|Plant Part and Time:||Sample 25 middle leaflet pairs from the mid-portion of terminal growth taken 56 to 84 days after catkin fall. (In Georgia July 7 through August 7).|
|Element and Sufficiency Range||Interpretation and Recommendations|
The N level for optimum production under non-irrigated conditions is in the range of 2.50-2.70%, under irrigated conditions the optimum range is 2.80-3.00%. If the N level is 2.30% or less, trees may be showing N deficiency symptoms. Low N is generally due to inadequate N fertilization and/or ineffective N application. If the N level is less than 2.50% apply 200 pounds N per acre; if between 2.50-2.70% apply 100-150 pounds N per acre; if between 2.70-3.00% apply 100 pounds N per acre; if greater than 3.00% do not apply any nitrogen. In instances where variable rates are given, the rate selected should be such that shoot growth on at least 50% of the trees is between 8-12 inches. For the Desirable variety, if the leaf content is greater than 2.30%, do not apply more than 100 pounds N per acre. If the N content is greater than 3.00% and early defoliation occurs, this may be a sign of excess N. In such instances check with pecan specialist before applying N fertilizer. (See potassium below.)
The P level for optimum production should be 0.14 to 0.30%. Less than sufficient due to low soil P level and inadequate fertilization. If the leaf content is less than 0.14%, apply 100 pounds P2O5 per acre. If greater than 0.14%, do not apply P fertilizer. When the soil test P level is high or greater, do not apply P fertilizer.
Less than sufficient due to low soil K level and inadequate fertilization. Leaf K level for optimum production and tree vigor should be maintained between 1.25 to 2.50%. Maintaining the K level between 1.25 and 2.50% reduces winter injury damage and leaf scorch. If the level is less than 1.25%, soil apply 100 pounds K2O per acre. Also application of foliar sprays using 2 to 4 pounds of potassium nitrate per 100 gallons of water with the second and third cover sprays may be beneficial in reducing K deficiency the first and second years after the deficiency is diagnosed. If the leaf K level is less than 1.25%, soil apply 100 pounds K2O per acre. If the K content is between 1.25% and 2.50%, soil test and follow the soil test recommendation. Early defoliation can be a sign of K deficiency or an imbalance between N and K. If N is 3.00%, the K level should be greater than 1.25%.
The level of Ca for optimum production should be maintained between 1.00 to 1.75%. Low Ca levels are due to low soil pH. Soil test and lime according to soil test recommendations.
Less than sufficient due to low soil pH (See Mn below), low soil Mg, and/or excessive K applications. If the Mg level is less than 0.30% and the soil pH is low, apply dolomitic limestone according to soil test recommendations. If no lime is needed, apply 20 pounds Mg per acre using a soluble Mg source. Also, apply a foliar application of Mg, using 3 to 5 pounds of magnesium sulfate per 100 gallons per acre in the first three leaf sprays.
Less than sufficient due to low soil S level. If the S level is less than 0.20%, S should be included in the fertilizer to supply a minimum of 20 pounds S per acre.
Mn may not be toxic or reach toxicity levels, but high Mn is an indicator of low soil pH. If greater than 800 ppm, soil pH may be 5.4 or less. If Mg is less than 0.30% and Mn greater than 500 ppm, liming with dolomitic limestone is essential. Soil test and lime according to the recommendation given. Mn deficiencies have not been observed in Georgia. Symptoms similar to "Mouse ear," a common problem in Florida due to Mn deficiency, have not been observed in Georgia. Mouse ear symptoms being seen with increasing frequency in Georgia are not Mn deficiencies.
Fe deficiency seems to be on the increase. It is associated with older trees and occurs only in certain trees. Fe deficiency may be genetically controlled and can be induced by excessive zinc application. It is difficult to correct. Foliar applications of Fe may or may not be effective. If Fe deficiency is suspected, leaves should be washed in a mild detergent solution before drying and sending to the laboratory for analysis. (See section on washing samples to remove contaminates). There are a number of foliar Fe spray materials available. Follow the label instructions.
Low B can occur on sandy soils that have been limed to pH 6.5 or higher. If leaf B is low, include 1 pound B per acre in next year's fertilization program. Boron concentrations of approximately 400 ppm have been associated with toxicity.
Low levels of Cu have been observed in many orchards in Georgia. If Cu is less than 6 ppm, make one application of copper sulfate or copper chelate at a rate of 8 to 12 ounces per acre 3-4 weeks after budbreak.
Visual Zn deficiency symptom may occur when the leaf content is less than 30 ppm. Apply 100 to 150 pounds zinc sulfate per acre. if the Zn content is less than 30 ppm. In addition, apply 2 pounds zinc sulfate per 100 gallons of water with the first three leaf sprays. If the Zn content is less than 50 ppm, but greater than 30 ppm, apply 30 to 50 pounds zinc sulfate per acre. If the Zn level is greater than 50 ppm, discontinue Zn treatment. Zn levels in excess of 250 ppm may induce an Fe deficiency. (See Fe above.) The Zn soil test is not as effective in determining Zn needs as a plant analysis. If Zn was foliar applied, the Zn analyses are invalid since some of the applied Zn may be on the surface of the leaves rather than in the leaves. Therefore, an evaluation of the Zn status of trees where foliar Zn applications have been made is difficult even if leaves are washed.
It is uncertain whether Al concentrations in excess of 2000 ppm are detrimental. High Al suggests low soil pH or poor aeration. If both Fe and Al are high, it is probably due to soil or dustcontamination. See Fe discussion above.
If the Ni level is less than 5 ppm, apply 24 ounces of nickel lignosulfonate (containing 6% Ni) per acre or an equivalent product that supplies 1 and one half ounces of Ni per acre. Make the first application at 10-24 days following budbreak, followed by an additional application 2-4 weeks later. Where mouse ear symptoms persist, an additional application may be warranted in September or early October before leaf fall.