Biological Systems Engineering
First Advisor
Amy M. Schmidt
Date of this Version
12-2018
Abstract
Organic products that have historically been viewed as waste products may improve soil health by adding carbon (C) and nutrients to soil. Two such products are woodchips, generated from forest or rangeland management activities, and livestock manure. In Nebraska, eastern redcedar (Juniperus virginiana L.) is a native but invasive tree species inhibiting rangeland productivity. Livestock manure that is underutilized while inorganic fertilizers are imported for crop production presents a water quality risk by contributing to local- and regional-scale nutrient imbalances. Increasing the responsible use of livestock manure in crop fertility programs to improve sustainability of both livestock and crop farms necessitates equipping farmers and their advisors to recognize fields with the greatest potential for economic and natural resource benefits from manure. This dissertation included evaluating the body of research reporting effects of manure and municipal biosolids on soil health properties. Further, the effects of eastern redcedar woodchips applied as a soil amendment alone or co-mingled with swine manure, cattle manure, or inorganic nitrogen (N) on soil health properties, water quality indicators, and greenhouse gas emissions were assessed. Manure application increases soil microbial abundance, improves nutrient cycling and enhances soil structure. Results from field and laboratory studies indicated that surface application of woodchips, with or without other amendments, did not affect soil nor leachate nitrate-N concentrations. Woodchip amendments increased soil organic matter concentration and decreased soil bulk density in less than three years. Methane and nitrous oxide emissions from soil were unaffected by woodchip application, but carbon dioxide emissions increased. Because the field plots were irrigated, no differences in soil moisture were observed by treatment, but soil temperature fluctuations under the woodchips were diminished. Overall, manure and woodchips are viable amendments for improving soil health. A survey of stakeholders revealed that improving soil health is important to them, and they recognize the risks of eastern redcedar to sustainability. Thus, adoption of this novel conservation practice is likely with continued stakeholder engagement.
Advisor: Dr. Amy M. Schmidt
Comments
A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Major: Biological Engineering, Under the Supervision of Professor Amy M. Schmidt. Lincoln, Nebraska: December, 2018
Copyright (c) 2018 Linda R. Schott