Document Type

Thesis - University Access Only

Award Date

1996

Degree Name

Master of Science (MS)

Department / School

Biology

First Advisor

Bruce H. Bleakley

Abstract

How agricultural management systems may change or affect the numerous activities of wetlands is not understood. This study was an initial attempt to acquire information which may help to one day achieve such understanding. The study was designed to investigate six primary objectives: (1) to screen for differences in denitrifying enzyme activity (DEA) values of wetland-associated soils of three different farms, where each farm used a different management system; (2) to determine differences in DEA values of wetland-associated soils relating to season and location; (3) to assay selected lowland sites of semi-permanent wetlands on the farms for numbers of sulfate-reducing bacteria (SRB); (4) to assay selected lowland sites of semi-permanent wetlands on the farms for oxidation-reduction (redox) potential values; (5) to ascertain what interrelationships might exist between these anaerobic measures; and (6) to ascertain whether the three farms of the study differed significantly in these anaerobic measures. Wetland-associated soils on three different farms were investigated. Each of the farms was chosen to represent a different agricultural management system. The three agricultural management systems that were represented were conventional (CON), transitional no-till (TNT), and organic (ORG). The CON and TNT systems used synthetic fertilizers and chemical pesticides, whereas the ORG system used no synthetic fertilizers and generally no chemical pesticides. The three farms had very similar soil types and were located close together in northern Minnehaha and southern Lake counties of east central South Dakota. Upland and lowland soils associated with selected seasonal and semi-permanent wetlands on the three farms were investigated for DEA values. Selected lowland soils associated with semi-permanent wetlands were assayed for redox potential using a portable redox electrode and meter, as well as for populations of sulfate-reducing bacteria (SRB) by using most probable number (MPN) methodology. It appeared, from the limited data available on the denitrification rates of semi-permanent wetlands, that no consistent difference existed between the denitrification potential of the lowlands of seasonal wetlands versus the lowlands of semi-permanent wetlands. Most probable number (MPN) data for SRB indicated differences in SRB numbers between wetlands and between upland versus lowland sites of individual wetlands. Oxidation-reduction potentials were measured seven times between June 15 and September 24, 1995. All measurements were less than +100 mV, indicative of reducing soil environments which are believed to be more favorable to SRB (-240 mV) than to denitrifiers (+740 mV). There seemed to be a correlation between semi-permanent redox values and SRB-MPNs.

Library of Congress Subject Headings

Agricultural systems -- South Dakota
Wetlands -- South Dakota
Denitrification
Soil oxidation
Sulphates

Format

application/pdf

Publisher

South Dakota State University

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Rights Statement

In Copyright