氮肥运筹对苗期受渍夏玉米干物质和氮素积累与转运的影响

Effects of Nitrogen Fertilization Application Regime on Dry Matter, Nitrogen Accumulation and Transportation in Summer Maize under Waterlogging at the Seedling Stage

以玉米品种郑单958为试验材料,研究不同氮肥运筹方式[氮肥全部基施（N1）、基肥70%＋拔节肥30%（N2）、基肥50%＋拔节肥50%（N3）和基肥30%＋拔节肥50%＋大喇叭口肥20%（N4）]对苗期受渍夏玉米叶面积指数（LAI）、干物质积累、氮素吸收积累及产量的影响,以期为苗期受渍夏玉米合理施肥提供理论依据。结果表明,苗期渍水7 d降低夏玉米产量,降幅达24.2%~25.7%,氮肥后移能够减轻苗期渍害对产量的影响。玉米产量与穗粒数的相关性大于与千粒重的相关性；吐丝期最大 LAI 和收获指数与产量存在极显著相关性,但粒叶比与产量间无显著相关性。苗期渍水7 d降低群体LAI,氮肥后移能增大穗位层和穗上层叶片的LAI以弥补穗下层LAI降低导致的群体LAI下降,且弥补的效应大于渍害导致穗下层LAI降低的效应,进而使得苗期渍水7 d下氮肥后移的群体LAI较氮肥前移增大。苗期渍水7 d显著降低吐丝后干物质积累量,渍水使营养器官干物质积累转运量增大；氮肥前移处理使营养器官干物质向籽粒的转运量增大,但不利于吐丝后籽粒干物质积累,氮肥后移处理则显著提高了吐丝后籽粒干物质积累量及其对籽粒产量的贡献率。苗期渍水7 d使夏玉米各器官氮素积累量下降,吐丝后营养器官贮藏氮素向籽粒的转运量和吐丝后籽粒氮素积累量低于对照,表明苗期渍水7 d处理不利于籽粒中氮素的积累。氮肥后移能够提高成熟期籽粒及营养器官氮素积累量。渍水7 d处理使氮素吸收效率和偏生产力显著低于对照,随着氮肥后移,氮素吸收效率提高0.9%~18.2%、偏生产力提高1.0%~17.5%。

Field experiments were carried out from 2011 to 2012 to clarify the leaf area index, dry matter accumulation, nitrogen assimilation, nitrogen use efficiency and grain yield under waterlogging at the seedling stage in summer maize cultivar “Zheng-dan958”. Under both waterlogging and control （normal watering） conditions, we implemented four treatments with total N amount of 240 kg ha–1in all treatments and different N application ratios at land preparation, jointing, and big trumpet stages （10：0：0 for N1, 7：3：0 for N2, 5：5：0 for N3, and 3：5：2 for N4）. The results showed that waterlogging stress in the seedling stage significantly decreased grain yield by 24.2%–25.7%, postponement of nitrogen application was able to alleviate the effect of wa-terlogging on grain yield. The grain yield was affected more by kernel number per ear than by 1000-kernel weight, and grain yield was positively correlated to the maximum LAI at silking stage and harvest index, while not to grain-leaf ratio. Waterlogging stress in the seedling stage significantly decreased leaf area index （LAI）, especially LAI of under-ear layer. Postponed nitrogen applica-tion increased the LAI of ear layer and above-ear layer to compensate the LAI decrease of under-ear layer, and the compensation effect was higher than the decrease effect of waterlogging stress, which resulted in higher LAI compared to the nitrogen applica- tion in advance. Waterlogging stress in the seedling stage significantly decreased dry matter accumulation, and increased the transportation amount after silking stage. Postponed nitrogen application enhanced the accumulation of dry matter and laid the foundation for increasing grain yield. Waterlogging stress in the seedling stage also significantly decreased nitrogen accumulation of different organs, and decreased nitrogen translocation from vegetative organs to the grain, and nitrogen accumulation amount after silking stage. Compared with nitrogen applied in advance, postponed nitrogen application significantly increased the nitro-gen content of different organs, and nitrogen accumulation amount after silking stage. Waterlogging stress decreased nitrogen uptake efficiency and partial factor productivity from applied nitrogen, postponed nitrogen application increased the nitrogen up-take efficiency by 0.9% to 18.2%, and partial factor productivity from applied nitrogen by 1.0% to 17.5%.