Background and aims: The concepts of critical nitrogen (N) concentration and nitrogen nutrition index (NNI) provide effective tools for assessing the N nutritional status of pastoral systems. However, no conclusive data exist concerning the effects of stubble height at harvest on the N dilution curve [N concentration (N%) = a(biomass)^−b] and mixed species cultivation on N nutritional status of forage plants with contrasting growth strategies. To evaluate these effects, three cool‐season perennial grasses (exploitative, Arrhenatherum elatius L.; moderately exploitative, Dactylis glomerata L.; conservative, Festuca arundinacea Scherb.) were grown under different cultivation methods either as pure stands or as a mixture and conducted two experiments.

中文翻译：

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落叶条件下多年生禾草的氮营养状况：茬高和混合栽培重要吗？

背景和目的：临界氮（N）浓度和氮营养指数（NNI）的概念为评估牧区系统氮营养状况提供了有效的工具。但是，没有关于收割时残茬高度对氮稀释曲线[N浓度（N％）= a（生物量） ^-b ]和混合物种栽培对饲草植物N营养状况（具有相反的生长策略）的影响的结论性数据。为了评估这些影响，使用了三种凉爽的多年生多年生禾本科草（剥削性的无花果草；中度剥削的Dactylis glomerata L .；保守的无花草 Scherb。）在不同的栽培方法下以纯林或混合物的形式进行生长，并进行了两次实验。