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Document Type

Thesis - University Access Only

Award Date

2015

Degree Name

Master of Science (MS)

Department / School

Agricultural and Biosystems Engineering

First Advisor

Christopher Hay

Abstract

Subsurface tile drainage has increased over several years in eastern South Dakota. This can be attributed to increases in precipitation and, - commodity and land prices. Advances in technology have also made tile installation easier and less costly. Many benefits of tile drainage have been documented in the literature, including yield benefits, agronomic benefits and environmental benefits. However, there is a great concern that tile drainage accelerates nitrate-nitrogen (NO3-N) loss to receiving surface water bodies. In fact, tile drainage has been implicated as contributing to the hypoxia problem in the Gulf of Mexico. There are also public health concerns associated with drinking water contaminated with nitrate-nitrogen. Infants who drink water contaminated with nitratenitrogen have been found to be at increased risk of methemoglobinemia, a condition in which the skin turns blue from reduced oxygen in the blood. With this in mind, this project set out to investigate three main objectives: examine the impact of subsurface drainage on corn and soybean production, investigate the effect of nitrogen stabilizers on nitrate reduction, and examine the impact of these stabilizers on corn yield. Soybeans and corn were raised on the research plots in 2013 and 2014. SuperU® (urea with urease and nitrification inhibitors) enhanced fertilizer was xiii used, and corn yield response and nitrate reduction compared to that of urea with urease inhibitor. Nitrate-nitrogen concentrations were measured from drain flow and shallow groundwater. Other field measurements made included soil penetration resistance, leaf area index (LAI), evapotranspiration (ETc), soil moisture, and drain flow. Soil penetration resistance was measured and compared for drained and un-drained conditions. Leaf area index measurements were taken to compare crop development. Soil moisture measurements were also taken to compare drained and un-drained plots. Drainage resulted in 15% increase in soybean yield in 2013. However, the difference was not statistically significant. Corn yields were very similar among drainage and nitrogen treatments in 2014. The nitrate concentrations of water in the tile system were also similar among drainage and nitrogen treatments. Soil penetration resistance was found to be significantly different, with drained plots having higher soil strength (mean of 1275 kPa) than un-drained plots (mean of 1105 kPa). Similarly, the drained plots had a higher LAI (mean of 4.6) than un-drained plots (mean of 3.9). However, the difference in LAI was not statistically significant. Corn consumed 77% of the total precipitation over the entire 2014-growing season. This water was used to meet evapotranspiration demands for corn. Soil water contents tracked very closely except for the period following heavy rainfall in June 2014 when soil moisture increased more dramatically in the un-drained plots and remained elevated over a longer period than drained plots.

Library of Congress Subject Headings

Subsurface drainage--South Dakota
Corn--Yields--South Dakota
Soybean--Yields--South Dakota
Water--Nitrogen content--South Dakota
Nitrates--Environmental aspects--South Dakota

Description

Includes bibliographical references (pages 50-56)

Format

application/pdf

Number of Pages

87

Publisher

South Dakota State University

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Rights Statement

In Copyright