Adsorption of l-butyl-3-(3,4-dichlorophenyl)-l-methyl-urea (neburon), determined spectrophotometrically, varied considerably among representative soils of six Hawaiian great soil groups, ranging from 29% in Lualualei soil to 94% in Honouliuli soil. The adsorption of neburon was strongly correlated with organic matter and total soil nitrogen; other soil properties were not related.
Initial and residual neburon phytotoxicity to oats in the greenhouse was dependent on total soil nitrogen, organic matter, and the degree of neburon adsorption. Based on ED50 values, neburon toxicity in soil types decreased in the following order: Lualualei, Wahiawa, Mahana, Paaloa, Waimanalo, Kapaa, and Honouliuli. Complete neburon inactivation was obtained in Honouliuli and Waimanalo soils within the 150-day duration of this experiment, and nearly complete inactivation in Mahana and Kapaa soils.