Document Type

Thesis - Open Access

Award Date

2017

Degree Name

Master of Science (MS)

Department / School

Agricultural and Biosystems Engineering

First Advisor

Laurent Ahiablame

Keywords

agriculture, controlled drainage, crop, drainage water management, subsurface drainage, water

Abstract

Subsurface drainage is a common water management practice for improving crop production in poorly drained soils; however, the practice is associated with several environmental concerns such as nutrient losses to downstream surface waters. These environmental concerns from subsurface drainage have prompted interest in drainage water management strategies such as controlled drainage. This study assessed the agronomic and environmental impacts of drainage water management in eastern South Dakota by using two demonstration plots for controlled and conventional drainage. Drain flow, nitrate and dissolved phosphorous concentration in drain water, shallow groundwater, crop yield, residual soil nitrate, soil moisture and temperature, soil penetration resistance, bulk density, soil pH, and leaf area index (LAI) were measured from 2014 to 2016 from the two adjacent drainage plots. Soybean, oats, and corn were planted in 2014, 2015, and 2016, respectively with urea fertilizer applied during the corn year. Results showed that controlled drainage reduced drain flow by 58% compared to conventional drainage. Nitrate concentration in drain water increased and exceeded maximum contaminant level (10 mg/L) for drinking water in both controlled and conventional drainage plots during the second project year. Annual nitrate load was reduced by 55% with controlled drainage compared to conventional drainage. Nitrate concentration in shallow groundwater was slightly higher in the conventional drainage plot than in the controlled drainage plot, and generally higher than 10 mg/L for both plots. Dissolved phosphorous concentration in drain water and shallow groundwater exceeded the critical level of 0.03 mg/L for freshwater eutrophication. The dissolved phosphorous concentration in drain water was higher in controlled drainage compared to conventional drainage; but significantly higher in conventional drainage compared to controlled drainage in shallow groundwater samples (p < 0.05). Unlike nitrate load, controlled drainage increased dissolved phosphorous load by 35% compared to conventional drainage. Shallow groundwater table was significantly higher in the controlled drainage plot than in the conventional drainage plot. The soil moisture content near the outlet and middle of plots was higher in the conventional drainage plot than in the controlled drainage plot at all depths, except for 20 cm depth in the middle of controlled drainage plot and 105 cm depth near the plot outlet in the conventional drainage plot. Soil temperature and penetration resistance showed no statistical difference in mean between the controlled and conventional drainage plots. However, the controlled drainage plot had slightly higher soil temperature than the conventional drainage plot, and slightly higher soil penetration resistance was measured in the conventional drainage plot. Mean residual soil nitrate content in the controlled drainage plot was significantly higher than in the conventional drainage plot. Controlled drainage showed 8% less yield for soybean, and 9% less yield for corn, while 5% increase in yield for oats was observed in controlled drainage compared to conventional drainage. Comparison of LAI between the controlled and conventional drainage plots was statistically not significant. However, the controlled drainage plot had slightly higher LAI than the conventional drainage plot.

Library of Congress Subject Headings

Drainage -- South Dakota.
Subsurface drainage -- Environmental aspects -- South Dakota.
Agricultural pollution -- South Dakota -- Management.
Water quality management -- South Dakota.

Description

Includes bibliographical references (pages 63-77)

Format

application/pdf

Number of Pages

93

Publisher

South Dakota State University

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Rights Statement

In Copyright