Biological Systems Engineering


First Advisor

Amy Schmidt

Date of this Version



Melgar, K. (2021) Evaluation of a novel approach for assessing biological activity in agricultural soils. Biological Systems Engineering – Dissertations, Theses, and Student Research.


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: Mechanized Systems Management, Under the Supervision of Professor Amy Millmier Schmidt. Lincoln, Nebraska : December, 2021

Copyright © 2021 Karla M. Melgar Velis


Soil health is a key factor impacting soil resilience and fertility in crop production systems. Favorable soil physical and biological conditions facilitate plant nutrient absorption and nutrient cycling. Demonstrating to farmers the impacts and changes in soil biological activity under different soil management practices has been a challenge due to the limited availability of inexpensive tools for quantifying this component of soil health. The primary goal of this study was to present a simple and readily accessible tool for evaluating soil biological activity to promote the use of organic amendments in crop fields. Research plots were established in two studies to evaluate percent cotton fabric degradation using manual assessment and image analysis methods, and to demonstrate fabric degradation under organic soil amendment treatments in relation to established measures of soil biological health that included soil CO2 respiration and soil arthropod analysis abundance and through soil biological quality index (QBS). To obtain QBS index, arthropods were classified to order level and a score form 1 to 20 was assigned based on their level of adaptation to soil living conditions. Treatments for study #1 included the application of beef feedlot manure (BM) and a control with no organic amendment (CON) during the fall to fallow soil. Image analysis to determine percent degradation of fabric samples was initially made with Adobe Photoshop and compared to degradation estimated by manually counting degraded areas on the pieces of fabric. In study #2, treatments included swine slurry (SS), SS top-dressed with red cedar woodchips (SSW), and no treatment (CON) applied to land planted to corn during a summer growing season. Fabric degradation was assessed manually and with Photoshop and ImageJ. Across both studies, image analysis of fabric degradation with either software did not vary significantly from manual hand counting. In study #2, no difference in percent fabric degradation or rate of degradation were found among treatments and soil microbial respiration was also unaffected by the treatments. However, the SSW treatment yielded greater arthropod abundance than SS and CON treatments, resulting in a higher QBS for SSW. While this novel method for demonstrating soil biological activity requires additional refinement to improve automatization of the process and reduce sources of error, image analysis of fabric degradation is a promising tool that may be easily adapted to visually demonstrate soil biological activity under different soil management practices in an on-farm setting.

Advisor: Amy Millmier Schmidt