Abstract: ‘Jimai No.22’ was used as a test variety to study the effects of different amounts of nitrogen fertilizer on wheat agronomic traits, grain and straw yield and crude protein yield at jointing and heading stages. The results showed that topdressing nitrogen fertilizer at jointing stage had greater effect on plant height and 1 000-grain weight of wheat, but had less effect on panicle length and grain number per panicle. Nitrogen application at heading stage had greater effect on plant height of wheat than other agronomic traits. Comparing the effects of fertilization in two periods, the effect of topdressing nitrogen fertilizer at jointing stage was better than that in heading stage. When topdressing nitrogen fertilizer at jointing stage, the yield of wheat grain and straw increased and then decreased with the increase of nitrogen application rate. When pure nitrogen 233.5 kg/hm² was applied at jointing stage, the yield of grain and straw was the highest, which increased by 25.79% and 35.27% respectively. At this time, the yield of crude protein of straw was also the highest. It is concluded that topdressing pure nitrogen 233.5 kg/hm² at jointing stage is the best fertilization measure for wheat to obtain high yield of grain and straw as well as high quality of straw for feeding.

Key words: nitrogen application stage, nitrogen application rate, wheat, agronomic characters, straw, yield, crude protein yield