Due to increasing fertiliser costs as well as environmental concerns, N-efficiency became an attractive breeding topic. Genotypes can be considered as N-efficient if they realise an above average yield at low N level or if they convert high N input comparatively better into yield than other genotypes. To evaluate potential of Oryza sativa L. in nitrogen use efficiency compared to Oryza glaberrima Steudt., a two years field experiment was conducted. Twelve O. sativa genotypes were tested in a split-plot design with two N-levels (without N fertiliser and with 150 kg N/ha). For comparison, one genotype of African rice, O. glaberrima, was included in the experiment. Variability about grain yield at harvest and N-uptake was observed between O. sativa and O. glaberrima and within O. sativa genotypes. O. glaberrima had lower yield as O. sativa. In low N-level, a close relationship between total N-uptake in plant and grain yield was observed. In high N-level, no correlation was observed. An effect of O. glaberrima genotype on the variance component GN was demonstrated. Variation in N uptake and in N utilisation efficiency depends on N fertilisation. At low N level variation in N uptake were higher than at high N level. At the opposite, variations in utilisation efficiency were lower without fertilisation than with fertilisation. Genotypes Farox 304 and Farox 239 gave best yields at high N input as well as under low N input conditions. At low N input, variation in uptake efficiency was higher than variation in utilisation efficiency. In contrary at high N level, variation in utilisation efficiency was higher than variation in uptake efficiency. Improving N-efficient genotype through classical breeding or using biotechnology linked with innovative agronomic management could be exciting prospects to improve N use efficiency.
Key words: Fertiliser, environment, nitrogen, N-uptake, N-efficiency, breeding, genotypes, yield, Oryza sativa L., Oryza gaberrima Steudt.
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