Transport of herbicides and nutrients in surface runoff from corn cropland in southern Ontario

agricultural soils agua superficial ammonium compounds ammonium nitrogen atrazina atrazine azote calidad del agua choix de la date compuestos de amonio contamination eau de ruissellement eau superficielle escorrentia fosforo lluvia losses losses from soil metolachlor metolacloro nitrate nitrates nitratos nitrogen nutrientes nutrients ontario perte phosphore phosphorus pluie pollution de l'eau procesos de transporte en el suelo rain runoff soil transport processes sol agricole substance nutritive surface water timing transport dans le sol water pollution water quality zea mays