Q: What should my fertilizing and irrigation schedule be for my fruit trees during the cool season?
A: In the heat of the summer, the watering schedule should be about once a week and long enough to penetrate the ground from 2 to 3 feet.
December is generally the coldest month of the year with temperature in the 60s, and you should water your fruit trees about once a month. The length of the irrigation is the same for all seasons. Only the interval between irrigations will lengthen or shorten depending on temperature. All other months and temperatures should be adjusted accordingly.
Fruit trees that have been in the ground for at least one year up to five years will benefit from a complete fertilizer like 16-8-4 or something near that. Trees that have been in the ground five years and longer won’t need the phosphate and potassium, the second and third number in the fertilizer ratio. Fruit trees in the ground five years and longer really only need nitrogen so apply 21-0-0 ammonium sulfate in February, May, and the end of October.
“Water — fertilize — water” is the method to apply any dry fertilizer to any plant. In other words, in the middle of your irrigation cycle apply the fertilizer so it will dissolve into the root zone in a diluted form. If the fertilizer is applied on dry soil and then irrigated, the fertilizer hasn’t been diluted enough and may burn the roots. Some of it volatilizes and evaporates, so sprinkle the fertilizer on the ground like you would pepper on your food on the outer two thirds of the canopy and a little beyond during the irrigation. The uptake feeder roots are near the drip line and beyond.