Relative Nitrogen Translocation and Accumulation in Grain of Winter Wheat Cultivars

Field experiments with 12 winter wheat cultivars differing in N grain concentration were carried out during the vegetative years 2004/05 and 2005/06 using three variants of N fertilization (N1 = 0 kg N ha−1, N2 = 100 kg N ha−1, N3 = 200 kg N ha−1). The aim was to determine the effect of cultivar, N fertilization and weather conditions of the respective years on the relative N translocation and grain quality. Biomass N concentration at the stages of heading (Nbh) and maturity (Nbm), grain N concentration (Ng) and straw N concentration (Nv) were determined. The decrease of N concentration in vegetative biomass during grain filling Nv / Nbh was denoted as a relative N translocation — RNT and ratio Ng / Nv as a relative N accumulation — RNA. Low differences in Nbh and Nbm were observed between years and significant difference in Ng and Nv was due to different RNT and RNA efficiency. In the year with low RNT efficiency, Nv was high and Ng and RNA low. N fertilization increased biomass N concentration, more in the vegetative organs than generative ones. Higher N rates decreased efficiency of fertilization which was expressed in RNT and RNA decrease. In the year with low RNT efficiency, the decrease of fertilizer efficiency had a multiplier effect. Cultivars have differed in Nv, Ng, RNT and RNA but their response to N fertilization was similar. Only some cultivars (Zlatka, Renan and Tamaro) possessed N grain concentration answering food end-use without N fertilization but only in the year favourable for N translocation. Certain cultivars (Sonata and Malyska) did not have food quality at all, not even at rate 200 kg N ha−1. Straw N concentration depended strongly on the cultivar efficiency of decreasing N concentration in vegetative biomass during grain filling (RNT). On the contrary, a negative relationship was observed between straw N concentration and Nbh. Cultivars with high RNT efficiency had low Nv, high Ng and high RNA. Possibilities of utilization RNT and RNA as selection criterions on high Ng were recommended.