AbstractThe degradation of the wild‐oat herbicide flamprop‐isopropyl, [isopropyl (±)‐N‐benzoyl‐N‐(3‐chloro‐4‐fluorophenyl)alaninate], in four soils has been examined under laboratory conditions with sampling times of up to 45 weeks after treatment. The major degradation product of [14C]flamprop‐isopropyl in all soils at up to 10 weeks after treatment was the carboxylic acid (±)‐N‐benzoyl‐N‐(3‐chloro‐4‐fluorophenyl)alanine. This compound in turn underwent degradation by loss of the benzoyl group and the propionic acid moiety, with evolution of [14C]carbon dioxide to form 3‐chloro‐4‐fluoroaniline (CFA). The CFA was formed slowly in soil and occurred mainly as a bound form. There was evidence to show that the CFA was subsequently converted into other polar products. The time for depletion of 50% of the applied herbicide was approximately 10 weeks in sandy loam and medium loam soils, 11 weeks in a c