Manganese - a problem or not?

In my last blog I talked about the different kind of chelates that are on the market and what the best chelate is in combination with iron. In this blog I'm going to the tell you the story behind manganese (Mn) and I shall explain why it can be use full to use manganese chelate. But first I shall react on a question I received about the preparation of the iron chelate.

How to Kill your (iron)chelate!
This is maybe a strange start but what do I see in practice.
The solid (iron)chelates are difficult to mix in the fertilizer tank and to make it easier you can first dissolve the (iron)chelate in a small bucket and then add this solution to the fertilizer tank. It goes wrong when you don't use clear water but acid ore heated water. Acid and heat can kill the chelate. There is a simple rule to check if what you are doing is correct, put your hand in the water before you add the (iron) chelate, if nothing is happening you can add the chelate, if your hand is damaged don't add the chelate because you also damage the chelate.
Please don't do this test but just keep it in mind!


Manganese is normally no problem in modern systems but when you don't have the pH in control it can become a big problem. When the pH is above 6,5 manganese become deposit and is not available for the plant anymore. The normal reaction on this low amount in the water is to add more manganese sulfate to the feeding solution but this can be very dangerous.
As long as the pH is above 6,5 adding more manganese shall only result in more deposit of it and shall not solve the problem.
It becomes even dangerous at the moment the pH drop down below 6,5
All the deposit manganese becomes free again and is available for the plant what result in a to high level of manganese in the plant.

To high manganese result finally in almost dead young leaves, when this happened there is no solution to fix this leaves.

To low manganese result in low quality plants, the dry matter in the plant is low what result in low weight of the fruits and flowers (for flowers the lifetime of the flower become shorter, in chrysanthemum I saw a difference of more than 4 days)

The difficult is that to low and to high manganese in the leaves looks like the same, so when you don't know the history of pH and amount of manganese in the fertilizer tank you can't tell what the problem is. The only way to know for sure is when you sent some leaves to the laboratory for a leaf analyze.

When you can't change the pH of the dripping water the best thing to do is changing from manganese sulfate to manganese chelate. Instead of iron where you need to use DTPA or EDDHA chelate you can use the cheaper EDTA chelate. The connection of manganese to EDTA is strong enough even when you use it in a recirculation system.

About me:
All my blogs are based on the modern Dutch greenhouse technology, controlled recirculation soilless water systems. In other systems things can react different. If you have questions please react on my blogs and I shall try to answer them.

Tot de volgende blog, See you next time.