Leaching of Mineral and Organic Nitrogen from Putting Green Profiles Supporting Various Turfgrasses

Nitrate (NO 3 − ) leached from golf greens has the potential to impair water quality. Dissolved organic N (DON) is also increasingly recognized as a form leached from fertilized soils. A controlled experiment was conducted to determine (i) the significance of DON in total N leaching losses under simulated golf‐green profiles and (ii) the short‐term contribution of fertilizer to leaching of inorganic and organic N forms. Various turfgrasses were grown in lysimeter columns designed to simulate a golf‐green profile. Fertilizer was applied at 25 kg N ha −1 every 14 d for 55 d, and the last application was labeled with 15 N. Leachates were analyzed for NO 3 − ‐N, NH 4 + ‐N, and DON. The 15 N recovery was assessed in plant, soil, and leachates. In the presence of plants, 10 to 70% (average 40%) of total N leached was accounted for by DON. Application of 15 N revealed that one‐half to two‐thirds of NO 3 − ‐N leached in the following 14 d was derived from the fertilizer, whereas the majority of leached DON was derived from soil residual N. Nevertheless, DO 15 N was present in most leachate samples collected for 14 d after fertilizer application, indicating that only a few days were required to convert mineral fertilizer to leachable organic forms. We conclude that DON may be a significant component of total N leaching losses from putting greens and would account for part of the N losses traditionally attributed to volatilization and denitrification.