| In order to clarify the effects of irrigation times and nitrogen application rate on population dynamics and grain yield, field experiments were carried out during 2006-2007 in Gaocheng and 2007-2008 in Baoding with local commecial winter wheat cultivar Henong 822 and Shixin 616, respectively. The experiments during the two years were designed as split plot arrangement, with irrigation times as main plots (including 0, 1, 2 and 3 times, expressed as W0, W1, W2 and W3, respectively), and nitrogen application rate as split plots (including N 0, 112.5 and 225 kg/ha, respectively). The results showed that, during 2006-2007, irrigation times and nitrogen rate had significant effect on population culm (spike) amounts. The spikes of W1, W2 and W3 were significantly higher than that of W0. The difference of culms among W1, W2 and W3 was not significant. The culms among the three levels of nitrogen application rates were significantly different and increased with the increase of nitrogen rate. The difference of LAI among the four irrigation levels was insignificant at most growing stages, but that among the three nitrogen application rates was significant, with the LAI of N2 significantly higher than those of N1 and N0. The effects of irrigation times on spikes per ha and 1000 grain weight were statistically significant, and the effects of nitrogen rate on spikes per ha and grain number per spike were significant, so that the main effects of irrigation times and nitrogen rate on grain yield were all statistically significant. The grain yield of W3 was the highest, and that of W0 the lowest among the four levels of irrigation, and the grain yield of N1 was the highest, and that of N0 was the lowest among the three levels of nitrogen rates. The interaction of irrigation times and nitrogen rate on grain yield and the three yield components was statistically significant. The grain yield increased with the increase of nitrogen rate under W0 and W1 rigimes. Under W2 and W3 rigimes, however, the grain yield of N1 was the highest, and was significantly higher than that of N0. In 2007-2008 experiment, however, the effects of irrigation times and nitrogen application rate on population culm amount and LAI at various growing stages, and on grain yield of wheat were all statistically insignificant. According to the results, it was recommended that three irrigations during the whole growing period be needed, with 112.5~225 kg/ha N applied for satisfactory grain yield of winter wheat under moderate rainfall (about 100 mm during winter wheat growing period) and fertility in Hebei Plain of China. In rich rainfall year and high fertility, however, one or two irrigations could be sufficient, with the corresponding nitrogen application rate of 225 or 112.5 kg/ha. |
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