Here is some good advice for planting apple trees. Best native soils are sandy loam or black loam. Avoid clays, wet areas, and shallow areas to ledge or hard pan. Peat Moss has a low PH of around 4.5 and is not recommended. Lowering the soil PH will inhibits nutrient uptake. Ideal PH for apple trees is 6.2 to 6.7. Use of animal waste (manures) will increase acidity (lowering PH) and is not recommended. Wood ash acts a lot like lime and raise PH. Since most sites are slightly acidic use can improve PH within target range but apply along the drip edge as too much in the hole could damage the root system. If your soils are poor lacking in organic matter, mostly a subsoil base, or very sandy, a mixture of rich black loam soil added to the planting hole will start your trees off right. After planting, wait until the tree starts to leaf and apply .5 lbs of either the following: 10-10-10 or CA Nitrite, or PA Nitrite. Apply one application in the first year of planting. The following years add .5lbs of fertilizer per year of tree, once when the green leaf start to show and again 6 weeks later but before July 1st ( application after July 1st will encourage growth giving tender shoots not enough time to harden off for winter in colder climates). Some Nutrients like CA and Boron are untaken more readily through the leaf and not the root system. Foliar sprays are used for this purpose, but follow the label carefully.