The 2012 ASHS Annual Conference

Iron (Fe) deficiency in Florida vegetable crops is a frequent nutritional problem when Fe fertilizer was soil leachate, poor soil aeration, low soil organic matter and temperature, high soil pH, high soil or water bicarbonate content and/or interactions with high levels of manganese (Mn) and calcium (Ca). Characteristics Fe deficiency will be interveinal chlorosis of the base of the younger leaves near the top of the plant due to Fe immobility and poor translocation. Iron deficiency in tomato is characterized by a drastic reduction of the leaf chlorophyll content (bleached leaf) ending in necrotic spots. Iron deficiency can have a great economic impact and is depend when the deficiency occurs in the production cycle. Furthermore, the ability of the root system of tomato to acquire Fe can be influenced by genotypic variations among varieties. Since, Fe availability will be dependent on complex soil and environmental factor; no reliable soil test method can predict Fe deficiency. In soils that are calcareous or alkaline often due to over liming, Fe becomes unavailable with significant reduction of Fe at pH of 7.5.  Therefore, do not use calcitic lime to raise Ca levels if pH is adequate (6.5), instead use products such as gypsum or calcium nitrate to increase soil Ca. Iron sulfate (inorganic form) is the most commonly used Fe fertilizer in Florida. Chelates Fe will be an effective, but an expensive Fe alternative. Among chelate sources FeEDDHA should be the preferred chelate fertilizer source for soil application, but the most expensive or soil acidification to lower the pH and allow for the soil Fe availability. Organic matter in animal manures and composts are an effective alternative to increase Fe with positive results in Florida tomatoes. Soil acidification can be an option that will lower the pH and allow for the soil iron to become available. However, Fe applied to the soil will be converted into unavailable forms with high soil pH, thus foliar application is recommended if Fe deficiency symptoms are early, but not late in the production cycle.