The control of sourgrass, has been one of the great challenges in the soybean culture, and the pre-emergent herbicides appear as a management option. The objective of this work was to evaluate the control of sourgrass using pre-emergent herbicides positioned under different irrigation regimes and amounts of straw. Two experiments were carried out, the first with corn straw + Urochloa ruziziensis (0 and 3 t ha(-1)) and the second without straw, both in a greenhouse with a completely randomized design in a 6 x 3 factorial scheme, in the first factor irrigation regimes (initial of 5 mm and after 48 hours 10 mm for maintenance, initial of 20 mm and after 48 hours 10 mm for maintenance, initial of 5 mm and after, 5, 10, 15 or 20 days a rain of 20 mm) and in the second, the pre-emergent herbicides: (diclosulam (29.4 g i.a ha(-1)); flumioxazin + imazethapyr (50 + 106 g i.a ha(-1)) and diuron + sulfentrazone (420 + 210 g i.a ha(-1)). When applied directly to the soil and on straw, diclosulam showed the lowest percentages of control in all irrigation regimes with the first rain of 5 mm and the second of 20 mm. Diuron + sulfentrazone and flumioxazin + imazethapyr did not present significant differences in the irrigation regimes, effectively controlling the sourgrass. The effectiveness of diclosulam was influenced by drought intervals after application, diuron + sulfentrazone and flumioxazin + imazethapyr showed an effective control of sourgrass in all treatments.