Pecan trees are a significant agricultural and backyard crop in Alabama. While deep-rooted, consistent production of high-quality nuts depends heavily on external nutrient support. A well-timed and balanced fertilization program is necessary to maintain tree health, support new growth, and ensure a generous harvest. This practice addresses the high demands of the pecan tree during its annual growth and nut-bearing cycles.
Assessing Soil and Tree Needs
A successful fertilization strategy begins not with applying nutrients, but with a precise diagnosis of the tree’s requirements. This process involves two distinct but complementary analytical tools: soil testing and leaf tissue analysis. Soil samples are taken to determine the soil’s pH level, which ideally should be maintained between 6.0 and 6.5, and to assess the availability of nutrients like Phosphorus and Potassium.
The most accurate way to understand what the tree is actually absorbing is through leaf tissue analysis. This involves collecting samples, typically the middle pair of leaflets from the current season’s growth, during July or early August. The results of this analysis directly indicate the tree’s nutritional status for elements like Nitrogen and Zinc, which are commonly the two most important nutrients needed in Alabama pecan orchards.
A visible sign of nutritional stress is “pecan rosette,” the classic symptom of Zinc deficiency. Affected trees exhibit small, narrow leaves with wavy margins, shortened internodes, and a pale appearance. Leaf tissue concentrations below 40 parts per million (ppm) of Zinc are often associated with these symptoms, signaling the need for corrective action. Nitrogen deficiency, by contrast, generally manifests as a uniform yellowing of older leaves, indicating an insufficient supply for vigorous new growth.
The Annual Fertilization Schedule
The timing for applying fertilizer is important for maximizing nutrient uptake and supporting the tree’s growth phases. The primary application window occurs in late winter or early spring, ideally just before buds break dormancy (late February or March in Alabama). Applying the bulk of the fertilizer at this time ensures nutrients are available when the tree initiates its first flush of growth.
For older, established trees, a single application may suffice, but a split application strategy is generally recommended, especially for Nitrogen. This involves applying half of the total Nitrogen requirement in the early spring and then applying the remaining half later in the growing season, typically around June. Splitting the application helps sustain the Nitrogen supply throughout the period of intense vegetative growth and nut development.
Zinc applications follow a different, more targeted schedule. Since Zinc is immobile within the tree, it must be applied directly to the young, expanding leaves to be absorbed effectively. Growers should begin foliar applications at bud break and repeat them every two to three weeks for approximately two to three months. This ensures that all new foliage receives the necessary micronutrient during the rapid leaf expansion phase.
Application Methods and Nutrient Selection
When a soil or leaf tissue analysis is not available, a general rule of thumb can be used to calculate the required amount of fertilizer for individual trees. For instance, a common recommendation for established trees is to apply one pound of a balanced formula like 13-13-13 for every year of the tree’s age, up to a maximum of 25 pounds per tree. This initial application provides a foundation of Nitrogen, Phosphorus, and Potassium.
To meet the high Nitrogen demand of a mature, bearing pecan tree, a supplemental Nitrogen source, such as Ammonium Nitrate (34-0-0), is often added. This is typically applied at a rate of one pound per year of age, up to a maximum of 20 pounds per tree, usually as part of the split application schedule. For Zinc, a rate of about one-tenth of a pound of Zinc Sulfate per year of age, up to two pounds per tree, is often suggested for ground application.
The granular fertilizer should be broadcast evenly across the soil surface, extending from near the trunk out to the drip line, where active feeder roots are located. Avoid piling the fertilizer directly against the trunk, as this can cause bark injury. While major nutrients like Nitrogen and Potassium are absorbed through the roots, Zinc is often most effective when applied as a foliar spray directly onto the leaves. This method ensures rapid absorption, which is beneficial for quickly correcting a diagnosed Zinc deficiency.