25 mm per week) or standard + historical weekly precipitation amounts], with grass clippings either returned or removed. Higher percolate NO3-N concentrations and mass losses were found when clippings were returned, as N rate increased, and with the higher irrigation treatment. Flow-weighted concentrations of NO3-N in percolate ranged from 0.13 to 21.0 mg L -1 and the percent of applied N lost as leachate ranged from 0.9 to 63%. These findings suggest that water quality goals may not be reached if N fertilization rates are not reduced when clippings are returned to bentgrass fairways or in cases of over-watering.