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United States Department of Agriculture

Agricultural Research Service

Research Project: Processes Controlling the Source, Movement, and Release of Soil Phosphorus in Midwestern Streams from Pasture and Crop Land CFDA#10.310 Project Number: 5030-13000-010-32
Project Type: Reimbursable

Start Date: Oct 17, 2013
End Date: Aug 31, 2016

Objective:
Specific objectives of the proposed research are to: 1) Quantify stream bed and bank erosion and resulting sediment and phosphorus (P) flux from a first-order, warm-water stream in central Iowa; 2) Provide data to establish process-based relationships between stream bed and bank erosion and watershed hydrology and land management along pasture and cropland streams; and 3) Determine the relationship of P adsorption/desorption processes of soils and sediments within the watershed, and use this information to evaluate the risk of P losses within this and similar Iowa streams.

Approach:
This project will be conducted primarily within the Walnut Creek Watershed in south-central Iowa and will utilize an extensive existing monitoring network and leverage long-term datasets within the watershed. One goal of this project is to ensure that stream monitoring continues. The watershed has a variety of riparian land uses typical of the region, and we have long-term landowner agreements already in place. Riparian land use and management have been shown to be important factors affecting phosphorus (P) flux to streams via bank and bed processes, with previous studies illustrating the importance of vegetation and properly managed grazing. After sediment-bound P has entered a stream, the environmental risk is controlled by the rates of sediment transport and factors affecting P retention and release (adsorption/desorption) from the sediment. Sediment transport will be affected by the intensity and frequency of flooding events. Previous work has shown that the release of sediment-bound P into the stream water is controlled by both the concentration of poorly crystalline iron oxides and organic matter in Iowa soils and the P concentration in the overlying water. Our approach in this research will be to characterize sediment properties in the Walnut Creek Watershed, and determine if these properties can be used to predict P concentrations in stream water during the year.

Last Modified: 11/24/2014
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