Date of Award:

5-2014

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Committee Chair(s)

Scott Jones

Committee

Scott Jones

Committee

Larry Hipps

Committee

Astrid Jacobson

Abstract

Growing populations, coupled with climate change and resource depletion, have heightened concern about water management. The growing need to better manage agricultural systems, including irrigation and fertilizer application, as well the lasting consequences of excess application of nitrogen and other nutrients, could be remedied with an improved method to monitor soil water movement. Despite huge technological advances, a tool to measure soil water flow at the low rates found in the field has not been developed. Current methods lack the precision to provide the needed accuracy to fully understand soil-water dynamics, as well as the ability to provide instantaneous information.

This research project attempted to modify and improve two emerging water flux measurement tools. These methods are 1) streaming potential – which involves measuring small voltages in the soil that result from water movement – and 2) a heat pulse method – which involves a heated needle and monitoring of its temperature rise and fall, which allows calculation of soil properties and water flow rate. Both of these methods have previously demonstrated promising results, although more work needs to be done to fully understand their behavior and limitations.

The work performed provided numerous insights into both of these methods. Streaming potential measurements made in the laboratory were difficult to control and lacked consistency, leading us to conclude that we have not yet uncovered the fundamental principles controlling this phenomenon despite our best efforts to understand them. However, through a series of modifications we were able to improve previous heat pulse probe measurement resolution. This is promising for developing a long-sought method to instantaneously and accurately measure soil water flow rates.

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