Earth and Atmospheric Sciences, Department of


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Gibson, J.P. 2015. Estimation of Deep Drainage Differences between Till and No-Till Irrigated Agriculture (MS Thesis). University of Nebraska, Lincoln, NE


A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Earth and Atmospheric Sciences, Under the Supervision of Professor Vitaly A. Zlotnik. Lincoln, Nebraska: December, 2015

Copyright 2015 Justin Gibson


Deep drainage was monitored under two center pivot irrigation sites located in south-central Nebraska during the 2013, and part of the 2014, growing seasons. Both fields underwent similar land management except for tillage practice: no-till in one and disk till in the other. Long term deep drainage rates were also estimated from chemical analysis of extracted soil cores, with the aid of the chloride mass balance equation. Mechanisms underpinning differences in deep drainage between the two fields were investigated through the use of unsaturated zone numerical modeling.

Deep drainage estimates from field monitoring indicated that a greater amount of deep drainage occurred in the till field (250 mm/yr) than in the no-till field (50 mm/yr) over the 2013 growing season. In contrast, the chemically based tracer deep drainage estimate indicated more deep drainage in the no-till field (210 mm/yr) than in the till field (100 mm/yr) over the 5 years considered in the analysis. Based on evidence from numerical modeling and water balance estimates, the inference that the tilled site had higher drainage in 2013 but lower drainage averaged over 2008-2013 is attributable to greater irrigation rates at the tilled site in 2013.

Adviser: Vitaly A. Zlotnik

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