Tebuthiuron Distribution in Soil following Application of Pellets
1987
Whisenant, Steven G. | Clary, Warren P.
Persistence, activity, and distribution of tebuthiuron {N-[5-(1,1 dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea} in two soils were studied following application of 40% active ingredients (a.i.) extruded pellets. Tebuthiuron dissipation from the surface 3 cm and within 2 cm of the point of pellet placement was best explained by the nonlinear regression equation: Y = bXᵃ, where Y is the tebuthiuron concentration in milligrams per kilogram, b is 7.05 × 10⁶, X is time (d) after pellet placement, and a is −2.272 (ʳ² = 0.97). Applications of 40% tebuthiuron pellets at 0.6 or 1.1 kg ha⁻¹ left a detectable residue on 9 to 21 and 17 to 38% of the treated areas, respectively. The lower percentages were on a loam soil with 47 g kg⁻¹ soil organic carbon (OC) content and the higher percentages were on loam soils with 17 and 18 g kg⁻¹ OC. Crested wheatgrass [Agropyron cristatum (L.) Gaertn.] seedling growth was reduced 50% (GR₅₀) by tebuthiuron concentrations of 0.04 to 0.20 mg kg⁻¹, depending on soil OC content. Two years after application of 0.6 kg ha⁻¹, 40% tebuthiuron pellets to a big sagebrush (Artemisia tridentata Nutt.) community, with a loam soil that had a 30% shrub cover (17 g kg⁻¹ OC in interspaces and 48 g kg⁻¹ OC under former shrub canopies), <20% of the surface soil contained the crested wheatgrass GR⁵⁰.
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