Determining the dynamics of crop nitrogen (N) uptake is essential to optimize N management and increase the sustainability of crop production. The concept of critical N concentration helps to achieve this goal by defining the minimum shoot N concentration required to produce the maximum aerial biomass at a given time during the crop cycle. The objective of this study was to determine new critical N dilution curves of the main annual field crops used in Canada (spring wheat, canola and corn) using a classical approach well established and a new Bayesian approach and compare these curves with the curves previously published. A total of 557 data for the three crops were used, covering a wide range of pedoclimatic conditions, crop management and cultivars across Canada. These data were processed following a classical statistical approach involving two steps to determine critical points used to calculate the parameters of the critical N dilution curve and then validate these curves against N limiting and non-limiting points. Data were also processed with a new one step Bayesian approach which allows estimating the 95% credibility intervals of the calculated critical curves. For spring wheat, our analysis confirmed the results of a previous study showing that the critical N curve established for winter wheat was not adequate for spring wheat. The critical N dilution curve determined with the classical approach (N_c = 4.14 W^−0.51) performed well in separating the N limiting to the N non-limiting data of the validation dataset. The use of a larger dataset than in the previous study conducted for spring wheat in eastern Canada allowed us to demonstrate that new critical, minimum and maximum N dilution curves for spring wheat has a larger domain of validity than suggested by results of previous studies. Our study shows the strong interaction between plant N and water status, and that N dilution concept allowed us to reveal the occurrence of interaction between water and N stresses for crops in Western Canada, explaining the lower efficiency of N fertilizer in western than in eastern regions.

For corn, the refined critical N dilution curve was very close to the critical N dilution curve determined in France and in eastern Canada, but the Bayesian approach allowed to propose a specific critical N curve for Canada (N_c = 3.07 W^−0.40). In addition, minimum and maximum N dilution curves for corn were determined in Canada’s pedoclimatic conditions. For canola, the new critical (Nc = 4.26 W^−0.26), minimum and maximum curves determined in this study were close to the curves found in previous studies during the vegetative stages. In addition, a new critical N curve valid after the flowering stage was determined.

确定作物氮 (N) 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。临界氮浓度的概念通过定义在作物周期中给定时间产生最大空中生物量所需的最小芽氮浓度来帮助实现这一目标。本研究的目的是使用成熟的经典方法和新的贝叶斯方法确定加拿大使用的主要一年生大田作物（春小麦、油菜和玉米）的新临界 N 稀释曲线，并将这些曲线与之前发布的曲线进行比较. 共使用了三种作物的 557 个数据，涵盖了加拿大各地广泛的土壤气候条件、作物管理和栽培品种。这些数据按照涉及两个步骤的经典统计方法进行处理，以确定用于计算临界 N 稀释曲线参数的临界点，然后针对 N 限制和非限制点验证这些曲线。数据还使用一种新的一步贝叶斯方法进行处理，该方法允许估计计算的关键曲线的 95% 可信区间。对于春小麦，我们的分析证实了先前研究的结果，表明为冬小麦建立的临界氮曲线不适用于春小麦。用经典方法确定的临界 N 稀释曲线（N 数据还使用一种新的一步贝叶斯方法进行处理，该方法允许估计计算的关键曲线的 95% 可信区间。对于春小麦，我们的分析证实了先前研究的结果，表明为冬小麦建立的临界氮曲线不适用于春小麦。用经典方法确定的临界 N 稀释曲线（N 数据还使用一种新的一步贝叶斯方法进行处理，该方法允许估计计算的关键曲线的 95% 可信区间。对于春小麦，我们的分析证实了先前研究的结果，表明为冬小麦建立的临界氮曲线不适用于春小麦。用经典方法确定的临界 N 稀释曲线（N_c = 4.14 W ^-0.51 ) 在将 N 个限制与验证数据集的 N 个非限制数据分开时表现良好。使用比之前对加拿大东部春小麦进行的研究更大的数据集，使我们能够证明春小麦新的临界、最小和最大 N 稀释曲线具有比先前研究结果建议的更大的有效性域。我们的研究表明植物氮和水分状况之间存在很强的相互作用，氮稀释概念使我们能够揭示加拿大西部作物水分和氮胁迫之间相互作用的发生，解释了西部地区氮肥的效率低于东部地区.

对于玉米，细化的临界 N 稀释曲线非常接近在法国和加拿大东部确定的临界 N 稀释曲线，但贝叶斯方法允许为加拿大提出特定的临界 N 曲线 (N _c = 3.07 W ^-0.40 )。此外，玉米的最小和最大氮稀释曲线是在加拿大的土壤气候条件下确定的。对于油菜，本研究中确定的新临界 (Nc = 4.26 W ^-0.26 )、最小和最大曲线与先前研究在营养阶段发现的曲线接近。此外，确定了在开花期之后有效的新的临界 N 曲线。