Selectivity of halosulfuron-methyl applied in preemergence of castor bean crop/Seletividade do halosulfuron-methyl aplicado em pre-emergencia da cultura da mamoneira

Castor bean is very sensitive to competition, being necessary to expand the alternatives for weed management, principally considering the selective herbicide options, aiming to contribute to the expansion of the cultivated areas. The aim of this study was to evaluate the selectivity of the herbicide halosulfuron-methyl applied to castor bean crop in preemergence, before seeding. Two trials were conducted under greenhouse conditions, one with sandy and other with sandy clay loam soil, in a completely randomized design with four replications. The treatments corresponded to five periods between herbicide application and seeding (0, 7, 14, 21 and 28 days) and a control without application. The evaluations made were: plant height at 7, 14, 21 and 28 days after emergence (DAE); stem diameter, leaf area, root volume, dry mass of aerial part and roots at 28 DAE. Halosulfuron-methyl (112.5 g [ha.sup.-1]) is selective to castor bean crop, when applied at preemergence modality, before seeding.