Nitrogen (N) is the most limiting nutrient for crop growth. Determining the dynamics of N uptake by crops is essential to optimize N management and improve the sustainability of crop production, especially for winter oilseed rape (Brassica napus L.), a highly N-dependent crop. The concept of critical nitrogen concentration is an effective way to diagnose plant nitrogen status, defining the minimum concentration of nitrogen in the aerial parts needed to maximize shoot biomass at a given time in the crop growth. For winter oilseed rape the existing nitrogen dilution curve was developed in the 1990s, but the curve was established only until the beginning of flowering, the reproductive part not being covered. The main objective of this study is to determine new critical N dilution curves for winter oilseed rape over the whole crop cycle. To achieve this, we used data from 36 field trials, conducted between 2003 and 2020 under various N application rates and cultivars, and a new Bayesian statistical framework. For the vegetative phase, the critical curve (Ncvege=4.556 W-0.241) determined in this study was close to the curves found in previous studies. In addition, new critical N dilution curves were determined for the first time in winter oilseed rape, for the reproductive phase (Ncrepro =4.764 W-0.424) and for the entire growth period (Ncunique=7.364 W-0.582). Interestingly the parameters differed markedly from those recently obtained in spring canola. These new dilution curves should provide useful tools for determining the N nutritional status of winter oilseed rape over a longer period, and thus improve nitrogen nutrition diagnosis and enable optimal nitrogen management.

中文翻译：

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冬季油菜 （Brassica napus L.） 在整个作物周期中的临界氮稀释曲线：贝叶斯分析


氮 （N） 是作物生长最有限的营养物质。确定作物对氮吸收的动态对于优化氮管理和提高作物生产的可持续性至关重要，尤其是对于冬油菜 （Brassica napus L.） 这种高度依赖氮的作物。临界氮浓度的概念是诊断植物氮状况的有效方法，它定义了在作物生长的给定时间最大限度地提高地上生物量所需的地上部分氮的最低浓度。对于冬季油菜，现有的氮稀释曲线是在 1990 年代制定的，但该曲线仅在开花开始之前建立，生殖部分没有被覆盖。本研究的主要目的是确定整个作物周期中冬季油菜的新临界氮稀释曲线。为了实现这一目标，我们使用了 2003 年至 2020 年间在各种氮施用量和品种下进行的 36 项田间试验的数据，以及一个新的贝叶斯统计框架。对于营养期，本研究确定的临界曲线 （Ncvege=4.556 W-0.241） 接近以往研究中发现的曲线。此外，在冬季油菜、生殖期 （Ncrepro =4.764 W-0.424） 和整个生长期 （Ncunique=7.364 W-0.582） 中首次确定了新的临界氮稀释曲线。有趣的是，这些参数与最近在春季油菜籽中获得的参数明显不同。这些新的稀释曲线应为确定冬季油菜在较长时间内的氮营养状况提供有用的工具，从而改进氮营养诊断并实现最佳氮管理。