Optimizing the use of phosphorus (P) fertilizers is essential considering the environmental issues linked to over fertilization and the limited rock phosphate reserve. Diagnosing the crop P status by calculating a phosphorus nutrition index (PNI) based on the plant critical P concentration (P_c) could help determine the minimum amount of P fertilizer to ensure maximum crop yield. This study investigated (i) the effect of P fertilization on winter wheat (Triticum hybernum L.) shoot biomass and grain yield after several decades of different annual P fertilization rates, (ii) the stability over several site-years of the P_c expressed either as a function of shoot biomass or shoot nitrogen (N) concentration, and (iii) the possibility of using the PNI or the shoot N-to-P_c ratio as nutritional indicators to diagnose P deficiency and predict the expected response to P fertilization. Shoot biomass and its P and N concentrations were measured weekly at five site-years along with grain yield after several decades of P fertilization treatments that ranged between 0 and 5/3 of the theoretical P crop uptake. The P fertilization did not affect the grain yield, but it generally increased shoot biomass especially at the CD 27- -37 developmental stages. The P_c expressed either as a function of shoot biomass or shoot N concentration differed among site-years and this was attributed to differences in crop N status. When N was not deficient, we developed a P_c dilution curve as a function of shoot biomass (SB) (4.56 × SB^−0.279) along with a linear relationship (P_c = 1.10 + 0.061 × N) and a power function (P_c = 0.34 × N^0.632) between P_c and shoot N concentration. The N-to-P_c ratio was related to shoot biomass accumulation according to a power function, but the relationship also differed among site-years. The relative shoot biomass responded positively to the PNI up to different thresholds for limiting and non-limiting N conditions. The relative grain yield, however, was not related to the PNI. The PNI, based on the P_c dilution curve, has potential as a nutritional indicator to diagnose P deficiency and the expected response to P fertilization, but more research is needed to clarify the effect of N deficiencies on the P_c dilution curve.

考虑到与过度施肥和磷酸盐岩储量有限相关的环境问题，优化磷（P）肥料的使用至关重要。通过基于植物临界磷浓度（P _c）计算磷营养指数（PNI）来诊断作物磷状况，可以帮助确定磷肥的最小量，以确保最大的农作物产量。这项研究调查了（i）几十年不同的年度P施肥量后，P施肥对冬小麦（Triticum hybernum L.）苗生物量和籽粒产量的影响;（ii）P _c的数个站点年的稳定性表示为苗生物量或苗氮（N）浓度的函数，并且（iii）使用PNI或苗N / P _c比作为营养指标来诊断P缺乏和预测对P的预期反应的可能性受精。在几十年的磷施肥处理（理论磷吸收量的0到5/3之间）之后，每周在五个地点年份每周测量一次枝条生物量及其磷和氮浓度，以及谷物产量。磷肥不影响籽粒产量，但通常增加了枝条生物量，尤其是在CD 27- -37发育阶段。在P _Ç地上部年间，根据地上生物量或地上氮含量的不同而表达的氮含量不同，这归因于作物氮素状态的差异。当N不亏缺时，我们根据茎生物量（SB）（4.56×SB ^-0.279）^绘制了P _c稀释曲线，以及线性关系（P _c = 1.10 + 0.061×N）和幂函数（P在P _c和芽N浓度之间，_c = 0.34×N ^0.632）。N对P _c比例与幂函数相关，与枝条生物量的积累有关，但该关系在站位年间也有所不同。在限制和非限制氮条件下，相对的茎生物量对PNI呈正响应，直至达到不同的阈值。但是，相对谷物产量与PNI无关。基于P _c稀释曲线的PNI有潜力作为诊断P缺乏症和对P施肥的预期反应的营养指标，但需要更多的研究来阐明N缺乏对P _c稀释曲线的影响。