This investigation had the objective of evaluating the biological persistence of pre-emergence herbicides under greenhouse conditions. Oat plants were used as test organisms. The experiment was established at Boliche Experiment Station, Província Guayas, Ecuador from October to December/2002. The experimental design was a randomized block, in a 3 x 4 x 4 + 1 factorial scheme, involving three herbicides (ametryn at 2.0 kg ha-1, diuron at 3.2 kg ha-1, and oxyfluorfen at 0.48 kg ha-1), plus a control. After herbicide applications soils were sampled in four different depths (0-5, 5-10, 10-15, and 15-20 cm) at four dates (10, 20, 30, and 40 days after herbicide applications). Soil layers were colleted from field using PVC pipes, which were planted with 10 oat seeds. The herbicides did not promote oat seeds emergence reduction. Diuron at the 0-5 cm layer showed the highest visual symptoms of phytotoxicity and the lowest production of dry matter (total, shoots, and roots) per oat plants at all sampling dates (10, 20, 30, and, 40 days after herbicide applications). Oat plants showed good sensitivity to the herbicide residues. Diuron was more persistent in the soil when compared with ametryn and oxyfluorfen.
Leaching; herbicide; bioassay
