Date of Award

Fall 2019

Document Type

Open Access Dissertation

Department

Environmental Health Sciences

First Advisor

R. Sean Norman

Abstract

The agricultural ecosystem has become the largest non-ice-covered terrestrial ecosystem on the planet and has significant direct and indirect impacts on the global health of both the environment and humanity. Recent shifts in modern agriculture are beginning to focus on the health of soil versus a focus traditionally on crop health and yield at any cost. By managing farmland regeneratively, systems are able to reverse many of the problems created by conventional land management such as erosion and unwanted nutrient runoff, and simultaneously create opportunities to move C from the atmosphere back into the soil. While the ways in which farmland is managed are beginning a necessary shift, the ways in which soil fertility is measured in the process of monitoring and understanding these management changes also need to be adjusted. This dissertation aims to begin that adjustment by evaluating data commonly overlooked in traditional soil tests and the effectiveness of both standard and new soil health tests at prescribing fertilizer recommendations in regeneratively managed soils, and exploring the potential of high-throughput metagenome analyses as a means to measure soil health.

Organic Matter data collected from standard soils tests shows that statewide, SC has the potential to sequester 500,647 – 1,558,092 tons of atmospheric carbon per year with the adoption of no-till and cover cropping practices on its 1,967,288 acres of cropland. The yield-predictive capability of these same soil tests, as well as with Haney Soil Health tests, confirmed an expected yield-response to N fertilizer based on field trials, but both showed almost no soil test value that consistently correlated with actual crop yields through two full corn-wheat-soybean crop rotations in the coastal plains of SC, bringing into question the effectiveness of current soil testing methods. Finally, the examination of 6” soil metagenomes throughout a single winter wheat crop showed that traditional versus regenerative land management practices had some significant impacts on the soil microbiomes’ potential ability to cycle and recycle nitrogen. These data show the need for continued reexamination of both current agricultural systems as well as the tools by which these systems are measured, and their management decisions made.


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