Document Type

Thesis - Open Access

Award Date


Degree Name

Doctor of Philosophy (PhD)

Department / School


First Advisor

W. E. Arnold


Corn (Zea mays L. 'Sakata TS60’), grain sorghum [Sorghum bicolor (L.) Merr. 'Sokota 844'], and flax (Linum usitatissimum L. 'Culbert 79') were tested to determine suitability for petri dish bioassays of chlorsulfuron {2-chloro-N-[[ (4-methoxy-6-methyl-1,3, 5-triazin-2-yl) amino]carbonyl]benzenesulfonamide}, metsulfuron {2-[[[[ (4-methoxy-6-methyl-1,3,5-triazin-2-yl) amino] carbonyl]amino]sulfonyl-]benzoic acid} and chlorimuron {2-[[ (4-chloro-6-methoxypyrimidine-2-yl) amino carbonyl] aminosulfonyl]benzoic acid, ethyl ester}. Sorghum was not an acceptable bioassay species. Corn had a significant response to all three herbicides. Flax was the best indicator species in both soil types tested. The effects of herbicide concentration, temperature, moisture, and pH on decomposition rate of chlorsulfuron and metsulfuron were studied. Both chlorsulfuron and metsulfuron deviated from first-order kinetics. The Arrhenius equation was used to describe temperature influence and gave thermal activation values of 21.1 and 22.8 kcal/mole for chlorsulfuron and metsulfuron, respectively. Moisture response was curvilinear for both compounds as was pH response. The influence of the factors examined in this work was almost identical for both herbicides.The objectives of these studies were: 1) Establish a sensitive sulfonylurea bioassay. 2) Determine what kinetics law should be applied to chlorsulfuron and metsulfuron decomposition in soil. 3) Determine the quantitative effects of soil temperature, moisture, and pH on chlorsulfuron and metsulfuron decomposition in soil. 4) Compare the relative decomposition rates of chlorsulfuron and metsulfuron.

Library of Congress Subject Headings

Herbicides -- Biodegration

Soils -- Herbicide content

Plants, Effect of herbicides on



Number of Pages



South Dakota State University