A method for controlling the growth of unwanted plants in crop plants at a locus using a sulphonylurea herbicide, wherein the sulfonylurea herbicide exhibits phytotoxicity to the crop plants is provided, the method comprising applying a sulphonylurea herbicide to the locus； and planting the crop plants at the locus after a period of time following the application of the sulphonylurea herbicide. The unwanted plants may be glyphosate-resistant sourgrass (Digitaria insularis) and the crop plants may be soybean or corn. The exemplified method comprises treating glyphosate-resistant sourgrass with a combination of nicosulfuron and glyphosate and planting soybean plants at least 20 days after the sulfonylurea/glyphosate treatment. Burndown treatment may take place during the period following herbicidal treatment before the planting of the crops. The period of time (N) following herbicidal treatment before the planting of the crops may be determined by the following formula (I), N = 22.87e1.71/T – ((RH% x Y)/10.2) – ((HS x Y)/151.8) – 1.79 (I) wherein T is the ambient or atmospheric temperature at the time of treatment (Kelvin), RH is the relative humidity, HS is the hours of sunlight at the time of treatment, and Y is determined by formula (II), Y = -In(ARw x (1/ARv) x (1/410.4) (II) where ARw is the wwight application rate of sulphonylurea (g/ha) and ARv is volumetric application rate of the sulphonyura (l/ha).
