Weed control in sunflower on clay textured soil

Abstract

Lack ofbroadleaf chemical control options in sunflower is a major production problem. An experiment was conducted at Embrapa Soja in Londrina, Paraná State, Brazil, to evaluate broadleafweed control and agronomic efficiency ofpreemergence herbicides applied on clay soil. The treatrnents were: sulfentrazone (350 and 600 g/ha), acetochlor (2100 and 2520 g/ha) and oxyfluorfen (360 and 480 g/ha), weed and hand hoeing treatments. Sulfentrazone applied at 350 g/ha was seletive to sunflower cultivar M 734 and efficient in controlling wild poinsettia tEuphorbia heterophylla) and momingglory (Ipomoea grandifolia). Acetochlor was not efficient in wild poinsettia control. Oxyfluorfen applied at 360 g/ha was seletive to sunflower cultivar M 734 and efficient in wild poinsettia control. The risk offitotoxicity appears to be greater on low organic matter and coarse textured soils.