Published online by Cambridge University Press: 12 June 2017
Canada thistle [Cirsium arvense (L.) Scop.] infestations were treated with 3-(p-chlorophenyl)-1,1-dimethylurea (monuron) at 10 rates ranging from 5 to 160 lb/A. Depths to which monuron leached were determined annually by bioassays with flax, peas and wheat. Toxicity at all rates continued for 3 years. The low sand, high clay, and high organic matter contents of this soil combined with cool or dry climatic conditions inhibited leaching and prolonged the toxicity of monuron.