It is important to add all nutrients in the right proportion to each other to a substrate, so that it has the desired positive and no negative effects on the cultivation. Zinc is a trace element that a plant needs in order to grow well. It ensures the production of growth substance.
Zinc (Zn) is part of the enzymes in the plant. A plant needs only a small quantity of it that is essential for the formation of the growth substance in the plant called auxin. A plant usually absorbs zinc as a zinc ion (Zn2 +), but it can also be in chelate form. A chelate is a chemical compound that is able to bind a cation. This way it remains in the solution and therefore available to the plant. The word chelate is derived from the Greek word chelate, which means 'claw'. Zinc is reasonably mobile in a plant, but this mobility can be inhibited strongly by the presence of a large quantity of phosphate. The zinc content in the plant mostly varies from 0.002 to 0.005 percent of the dry matter.
In what forms does zinc occur?
Zinc is added to most potting soil fertilizers. The behavior of zinc in a growth medium is fairly normal. However, the phenomenon of chelate exchange can lead to problems. This may occur when the pH rises in the growth medium in the presence of iron chelate. This creates a process whereby zinc can displace iron from the present iron chelate. Also zinc bound to organic matter, which is not visible in a regular analysis, participates in this process. The result is that even more zinc enters the solution, causing the iron level to drop. This iron content can fall so far that there is hardly any soluble iron left. It is very difficult to restore such a situation.
What is the effect of zinc?
Zinc deficiency manifests itself in the form of stunting of growth and small leaves. Too little zinc also may cause chlorosis (degradation of the chlorophyll), which can be followed by necrosis (browning leaves). Zinc excess gives a clear growth inhibition, sometimes with a purple discoloration of the veins. Chlorosis in the top of the plant is also a common feature. This chlorosis is then due to iron deficiency caused by the zinc / iron antagonism, being the iron displacement by zinc from the chelate.
What is the RHP standard for zinc?
Zinc is added to most potting soil fertilizers. RHP-certified products for use in a substrate are checked for, among other things, the zinc content. For growth media with the RHP Horticulture quality mark, there is a maximum level of zinc. Within this standard, the substrate producer and grower together determine what the zinc content should be, suitable for the crop.