Fruit trees, like all plants, need 13 mineral elements plus water, sunlight and oxygen to grow and thrive. If the site was well prepared, most of the required nutrients will be readily available in the soil. Since fruit trees are perennial plants, not all nutrients must come from the soil each year. Much of the nutrients that are taken up one year are available in subsequent years for growth and metabolism. The most common nutrient deficiencies on fruit trees in Utah’s home orchards come from a lack of nitrogen, iron, or zinc.
Iron deficiency will also show up as a light green color on young leaves. As conditions worsen, the area between the veins becomes yellow or white (interveinal chlorosis). Utah soils actually contain large amounts of iron, but at higher soil pH, the iron is not available to the plant. Over-irrigation in the spring can make iron deficiencies more severe.
Zinc deficiency is most easily identified by small leaves (little leaf symptom) which come out in a rosette. On previous years growth, there may also be a portion of the shoot that has no leaves immediately in front of the rosette.
Minor element deficiencies are less likely in soils with sufficient organic matter content. Therefore, adequate site preparation will reduce the likelihood of subsequent problems. When iron or zinc deficiencies develop, the best remedy is to apply supplemental iron or zinc in “chelate” products. Chelates keep the iron or zinc fertilizers in a form that can be utilized by the plant. They work best when applied to the soil within the drip line of the tree, just prior to the growing season. This will likely have to be repeated each season. See the USU Extension Publication “Iron Chlorosis in Berries” for more information. (http://extension.usu.edu/files/publications/publication/Horticulture_Fruit_2009-02pr.pdf)