Physiologic and morphologic characters of soybean and Urochloa sp. intercropped under reduced rates of glyphosate

Abstract

The intercropping between soybean and Urochloa spp. is an alternative for the use of the area, straw formation, and pasture. In coexistence, the use of herbicide underdoses for forage suppression is required to reduce its in­terference with soybean plants. The aim of this study was to assess the effects of densities of Urochloa spp. in coexistence with soybean plants and treated or not with glyphosate underdoses. Two experiments with U. brizantha and U. ruziziensis under coexistence with RR (Roundup Ready^®) soybean plants were assessed in a randomized block design with four replications. The absence and application of glyphosate underdoses (120 g a.e. ha^-1) and five densities of each forage (0, 1, 2, 4, and 6 plants per pot) in coexistence with soybean plants were tested in a   2 × 5 factorial scheme. The action of glyphosate on forages promoted a reduction in their com­petitive capacity with soybean plants. Glyphosate decreased the size, tillering, and dry matter accumulation of forages. When glyphosate was not applied, forages interfered negatively in soybean development, especially when in coexistence with U. ruziziensis. The increased forage density raises the degree of interference on soy­bean plants when forages are not treated with glyphosate.