Elevated temperature, water deficit, low nitrogen availability and their interactions, constrain wheat yield in Mediterranean-type environments. Our working hypothesis is that, owing to the non-linearity of yield response to water and nitrogen and the non-linearity of biological processes in response to temperature, the outcome of the interactions between temperature, nitrogen and water is range-dependent. To generate a broad range of conditions in testing this hypothesis, we established two experiments. Experiment 1 combined factorially four sowing times, six cultivars and four nitrogen rates in four locations-seasons. Experiment 2 combined factorially two cultivars, two nitrogen rates, and two thermal regimes to further untangle interactions. Thermal regimes were unheated controls, and crops heated with passive open-top heating chambers increasing temperature by 0.5 °C during grain set or grain filling.

Across the 384 combinations of treatments in Experiment 1, yield ranged between 0.12 t ha^-1 and 5.96 t ha^-1. The duration of the critical period (300 °C d before anthesis to 100 °C d after anthesis) decreased with mean temperature at an average rate of 5 d °C^-1 and accounted for 75% of the variation in yield. We used quantile regression to calculate a temperature-limited yield potential Y_T and derived a linear function between Y_T and mean temperature in the critical period, returning a slope of -0.53 t ha^-1 °C^-1. Yield gap, i.e., the difference between Y_T and actual yield, was larger in nitrogen and water-deficient crops. Yield-temperature relationships crossed over in response to nitrogen fertilisation. Fertilised crops (100−200 kg N ha^-1) outyielded their unfertilised counterparts when mean temperature during the critical period was below 13 °C, and unfertilised controls were superior above this threshold. Locally calibrated thresholds can be used as a rule-of-thumb adding a further dimension to the management of combined stresses and risk of wheat in Mediterranean-type environments.

In Experiment 2, yield responded to the interaction between temperature and nitrogen, whereby elevated temperature during grain set reduced yield by 17% in unfertilised crops with no effect on crops with 100 kg N ha^-1. Elevated temperature during grain fill reduced yield by 14% with no effect of nitrogen or nitrogen x temperature interaction on grain yield.

温度升高，缺水，氮素利用率低以及它们之间的相互作用，限制了地中海型环境中小麦的单产。我们的工作假设是，由于产量对水和氮的响应呈非线性关系，以及生物过程对温度的响应呈非线性关系，因此温度，氮与水之间相互作用的结果取决于范围。为了在检验该假设时产生广泛的条件，我们建立了两个实验。实验1在四个季节中将四个播种时间，六个品种和四个氮肥因子相结合。实验2将两个品种，两个氮比率和两个热态因子分解相结合，以进一步阐明相互作用。热态是未加热的对照，

在实验1的384种处理组合中，产量介于0.12 t ha ^-1和5.96 t ha ^-1之间。临界期的持续时间（花前300°C到花后100°C）以平均温度以5 d°C ^-1的平均速率减少，占产量变化的75％。我们使用分位数回归来计算温度限制的屈服势Y _T，并得出临界期间Y _T与平均温度之间的线性函数，返回-0.53 t ha ^-1  °C ^-1的斜率。产量差距，即Y _T之间的差氮和缺水作物的实际产量较高。产量-温度关系因氮肥而交叉。当关键时期的平均温度低于13°C时，受精农作物（100-200 kg N ha ^-1）的产量比未受精农作物高，而未受精对照的农作物高于该阈值。可以将本地校准的阈值用作经验法则​​，为地中海型环境中小麦的综合胁迫和小麦风险管理增加了新的维度。

在实验2中，产量对温度和氮素之间的相互作用产生响应，因此在未受精作物中，结实期温度升高会使产量降低17％，而对100 kg N ha ^-1的作物没有影响。籽粒灌浆期间温度升高会使产量降低14％，而氮或氮x温度互作对籽粒产量没有影响。