Date of Award

January 2015

Degree Type

Thesis

Degree Name

Master of Science in Engineering (MSE)

Department

Agricultural and Biological Engineering

First Advisor

Jane R Frankenberger

Committee Member 1

Laura C Bowling

Committee Member 2

Eileen J Kladivko

Abstract

Understanding the risks or benefits to crop yields is an important factor in implementing a water management practice such as controlled drainage. Soil moisture from monitoring sites in Minnesota, Iowa, Indiana, and Ohio were used to compare deficit and excess moisture conditions in free-draining and controlled drainage sites and understand those inconsistent impacts. Time and magnitude of soil moisture deficit and excess stress were determined using metrics based on thresholds, depths in the soil profile, and corn growth stages. Seventeen metrics were found to show statistically significant correlation with yields as well as a difference in the quantity of stress between controlled and free-draining fields. Based on one metric of soil moisture deficit stress, free-draining plots experienced 77 additional cm-days of moisture deficit stress from the R3 stage until maturity compared to controlled plots and an additional 118 cm-days over the entire season. Meanwhile, controlled drainage plots were found to experience between 0.5 and 3.19 additional cm-days of excess stress during the period from seedling emergence to V6 compared to free-draining plots. In general at the sites studied, moisture deficits occurred during the latter half of the growing season while moisture excesses occurred during the earlier half; both types of stress were shown, when quantified with several different metrics, to correlate negatively with yield. While moisture excess was greater with controlled drainage, the differences were small and often not statistically significant; meanwhile greater differences were found in moisture deficit between free and controlled drainage. Due to a reduction in soil moisture deficit, controlled drainage has the potential to provide yield benefits in years when deficit stress occurs.

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