It is frequently argued that trees should be given a balance ration of nitrogen ,phosphorus and potassium,just as men and animals require a balance diet.The fallacy lies in disregarding the fact that the tree gets its food from the soil,and that the aim of fertilizer is only to make good of any deficiencies.
Organic fertilizers improved the soil's structure while feeding your plant. Soils with lots of organic material, remain loose and airy, are better able to hold moisture and nutrients and have good drainage, especially in Phoenix where most of the soil is clay .Organic fertilizer foster growth of the soil organisms, including beneficial bacteria ,fungi ,earthworms, and promote healthier root development. Building a healthy soil is the key to successful organic gardening.
Most fruit trees need balance fertilizer 2-3 times a year I prefer organic fertilizer.If you want to use synthetic fertilizer, use slow release fertilizer containing  N_K_P (nitrogen -potassium- phosphate)in 10-10-10 or 20-20-20 ratio  with trace elements.
Start fertilizing the fruit trees early in  the spring.
I have 3 to 5 inch thick layer of partially compost mulch around the drip line for all my fruit trees.I continue to add mulch 2-3 times a year.
Method of Composting
I make my own compost and use as a  mulch  around the fruit trees.I add  fifty percent of manure from the animals which i raised in my ranch house (alpaca,mini horse ,chicken and other farm animals.) and mixed  them with grass clipping ,leaves,pine needle and kitchen waste.I make a pile  of three to four feet tall and keep it moist like a
wrung-outsponge by adding water every few days The pile need to be turned every week.Its temperature rises above 150 F in few hours I keep it turning for about a month until it cool down to normal temperature and turn to a dark brown earthy material with sweet smell This is Black Gold ,which provide all nutritional need of the plants It is the food for the microbes and earth worm.It improve the structure and drainage of soil.Help in maintaining the PH of the soil.For those plants for extra need there are other organic fertilizer available in the market

Organic gardening
About 2,400 years ago Aristotle had said. “Earthworms are intestines of the earth”. Only in the twentieth century has the truth in this statement been verified and found correct. He was ahead of our times by two and half of millennium. Darwin was another one to state: “No other creature has contributed to building of earth as earthworm.
organic gardening is the way to grow fresh food in a healthy and more sustainable way.. It is a way of working with nature rather than against it. Organic gardening is the practice of growing vegetables, herbs and fruits using only things found in nature. objective is to recycle organic matter back into the soil.

Organic gardening is much more than just growing plants without chemical and a fertilizers and artificial sprays. It is a way of life

Soil is full of living organism. Chemical fertilizer can harm those living organism which help in the growth cycle of the plants. Excessive amount can burn the roots.

Common organisms found in 1 gram (1/5th teaspoon) of soil:

 bacteria- 4,000,000 to 500,000,000

 actinomycetes-1,000,000 to 20,000,000

 fungi- 4,000 to 1,000,000

 protozoa- 1,000 to 500,000

For the past few decades we have massacred earthworms and living organism of soil mercilessly. This coincided with beginning of Green Revolution in the world, synthetic fertilizers replaced cumbersome green manure and bulky farm yard manure. Plant insects, pests and diseases were overcome with the use of synthetic chemicals

Mature earthworms weight about one gram each and consume mulch material mixed with earth. Every day, they excrete small porous balls, called vermicast, weighing about one gram. Vermicast is most wonderful thing one can imagine of and is beyond today’s technology to reproduce it synthetically.

Every fall,you can collect autumn leaves that make an excellent organic fertilizer & great mulch in our gardens.
The simplest way to improve your soils structure is to add soil amendments, such as compost, manure, chopped leaves, and mulches in and onto the surface of the soil. As it decomposes it will become humus. It will provides all nutrient important for plant growth It helps in drainage and lower the pH of the soil.