Avocado trees can bear healthy fruit when the tree growth has been sufficiently maintained. For avocado trees to grow healthy it's important that they receive a balanced amount of nutrients, including nitrogen, and that they are watered properly. The tree should never receive too much water or the roots may not receive the oxygen they need for growth. When using commercial or organic fertilizer for your avocado tree it's also important to not add more nutrients than what the soil requires.
Wait at least one year before you begin to fertilize your avocado tree. It's not recommended to fertilize trees that are any younger, and it's also best to fertilize between February to November.
Apply a commercial nitrogen fertilizer after the first year during the end of February. Spread a layer that is a least 1/4 inch thick over the tree bed.
Apply fertilizer again every six months when you irrigate the area. Drip emitters that produce no more than 1/2 gallon of water are recommended to keep the soil moist. If you don't use an emitter it's recommend that you water the area well every six weeks.
Use a nutrient foliar test by collecting a sample of soil between August and October to know the amount of nutrients and nitrogen in your soil. Use a home pH balance test or have the soil tested in a laboratory.
Continue fertilizing every six months. Consider using organic fertilizer once your tree continues to grow healthy over the years and if much nitrogen is not necessary. An example is using a 1/4 inch layer of compost, fish emulsion or coffee grounds.