Fertilizing Citrus Trees

Between now and the middle of September is a critical time to fertilize citrus trees.

The fertilizer given now will be in the rootzone just in time for the roots to absorb it and deliver it to the growth spurt soon to happen.

The nutrient primarily neede by citrus is nitrogen. Nitrogen is used by plants for the green, or vegetative growth.

For some types like oranges and tangelos this fertilizing is critical for fruit size.

Amounts to apply vary as to the age of the tree, the strength of the fertilizer and by type in the case of grapefruits. Grapefruits need less than other citrus types. Over fertilized grapefuit trees and run the risk of growing mammonth looking fruits with grotesquely lareg rinds.

Usually the directions on the bag are acceptable. If you water heavily or it rains alot remember the translated words of a beautiful Spanish dicho. "Throw an extra handful for the pig."

This is not to say double the recommended rate, just a little extra if excess water is involved.

When applying the fertilizer ensure even distribution over the soil surface. Mounds or piles can be too concentrated and burning might happen.

equally important thing to remember is to water it in immediately. Nitrogen fertilizer applied dry to the hot soil surface in August gets lost quickly. On a hot summer day you can lose up to one third of the nitrogen within an hour. The unstable form of nitrogen found in fertilizer reacts to the heat and volitalizes into a gas and is lost to the air.

Many people dissolve the fertilizer in water then pour it on the ground. This helps but water must be added to carry the nutrients into the soil to the roots.

There are many fertilizers on the market that can be used from the generic ammonium sulphate to more expensive blended and pelleted citrus fertilizers.

Any one choosen can be used acceptably. Just read the directions and follow the rates recommended. The professionals in the nursery or garden center will be able to help if specific questions arise.

Written by Terry Mikel, College of Agriculture and Life Sciences, the University of Arizona, 602-470-8086.
Material originally appeared in Arizona Republic
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