氮肥后移对超高产夏玉米产量及氮素吸收和利用的影响

采用田间试验研究了氮肥后移对超高产夏玉米产量、氮素吸收积累和氮肥效率的影响，旨在了解超高产夏玉米(≥ 12 000 kg hm^-2)的氮素吸收和转运特性，为实现夏玉米超高产合理施肥提供依据。结果表明，夏玉米施氮显著增产，增产幅度为9.62%~15.95%，氮肥后移比习惯施氮增产2.27%~5.33%。超高产夏玉米吐丝后氮素吸收积累量占总积累量的40.30%~47.78%，保证后期氮素养分充足供应对于夏玉米达到超高产水平至关重要；氮肥后移可促进超高产夏玉米后期的氮素吸收积累，降低夏玉米茎和叶片氮素的转运率，显著增强灌浆期夏玉米穗位叶硝酸还原酶活性，提高灌浆期叶片游离氨基酸含量，增加蛋白质产量；氮肥后移比习惯施氮的氮肥利用率提高1.88%~9.70%、农学效率提高0.96~2.21 kg kg^-1，以“30%苗肥+30%大喇叭口肥+40%吐丝肥”方式施用氮肥的产量和氮肥利用效率最佳。

Effect of Postponing N Application on Yield,Nitrogen Absorption and Utilization in Super-High-Yield Summer Maize

Maize (Zea mays L.) is the largest grain crop in China. Realizing super-high-yield (≥12 000 kg ha^-1) of summer maize plays an important role in ensuring the country food security. However, there exist some problems in summer maize production such as excessive dosage and unreasonable period of nitrogen application, which hinders the realization of super-high-yield. In order to increase the use efficiency of fertilizer and grain yield of summer maize, field experiments were conducted and the effects of postponing N application on nitrogen absorption, use efficiency of nitrogen fertilizer and grain yield in summer maize were studied. The results showed that yield was increased by 9.62%–15.95% by applying nitrogen fertilizer. Compared with conventional fertilizer application, postponing N application increased grain yield by 2.27%–5.33%. The N absorption proportion after silking stage was 40.30%–47.78% of the total, so it is important to provide maize plants with sufficient N in later growth stage for realizing super-high-yield. It was indicated that postponing N application could promote N absorption and accumulation of super-high-yield summer maize at later stage, decrease N transfer efficiency in stem and leaf, increase activity of nitrate reductase and content of free amino acids in ear leaf at filling stage, and raise protein yield of summer maize. In comparison with conventional fertilizer application, the N fertilizer utilization rate and N fertilizer agronomy efficiency were increased by 1.88%–9.70% and 0.96–2.21 kg kg^-1 respectively by postponing N application. The highest yield and nitrogenous fertilizer use efficiency were obtained by applying 30% of nitrogen fertilizer at seedling stage and trumpeting stage respectively and 40% of nitrogen fertilizer at silking stage.