Combining constituents responsibly?

30 november 2017

To what extent are there risks associated with combining different constituents in one substrate? The use of constituents in a mixture can lead to a, not always favourable, effect of properties. How can constituents responsibly be combined? That is one of the topics that RHP is currently investigating. Do you have experience or ideas concerning combining constituents? Let us know!

Nowadays more and more constituents are used in recipes for substrate mixtures. For a couple of constituents there is a maximum quantity allowed in substrates under the RHP quality mark. This has mainly to do with plant toxicity and nitrogen fixation. Currently it is not allowed to combine constituents with a dosage limit each with their maximum dosage in a mixture.


RHP is currently researching the effect on the plant toxicity when two or more constituents with a maximum quantity are combined in one mixture. The goal is to achieve a way to combine these constituents safely in substrate mixtures, even if the current maximum quantity is exceeded.

Step by step

The research lasts until mid-2018 and is carried out more or less in the following steps:

1. Defining the constituents
In this step of the research the characteristics of several constituents is described. This includes: the water soluble elements, bound elements and nitrogen fixation of the constituents. The maximum quantity per constituent based on plant toxicity is determined with bio assays.

2. Combining constituents
The next step is combining constituents to substrate mixtures and analysing these further. The effect of the adding of nutritional elements is tested simultaneously. It is also researched how these can be adjusted for a proper balance in the substrate. Apart from that, nitrogen fixation and plant toxicity of the substrate mixtures are looked at.

3. Storage test and bio assays
The last step in this research is performing storage tests and bio assays with the combined mixtures. These include tests with and without compensation of nitrogen. How nitrogen availability endures during storage, transport and in the culture is researched.

Guidance committee

Because of the complexity of the subject and the step by step approach of this research, several members of the steering group Research are closely involved with its execution as a guidance committee.

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