Nitrogen (N) management in modern farming needs to balance the interests of yield quantity and quality with environmental impact of reactive N lost to the atmosphere and aquatic environments. Mechanistic agroecosystem models are useful tools to analyse the combined effects of management options and natural conditions, including soil fertility and climate, site‐specific optimal N application rates and environmental impact. An important component of the system description is the crop module, including the responses to N status and N stress. To improve the description of crop growth response to N status in the DAISY model system, we implemented an empirical model for N status effects in winter wheat on the partitioning of assimilated dry matter and N between leaves and stems, originally described by Ratjen and Kage (Journal of Agronomy and Crop Science, 2016, 202, 576s). To our knowledge, this mechanism has not been included in any of the most widespread and commonly used mechanistic agroecosystem models. We tested and compared the model performance with and without the new N status response against data from a two‐season winter wheat experiment in Denmark, where crop growth and partitioning of dry matter and N were measured. Implementation of the new N status response function improved model performance and ensured a more robust crop growth description, especially in scenarios with periods of low crop N status or N stress. The mechanism mimics an adaptation strategy, where the crop balances N stress and growth potential by dynamically adjusting the leaf‐stem ratio and thereby N demand. This behaviour opens a discussion regarding the empirical concept of a biomass driven critical N curve.

中文翻译：

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机械农业生态系统模型DAISY中冬小麦氮素形态对同化和氮素分配的影响。

现代农业中的氮（N）管理需要在产量和质量的利益与损失到大气和水生环境中的反应性N对环境的影响之间取得平衡。机械农业生态系统模型是分析管理选择和自然条件（包括土壤肥力和气候，特定地点的最佳氮肥施用量和环境影响）的综合影响的有用工具。系统描述的重要组成部分是农作物模块，包括对N状态和N胁迫的响应。为了改善DAISY模型系统中作物生长对N态响应的描述，我们实施了一个关于冬小麦N态效应对同化干物质和N在叶和茎之间分配的影响的经验模型，最初由Ratjen和Kage（农学与作物科学杂志，2016，202，576s）。就我们所知，此机制尚未包含在任何最广泛且最常用的机械农业生态系统模型中。我们测试了有无氮素状态响应和没有氮素状态响应的模型性能，并与丹麦进行了两个季节的冬小麦试验的数据进行了比较，该试验测量了作物的生长以及干物质和氮的分配。新的氮素状态响应函数的实施改善了模型的性能，并确保了对作物生长的更健壮的描述，特别是在氮素含量低或氮素胁迫时期的情况下。该机制模仿了一种适应策略，在该策略中，农作物通过动态调节叶茎比率和氮需求来平衡氮胁迫和生长潜力。这种行为引发了有关生物量驱动的临界N曲线的经验概念的讨论。