EFFECT OF NITROGEN FERTILIZATION ON SUGARS, ASCORBIC ACID AND PHENOLIC COMPOUNDS IN WHITE CABBAGE (Brassica oleracea var. capitata alba L.)

The aim of this research was to determine the influence of various forms, diverse doses, and methods of application of nitrogen fertilizers and foliar nutrition on the concentration of soluble sugars, ascorbic acid and phenolic compounds in cabbage. The three year (2005-2007) field experiment was carried out with 'Galaxy' F1 white cabbage. Two factors were examined: the type of N fertilizer ammonium sulphate and RSM (solution ammonium nitrate and urea I : I), and method of N application (placement and top dressing - broadcasted with or without foliar nutrition). Climatic conditions considerably affect the concentration of compounds in cabbage. The highest concentration of soluble sugars was fund in cabbage receiving N as RSM in comparison to ammonium sulphate and with foliar nutrition treatment. In each year of the experiment plants fed RSM were characterized highest concentration of ascorbic acid. For means of year 2005-2007 foliar nutrition led to a marked decline in the concentration of ascorbic acid in cabbage. In 2005 and 2007 highest concentration of phenolic compounds was assessed in cabbage plants fed RSM. Cabbage plants fertilized 75% N broadcasted at planting of seedlings with foliar nutrition characterized the lowest concentration of phenolic compounds means for 2005-2007.