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Soil Column Mobility of Metribuzin from Alginate-Encapsulated Controlled Release Formulations of metribuzin

Johnson, Richard M., Pepperman, Armand B.
Journal of Agricultural and Food Chemistry 1995 v.43 no.1 pp. 241
calcium chloride, encapsulation, herbicide residues, kaolin, leaching, linseed oil, metribuzin, sodium alginate, soil horizons, soil profiles
The mobility of metribuzin [4-amino-6-(1,1-dimethylethyl)-3-methylthio)-1,2,4-triazin-5(4H)-one] from alginate-encapsulated controlled release (CR) was investigated in four contrasting soil profiles. Two CR formulations based on sodium-alginate (1%), kaolin (10%) and Tween 20 (0.5%) were compared to technical grade (TG) metribuzin and to a commercial liquid (CL) metribuzin formulation (Sencor 4L). In addition to the basic components, the CR-Oil formulation contained 4% linseed oil and the (CR-N) formulation did not. All herbicide treatments were labeled with [14C]-metribuzin and were applied to duplicate soil columns containing a surface and a subsoil horizon. Each horizon was packed to a depth of 12.5 cm, giving a tolal column length of 25 cm. The columns were leached with 21 (420 mL) to 30 cm (600 mL) of 0.01 M CaCl2 for a period of 7-10 days. For the TG treatment, the total amounts of [14C]metribuzin leached were 85, 62, 66 and 58% for the Evesboro, Ocholocknee, Conover and Commerce soils, respectively. This is compared to 91, 52, 51 and 43% for the CL formulation. The CR-Oil formulation leached 9, 13, 9, and 9% of the applied [14C]metribuzin, compared to 49, 53, 41, and 48% for the CR-N formulation. The CR-Oil formulation also increased the amount of [14C]metribuzin retained in the soil surface horizon (13-27%), compared to CR-N (2-5%), TG (2-3%,) and CL (1-2%) formulations.