The chlorosis is one of the main deficiencies in crops, if not, at the least, the best known. In general, it is characterized by an alteration in the color of the leaves. But there are many shortcomings that show very similar changes.

That is why it is necessary to go deeper into the subject.

 ORIGIN OF IRON CHLOROSIS

 Iron chlorosis is treated, in most cases in secondary or induced deficiencies, known as “chlorosis”, as it is a chlorophyll deficiency.

Symptoms begin in young leaves, due to the low mobility of iron.

CAUSES OF IRON DEFICIENCY:

•  Soils rich in limestone: Ca ²⁺ is an antagonist of Fe. Iron chlorosis usually appears from contents between 7-8% Ca ²⁺ .
•  Basic floors
•  Contrary to what one might think, iron deficiencies can also appear in acid soils, rich in soluble phosphates. (Origin of iron chlorosis by precipitation of Fe ³⁺ in the form of phosphoric acid).
•  Action of metallic elements:

Applications for fungal treatments (fungicides) based on Zinc or Copper can cause a lack of iron in the crop. In the case of zinc, the cations of this element interfere in the transport of Fe from roots to the aerial parts.

Presence of antagonists: manganese

Manganese in soluble state causes iron deficiencies. When Mn is oxidized, the reduced Fe is oxidized, going from Fe ²⁺ to Fe ³⁺

 The ratio in a Fe / Mn culture is between 1.5 and 2.6. Below 1.5, symptoms of Fe deficiency (excess Mn) appear.

CLIMATIC FACTORS OF IRON CHLOROSIS

•  Cold: low temperatures affect the development of chlorophyll, both in the formation (it is reduced) and in the destruction.
•  Puddling: produces a deficiency of O ₂ and an excess of CO ₂ that with the soil water originates HCO ₃ – in soils with limestone content.

HOW TO DEAL WITH THE PROBLEM

•  Add iron to the soil or plant: currently the most effective solution to remedy iron chlorosis is the use of chelates. Iron chelates are photosensitive, so application to the ground is more effective.
• The application of chelates of Fe can be carried out by means of applications to the ground or sprays for its foliar absorption.
• The best time to apply iron chelates is preferably late winter or early spring.
•  Pressure injection of iron sulfate into trees is also a possible solution.
• Foliar applications are not very successful.
•  If the problem persists or is repeated on occasions, the problem must be addressed in order to make the Fe more assimilable in the soil.
•  Regulation of humidity in the soil or acidifying it (not very effective in practice)

To acidify the soil there are several solutions : you can apply peat with low pH, which in the long term and in mixed substrates 50% peat 50% earth or 1-2 kg per square meter reduces the basicity of the soil. You can opt for sulfur soil applications (usually cheap) at a rate of 100 gr / square meter and with a period of action of several months. These applications are made for crops that require acidic soils, and the ground is usually prepared before planting. Performing this practice when the chlorosis problem has arisen will not solve the problem in the short term.

Soil applications of iron sulfate  have the function of reducing the pH of the soil (3-5 gr / L water), like sulfur or peat and it is also profitable. These applications must be replaced at the moment in which the soil recovers its basicity. Generally, the soil has a great buffer capacity to regulate the soil pH, and it can be a very long and expensive process to achieve the required pH.

Chelates offer the most successful and short-term solution. They can be applied both to the soil and in foliar application (in a matter of days the plant can recover its iron deficiency). The drawback results from the price for obtaining these products.