COWPEA TOLERANCE TO OXADIAZON

The use of herbicides for weed control in cowpea [Vigna unguiculata (L.) Walp.] can result in highly effective control and lower production costs, if compared to mechanical control, especially weeding. However, not many studies were conducted in order to evaluate crop tolerance to herbicides. The objectives of this study were to evaluate cowpea tolerance, BRS Guariba cultivar, to the oxadiazon herbicide, applied in pre-emergence, at 200 g, 400 g, 600 g, 800 g, and 1,000 g of active ingredient (a.i.) ha-1, and weed control effectiveness. The weeds identified were Cleome affinis, Commenlina benghalensis, Cyperus rotundus, and Euphorbia heterophylla. The cultivar BRS Guariba was very tolerant to all doses tested, and the weed control level was good. Grain yields obtained with doses above 600 g a.i. ha-1 were excellent, comparable to weeding performance during the critical period of weed competition, between 20 and 40 days after seedling emergence (1,561 kg ha-1). The negative interference of weeds, throughout the cowpea life cycle, decreased yield by 59%. KEY-WORDS: Vigna unguiculata; chemical weed control; floristic inventory.