EN
Nitrogen is the dominant factor affecting the rate of wheat growth and yielding. Water supply during the critical stages of yield component formation is a factor limiting nitrogen use efficiency. A study dealing with this problem has been conducted, based on a long-term field experiment with four N levels (0, 60, 120, 180 kg N ha -1 ) against the background of four systems of potassium management, including: medium and high K soil fertility levels without and with K fertilizer (MK-, MK+, HK-, HK+). The objective of the study was to evaluate the wheat nitrogen nutritional status during the vegetative period of wheat growth according to nitrogen concentrations in leaves and stems. The research was run in 2003, with severe deficit of water, and in 2004, under semi-dry water conditions. Grain yield of wheat responded to both experimental factors only in 2004. Nitrogen concentration in plant parts was dependent only on N doses, thus underlying good adaptation of wheat to the seasonal course of water supply. Nitrogen concentration in leaves followed the quadratic regression model. This type of response indicates an N saturation status, i.e. a non-limiting effect of this factor on plant growth. The pattern of N concentration in stems was in accordance with the linear regression model. This type of response indicates the N-limited growth due to an insufficient supply of nitrogen. The Critical Nitrogen Concentration (CNC) pattern showed significant adaptability of wheat to N fertilizer levels. The Nitrogen Nutrition Index, calculated from the CNC, can serve as an indicator of N dilution during the vegetative period of wheat growth.