Answer: Fruit and nut trees can be fed with an 8-8-8 fertilizer at the rate of about one pound per year of age of the tree. Before feeding, though, I would suggest having your soil tested to see what minerals might be missing from your soil. Your description of poor soil leaves me wondering if you have poorly draining clay soil or soil that's very acidic or very alkaline. If your soil is acidic, lime will help mellow it and make the nutrients more readily available to the tree roots. However, if your soil is alkaline, lime applications can really upset the balance and cause problems with your trees. I think the first step would be to have your soil tested and then to feed your trees based upon what the soil test shows. You didn't indicate which part of the country you're gardening in so I can't suggest a soil testing lab. You can check with your local cooperative extension office for soil test labs and other suggestions about fertilizer and soil amendments specific to your gardening region.
Best wishes with your landscape!
Q&A Library Searching Tips