How to Fertilize Fruit Trees
Before you fertilize your fruit trees, send a small sample of soil to a local agricultural extension office to have an analysis done that will determine your soil's pH level and which nutrients are present in the soil. Use this information to choose the right fertilizer for your fruit trees, then mix this fertilizer according to the instructions on the packaging. In early spring, drip the fertilizer into the ground in a circle about a foot away from the trunk of the tree, then spread of the rest of the fertilizer outside of the circle.
Perform a soil test. Before you attempt to fertilize a fruit tree, make sure the tree actually needs fertilizer. Fertilizing unnecessarily can cause poor plant growth, so have a soil test performed to see if your trees need fertilizing. To do a soil test, you would take a small sample of soil from the base of your tree. From there, you can take your soil to the state's agricultural department and get a test done from somewhere between $0 to $30. The test will show you your soil's pH level, as well as the types of nutrients present in the soil. Ideally, your soil level should be between 6 to 6.5. Soils out of this range need fertilizer. Consider the age of the trees. How long a tree has been growing makes a big difference in fertilizer. If a tree is about 1 to 2 years old when planted, you can probably withhold fertilizing for a few years. You can instead focus on weed control and providing adequate moisture. However, track how much a tree grows each season. If a young tree is not growing fast enough, you may need to add fertilizer despite its age. In general, branch length of trees should grow about 10 to 12 inches per year – though you'll need to check the target growth rate of your specific tree. If your branch length is growing less, you may need fertilizer. If branch length exceeds this, however, you may not need to add fertilizer to your tree for several years. Select a type of fertilizer. If you've determined you need fertilizer, select the right type for your needs. In order to fertilize fruit trees safely, you want to get what is called a balanced fertilizer. This is a fertilizer made with equal parts nitrogen, phosphorous, and potassium. This is known as the N-P-K ratio. The fertilizer should list the N-P-K ratio somewhere on the label. It should say something like 10-10-10 or 12-12-12. This indicates it is balanced and will be safe for use on fruit trees. You can also consider an organic option, like blood meal, cottonseed meal, composted chicken manure, or feather meal. To figure out how much fertilizer you'll need, you need to consider the tree's age or the diameter of the trunk. In general, you need one pound of fertilizer per year or one pound of fertilizer per inch of the trunk's diameter. Wear protective gloves when handling fertilizer. Fertilizer can be harmful to the skin. During the process of handling fertilizer, make sure to wear gloves the entire time. You can purchase thick garden gloves at most hardware stores. You may also want to consider protective covering for your eyes and mouth, especially if it's a windy day. Mix the fertilizer as recommended. Once you've obtained the proper amount of fertilizer, mix as directed. Here, you will have to refer to the directions that came with your fertilizer. Many fertilizers must be diluted with a certain amount of water prior to use. To figure out the right water-to-fertilizer ratio, read your instruction's manual. Unless you're using organic or homemade fertilizer, it's very important to read the instructions. You should also follow safety instructions carefully. If you went for a pellet based fertilizer, it probably does not require mixing. You will simply scoop out the pellets and drop them around your tree. Drip the fertilizer into the ground a foot away from the trunk. Dripping fertilizer too close to the trunk can harm your tree. Drip a circle of fertilizer about a foot away from the trunk. The precise amount you'll use depends on your tree's age and the instructions that came with your fertilizer. If you're using pellets, sprinkle the pellets in a circle a foot away from the tree's trunk. Spread the fertilizer just past the drip line. The drip line is the perimeter formed by the furthest reaching branches of the tree. Again, you'll want to start the fertilizer about a foot from the trunk and spread it evenly until it's just past the drip line. The tree's roots extend at least this far and this will encourage the roots to spread out, strengthening the tree in the long run. You can use a rake or other tool to spread the fertilizer. It can help to draw a line signifying the drip line in the ground before you start. This can help you see how far to spread the fertilizer. Stay within the maximum limits of nitrogen. The maximum amount of nitrogen fruit trees can handle is one pound. If you're using 10-10-10 ratio fertilizer, 10 pounds would be the maximum you could use. If you were using 12-12-12 ratio fertilizer, do not exceed 8.3 pounds. Overuse of fertilizer can actually lessen fruit growth. Avoid fertilizing fruit trees too soon after planting. Most experts recommend not fertilizing a tree in the first year, as it needs to develop its roots. In following years, you should withhold fertilizing a tree unless it is growing. Too much fertilizer early on can affect fruit growth and actually cause the tree to grow slower. Fertilize at the right time of year. For best results, you would fertilize your trees in early spring before bud growth. If you fail to fertilize before buds grow, you can still fertilize in late June. However, avoid fertilizing in late summer and early fall. New growth on the trees during these times will be damaged by frost in the winter. Monitor tree growth. In order to assess when to increase the level of fertilizer, you'll need to measure tree growth. Trees have what are called growth rings. These are rings that mark the point where a branch started growing the previous year. To measure tree growth, measure each branch from its growth ring to the end of the branch. Then, take the average of all your measurements. This average is the level which your tree grew that year. Increase the amount of fertilizer as needed. Based on the amount your trees are growing, you may need to adjust how you use fertilizer. Make sure you know what's normal for your types of fruit trees. Younger apple trees should be growing at a rate of 12 inches per year. If they grow less, increase your fertilizer by 50% between years 2 and 3. For pear trees, make sure to fertilize if they're growing less than 6 inches per year. For other types of fruit trees, withhold fertilizer until the tree begins to bear fruit. Once fruit begins to grow, start fertilizing the tree each year with fertilizer with a 10-10-10 ratio. Calculate how much fertilizer to use. The amount of fertilizer you need depends on the age and size of your tree. A simple calculation can be used to determine the precise amount of fertilizer to use. Trees need one tenth of a pound (0.10 pound) of nitrogen per year of growth (0.20 for a 2 year-old tree, 0.30 for a 3 year-old tree, etc.), or per inch of trunk diameter. Divide the amount of actual nitrogen your tree needs by the amount of nitrogen in your chosen fertilizer to determine how much to use. You can use an online calculator to determine how much fertilizer to use if you're not good at math. You shouldn't apply more than 1 pound of nitrogen in a year to any tree, maximum. 
Perform a soil test. Consider the age of the trees. Select a type of fertilizer. Wear protective gloves when handling fertilizer. Mix the fertilizer as recommended. Drip the fertilizer into the ground a foot away from the trunk. Spread the fertilizer just past the drip line. Stay within the maximum limits of nitrogen. Avoid fertilizing fruit trees too soon after planting. Fertilize at the right time of year. Monitor tree growth. Increase the amount of fertilizer as needed. Calculate how much fertilizer to use. 