Degree Name

Master of Science (MS)

Semester of Degree Completion

1979

Thesis Director

Roger Darding

Abstract

The leachability of the acetanilide herbicide, CP55097 was determined using a soil column system. This herbicide, which is used as a preemergent against certain grasses and broadleaf weeds, was leached through four different soils (sandy clay, sandy loam, sandy clay loam and clay loam) using the following procedure. Plastic columns consisting of 8 rings (2 in. dia. x 1 in.) were assembled and their bottoms covered with cheesecloth. They were then filled with soil and prewetted with water to attain field capacity. Herbicide concentrations equalling 0, 1, 3, 6 lb/A were pipetted onto the soil surface and 0, 1, 2, 4 in/A of water was applied at an approximate rate of 1 ml/minute. The columns were leached for two days, then disassembled and the soil placed in styrofoam cups. The extent to which CP55097 leached through the soil columns was determined by an oat bioassay (Avena sativa var. Noble). After the soil dried for two days, 10 oat seeds were planted with the hilum end down. The plants were grown at a temperature of approximately 80 F and illuminated with cool white fluorescent light at 300 ft-c on a 15 hour photoperiod cycle. The plants were watered twice a day for a duration of eight days after which the shoots were weighed and the percent germination recorded.

The organic matter and clay content of the soils was found to have a significant effect on the movement of the herbicide. In general, the herbicide moved less in soils with higher organic matter and/or clay content. Of the two, organic matter was more effective in reducing herbicide movement. Only in the low clay-low organic matter sandy loam was the herbicide leached throughout the eight inches of soil.

Statistically at a significance level of 0.05 all factors; soil type, CP55097 concentration, water application and soil depth separately and all interactions thereof significantly affected oat growth. However, the depth of leaching as determined by growth reduction, was not correlated with the concentration of CP55097 applied. Even though increasing concentrations of herbicide did reduce oat growth at specific depths, the maximum depth of observable effect was constant for each initial concentration tested.

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