ABSTRACT:
Erosion of agricultural land and transport of associated fertilizer chemicals nitrogen (N) and phosphorus (P) in runoff, can be detrimental to both soil productivity and water quality. In the Southern Plains, gully erosion is of concern due to periodically intense rainfall and a large acreage of erodible soils. As little information is available, we studied the loss of sediment, N, and P in runoff over 13 yr (1980-1992) from two adjacent extensively gullied native grass watersheds (3.8 and 5.7 ha of 5% slope and class 4 erosion) in the Little Washita River Basin, OK. In 1983, the gullies on one of the watersheds were treated by land shaping, Midland Bermudagrass [Cynodon dactylon (L.) Pers] establishment, and construction of a runoff detention pond. Prior to gully treatment, greater (p > 0.05) amounts of sediment, N, and P were lost from the subsequently treated than untreated watershed. Following gully treatment, 27,500 kg sediment, 7.1 kg N, and 4.1 kg P ha−1 yr−1 were lost from the gullied watershed, while only 4,900 kg sediment, 3.1 kg N, and 1.6 kg P ha−1 yr−1 were lost from the treated watershed. While gully treatment had no effect on nitrate-N and ammonium-N loss, dissolved P and bioavailable P losses were increased six-and threefold, respectively. This was attributed to the application of fertilizer N and P to the treated watershed only. The loss of N and P in runoff from gullied and treated watersheds was accurately predicted using kinetic and enrichment ratio approaches with soil properties reflecting the main zone of runoff and soil interaction. Subsoil (5-20 cm) properties accurately predicted N and P release and transport in runoff from the gullied watershed, whereas accurate predictions for the treated watershed were obtained with surface soil (0-5 cm) properties. The cost of gully treatment was $1,098 ha−1, with a reduced loss of 210 kg sediment, 5 g N, and 3 g P in the ensuing 10 years for every dollar spent on treatment.
Footnotes
Andrew Sharpley is a soil scientist and J.A. Zollweg is a hydraulic engineer, USDA-ARS, Pasture Systems and Watershed Management Research Laboratory, Curtin Road, University Park, PA 16802-3702, (814) 863-0948; S.J. Smith is a soil scientist and G.A. Coleman is a hydraulic engineer (retired), USDA-ARS, National Agricultural Water Quality Laboratory, P.O. Box 1430, Durant, OK 74702-1430, (405)924-5066.
- Copyright 1996 by the Soil and Water Conservation Society
This article requires a subscription to view the full text. If you have a subscription you may use the login form below to view the article. Access to this article can also be purchased.