Maintaining a good fertilization program can keep your plants vigorous and help prevent infections of bacterial blast or canker, oak root fungus, and powdery mildew.
As a general rule, nitrogen should be applied annually, usually during the growing season. To improve fruit quality and color, nitrogen levels should be low but not deficient as the harvest nears. Nitrogen fertilizer can be applied in the spring or split between spring and just after harvest. Excessive nitrogen can cause softer fruit, poor fruit color, and reduced storage and shelf life; it can also increase problems with numerous pests. Typically, mature trees should receive about 3 to 5 pounds of ammonium sulfate per year or 2 pounds of urea per year depending upon soil fertility and local growing conditions. Apply well away from the trunk and water thoroughly after application.
Zinc is also commonly deficient. Affected trees have small new leaves. This deficiency is best corrected by spray applications. Spray with a "chelated zinc" during the growing season. Repeat if new growth still shows deficiency symptoms.
 Zinc-deficient apricot leaves |
 Iron-deficient cherry leaves |
 Iron-deficient prune leaves |
 Nitrogen-deficient peach leaves |
 Zinc-deficient apple leaves |
