Effect of DBCP on Fluchloralin Persistence

Abstract

Three field studies were conducted over a 2-yr period to evaluate the persistence of fluchloralin [N-(2-chloroethyl)-2,6-dinitro-N-propyl-4-(trifluoromethyl) aniline], and to determine whether DBCP (1,2-dibromo-3-chloropropane) affected persistence. Fluchloralin was applied to field plots at 1.1 kg/ha with and without DBCP at 20.5 kg/ha. In the first study, soil samples were taken periodically over a 1-yr period and assayed for fluchloralin by both gas chromatography (GC) and a sorghum (Sorghum bicolorL. Moench ‘AKS-516’) root-elongation bioassay. Both methods of analysis indicated that fluchloralin persistence was unaffected by DBCP. An oat (Avena sativaL. ‘Ora’) bioassay of soil from the field plots 41 weeks after treatment showed no residual herbicide activity. In the next two field studies, soil samples were taken periodically over a 32-week period and assayed by GC for fluchloralin. A greenhouse sorghum bioassay of soil samples taken from both tests 32 weeks after application showed residual activity of fluchloralin in one test, but differences were not attributable to DBCP. A two-phase process of fluchloralin dissipation in field soil was indicated from analysis of the data using a complex first-order regression, as opposed to a simple first-order regression. Half-life values describing fluchloralin persistence, using the complex first-order regression, ranged from 2.3 to 3.7 weeks for the first phase and 9.5 to 26.7 weeks for the second phase.