Herbicide, soil mobility related

Wherever mobility of the herbicides was studied in differing soil types, the compounds moved most readily in coarse-textured (sandy) soils and least readily in fine-textured (clay) and organic soils. The organic matter content of the soil was the soil factor related most highly to the relative movement of the acid pesticides 141, 142, 143, 152, 156, 161, 162, 164, 165,169,170,173,174,175). 

The migration of herbicides depends on (1) application factors (amovmt, place, period, frequency, type of formulation, and method of application) (2) persistence and mobility (related to molecular structure and intrinsic physical/chemical properties) (3) soil composition (geomorphology of the application site) ... 

Fenuron was mobile in soil systems compared with other phenylurea herbicides (87, 356), Movement was related to the water solubilities of the compounds (87). Fenuron s leachability was also greater in coarse textured soils than in fine textured ones and was related to the organic matter content of the soil. In a recent field experiment fenuron moved substantially in a lateral direction over the soil surface and in a vertical direction into the subsoil (63). Femuron moved into the subsoil much more on coarse textured soils than on fine textured ones, but it moved only when excessive amounts (80-160 pounds per acre) were used (356). 

CDAA, molinate, EPTC, vernolate, pebulate, CDEC, and cycloate are all relatively mobile in soil systems (123, 385, 386, 387, 388 389, 390, 391). The herbicides leached more readily in coarse textured soils than in fine textured ones and did not significantly leach in peat or muck soils (386, 387, 388, 391), Leachability of the compounds was related to their water solubilities (compounds of higher solubilities moved more than less soluble ones) and to the organic matter and clay contents of the soils (less movement as the organic matter and clay content increased). 

Bentazone was mobilized from the soil when submitted to the action of an electric field, toward both electrode compartments, but mostly toward the anolyte. At the end of the experiments, more than 90% of the bentazone initial quantities were removed. It seems that an application of a lower current intensity (10 mA) is related to a higher mobilization of this herbicide toward the cathode compartment, whereas higher current intensities (20 mA) promoted greater rate of bentazone mobilization also toward the anolyte. 

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