Date of Award:

5-1996

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Department name when degree awarded

Plants, Soils and Biometeorology

Committee Chair(s)

John O. Evans

Committee

John O. Evans

Committee

Steven A. Dewey

Abstract

An integrated management approach for jointed goatgrass control was investigated at two farms in northern Utah using three tillage regimes and tree herbicides. The tillage regimes included no tillage, conservation tillage, and conventional tillage. Each regime was composed of different tillage practices common in the Intermountain West. A preemergence herbicide, clomazone, and two postergance herbicides, 2, 4-D and glyphosate, were investigated. Greenhouse studies were also conducted to investigate clomazone efficacy and depth of planting of winter wheat and jointed goatgrass.

Differential sensitivity to clomazone between jointed goatgrass and winter wheat did not occur in the greenhouse for the rates tested. A treatment of 0.11 kg ai ha-1 clomazone reduced wheat and jointed goatgrass fresh weights similarly by 49 and 63% respectively.

Jointed goatgrass did not germinate below 6.4 cm and emergence was initially reduced at the 2.5 cm soil depth. Winter wheat emergence was not lowered until the seed was planted 5.0 cm deep or deeper and continued to 8.9 cm deep.

2, 4-D plus glyphosate provided over 95% jointed goat grass control initially and by midsummer fallow especially when followed by tillage. However, extensive populations of jointed goatgrass seedlings and spikelets were found in the fall prior to initiation of the cropping season. Herbicides did not provide meaningful differences in the jointed goatgrass spikelet or seedling populations. Conventional tillage practices, such as fall or spring chiseling accompanied by three summer rodweedings, provided the greatest control of jointed goatgrass spikelets and seedlings in the fall following the fallow season. Winter wheat yields reflected this relationship by having five times greater yields in the conventional tillage than in either no tillage or conservation tillage.

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