Document Type

Thesis - Open Access

Award Date

1998

Degree Name

Master of Science (MS)

Department / School

Plant Science

Abstract

This study investigated the nutrient filtering capability of four seasonal and two semipermanent wetlands in the Prairie Pothole Region of eastern South Dakota. The wetlands were situated in two farming systems near Madison, SD. Wetlands were instrumented with observation wells arranged in two axes extending from the wetland border to upland sites. Nitrate-nitrogen and orthophosphate concentrations from wetland surface water and surrounding groundwater were determined on a two-week cycle throughout the 1994 and 1995 growing season using a Hach DR/2000 spectrophotometer. Results indicated that N03-N concentrations were higher in semipermanent wetlands (8.63 mg L·1) than seasonal wetlands (4.29 mg L" 1) in 1994 and followed the same trend in 1995. Orthophosphate concentrations were higher in seasonal wetlands (0.57 mg L") than in semipermanent wetlands (0.27 mg L·1) in 1994 and also followed the same trend in 1995. Soil nutrient analysis on all observation well soil cores was determined by the SDSU Soil Testing Laboratory. Soil nitrate-N, total-N, and available phosphorus concentrations were analyzed according to landscape position and depth. Results indicated that seasonal wetland landscapes may be better denitrifiers than semipermanent wetland landscapes. Significant differences in nitrate-N concentrations by landscape position and depth were found in seasonal wetland landscapes, but not in semipermanent wetland landscapes. Determination of total phosphorus concentrations from the top 15 cm of the observation well soil cores showed an increase in total P from upland landscape positions to lowland landscape positions. Total P concentrations were also determined from sediment samples from one seasonal wetland. Results showed a concentric zonation of phosphorus with concentrations ranging from 0.673 mg P g-1 soil in the outer edges to 0.513 mg P g·' soil near the center of the wetland. A phosphorus adsorption isotherm was determined on the same sediments and showed the maximum adsorption concentration calculated from the Langmuir equation averaged 0.36 mg P g·' soil more than existing phosphorus concentration in the wetland sediment. Although the wetland still retained the capacity to sorb phosphorus, the overall capacity for agricultural wetlands to sorb P may be accelerated due to erosion and direct fertilization compared to non-agricultural wetlands.

Library of Congress Subject Headings

Wetlands -- South Dakota
Wetlands -- Prairie Pothole Region
Soil chemistry
Water chemistry

Format

application/pdf

Number of Pages

115

Publisher

South Dakota State University

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