Graduate Studies

 

Date of Award

12-5-2023

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Agronomy

First Advisor

Rhae Drijber

Abstract

The growing focus on soil health and regenerative agriculture has brought about the need for new integrated approaches for the analysis of soil. Prior, commercial agricultural laboratories relied on methods to measure chemical properties of the soil, such as pH and nutrients. The Soil Health Nutrient Tool (aka. Haney Test) developed by Dr. Rick Haney (USDA-ARS Blackland Research and Extension Station, Temple, TX) integrates chemical and biological properties to provide a more holistic understanding of soil fertility management. Following adoption by commercial laboratories in 2013, criticisms regarding variability in measurements and lack of calibration were apparent. In this research, we present the development of new tools and instrumentation to reduce variability of specific measures, namely soil respiration, used as part of the test. The development of the Soil Respiration-1 (SR-1) instrument, which employs an infrared gas analysis (IRGA) detector for measuring carbon dioxide (CO2) was compared to the Solvita® gel system. The data suggest that Solvita® underestimates CO2 respiration at values above 100 mg CO2-C kg-1 and overestimates values below 30 mg CO2-C kg-1, compared to the SR-1, leading to compounding effects on the overall results of the Haney Test. These findings led to the development of the Mini-Cube using nondispersive infrared (NDIR) microsensor technology as a potential cost-effective solution compared to the SR-1. The comparison yielded a strong correlation (r2=0.99, p<0.001) and suggests that the Mini-Cube could be a viable, cost-effective option for soil respiration in commercial laboratories. We then explored complimentary measures to CO2 respiration by coupling an IRGA CO2 sensor with UV Flux to measure oxygen (O2) consumption. The results show that O2 uptake is correlated (r2 = 0.97, p < 0.001) to CO2 efflux, and could be used in lieu of CO2 measurements for biological activity. Finally, we explore the utility of the Haney test as a tool for regenerative agriculture verification processes using Regen Certified® and Microbially Verified Carbon scoring. Advisor: Rhae A. Drijber

Comments

Copyright 2023, Lance Michael Gunderson

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