Persistence of Several Dinitroaniline Herbicides as Affected by Soil Moisture

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Abstract
The Persistence of substituted dinitroaniline herbicides in soil varied widely. First-order kinetics were used to describe the dissipation rates. Half-lives of the herbicides in moist soil ranged from 29 to 124 days in two soil types under greenhouse conditions. Flooding the soil significantly increased the dissipation rate of trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine), fluchloralin [N-(2-chloroethyl)-2,6-dinitro-N-propyl-4-(trifluoromethyl)aniline], profluralin [N-(cyclopropylmethyl)-α,α,α-trifluoro-2,6-dinitro-N-propyl-p-toluidine], and pendimethalin [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine]. Dissipation rates of dinitramine (N 4,N 4-diethyl-α,α,α-trifluoro-3,5-dinitrotoluene-2,4-diamine) and butralin [4-(1,1-dimethylethyl)-N-(1-methylpropyl)-2,6-dinitrobenzenamine] were affected to a lesser extent by flooding. Volatilization of trifluralin, fluchloralin, and ethalfluralin [N-ethyl-N-(2-methyl-2-propenyl)-2,6-dinitro-4-(trifluoromethyl)benzenamine] from Bosket sandy loam was reduced by flooding when compared to volatilization from the same soil with a moisture content equivalent to field capacity. Pendimethalin exhibited low volatility. The effect of flooding on dissipation rates is apparently not due to increased volatilization.