Masters Theses

Date of Award

5-2010

Degree Type

Thesis

Degree Name

Master of Science

Major

Environmental and Soil Sciences

Major Professor

Neal S. Eash

Committee Members

Forbes R. Walker, Brandon R. Smith

Abstract

The integration of organic farming and conservation tillage (CT) holds potential for sustainable field and vegetable crop production. The purpose of this study was to investigate the effect of soil management systems in organic vegetable production on weed management and yield, and to evaluate cover crop utilization of phosphorus (P) from Tennessee brown-rock phosphate (TBRP) for no-till, organic corn (Zea mays) production. For organic no-till management, cover crops were mechanically killed with a frontmounted roller (I & J Manufacturing, Gap, PA). The roller effectively killed an oat (Avena sativa L.) and crimson clover (Trifolium incarnatum L.) biculture. Two passes was as effective as three passes, while application of pressure on the roller and higher operating speed improved mortality rates of cover crops, and no-till corn planting, respectively. In organic tomato (Lycopersicon esculentum L. var. Crista) production, a soil spader (Imants USA, Haven, Mi) produced higher yields than a rototiller, an off-set disk or no-till. Less melon (Cucumis melo L. var. Galia) plants died from bacterial wilt (Erwinia tracheiphila [E. F. Sm.]), transmitted from the spotted cucumber beetle (Diabrotica undecimpunctata howardi) and the striped cucumber beetle (Acalymma vittata [Fab.]) under no-till management, which produced the highest melon yields at the end of the season when market prices were higher. However, the rototiller treatment produced the highest overall melon harvest for the season. The 19% residue cover left by the soil spader did not meet conservation tillage standards, while the 97% residue cover in the no-till met CT standards and reduced labor for weed management. vii There was no significant increase in organic corn yields when TBRP was applied at either 448 kg ha-1 or at 1344 kg ha-1, based on citrate soluble or total P, respectively. However, Mehlich-I P increased and soil carbon decreased with increased TBRP application rate. Barley produced the most biomas, had the highest P uptake per unit soil surface area, and reduced estimated soil erosion to slightly below the threshold under which yields are not effected, while maintaining similar yields to the tilled control. This systems can, therefore, reduce negative environmental impacts related to erosion without compromising yields.

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