Publication Date


Advisor(s) - Committee Chair

Elmer Gray, James Worthington, Ray Johnson

Degree Program

Department of Agriculture

Degree Type

Master of Science


Breeding herbicide-tolerant cultivars is a means of extending herbicide utilization. In 1983 and 1984, 20 soybean [Glycine max (L. Merr] cultivars were screened for their reactions to the following herbicides: metribuzin 4-amino-6-(tert)-butyl-3-(methylthio)-astriazin-5-(4H)-one]; vernolate (S-propyl dipropylthiocarbamate); and fluchloralin [N-(2-chloroethyl)-2,6-dinitro-N-propyl-4-(trifluoromethyl) aniline]. Each herbicide was applied at the recommended rate X, 2X, and 4X in 1983. An 8X rate was added in 1984. The recommended rates (X) for the herbicides were as follows: metribuzin 0.42, vernolate 2.80, and fluchloralin 1.12 kg/ha. The cultivars were Pella, Pixie, Cumberland, Williams, Essex, Union, Semmes, Tracy, Tracy M; North American Plant Breeders 350, 68225, 420, and 330; Northrup King 8069 and 8047; and Farmers Forage Research 339, 340, 560, and 561.

Plant vigor, height, and herbicide injury were the criteria used in estimating herbicide effects. Statistical differences were found among herbicides, rates, and cultivars. Also, there were significant interactions involving herbicides x rates, herbicides x cultivars, rates x cultivars, and herbicides x rates x cultivars. Although not always statistically significant, average vigor ratings decreased with increased herbicide application rate. Pronounced differences in the study results for the two years, likely reflecting rainfall patterns, were evidence of uncontrolled variability. However, a small number of the cultivars exhibited herbicide tolerance.


Agricultural Science | Agriculture | Life Sciences | Plant Sciences | Weed Science