Persistence and Movement of Ten Herbicides in Soil

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Abstract
Ten herbicides were each applied at two rates to Panache loam for 5 or 6 yr as soil-incorporated broadcast sprays directed to the base of cotton (Gossypium hirsutum L. ‘Acala SJ-1’) at last cultivation. Chemical determinations 6 months after annual treatment showed that trifluralin (a,a,a-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine), nitralin [4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline], benefin (N-butyl-N-ethyl-a,a,a-trifluoro-2,6-dinitro-p-toluidine), DCPA (dimethyl tetrachloroterephthalate), and prometryn [2,4-bis(isopropylamino)-6-(methylthio)-s-triazine] residues were essentially confined to the tilled zone of soil; whereas, bensulide [O,O-diisopropyl phosphorodithioate S-ester with N-(2-mercapteothyl)benzenesulfonamide], fluometuron [1,1-dimethyl-3-(a,a,a,-trifluoro-m-tolyl)urea], linuron [3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea], and diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] residues were found below the tilled zone. At time of retreatment, annual residue determinations from the upper 15 cm of soil showed that nitralin and prometryn had dissipated completely and residues of the other herbicides and were notably reduced as compared to levels at cotton harvest. One year after final treatment herbicide residues below the tilled zone were essentially nondetectable, except for diuron, linuron, and fluometuron. There was no evidence of herbicide accumulation in soil with repeated applications.