Nitrogen (N) supply can limit the yields of soybean [Glycine max (L.) Merr.] in highly productive environments. To explore the physiological mechanisms underlying this limitation, seasonal changes in N dynamics, aboveground dry matter (ADM) accumulation, leaf area index (LAI) and fraction of absorbed radiation (f APAR) were compared in crops relying only on biological N₂ fixation and available soil N (zero‐N treatment) versus crops receiving N fertilizer (full‐N treatment). Experiments were conducted in seven high‐yield environments without water limitation, where crops received optimal management. In the zero‐N treatment, biological N₂ fixation was not sufficient to meet the N demand of the growing crop from early in the season up to beginning of seed filling. As a result, crop LAI, growth, N accumulation, radiation‐use efficiency and f APAR were consistently higher in the full‐N than in the zero‐N treatment, leading to improved seed set and yield. Similarly, plants in the full‐N treatment had heavier seeds with higher N concentration because of greater N mobilization from vegetative organs to seeds. Future yield gains in high‐yield soybean production systems will require an increase in biological N₂ fixation, greater supply of N from soil or fertilizer, or alleviation of the trade‐off between these two sources of N in order to meet the plant demand.

中文翻译：

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共生固定造成的氮供应不足会降低高产大豆作物的季节性作物生长和种子的氮动员。


在高产环境中，氮 (N) 供应会限制大豆 [ Glycine max (L.) Merr.] 的产量。为了探索这一限制背后的生理机制，我们比较了仅依赖生物 N ₂固定的作物的氮动态、地上干物质 (ADM) 积累、叶面积指数 (LAI) 和吸收辐射分数 ( f APAR) 的季节变化土壤有效氮（零氮处理）与接受氮肥的作物（全氮处理）。实验在七种无水限制的高产环境中进行，作物在这些环境中得到了最佳管理。在零氮处理中，生物N ₂固定不足以满足生长作物从季节初期到灌浆开始的氮需求。因此，全氮处理中的作物 LAI、生长、氮积累、辐射利用效率和f APAR 始终高于零氮处理，从而提高了结实率和产量。同样，全氮处理中的植物种子较重，氮浓度较高，因为从营养器官到种子的氮动员较多。高产大豆生产系统未来的产量增长将需要增加生物 N ₂固定、从土壤或肥料中提供更多的氮，或者减轻这两种氮源之间的权衡，以满足植物的需求。