NITROGEN EFFICIENCY COMPONENTS OF WINTER CEREALS

A model to describe the importance of different physiological processe s to explain grain yield differences (Delta G(w)) between cropping sys tems (Huggins and Pan, 1993) was modified to evaluate the nitrogen use efficiency of different cereals. The method uses measurements of grai n yield (G(W)), grain N (N-g), above-ground plant biomass (B), above-g round plant N (N-t), applied fertilizer N (N-f), and post-harvest inor ganic soil N in control plots without fertilizer (N-h) The components are N supply (N-s), N uptake efficiency (N-t/N-s), assimilation effici ency (B/N-t), harvest index (G(w)/B) and N harvest index (N-g/N-t). Fo r a first verification of the model different winter cereal species, i .e., one genotype of winter wheat, one of winter rye and one of spelt wheat, were compared in a 2-year field experiments at two sites with d ifferent soil fertility and climate. The modified nitrogen efficiency component analysis provided a good understanding of yield differences at different levels of applied N and soil fertility. The method could be useful for selection of genotypes with a high N use efficiency in b reeding programmes.