Simulated rainfall following the preplant application of 2,4-D and dicamba in soybean

ABSTRACT Soil residues following the application of 2,4-D and dicamba for weed control may delay the establishment and initial development of soybean, but rainfall can reduce the interval required between application and sowing. Rainfall volumes (0; 10; 30; 60; and 90 mm) were simulated following the application of 2,4-D (300 and 600 g a.e. ha-1) and dicamba (120 and 240 g a.e. ha-1), and the effects on soybean were evaluated. The application of 2,4-D did not affect the soybean establishment or initial development, regardless of the simulated rainfall volume. However, the dicamba residual reduced the soybean establishment for the lower rainfall volumes. Phytotoxicity was more severe for the highest dicamba rate (75-100 %), being 50-100 % for the lowest rate. The higher volumes of simulated rainfall reduced the phytotoxicity of dicamba in soybean, but were not sufficient to reduce the deleterious effects on the initial development of the crop.