Small Scale Evaluation of New Granular Formulations for Reducing Herbicide Runoff From Bare Clay Soil.

In an effort to help address concerns about herbicide runoff of tebuthiuron (TEB) herbicide from bare clay soils, The Ohio State University has collaborated with The Andersons in the evaluation of two novel prototype granule formulations which are intended to be used as dry-applied, water dispersible compositions. The first is a granular formulation concept based on the inert carrier which is sold as DG Lite ^®, and the second is a modified composition designed to disrupt the structure of the clay soil, called “Ground Break DG.” A current commercial granular tebuthiuron formulation was used as a control, and all three formulations tested had the same concentration, 20% active ingredient by weight.

OSU constructed runoff box-plots with dimensions of 1 m x 0.5 m oriented to allow water to flow down the slope set at 5%. The boxes were filled (8cm) with high clay soil (> 50%) with a runoff collection system at the down slope edge of each plot to divert runoff to a collection point. An overhead watering system simulated a heavy 30 minute rainfall event to generate runoff of the clay soil plus herbicide.

On a mass basis, based on chemical assay and weight of the collected runoff, the mean runoff mass of the TEB herbicide ranged from 0.173 to 1.26 g/plot, out of 2 grams applied. Analysis of variance showed significant differences in grams of herbicide per plot in runoff across the treatments. The mean herbicide runoff mass from “Ground Break DG” was significantly lower than the other two treatments, and the runoff from the DG Lite formulation was significantly lower than the commercial TEB 20% formulation, which had the highest mean runoff mass in the test.

Results of ANOVA for TEB Runoff study. Within each column, values with the same letter are not significantly different from each other (P<0.05)

Treatment	Runoff Vol. L	Herbicide Concentation mg/L	Herbicide Mass g	Herbicide Recovered %
DG Ground Break	17	10.2 a	0.173 a	8.64
DG Lite	18,8	28.6 b	0.535 b	26.8
TEB 20% G	16.7	75.1 c	1,26 c	62.9

Additional work is planned in order to evaluate the new formulation approaches for commercial usage with the herbicide and to try the formulation approach for fertilizer as well.