Response of hybrid and open-pollinated maize cultivars to nitrogen fertilizer in southern Brazil

production at four sites (Alegrete Jaguari, Santa Maria and Sao Vicente) in the stale or Rio Grande do Sul Brazil, on three different soils. Nitrogen was applied at 0, 75 and 150 kg/ha. Hybrid cultivars generally produced more grain than open-pollinated cvs. Nitrogen fertilizer significantly increased grain production but there was no significant difference in yield between N at 75 and 150 kg/ha. Significant differences in silage yields were obtained with increasing rates of nitrogen. Silage production of the cultivars was different at each site with some hybrids having higher yields than open-pollinated cultivars.