How to Tell If Your Pecans Need Fertilizing
An annual soil test indicates whether or not to fertilize. Test the soil for:
- Phosphorous
- Potassium
- pH (the measurement of its acidity or alkalinity).
Expert gardener’s tip: Where pecans grow in USDA plant hardiness zones 5 through 9, alkaline soils are common in the Southwest.
How Soil Testing Helps
What testing reveals about your soil’s phosphorous and potassium levels dictates how much – if any — nitrogen your pecan trees need:
- Trees in soil with a phosphorous level greater that 35 ppm (parts per million) and potassium level greater than 125 ppm should get ½ pound (.27 kg) of ammonium nitrate fertilizer for each year of age until their fifth year.
- Trees in soil with phosphorus and potassium levels lower than that should get a balanced fertilizer with 10-10-10 N-P-K numbers. Start first-year trees with 1 ½ (1.6 kg) pounds, and increase the amount by 1 ½ pounds (1.6 kg) per year until the fifth year.
Expert gardener’s tip: Low nitrogen restricts the trees’ vegetative growth. Too much of it, on the other hand, encourages leaf growth at the expense of nuts.
How to Apply Nitrogen Fertilizer
For the first four years after planting, apply one-half of your ammonium nitrate or 10-10-10 fertilizer around the trees as soon as their new growth emerges in spring.
Using a broadcast applicator, scatter the granules evenly on the soil in a circle starting 1 foot from the trunk. Extend it to the drip line, where rain drips from the branch tips to the soil. Then water slowly and deeply so the fertilizer soaks in.
Repeat the application in midsummer. In the fifth year, start scattering the fertilizer only at the trees’ drip lines.
Soil pH and Zinc Fertilizer
Pecan trees in zinc-deficient soil suffer from stunted growth and deformed nuts. The pH level directly affects the zinc level. Acidic soil with a pH lower than 6 requires an annual spring application of ½ pound (.23 kg) of zinc sulfate for each year of the trees’ age, up to 10 years.
Soil with an alkaline pH reading much above 7.0 binds zinc so roots can’t absorb it. To get around this problem, give the trees zinc sulfate foliar spray. Treat them once when their buds break in spring and twice more before their leaves open completely. Use a spray solution with 2 pounds (.91 kg) of zinc sulfate powder in 100 gallons (378 liters) of water.
