All plants need 16 essential nutrients to grow. Three of these are non-minerals that plants get from sunlight and water: hydrogen, carbon and oxygen. The other 13 are minerals that plants get from the soil. Among these, several are essential for pecans. The best gauge of the nutrient levels for pecan trees is a foliar or leaf analysis. According to the University of Georgia cooperative extension, this analysis should be done between July 7 and August 7. After the analysis, you can compare the results and see if they fall within the sufficiency range.
Nitrogen (N) is essential for pecan trees, especially during early foliage growth and kernel filling. Without it, the tree suffers growth deficiencies and poor health. However, too much nitrogen can cause excess foliage, shading and reduced yield. The sufficiency range for nitrogen should be between 2.5 to 3.3 percent.
Phosphorous (P) is used for energy storage and to produce wood and nuts. When deficient, leaves usually turn a dull green color or, if the variety is heavy bearing, as a marginal leaf scorch that appears about 7 to 10 days before suck split and premature defoliation. If the phosphorous level is too high, it may inhibit the uptake of nitrogen, iron, zinc and copper. The sufficiency range for phosphorous should be between 0.12 to 0.3 percent.
Potassium (K) helps activate enzymes, move carbohydrates, and regulate osmosis within pecan trees. Potassium levels also influence the resistance of pecan trees to winter injury. It is important to balance the levels of potassium and nitrogen since an imbalance can lead to a condition called nitrogen scorch. The sufficiency range for potassium should be between 1.25 to 2.5 percent.
A magnesium (Mg) deficiency is common in pecan trees that are grown on dry, acidic or sandy soils, especially if the soil have a high potassium level. Signs of deficiencies include a “Christmas tree” pattern on the leaf, known as intervienal chlorosis, followed by marginal leaf scorch. The sufficiency range for magnesium should be between 0.35 to 0.6 percent.
Zinc (Zn) levels affect a pecan trees flowering, fruit size, leaf efficiency, leaf expansion, shoot elongation, and nut yield. Signs of a zinc deficiency includes a curling of young leaves, a rosette pattern on the leaves, narrow leaves and terminal die-back. The sufficiency range for zinc should be between 50 to 100 ppm.
Iron (Fe) is necessary during photosynthesis. Deficiencies are usually caused by cold, wet springs, over-liming or a high concentration of zinc, phosphorous or manganese in the soil. Symptoms of iron deficiencies are very similar to nitrogen deficiencies and usually occur early in the growing season and is more common in older pecan trees. The sufficiency range for zinc should be between 50 to 300 ppm.
Boron (B) helps carbohydrates move across cell walls and stabilizes the pollen germ tube. If Deficiencies in pecan trees can reduce fertilization. A pecan tree will experience symptoms of boron deficiencies if the foliar level is below 15 ppm. However, the sufficiency range for boron is between 50 to 100 ppm.
Although it is not considered an "essential" nutrient, nickel (Ni) is important for pecans. When deficient, it causes a condition called mouse ear. Mouse ear causes rounded leaf tips and reduces the size of affected leaves. These symptoms indicate that a buildup of urea has occurred. Symptoms usually occur when the foliar levels of nickel is below 3 ppm.
The range for calcium should be between 1.3 to 1.5 percent. Manganese (Mn) deficiencies are rare and will only occur if the levels are less than 1 ppm. However, the sufficiency range for manganese should be between 100 to 800 ppm. Copper (Cu) aids in root metabolism, helps the tree utilize proteins and is essential for reproductive growth. The sufficiency range for copper should be between 6 to 30 ppm.