Masters Theses

Date of Award

8-2017

Degree Type

Thesis

Degree Name

Master of Science

Major

Environmental and Soil Sciences

Major Professor

Forbes Walker

Committee Members

Sindhu Jagadamma, Neal S. Eash

Abstract

Integration of cover crops (CCs) can provide several benefits to row crop production systems. Comprehensive studies to understand the effectiveness of a mixture of CCs versus single or double species CCs are limited. In this study, we evaluated the effect of single and double species CCs, and the soil health mix (SHM, a combination of five species recommended by the United States Department of Agriculture) on soil quality attributes and crop production in western Tennessee. The results showed an increase in soybean yield after 3-years of SHM treatment, which corresponded with significantly higher soil moisture content and soil inorganic nitrogen content compared to less diverse CC treatments and no-cover control. Overall the multi-species SHM showed potential for enhancing soil quality and crop yield.

The Haney’s soil health test is a new approach to quantify the soil health status with heavy emphasis on soil biological properties. It introduced a new extractant for determining soil available nutrients, H3A; a new method of soil respiration measurement using Solvita gel system; and two new soil bioavailability parameters: water extractable organic carbon (WEOC) and water extractable organic nitrogen (WEON). The final Haney soil health score is calculated from the Solvita respiration, WEOC and WEON. In this study, components in Haney’s soil health test were evaluated to test their effectiveness in Tennessee soils. The H3A extractant showed significant but weak correlation with the traditional extractants such as Mehlich-1 and Mehlich-3. The Solvita test did not provide a reliable estimation of potential mineralizable nitrogen, however, it correlated with many soil properties including soil carbon and nitrogen pools as well as the WEOC and WEON. Although the soil health score showed some extent of sensitivity to long-term cover crop treatments, it did not capture the variation in soil health status after 4 years of cover cropping with different species of cover crops. This study is a first step towards simultaneous suitability evaluation of a suite of CCs for improving the sustainability of the agricultural belt of Tennessee. More similar studies are needed to help farmers make informed decisions of CC species selection for their cropping systems.

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