Mobility of Herbicides in Soil Columns Under Saturated- and Unsaturated-Flow Conditions

Abstract

Under unsaturated-flow conditions, bromacil (5-bromo-3-sec-butyl-6-methyluracil) was considerably more mobile than buthidazole {3-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-4-hydroxyl-1-methyl-2-imidazolidinone}. Because of their high water solubilities, both herbicides were much more mobile than atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), prometon [2,4-bis (isopropylamino)-6-methoxy-s-triazine], or diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea]. Under saturated-flow conditions, buthidazole was leached through Lakeland loamy sand in slightly greater amounts than tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea} or CN-10-3510 (formerly VEL 3510) {1-β,β-dimethoxyl-1-methyl-3-[5-(1,1-dimethylethyl)-1,3, 4-thiadiazol-2-yl] urea}. Distribution of the three herbicides in the leached soil was similar and relatively uniform. In Lakeland loamy sand, 30 times as much tebuthiuron was leached under saturated-flow conditions as under unsaturated-flow conditions. Intermittent saturated-unsaturated-flow conditions resulted in four times as much leaching of tebuthiuron as unsaturated flow alone. Only one-tenth as much tebuthiuron leached under intermittent saturated-unsaturated-flow conditions as under saturated-flow conditions. Tebuthiuron added to Lakeland soil and oven-dried was retained in significantly greater amounts than when added to moist Lakeland soil. Low amounts of tebuthiuron leached through Lakeland loamy sand, Portsmouth sandy loam, and Rains silt loam, but high amounts leached through Davidson clay. Greater amounts of the herbicide were retained in the surface zones of the three former soils, but the inverse was the case for the Davidson soil.

Glyphosate mobility in soils by phosphate application: Laboratory column experiments

“…Though batch experiments are necessary to get glyphosate adsorption information in various kinds of adsorbents and soils for process understanding (Gimsing et al, 2004a,b), the miscible displacement approach may simulate actual field conditions better with respect to leaching or mobility of glyphosate in soil (Weber and Whitacre, 1982), because under batch conditions the retention capacity of both glyphosate and phosphate is likely more than under flow conditions. To test our hypotheses mentioned above, the focus of the present study was therefore to investigate (1) pH-dependent glyphosate sorption onto the three studied soils using batch experiments, and (2) glyphosate mobility and leaching as influenced by phosphate application using miscible displacement column experiments.…”

Quinclorac and Aminocyclopyrachlor Movement in Sandy Soils

“…Movement of quinclorac and aminocyclopyrachlor in sandy soils of the SNG was determined using soil columns to simulate field soil conditions (Weber and Whitacre 1982). Soil was collected from the five dominant ecological sites found at the SNG during the summers of 2012 and 2013.…”

Mobility of fluometuron in soil columns sections

“…long of PVC pipe (inside diameter 8.8 cm) were prepared in the same manner as described by Webber and Whitacre. 1 Silicone sealer was applied to a cup that was later attached to the bottom of each column. A bead of silicone sealer was applied at 5 cm intervals to the inside of the columns to prevent movement of water and chemical down the side walls.…”