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Iron chelate vs iron sulphates | What is the difference?

Written by Jaap Lubbersen | Last update: 07-11-2020

The main difference between sulphates and chelates is the stability in case of different pH values in the root environment or the soil/the substrate. Trace elements can be applied in two different ways by using chelates or sulfates. In order to be able to grow well, all crops need proper and sufficient nutrients. A plant will neither be able to survive without the elements it needs less of, the trace elements. In this article our fertilizer specialist will explain about the administration of trace elements and their differences.

What are trace elements?

Trace elements, also known as micro nutrients are nutrients that the plant needs less of for stable growth. Boron, molybdenum, manganese, copper, zinc, and iron are trace elements, each with their own individual function. Even though trace elements are needed in a lower concentration, shortage can be prevented due to regular sampling. 

Administration of trace elements for plants

As previously mentioned, trace elements can be administered to the plant in different ways. How you do this entirely depends on the crop's demands. Trace elements can be supplied to the plant, for example in a trace mix. Here is a recipe, made of a mix of different trace minerals, often tailored to a specific cultivation or type of crop. The trace elements in such fertilizers can be present as chelate or sulphate. 

Additionally, in case of a more targeted dosage of trace minerals, separate administering of the required element could be possible, using sulphates and chelates. But what is the exact difference between those two? 


In fact a sulphate simply consists of oxidized sulphur, which can be absorbed by the roots of a plant. A trace element in sulphur-form means that an element was linked to this oxidized form of sulphur. A sulphate is immobile, this means that it can not easily spread through the plant. In the soil on the other hand, sulphate is very mobile, so ending up in the right place, it can quickly reach the roots. When using sulphates, the fact that it quickly leaches out must always be taken into account. Also, make sure to apply the trace-sulphates in the B-tank.


A chelate can be considered as the claw that firmly holds on to the nutrient. The chelate ensure that the element is being held on to longer, so that it does not precipitate when it is being dissolved into the fertilizer solution. Non precipitation of a chelated trace element depends on the type of chelate and thus the stability. Finally, a chelated trace element is also more mobile in the plant, ensuring a spread uptake of the element. 

Nutrients are relocated inside the plant because of evaporation. As it is less warm during winter, less evaporation will take place in the plant, making the relocation of elements a bit more difficult. For that reason it is wise to always use chelates in winter.

Always apply iron chelates to the A-tank, in contrast to the trace-sulphates. 

Difference between sulphates and chelates

As described above, the main difference between sulfates and chelates is the stability at different pH values in the root environment or soil/substrate. 

Sulfates have a significantly lower stability than chelates. This serves to have an element available throughout the band width. Chelates are stronger and more pure which makes the suitable to be used as fertilizer. However, as a result of this pure quality they are more expensive than sulphates. Sulphates can well be used to increase the pH value in the roots or the soil/substrate, but also to combat fungi and moss. Due to the lower price of sulphates they are more popular than chelates. 

Whether it is sensible to choose a chelated trace element or a sulphated trace element, as such entirely depends on the application. When fertilization is concerned, also both options can be chosen.

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Jaap Lubbersen About Jaap Lubbersen

Jaap Lubbersen is an internal crop care product specialist at Royal Brinkman and has had over 13 years of experience in glass horticulture. "As an internal product specialist, I deal with growers' issues on a daily basis. Every time again it is a challenge to seek the proper solution, in cooperation with the grower, whether it is about healthy and vibrant cultivation, legislation or safety."

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