Use of Herbicides in Off-Season Corn Intercropped with Brachiaria ruziziensis

This study aimed to evaluate the behavior of intercropped Brachiaria ruziziensis and off-season corn after application of the herbicides atrazine (1.760 ga.i ha(-1)), mesotrione (60 ga.i ha(-1)), mesotrione + atrazine (1.760 and 60 ga.i. ha(-1)), and nicosulfuron (8 and 16 ga.i. ha(-1)) on the 14th and 24th days after Brachiaria emergence. Corn was sown mechanically in 0.90 m spaced rows under a no-till system with an intermediary line of B. ruziziensis in Dourados, Mato Grosso do Sul Brazil, on March 7, 2008. Atrazine did not cause visible signs of toxicity on the Brachiaria leaves, while mesotrione caused bleaching of the tips of the leaves, resuming rapid growth. Nicosulfuron caused leaf chlorosis with necrosis and reduced growth of Brachiaria, without full plant recovery during corn growth, leading to low yield forage mass. The old stems, grown during corn cultivation, accounted for higher Brachiaria mass yield and were little affected by atrazine and mesotrione, which can be used in the intercropping system. Off-season corn grain yield was not significantly altered by the treatments.