The pecan, widely distributed throughout the southern United States, is commonly grown as a crop tree, producing large and sweet nuts. The tree is also prized as a landscape plant for its tall and stately form. When properly applied, certain fertilizers can help a pecan tree remain healthy and encourage the tree to reach its full potential and produce a heavy crop of nuts.
Nitrogen-based fertilizers encourage vigorous growth in both young and mature pecan trees when applied during the growing season. Two primary types of nitrogen fertilizer are available for this purpose. Typically applied to the surface of the soil around pecan trees, ammonium sulfate contains around 21 percent nitrogen and ammonium nitrate holds 33 percent nitrogen.
Nitrogen and Young Trees
In young pecan trees, nitrogen encourages rapid growth. Apply nitrogen-based fertilizers in small amounts frequently during the first few years, when the tree is first getting established. Texas A&M University recommends one application of 1/2 lb. of ammonium nitrate or ammonium sulfate per tree in the beginning of the summer during the first year of growth and the same amount applied three times at one-month intervals during late spring and early summer the following year. Through years 3 and 4, apply 1 lb. per tree and double that amount for trees aged 5 through 7 years.
Nitrogen and Mature Trees
In mature pecan trees over 7 years of age, Texas A&M University suggests a single application of 1 lb. of nitrogen-based fertilizer for each inch of diameter of the trunk. Apply the fertilizer in the spring, just before the new buds on the tree open. Broadcast the granules around the tree approximately 3 to 5 feet away from the trunk, then water the fertilizer into the soil.
Phosphorus and Potassium
In areas where soils are low in phosphorus and potassium, consider using a fertilizer that contains equal amounts of nitrogen, phosphorus and potassium. The North Carolina State University Extension indicates that a quality 10-10-10 fertilizer applied at a rate of 1 lb. for every year of growth for the first 3 years will work well for nut-bearing pecan trees. Mature trees should receive 4 lb. of fertilizer broadcast around the tree each year in the spring.
Pecan trees also need adequate amounts of zinc and benefit from regular treatments with a zinc solution. Zinc nitrate, at a formulation of 2 to 4 tsp. per gallon of water and zinc sulphate, at 2 tsp. per gallon of water, should be sprayed every 2 weeks every year for the first 7 years. Spraying should be conducted from spring through early summer onto the foliage of young pecan trees, when new growth is most prominent. For more mature trees, three separate applications of zinc during this time is sufficient.