The best yield and internal quality of kale plants was obtained at the N range between 100 and 200 mg N dm鈭?. Of these two, the lower N-level should rather be recommended for the red-leafy kale and in the case of the mud soil. Compared to control, there was no clear negative impact of increasing N-level (in the range 100-300 mg N dm鈭?) on non-enzymatic antioxidants determined in both kale genotypes in this study. N-fertility considerably affected glutathione reductase in both cultivars, whereas ascorbate peroxidase and catalase activity remained relatively stable. In general, kale plants grown on the lessive soil expressed significantly higher antioxidative enzyme activity as well as ascorbate, thiols and dry matter content as compared to mud soil. Green-leafy kale was characterized by a considerably higher yield and total ascorbate and glutathione contents, whereas red-leafy Redbor F1 expressed significantly higher concentration of global phenolics and total antioxidant ability (FRAP-assay). There were no substantial differences between cultivars in N-dependent response of the examined bioactives.