Eff ect of timing of additional N fertilization on spike number, grain yield, grain protein and N use effi ciency of winter wheat cultivar “Kitahonami”

Nobuhiko Fueki, Ryuichi Nakamura, Atsushi Sawaguchi,Kan Watanobe, Takeshi Suzuki, Tetsushi Uchida Masayuki Onodera

道総研農試集報．99，61-72 (2015)

　A new leading cultivar of winter wheat in Hokkaido “Kitahonami” having a high-yield ability requires a suitable method of additional nitrogen (N) fertilization because it tends to lodge with overexuberant stems and have lower grain protein. Therefore, we compared the timing of additional N fertilization at the booting stage and the panicle formation stage with the aim of avoiding these problems. Additionally, we analyzed the difference of timing of additional N fertilization among the panicle formation stage, fl ag leaf stage and fl owering stage.
Our results showed that additional N fertilization at the panicle formation stage rather than at the booting stage not only suppressed the overexuberance of stems and spikes but also increased the harvest index (HI), grain number per spike and grain protein without decreasing the grain yield. These results suggest that winter wheat cultivars having the tendencies of overexuberant stems and lower grain protein such as “Kitahonami” may prefer additional N fertilization at the panicle formation stage to at the booting stage.
Moreover, from the results of comparing the timing of N fertilization at the panicle formation stage, fl ag leaf stage and fl owering stage, the following features of the response of “Kitahonami” to additional N fertilization timing were clarifi ed: (1) earlier N fertilization tends to increase the risk of lodging through overexuberant stems and spikes, (2) later N fertilization does not tend to result in overexuberant stems and spikes, (3) later N fertilization tends to increase the 1000-grain weight, grain bulk density and grain protein through higher N effi ciency. The above results suggest means of ensuring the eff ective N fertilization of winter wheat cultivars with the tendency of overexuberance in later growth stages and lower grain protein such as “Kitahonami”.

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