限水灌溉冬小麦冠层氮分布与转运特征及其对供氮的响应

以高产冬小麦品种周麦18为材料,在大田春灌1水条件下,设置不同供氮水平和氮肥运筹处理试验,研究并探讨了在华北地区限水灌溉条件下氮肥施用对冬小麦冠层叶片氮素时空分布与转运及氮肥利用的影响。结果表明,冬小麦适量施氮可显著增产,2008-2009年以施氮量180 kg/hm²时(N21)产量最高,为8749 kg/hm²;2009-2010年以施氮量270 kg/hm²时(N32)产量最高,但施氮量210 kg/hm²(N22)处理与N32处理产量无显著差异,分别为8340 kg/hm²和8558 kg/hm²。氮肥利用效率和氮肥偏生产力均随施氮量增加而降低;氮肥利用率与氮肥农学效率均随施氮量的增加呈先升后降的趋势,分别在N21和N22处理时最高。冠层叶片氮素含量和积累量随叶层层次自上而下降低而下降,垂直梯度分明,各时期冠层叶片氮素垂直梯度随施氮量的增加总体呈先增大后减小的趋势。冠层叶片氮素转运量、转运率和对籽粒的贡献率均呈现为:第1层>第2层>第3层>第4层。相关分析表明,冠层叶片氮素梯度与叶片氮素转运率呈显著正相关关系(R²=0.722^*),与贡献率呈极显著正相关关系(R²=0.975^**)。适量施氮(120-210 kg/hm²)增大了叶层间氮素垂直分布梯度,促进了氮素在植株内的运移分配,有利于叶片氮素向外转运,提高了叶片氮素转运量和对籽粒贡献率,保持了较高的氮素利用率。施氮过多(330 kg/hm²)减小了叶层间氮素垂直分布梯度,减弱了氮素在植株内的再利用,叶片氮素转运不畅,导致叶片氮素转运量和对籽粒贡献率下降,氮素利用率显著降低。连续两年试验结果显示,通过适量氮肥调控可以增大冠层叶片氮素垂直梯度,有利于叶片中的氮素输出,促进氮素的再分配、再利用,从而提高氮素利用率,并可获得较高的籽粒产量和蛋白质含量。

Effect of different nitrogen supply on the temporal and spatial distribution and remobilization of canopy nitrogen in winter wheat under limited irrigation condition

To study optimum N application rates for winter wheat under limited irrigation in North China Plain and the influence of N fertilization on distribution and remobilization of leaf nitrogen in wheat canopy, field experiments were carried out in Xunxian Institute of Agricultural Sciences, Henan, China in 2008-2009 and 2009-2010, using the wheat cultivar Zhoumai 18 which has high yield potential. Under only one spring irrigation of 75 mm, six N application rates, i.e., 0, 120,180, 240, 300 and 360 kg/hm², and five N application rates, i.e., 0, 120, 210, 270 and 330 kg/hm², were set up in 2008-2009 and 2009-2010, respectively. The results showed that appropriate N fertilization rates increased winter wheat yield significantly, and the grain yield at N fertilization rate of 180 kg/hm² was the highest in 2008-2009, and the grain yields at N fertilization rates of 210 kg/hm² and 270 kg/hm² were 8340 kg/hm² and 8558 kg/hm² respectively in 2009-2010, higher than those of other treatments. N utilization efficiency (NUE) and partial factor productivity of N (PFPN) reduced with increasing N application rates, the recovery efficiency of applied N (REN) and agronomic efficiency of applied N (AEN) increased at first and then decreased with increasing N application rates, and reached the highest at 180 kg N/hm²and 210 kg N/hm² treatments respectively. Leaf N content and accumulation amount significantly increased after N fertilization and decreased with lowering leaf layers during grain-filling stage. Leaf N remobilization amount, remobilization efficiency and contribution of N remobilization to N content of grain declined in the order of the 1st leaf layer >2nd leaf layer > 3rd leaf layer > 4th leaf layer. With increasing N application rate, vertical distribution gradients of leaf N in canopy first increased and then decreased. Vertical canopy gradients of leaf N content were significantly correlated with leaf N remobilization efficiency (R²=0.722^*), and highly significant correlated with contribution of N remobilization to N content of grain (R²=0.975^**). Optimum N application rates (120-210 kg/hm²) enhanced leaf N vertical gradients in canopy, improved N recycling within plant, increased leaf N remobilization amount, remobilization efficiency and contribution of N remobilization to N content of grain and maintained higher REN. High N application rate (330 kg/hm²) reduced leaf N vertical gradients in canopy, inhibited N recycling within plant, reduced leaf N remobilization amount, remobilization efficiency and contribution of N remobilization to N content of grain and decreased REN significantly. The two-year results showed that under limited irrigation, the N application rates within 180-210 kg/hm² optimized vertical leaf N distribution, improved leaf N remobilization in canopy, and gained higher grain yield, grain protein content and REN.