不同施氮时期对夏玉米干物质积累及氮肥利用的影响

以提高夏玉米氮肥利用率、减少氮肥污染为目标，研究了不同施氮时期对夏玉米生长发育及氮肥利用率的影响。结果表明：施氮显著增加子粒产量和穗粒数，以3叶期施氮结合12展叶追氮处理的子粒产量最高，但对千粒重和单位面积穗数影响差异不显著。施氮使各处理植株的叶面积指数(LAI)均在生育后期保持较高值，延缓了叶片衰老，促进了干物质的积累。3叶期施氮结合12展叶追氮处理的夏玉米氮肥利用率最高，较3叶期施氮和12展叶施氮分别提高了21.8个百分点和22.8个百分点，较好地提高了夏玉米当季氮肥利用率，能够有效降低因氮素损失而造成的农田污染。

Effects of Nitrogen Application Time on Dry Matter Accumulation and Nitrogen Use Efficiency of Summer Maize

Aimed to reduce pollution of nitrogen fertilizer(NF) and heighten nitrogen use efficiency(NUE) in summer maize, effects of nitrogen application time on dry matter accumulation and NUE were studied. The results showed that treatments of nitrogen application increased obviously grain yield and grain per ear, the grain yield of treatment of applied nitrogen in 3-leaf stage and 12-leaf stage was tiptop, the effects of nitrogen application time on 1 000-grain weight and ears per unit was not prominent. LAI of treatment of nitrogen application time keeping more number in later stage and stopping consenescence of leaf and accelerating more dry matter accumulation. In treatments of three nitrogen application time, the NUE of treatment of applied nitrogen in 3-leaf stage and 12-leaf stage was top, and increased 21.8 percent pionts and 22.8 persent points than the others, it improved the NUE of summer maize in the stage, and reduced the farm pollution by losing of nitrogen.