ABSTRACT Intensive nitrogen (N) application during stem elongation is effective in increasing potential yield but it also increases the risk of lodging. Unfortunately, the increased lodging more than offsets any associated gains from the increase in potential yield. We test the hypothesis that lodging is not induced directly by N application during stem elongation but by increased light competition in the resulting excessively dense canopy. Our results show that lodging was more severe in plants given N early (before stem elongation) compared with in plants where N fertilisation was given later (during stem elongation). When N was given early, the lengths of the lower internodes of the tillers were significantly greater than when N was given later. For the early N application, dry weight of the above-ground plant was 75% greater, leaf area index 66% greater and green area index 81% greater than for the later N application. This likely indicates much greater competition for light in the denser canopy with the early N application. Shading treatments applied during stem elongation resulted in the lower internodes being longer and lighter, than for unshaded plants. The results suggest that by shifting intensive N application before stem elongation to during stem elongation, canopy development and thus light competition are reduced, the basal internodes of the tillers are shorter and lodging is minimised. GRAPHICALABSTRACT

中文翻译：

---

将密集施氮的时间推迟到茎伸长阶段降低了小麦的较低节间长度和倒伏风险

摘要 在茎伸长期间大量施氮 (N) 可有效提高潜在产量，但也会增加倒伏的风险。不幸的是，住宿的增加抵消了潜在收益增加带来的任何相关收益。我们检验了一个假设，即倒伏不是由茎伸长过程中施氮直接引起的，而是由过度密集的冠层中增加的光竞争引起的。我们的结果表明，与较晚施氮（茎伸长期间）的植物相比，早期施氮（茎伸长前）的植物倒伏更严重。早施 N 时，分蘖下部节间的长度显着大于晚施 N 时。对于早期施氮，地上植物的干重增加了 75%，叶面积指数比后期施氮大 66%，绿面积指数大 81%。这可能表明早期施氮在更密集的冠层中对光的竞争要大得多。在茎伸长期间应用的遮荫处理导致较低的节间比未遮荫的植物更长且更亮。结果表明，通过在茎伸长之前将密集施氮转移到茎伸长期间，树冠发育和光照竞争减少，分蘖的基部节间更短，倒伏最小化。图形概要 在茎伸长期间应用的遮荫处理导致较低的节间比未遮荫的植物更长且更亮。结果表明，通过在茎伸长之前将密集施氮转移到茎伸长期间，树冠发育和光照竞争减少，分蘖的基部节间更短，倒伏最小化。图形概要 在茎伸长期间应用的遮荫处理导致较低的节间比未遮荫的植物更长且更亮。结果表明，通过在茎伸长之前将密集施氮转移到茎伸长期间，树冠发育和光照竞争减少，分蘖的基部节间更短，倒伏最小化。图形概要