Graduate Studies, UNL

 

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

First Advisor

Trenton Franz

Degree Name

Doctor of Philosophy (Ph.D.)

Committee Members

Christopher Neale, Derek Heeren, Paul Hanson

Department

Natural Resource Sciences

Date of this Version

12-2025

Document Type

Dissertation

Citation

A dissertation presented to the faculty of the Graduate College of the University of Nebraska in partial fulfillment of requirements for the degree Doctor of Philosophy (Ph.D.)

Major: Natural Resource Sciences

Under the supervision of Professor Trenton Franz

Lincoln, Nebraska, December 2025

Comments

Copyright 2025, Sophia M. Becker. Used by permission

Abstract

High quality soil data is crucial for addressing numerous threats to human well-being such as water scarcity, food insecurity, and intensified natural disasters. True soil property values are determined by analyzing soil samples in a laboratory, but soil sampling is often expensive and time-consuming. Some in-field point sensors and remote sensing products are available to measure soil properties, but they have inherent limitations in measurement extent and resolution. Geophysical methods can fill the measurement scale gap between point measurements and remote sensing products, but various research questions remain open. This dissertation aims to advance understanding of geophysics-derived soil property measurements by providing contextual knowledge of the discipline’s evolution and analyzing experimental data to answer questions about the behavior and accuracy of specific geophysical signals. Chapter 1 provides an introductory overview of this dissertation. Chapter 2 is a review analyzing the trends in agricultural applications of geophysics (agrogeophysics) since the field’s emergence in 1986. Chapter 3 investigates the relationship between soil moisture and passive gamma-ray spectroscopy. Chapter 4 assesses network-wide calibration of cosmic-ray neutron soil moisture sensors in a mountainous watershed and presents a relationship between bare neutron counts and vegetation dynamics. Chapter 5 summarizes the research contributions of Chapters 2–4 and discusses directions for future research. Together, these dissertation chapters support progress in measuring soil properties with approaches that are accurate, spatially and temporally relevant, cost-effective, and scalable. Continued research will facilitate mitigation of threats to human well-being through accessible, high quality soil data.

Advisor: Trenton Franz

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