Western Canada isn’t the first place you think of when the subject is winter wheat, but there is some there. This video is from RealAgriculture and they talk about some higher fertilizer rates on winter wheat in the West.
For some applications, you really need to get the material out there at just the right stage. For example, for a PGR before jointing or a fungicide on the flag leaf, timing is everything. Here is a pdf that has information on using degree days to predict growth in not just wheat but also some other crops.
This would be nice. I hope it is true. A lot of claims are made about foliar applications and you never know which ones consistently increase yield and which ones of work sometimes. Anyway, here is a paper I found about foliar P application in wheat.
It is an easy calculation.
There are many ways to test fro soil phosphorous. Which test is used in your part of the world?