Citrus trees should be fed three or four times a year for the best results because they are heavy feeders. Along the coast, January is the best month to start; however cities where there may be a threat of frost should wait until March. To determine how much to feed your tree, consult the back of the fertilizer package for the total recommended amount per year and divide it by three (for inland cities) or four (cities along the coast) to be applied at each feeding.
Use a uniform measure like a one-gallon coffee can to make it easy to figure out the amounts. Apply around the drip line (the area defined by the outermost circumference of a tree canopy where water drips from and onto the ground) up to two to three feet beyond and water in deeply.
Do not try to work it into the soil because it will disturb the roots that live in the top two feet of the soil.