The study was carried out at the Research and Education Center Gorzyń with a branch in Brody (52°25’ N; 16°18’ E) in 2008-2009, in order to work out the effective way of weed control and protecting plantations against new weed emergences. Research combinations involved the herbicide Boreal 58 WG (flufenacet 48% + isoxaflutole 10%), Accent 75 WG (nicosulfuron 75%) and Mocarz 75 WG (tritosulfuron 25% + dicamba 50%) applied once at the dates and doses recommended by producers, 0.75 kg·ha^-1, 80 g·ha^-1 and 200 g·ha^-1, respectively, and in mixtures applied at two dates (at the stage of weed seedlings), in strongly reduced doses with an addition of the surfactant Trend 90 EC, Atpolan BIO 80 EC and ammonium nitrate. In divided treatments the single dose per hectare of herbicides Boreal 58 WG, Accent 75 WG and Mocarz 75 WG was 0.25 kg·ha^-1, 20 g·ha^-1 and 50 g·ha^-1, respectively. A dose of the adjuvant Atpolan BIO 80 EC was 1.5 dm³·ha^-1, Trend 90 EC was applied at a concentration of 0.1%, and ammonium nitrate in a dose of 2 kg·ha^-1. Carrying out one treatment often did not protect a maize plantation against secondary weed infestation. Applying mixtures of herbicides in reduced doses consisting Boreal 58 WG + Accent 75 WG + Mocarz 75 WG and an adjuvant based on methyl esters of acids or a non-ionic surfactant, with or without an addition of ammonium nitrate, in the system of divided doses, in two treatments, in comparison to a single treatment ensured a very high herbicidal efficiency and a full protection against secondary weed infestation. Lack of competition of weeds towards the crop created more favorable conditions for maize growth and development and favored a higher increase in grain yields. In spite of increased costs of protection against weeds, making the treatment two times ensured a higher profitability of maize grain production.

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