Fate of amended urea in turfgrass biosystems

Abstract

The fate of nitrogen (N) has been studied under several agronomic crops and agricultural profiles, but relatively little information has been collected from areas managed as turfgrass. The turfgrass industry has become the focus of environmental concerns in recent years and is often 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 bluegrass (Poa pratensis L.) turf under a heavy (one 2.54‐cm application) and a light (four 0.64‐cm applications) irrigation regime, and to ii) quantify the fate of ¹⁵N‐labeled urea when it is applied to an undisturbed soil columns having intact macropores. Clipping, verdure, and thatch/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 collection chamber was used to collect volatilized N and a plastic bag for leachate collection. All samples were analyzed for atom % ¹⁵N. Volatilization of N was negligible because irrigation was applied immediately after the application of N. The heavy irrigation regime significantly increased 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 leachate from the 50‐cm columns was in the urea form indicating that macropores may have played a major role in transport of surface applied N through the soil profile.

Notes

Published as Journal Paper No. 15375 of the Iowa Agric. and Home Economics Experiment Station., Ames, Iowa. Project No. 3149. Received 1/13/95.