In comparison to the more common fertilizer elements (N-P-K), only small amounts of micro-elements are required by each crop. Micro-elements are required for crop growth; for photo- synthesis and respiration; for the synthesis of enzymes; in the transport and transfer of molecules within the plant’s cells and tissues, and more. Micro- element deficiencies manifest themselves as changes in the tissue’s colour, as leaf spots, deformities in the plants’ organs and abnormal development: Small leaves, deformed leaves and fruit and short internodes.
Pathogens or agro-chemicals, such as herbicides, may be the cause of similar visual symptoms like micro element deficiency. Under such conditions, the application of micro- elements is unable to solve the problem. In many crops, the nutritional deficiency is “hidden”, so that there are no apparent visual symptoms. In such instances, the application of micro- elements may improve crop yield as well as quality.
|Micro-element deficiency symptoms. Iron (Fe)||
Chlorosis (yellowing) of young leaves. While the main veins remain green, the initial symptoms appear between them (inter-veinal chlorosis).
Inter-veinal chlorosis. Leaves develop a light-green colour. With most crops chlorosis develops first on the oldest leaves. Leaf margins remain green while the rest of the leaf has a mottled, spotted appearance.
No generalisations can be made for zinc deficiency in crop plants. In most species, the leaves are deformed or roll in. “Little-leaf” develops at the growing point and the inter-nodes are shorter than usual, so that leaves form a compact “rosette”. In some crops, brown, death spots develop, mainly on the older leaves. Zinc deficiency may lead to the failure of flowering or of the pollination of flowers.
It is extremely difficult to make generalisations on copper deficiencies. Chlorophyll disappears from older leaves, which remain white in colour till they wilt and die. Flowers are damaged and discoloured, leaves may be deformed and elongated, with pointed and dry tips.
Affects the development of the growing point and of young leaves.
(The only micro- element that is not a transitional- metallic element). Organs become brittle, leaf petioles detach prematurely from the stem. Corky tissue develops on stems and corms, fruit is brittle and cracks open. Boron deficiency affects the development of the growing points, inclusive that of roots. Whenever the symptoms appear, the damage incurred may be irreversible. Therefore the farmer must be aware of the risks involved, according to the combination of crop, soil, irrigation water and their management. Boron should be applied as a preventive measure when required.
|Low availability of the micro- element in the soil||Mainly on sandy soils or when soil nutrients have been leached by intensive rains.|
|Calcareous soils||Soils with more than 10% lime (CaCO3).|
|Heavy soils||Water- logged, undrained, compacted soils with deficient aeration.|
|High pH soils||In soils with a pH above 7.5, micro-elements are made unaivalable as compounds of low solubility.|
|Organic soils||Organic compounds adsorb and retain micro-elements.|
|The presence of a high concentration of antagonistic elements||Competition with phosphorus (P), etc.|
|Artificial growing media||Intensive exploitation of a reduced rooting volume, inert substrates.|
|Crops with a high sensitivity to deficiencies||As a function of crop species, variety and the relationship between stock and scion.|
Whenever micro-elements are of limited availability, optimal yields will be obtained only if and when, together with the application of the main fertilizer elements, micro-elements are supplied as required. Micro-elements may be applied via the soil, foliar spray or infusion into a tree’s stem. The application technique should be adapted to the crop’s characteristics.
Chelated micro-elements are organo-metallic compounds. The chelating molecule “traps” the metallic element and protects it from reacting with the soil. The crops’ roots are able to retrieve the micro- element from the chelate and absorb it in its tissues. Each micro-element creates a specific bond with the chelating agent. EDTA is one of the chelating compounds that forms strong and stable bonds with micro-elements in the pH range from 4 to 11, except for the EDTA-iron chelate which is unstable at pH levels above 7. Therefore, for soils with a high pH, other iron- chelating agents are indicated, mainly Fe-EDDHMA; Fe-EDDHA and Fe-DTPA – all of which are stable up to a pH of 11 and these are used in the preparation of Ferrogat and Ferrogat-Plus.
The possibility to combine, in a single mix, chelates with a combination of micro-elements, allows for ample flexibility in the preparation of fertilizer solutions adapted to the soil type, its pH and the propensity of the crop to micro-nutrient deficiencies.
The line of Micromix-Gat products provides the ideal response to farmers’ demand for satisfying his crops’ micro-nutrient requirements, by being able to provide the optimal combination and concentration of the various micro-elements.