Leaching rates and preferential flow of selected herbicides through tilledand untilled soil

Citation
Ja. Elliott et al., Leaching rates and preferential flow of selected herbicides through tilledand untilled soil, J ENVIR Q, 29(5), 2000, pp. 1650-1656
Citations number
23
Categorie Soggetti
Environment/Ecology
Journal title
JOURNAL OF ENVIRONMENTAL QUALITY
ISSN journal
00472425 → ACNP
Volume
29
Issue
5
Year of publication
2000
Pages
1650 - 1656
Database
ISI
SICI code
0047-2425(200009/10)29:5<1650:LRAPFO>2.0.ZU;2-E
Abstract
Pesticides can be transported to ground water more rapidly through preferen tial flowpaths than would be predicted from their physicochemical propertie s, The leaching rates of the herbicides 2,4-D, bromoxynil, clopyralid, dica mba, diclofop, MCPA, and mecoprop were compared in this study on plots till ed after harvest (conventional till, CT) and those that were not (fail till age operation omitted, NT), The soil-incorporated herbicides triallate and trifluralin were applied to the CT plot only, Herbicide was applied immedia tely prior to a leaching irrigation for salt removal, which represents a "w orst-case" scenario for pesticide leaching. Direct evidence of preferential now was obtained when the herbicides, with the exception of triallate and trifluralin, were detected in the first water reaching the tile drains. Alt hough the nonincorporated herbicides were transported preferentially at the same rate, the amounts transported depended on the solubility and adsorpti on coefficient (K-oc) of the herbicide. Only 0.01% of the application of th e least soluble herbicide, diclofop, was transported, compared with 0.46% o f the most soluble herbicide, dicamba, Preferential now was only slightly r educed by the tillage pass, The amounts of herbicide transported to the til e drain, however, were substantially reduced on the CT plot. The tillage ef fect was greatest for the more soluble and less strongly absorbed herbicide s. There was no clear relationship between amounts transported in the year after application and reported persistence but herbicides with the longer h alf-lives persisted in relatively greater amounts than the other herbicides .