Iron must be present in the soil in a form assimilable otherwise occurs deficiency manifested by green-sickness. Iron deficiency is associated with a yellowing of leaves. Yellowing of leaf tissue occurs in between the ribs that remain green. The result is a rod part of the upper leaves of plants. Yellowing suddenly manifest as iron in older leaves of plants can be mobilized and transported to the younger organs of plants.
Failure of iron, it produces destruction plant growth hormone, auxina, which slow down roots and plant growth in general.
Phosphorus is found in soil as organic and inorganic compounds. Soil organic phosphorus comes from the decomposition of organic residues from crop residues or organic fertilizers.
Calcium is taken from the environment. In plant cells and tissues to be present in ionic form and the form of inorganic and organic combinations.
Sulfur is present in the soil as organic and mineral.
Organic sulfur is the most important reserves of ground mineralization and progress to a more or less quickly depending on the activity of microorganisms.
Of all the elements, potassium is found in greatest quantity in plants, especially the young, in the form of inorganic salts.
Potassium deficiency is felt more strongly on soils with high salt content of calcium and magnesium and poor aeration. External symptom of potassium deficiency is the leaf color change, that the appearance of brown spots, especially near the extremities of the leaf.