Chlortoluron behavior in five different soil types

Chlortoluron transport was studied in five different soil types and under varying climatic conditions. The chlortolu-ron mobility in the monitored soils increases as follows: Albic Luvisol = Haplic Luvisol < Haplic Cambisol < Haplic Stagnosol < Greyic Phaozem. Significantly high concentrations in the top layer of Haplic Stagnosol were observed due to the high presence of coarse gravel (30–40%) and flow profile reduction up to 60%. The content of remaining chlortoluron in the soil profile corresponds to the herbicide mobility. The percentages of remaining chlortoluron were 46.1% in Albic Luvisol, 54.6% in Haplic Luvisol, 65.0% in Haplic Cambisol, 69.6% in Haplic Stagnosol and 102.9% in Greyic Phaozem. The highest herbicide degradations were at the locations with lower observed mobility and herbi-cide present mainly in the top layer. Occurrence of the remaining chlortoluron percentage in Greyic Phaozem higher than 100% was caused mainly by the herbicide transport through the preferential paths and restricted degradation in subsurface layers. Variability of chlortoluron distributions in the soil profiles observed at the three positions of the same location occurred due to the heterogeneity of the soil profile and an uneven distribution of chlortoluron on the soil surface. The BPS mathematical model (Kozak and Vacek 1996) connected with the soil database (Kozak et al. 1996) was used to simulate chlortoluron transport. The simulated chlortoluron concentrations follow approximately the measured data except for Greyic Phaozem, where a preferential flow highly influenced solution transport. The BPS model with the soil database can be used for estimation of the chlortoluron transport.Keywords: pesticides; chlortoluron; degradation; solution transport; field and numerical studySupported by the Ministry of Agriculture of the Czech Republic, Project No. QF 3250.