CHARACTERISTICS OF NITROGEN USE EFFICIENCY AND THEIR MUTUAL RELATIONSHIP IN WINTER WHEAT CULTIVARS

Field experiments with 12 winter wheat cultivars, which differed in N grain concentration, were established with three variants of N fertilisation (N0 = 0 kg N/ha, N1 = 100 kg N/ha, N2 = 200 kg N/ha) in the vegetative years 2004/05 and 2005/06 in Piestany (Borovce). The aims of experiment were to find out the effect of N applied (Nf) and available N (Nfs) on differences in N uptake and N utilisation. From the primary data of traits, grain yield (GY kg/ha), biomass production (BP kg/ha), and N concentration in grain (Ng) and in straw (Ns), other characteristics (NUP, NUE, NUTE) for available and applied N (Nfs, Nf, respectively) were calculated. In available N, significant differences were seen among cultivars in all characteristics but in applied N differences in NUP and NUTE among cultivars were not significant. Genetic correlations among traits and characteristics were modified by N environment. Grain N concentration (Ng) was, at the low N rate, in a negative correlation with NUE (r = -0.683+) and in a strong negative correlation with NUTE (r = -0.956++). At a high N rate, these correlations had the same character, but were weaker and not significant (r = -0.560 and r = 0.570). Grain N concentration (Ng) was more determined by efficiency of N translocation than by quantity of N uptake. Selection on the higher NUPE and NUE will be limited by negative correlation between BP and N biomass concentration and by low genetic variability of all characteristics of N uptake and utilisation.