I am following instructions (or attempting to) to plant a pecan tree and one of the steps is to add 5-10-15 fertilizer around the tree. I can find no 5-10-15, but readily find 5-5-5, 10-10-10 (and other varieties) If I cannot find the "right" mix, how do I determine what the 'best mistake' to make would be?
At first glance I would think "compromising" to 10-10-10 would be a good solution. However, some initial research suggests "Too Much" nitrogen and "Too Little" potash are both potentially problematic. But I can find no guidance as to what is the "safe range". If 5-10-15 is "just right" is 10-10-10 "too much/too little" or is that within an acceptable 'range' of 'OK'. The author of the article I'm looking at may believe 5-10-15 to be optimal, but plants would never grow in the wild if the "perfect" blend is required.
So, how do I calculate what is "close enough" when dealing with fertilizer?