The ability to utilise foliar-applied phosphorus (P) as a strategy to increase the P status and yield of grain crops grown in dryland regions with variable climates is attractive. Several P formulations with varying pH, accompanying cations and adjuvants were tested for their effectiveness as foliar fertilisers for wheat (Triticum aestivum L.) plants, first under controlled and then under field conditions. Experiments under controlled conditions suggested that several formulations with specific chemistries offered promise with respect to wheat fertiliser-P recovery and biomass responses. These formulations were then evaluated in two field experiments, and although wheat grown at the sites showed substantive responses to soil-applied P, there was no significant grain-yield response to foliar-applied P. Following the limited responses to foliar-applied fertiliser in the field, we used an isotopic dilution technique to test the hypothesis that the variation in responses of wheat to foliar addition of P could be explained by a mechanism of substitution, whereby root P uptake is downregulated when P is taken up through the leaves, but this was proven not to be the case. We conclude that foliar P application cannot be used as a tactical fertiliser application to boost grain yield of wheat in dryland regions.

利用叶面施用的磷（P）作为策略来提高气候变化的干旱地区谷物作物的P状况和产量的能力具有吸引力。测试了几种不同pH值的P配方，伴随的阳离子和佐剂作为小麦叶面肥的有效性（Triticum aestivumL.）植物，首先是在受控条件下，然后在田间条件下。在受控条件下进行的实验表明，几种具有特定化学性质的配方在小麦肥料-P的回收和生物量响应方面提供了希望。然后在两个田间试验中对这些配方进行了评估，尽管现场种植的小麦显示出对土壤施用的磷有实质性反应，但对叶面施用的P没有明显的粮食增产响应。在田间，我们使用同位素稀释技术来检验以下假设：小麦对叶面添加P的响应变化可以通过取代机制来解释，即当P通过叶吸收时，根部P的吸收被下调，但是事实证明并非如此。