Genotypic Difference In Nitrogen Use Efficiency In Wheat

This study was carried out in the experimental farms in Yangzhou University during 2004-2006. The experiment was carried our by 36 wheat genotypes as materials under 4 nitrogen levels including 0,9,12,15kgN/666.7m2 to study the genotypic difference of wheat growth period, grain yield, characteristics of dry matter production, characteristics of N uptake and P and K uptake in systemic. Based on these results, evaluation and classification of nitrogen use efficiency were done.The main results were as follows.(1) There were all significant differences in growth period of wheat genotypes under different N levels. Whole growth period was prolonged significantly and the genotypic difference increased gradually with increasing of N level. There was notable genotypic difference in growth period structure too, proper nitrogen application was advantaged to accelerate wheat to head, but heading presented delaying tendency and days from heading date to maturing prolonged gradually with increasing of N level. Seen from ratio of days during different growth period to whole growth period, ratio of days from sowing date to heading date to whole growth period decreased, while ratio of days from heading date to maturing date to whole growth period increased with increasing of N level.(2) There were all significant differences in grain yield of wheat genotypes under different N levels. The difference was most under 0 N level and decreased with increasing of N level. The effect of nitrogen on increasing grain yield decreased with increasing of N level.Through cluster analyses, we could find that there were 18, 9, 8 and 15 wheat genotypes which could be classified into high yield type under 4 N levels respectively. Yangmai 5, Yangmai 15, Xu 974 and so on could be all classified into high yield type; but many genotypes could be classified into different yield types under different N levels.(3) The dry matter accumulation at heading stage and maturing stage all increased and the genotypic difference decreased with increasing of N level. Ratio of dry matter accumulation from heading stage to maturing stage to total dry matter accumulation first increased and then decreased a little with increasing of N level.Through cluster analyses, we could find that there were 21, 9, 15 and 17 genotypes which could be classified into high yield type under 4 N levels respectively. Yangmai 10, Yangmai 15, Huaimai 19 and so on could be all classified into high yield type under 4 N levels.(4) N content and N uptake in plant of wheat genotypes at heading stage and maturing stage all increased with increasing of N level. The genotypic difference of N content in plant at heading stage first decreased and then increased, the genotypic difference of N content in plant at maturing stage and the N uptake in plant at heading and maturing stage decreased gradually with increasing of N level.Apparent N recovery efficiency, agronomic N use efficiency, physiological N use efficiency and nitrogen grain utilization efficiency decreased with increasing of N level. Through cluster analyses, we could find that Yangmai 5, Su 6, Xixi 22 and so on which could be all classified into high apparent N recovery efficiency type; Yangmai 11, Yangmai 6, Xixi 22 and so on which could be all classified into high agronomic N use efficiency type; Yangmai 15, Xu 974 and so on which could be all classified into high physiological N use efficiency type and Yangmai 9, Yangmai 13, Yangmai 15 and so on which could be all classified into high nitrogen grain utilization efficiency type under different N levels. By using grain yield and nitrogen grain utilization efficiency as indexes, cluster analyses of wheat genotypes under 4 N levels were done. The results showed that Yangmai 15 all represented high yield and high efficiency, but Hong 3, Yangmai 5 and Huaimai 19 represented high yield and high efficiency under 0, 9 and 12kgN/666.7m2 while represented another type under 15 kgN/666.7m2.(5) P and K content in plant of wheat genotypes at heading stage increased with increasing of N level, but K content decreased a little under high N level; P and K content in plant of wheat genotypes at maturing stage increased with increasing of N level too and all decreased a little under high N level. P and K uptake in plant at heading stage and maturing stage all increased gradually with increasing of N level, but the P uptake in plant at maturing stage was the highest while the K uptake in plant at heading stage was the highest. By using correlative analyses, we could find that the wheat genotypes which represented high efficiency on N using also represented high efficiency on P and K using.