Coating of fertilisers with micronutrients is the way of the future

A world first has been achieved in South Africa, with the ability to coat water soluble micronutrients onto NPK and MAP fertilisers. This technological breakthrough allows farmers to effectively administer much needed micronutrients to the soil, without having to alter his farming practice.
Never before was it possible to correct micronutrient deficiencies in their soil with hassle free, cost effective, single application products or process. Now it is possible. Micronutrients applies in sulphates and chelate forms are the optimal agronomical solutions to correct micronutrient deficiencies. However, it has never been easy to apply such a product as a normal part of farming practice either during or before the planting season. These products are usually supplied in crystal or pelletised forms.
Due to their fineness, crystals cannot be blended separately with NPK, because the fine particles will separate from the large pellets in the planter box. Consistent application in the soil will not be possible using crystals or powders.
Blending pelletised inputs into NPK fertilisers has been common practise for some time. However, this has been hampered by one main shortcoming. The zinc sulphate pellets (for example) may be diluted 1:100 or 1:200 NPK pellets. Thus, when applied to the soil, the micronutrient pellets are dispersed over a large area.
This means that the essential nutrients may not necessarily be available at the root zone of the germinating seed where it is needed. Blending zinc oxide into the bulk blender or chemical compound mixture also has its drawbacks. As soon as the fertiliser pellet comes into contact with water, the phosphorus (P) inside the NPK blend reacts chemically with the zinc oxide and converts it into zinc phosphate. The problem with zinc phosphate is that it is even more insoluble than zinc oxide and therefore even less available to the plant.
Coating the micronutrients onto the fertiliser pellets would be the best practical solution of all. But coating with fully water-soluble micronutrients is easier said than done. Coating with an insoluble source such as zinc oxide isn’t too difficult, but bioavailability to the plant is not ideal.
At germination, the plant requires the nutrients immediately in a soluble form. When you try to coat water-soluble materials using any type of bonding agent, you are confronted with a few dilemmas. Most bonding agents contain water which would dissolve the materials that are being adhered to.
Furthermore, various chemicals reactions occur, which causes caking dissolution of the NPK/MAP pellets and the degradation of the overall product. Also, adhesion success may only be temporary, and micronutrients may detach within a short time.