Runoff of Nitrate Nitrogen and Phosphorus from Turfgrass After Watering-In

Abstract

Fertilizer nutrients could be transported from turfgrass areas to surface waters, especially those areas intensively managed, such as golf courses. An experiment was initiated to determine effects of “watering-in” fertilizer on the amounts of nitrate nitrogen and phosphorus that is found in runoff water. Three rates of 10–10–10 fertilizer were added to bermudagrass [Cynodon dactylon (L.) Pers.] on a 5% slope and a 0.64 cm irrigation applied. Three days later a 50-mm simulated rainfall was applied [72 h after treatment (HAT)] with three subsequent events. A second experiment was similar except no watering-in was done and the first event was at 4 HAT. Phosphorus and nitrate nitrogen mass transported increased step-wise with rate increases for the first two runoff events. Watering-in and waiting three days greatly decreased the volume of runoff water and the amounts of phosphorus and nitrate nitrogen transported. Runoff volume was a function of soil moisture content before the simulated rainfall events. Percent runoff water of that applied ranged from 24.3 to 43.5% for the first two events where no watering-in was done, but only 12.1–29.7% where watering-in was done. Total percent of phosphorus in runoff of that added was 13.8% for without and 3.4% with watering-in for the high rate (11 kg P/ha) and total nitrate-nitrogen was 1.5 and 0.8%, respectively. Results indicate that watering-in fertilizer with a small amount of irrigation after application is beneficial in decreasing runoff of fertilizer nutrients. Other best management practices are to limit fertilizer amounts applied in one treatment and to avoid application when soils are very moist or when heavy rain is expected.

Keywords:

• Runoff
• Nitrate nitrogen
• Phosphorus
• Turfgrass

Acknowledgments

The author gratefully acknowledges Ray Pitts, Kathy Evans, and Garland Layton for technical assistance. This research as supported by the United States Golf Association, the Georgia Turfgrass Foundation Trust, and by State and HATCH funds allocated to the Georgia Experiment Stations.