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Nitrogen fertilization is one of the major issues of crop productions in west-Europe. Every year, large quantities of synthetic nitrogen are used to fertilize crops, such as winter wheat (Triticum aestivum), and ensure them high yielding conditions. In return, substantial amount of nitrogen ends up in the environment where it generates pollutions. The combination of strategic and tactical approaches has been suggested to improve the accuracy of nitrogen fertilization decisions and their implementation. Combining strategic and tactical approaches requires a detailed understanding of the dynamic of nitrogen use by the plant to both anticipate and adapt fertilization practices. Inspired by the concept of yield component phenotypic plasticity, this study aimed to analyze the influence of nitrogen fertilization dynamics on yield elaboration and infer strategic decision rules dedicated to wheat yield optimization in a Belgian context. The analysis, implemented from ten-year experiment, was conducted in two different steps. (1) We characterized the effect of nitrogen fertilization on yield and yield components when the crop was submitted to different agro-pedo-climatic contexts, (2) we analyzed the specific influence of nitrogen fertilization dynamic on yield elaboration, normalizing the variables of the experiment to exclude genetic and environmental influences. The study revealed that highest nitrogen fertilization did not automatically lead to the highest yields. High nitrogen fertilization contributed to increase the negative trade-offs between yield components, which limited the efficiency of nitrogen supplies. Conversely, a balanced dynamic of nitrogen supplies was essential to reach high yields while supplying effective amount of nitrogen. From this Belgian dataset, optimal nitrogen fertilization strategies supposed early nitrogen supplies split in two applications to support the initiation phases of grains per m² and another nitrogen supply at flag leaf stage to maintain components of grain per m² while still allowing grain filling. This fertilization structures, adapted to different pedoclimatic contexts would support strategic approach in crop nitrogen nutrition. • The effect of N on yield components plasticity was analyzed in a ten-year experiment. • Environmental influences were excluded by the normalization of experiment variables. • Highest yields did not always result from highest nitrogen fertilization. • Balanced nitrogen fertilization ensures high yields and rational nitrogen supply. • Decision rules were infered from the analysis to support N fertilization strategical approach. [ABSTRACT FROM AUTHOR]

• Empirical models of winter survival of winter wheat and triticale were developed. • Different weather variables affected the winter survival of both species. • Wheat was more susceptible than triticale to severe winter weather. • In a warmer climate, deacclimation from warm spells can reduce winter survival. Winter hardiness depends on the ability of plants to tolerate a wide spectrum of environmental stresses, which can be affected by climate change in complex ways. Here, empirical Partial Least Squares Regression (PLSS) models of winter survival (WS) of winter wheat (Triticum aestivum L.) and triticale (Triticosecale x Wittmack) were created using data from six years of field experiments at multiple locations throughout Poland. These included 553 winter wheat and 155 triticale accessions. Our aims were to: 1) predict WS on the basis of meteorological data; 2) identify the most critical weather events affecting WS of winter wheat and triticale under Polish conditions; and 3) predict WS for the simulated winters of 2040, 2060 and 2080 under climate change scenarios RCP2.6, RCP4.5, RCP6.0 and RCP8.5 for the experimental site with the lowest mean WS rate during the field experiments. The empirical models showed a high R2 for winter wheat (0.751), and a low R2 for winter triticale (0.160), because of the low winter damage to triticale observed during the experiments. The key climate factors affecting WS varied between species. Winter wheat was affected by winter severity, the number of freezing-thawing cycles, the thermal vegetation index and the freezing index in various winter months. Triticale was affected by late winter ice encasement and high numbers of freeze-thaw events. The predictions indicated that the WS of both winter wheat and triticale may decrease in the future, especially when more extreme climate change scenarios were considered. The main issue will be cold deacclimation connected with climate warming which will be more important for WS than the general increase in minimum winter temperatures. This finding indicates that deacclimation tolerance should be included in wheat and triticale breeding programs as a trait crucial for WS under future winters, at least in Central Europe. [ABSTRACT FROM AUTHOR]