Usually the use of some fertilizer with balanced nutrition (nitrogen, phosphorus and potassium) can bring many benefits. The main nutrients that plants need are nitrogen for leaf growth and chlorophyll. Phosphorus supports the root system as well as to produce blossoms, fruits, and seeds. Potassium develops the systems used for photosynthesis and transporting water and nutrients throughout the plant.You may choose to use a commercial fertilizer specialized for a certain type of tree, or you can use organic nitrogen sources such as manure, feather meal, or blood meal.
Conducting a soil test can help you get a good idea of the condition of your soil and apply fertilizer more precisely. For commercial fertilizers, you could use a balanced granular fertilizer with an NPK of 10-10-10 or similar if your soil does not have sufficient phosphorus and potassium according to your soil test. In most cases the nitrogen in the soil is continuously lost with rainfall. If your soil has sufficient levels of phosphorus and potassium, a high-nitrogen fertilizer with a ratio of 6-2-1 or 10-2-2 would be more suitable.