Date of Award:

5-1970

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Department name when degree awarded

Plant Science

Committee Chair(s)

John O. Evans

Committee

John O. Evans

Committee

D. R. McAllister

Committee

W. F. Campbell

Committee

O. S. Cannon

Abstract

Some of the factors influencing the performance of bromoxynil, 4(2,4-DB), or a companion crop for weed control in seedling alfalfa were studied in the greenhouse and at field locations in Farmington and Logan, Utah. The effect of application rate, stage of growth, temperature, and soil moisture on the phytotoxicity of bromoxynil and 4(2,4-DB) to alfalfa and weeds were studied.

Alfalfa yields were increased by 4(2,4-DB) at all rates and stages of application. All rates and stages of bromoxynil treatment except the one-fourth pound per acre three to four trifoliate application resulted in alfalfa yields below that of the control.

The use of a companion crop was not conducive to the growth and development of alfalfa although it did control the weeds. Bromoxynil at all rates and at both stages of application resulted in effective mustard control. Mustard control in the 4(2,4- DB) plots was excellent at the early stage of application but required three-fourths pound per acre for control at the later stage of weed growth. Pigweed control was rather ineffective in bromoxynil plots at Logan where moisture was optimum, but effective in plots at Farmington where moisture was limited for 18-20 days following application. The density of the pigweed stand in bromoxynil treatments at Logan was attributed to an influx of weed growth following initial control of weeds. Control of pigweed by 4(2,4- DB) was in excess of 90 percent at the four to five leaf stage of weed growth.

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