In your piece about fertilizing trees you refer to the amount of...
In your piece about fertilizing trees you refer to the amount of "P" in the mix. That to me would be phosphorus as potassium would be "K". Am I correct?
Caledonia County Vermont
You are correct! And the "N" is nitrogen. Off-the-shelf fertilizers typically list amounts of N-P-K. for instance a 5-10-10 fertilizer contains relative amounts of the three elements:
Here's more info about that: https://en.wikipedia.org/wiki/Labeling_of_fertilizer.
It is always a good idea to have your soil tested before adding fertilizer. Without testing, you are taking a shot in the dark, With testing you can fine tune the specific needs of your soil.
I don't know whether UVM provides this service but In NH you can find more about testing soil at http://extension.unh.edu/Problem-Diagnosis-and-Testing-Services/Soil-Testing
It is also important to know that different trees perform differently depending on the soil type. You can learn more about your soil by contacting the Natural Resource Conservation Service. I believe yours is in St Johnsbury.