Apple and peach trees need nutrients to develop properly and produce fruit. Fertilizing your trees at the right time is very important. Apply fertilizers in the late winter or early spring before the buds have broken open. This will allow the fertilizer to penetrate the soil for better availability for the tree. The amount of fertilizer, especially chemical fertilizer, varies, depending on whether the tree is an apple tree or a peach tree.
Organic fertilizers vary greatly in their composition and content. Organic fertilizers include fish and kelp emulsions, bone and seed meals, and compost. How much you should apply to your apple and peach trees will depend on the type of fertilizer and the fertilizer's concentration. Follow the instructions on the label for flowering plants for the best dilutions and ratios. If you are spreading compost around your trees, spread at a rate of around 6 tons per acre, if you are fertilizing an orchard. If you are fertilizing a single tree, spread 1 or 2 inches of compost as wide as the tree's branches.
Balanced Chemical Fertilizers
Balanced chemical fertilizers are often good for both apples and peaches. Use a balanced fertilizer for best results. The University of Missouri recommends 1 to 2 lbs. of 12-12-12 fertilizer per year of tree age up to a total of 5 lbs. 12-12-12 refers to the amounts of nitrogen, potassium, and sodium, or NPK, in the fertilizer. Scatter the fertilizer around the tree, but keep it at least 6 inches away from the trunk. If you are using a different ratio fertilizer, like 6-6-6, adjust the amount of fertilizer accordingly. For 6-6-6, use 2 to 4 lbs. of fertilizer per year of tree age up to 10 lbs.
If you choose to use a type of chemical fertilizer that has different NPK ratios, you will need to calculate nitrogen levels by weight. The first number in a fertilizer's NPK label is the percentage of nitrogen by weight. For example, in a 12-12-12 fertilizer, the fertilizer contains 12 percent nitrogen by weight. A 6-12-12 fertilizer contains 6 percent nitrogen by weight. For peach trees, add 1/8 lb. of nitrogen per inch of trunk diameter. For apples, add 1/10 pound of nitrogen per inch of trunk diameter. Measure the trunk diameter a foot above ground. So, if your peach tree is 10 inches in diameter a foot above the ground, add 20 lbs. of 6-12-12 fertilizer of 10 lbs. of 12-12-12 fertilizer. If your tree is an apple of the same diameter, add 16 lbs. of 6-12-12 fertilizer or 8 lbs. of 12-12-12 fertilizer.