For Apples: year 1 (3 weeks after planting): 1/2 pound 19-19-19 year 2: 1# 19-19-19 mid march & 1# urea 40-0-0 late May year 3+: 1# urea 40-0-0 late March & 1# urea 40-0-0 late May get treated urea if you can. If you cant get that work it into soil or water it in. I have also used slow release fertilizer spikes, but only when crunched for time. Not cost affective at all. If only doing 3 trees, probably OK. When you get hundreds... not so much.