Masters Theses

Date of Award

12-2001

Degree Type

Thesis

Degree Name

Master of Science

Major

Plant, Soil and Environmental Sciences

Major Professor

Thomas C. Mueller

Committee Members

Gaylon Morgan, G. Neil Rhodes Jr

Abstract

Tobacco is an Important crop in the southeastern United States. Approximately 25,500 hectares of tobacco grown in Tennessee with a value of $240 million in 1999. Tobacco is normally grown in cultivated fields. Cultivation is used primarily to control weeds and improve soil tilth. Cultivation leads to reduced plant residues on the soil surface, and subsequent rainfall may cause increased soil erosion, which reduces long-term productivity of the land. No-till systems would allow production on sloping fields while decreasing soil erosion and could reduce production costs.

This research evaluated the management of a wheat cover crop, different herbicide combinations, and tillage regimes in different tobacco production systems. Main plots were residue levels: high, medium, and low. The high residue plots were generated by a burndown 15 days before planting, medium residue by a burn-down 30 days before planting, and low residue by plowing to bury all residue. Sub-plot treatments were the herbicide treatments: sulfentrazone + pendimethalin (350 g ai/ha + 930 g ai/ha), sulfentrazone + clomazone (350 g ai/ha + 630 g ai/ha), a hand weeded check, and a non-treated weedy check. Pendimethalin was incorporated in the conventional plots and all other applications were applied pre emergent.

Weed control for smooth pigweed (Amaranthus hybridus L.) was greater than 95% for both herbicide combinations at 4 weeks after planting (WAP) in 1999 and 2000 in the dark-fired studies . Entire Leaf morning glory (Ipomoea hederacea var. integriuscula Gray) control was greater than 92% for both herbicide combinations 8 WAP in the burley tobacco study in 2000. Broadleaf signalgrass (Brachiaria platyphylla (Griseb.) Nash) control was 87% or greater for both herbicide combinations 4 WAP in the dark-fired studies in 1999 and 2000.

Yields across main plot effects in the no-till plots were lower than in the conventional plots for both types of tobacco in 1999 and for buriey in 2000. Yields in the weed-free plots were equal in all years except in the dark-fired study in 1999 suggesting no-till is possible in a weed free environment. Dark-fired yields in 2000 were the same across main treatments. Tobacco quality among treatments was the same in either study in both years. Residue level of the wheat cover did not affect the yield or quality in the two no-till treatments. Further research considering the economics of no-till production in tobacco need to be pursued in order to determine how much reduction in yield may be offset by input cost savings.

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