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Communication at the NABS Annual meeting, Keystone, 2000
(145) PHOSPHORUS BIOAVAILABILITY IN A MIDWESTERN AGRICULTURAL WATERSHED: FIELD TO STREAM.
L. Hatch, P. Brezonik, A. Feng, and D. Mulla. Water Resources Center, University of Minnesota, St. Paul, MN 55108
Nutrient pollution of streams due to agricultural activities impacts both river and reservoir ecosystems. The Minnesota River Basin (MRB), which drains nearly 40,000 square kilometers in southern Minnesota, has 92% of its land under rowcrop (corn, soybeans) and livestock (cattle, hogs, poultry) production. Water quality standards for fecal coliforms, turbidity, nitrate and dissolved oxygen are often exceeded. Agricultural best management practices and pollution trading with fixed-point industrial sources are being recommended to decrease Minnesota River phosphorus (P) loads, but without adequate knowledge of the bioavailable P (BAP) and erosion potentials of the land. Our study has examined the BAP content and erosion potential of soils collected throughout the MRB. Chemical analyses included pH, organic matter content, CCE, Bray-P, Melich III-P, NaOH-P, Fe-strip P, and TP. We have performed experiments on eighteen of these soils including P sorption/desorption analyses, rainfall runoff simulations and modeling, and soil-addition algal bioassays using a P-starved diatom culture (Stephanodiscus hantzschii), which is the dominant phytoplankton in the Lower Minnesota River during the late summer bloom (63% of total mean count). Results indicate that both soil BAP and erosion potentials vary significantly throughout the MRB, which is associated with varying soil properties, land steepness, and precipitation patterns.
Presented at 2:30 PM on Tuesday, May 30, 2000 in Nutrient Processes in Sediment
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