FATE OF AMENDED UREA IN TURFGRASS BIOSYSTEMS

The fate of nitrogen (N) has been studied under several agronomic crop s and agricultural profiles, but relatively little information has bee n collected from areas managed as turfgrass. The turfgrass industry ha s become the focus of environmental concerns in recent years and is of ten identified as a source of ground water contaminate. The objectives of this study were to: i) investigate the hydrology of 20-cm diameter by 50-cm deep undisturbed soil columns covered with a Kentucky bluegr ass (Poa pratensis L.) turf under a heavy (one 2.54-cm application) an d a light (four 0.64-cm applications) irrigation regime, and to ii) qu antify the fate of N-15-labeled urea when it is applied to an undistur bed soil columns having intact macropore. Clipping, verdure, and thatc h/mat samples were taken from each column, and the soil was excavated in 10-cm layers at the end of the 7-day test period. A glass collectio n chamber was used to collect volatilized N and a plastic bag for leac hate collection. All samples were analyzed for atom % N-15. Volatiliza tion of N was negligible because irrigation was applied immediately af ter the application of N. The heavy irrigation regime significantly in creased the transport of N below 30 cm by five times, compared to the light irrigation regime. Eighty-five percent of the N found in the lea chate from the 50-cm columns was in the urea form indicating that macr opores may have played a major role in transport of surface applied N through the soil profile.