Summary technical meeting organic fertilizers

18 december 2018

RHP has organised a technical meeting about organic fertilizers for RHP certified companies on December 13th in the World Horti Center. What are the most important points of attention? A brief summary…

RHP meeting World Horti Center

During the meeting RHP has shared knowledge about the application of organic fertilizers in substrates and among other things has showed a demo of a bio assay with organic fertilizers.

Points of attention organic fertilizers

RHP research has shown that the most important aspects to consider when applying organic fertilizers in substrates are the following:

  • The speed of ammonification. This depends on the fertilizer that is used and on the temperature.
  • The appearance of ammonia at a high pH value. This aggravates at a higher temperature.
  • The presence of nitrifying bacteria.
  • The initial pH value of the substrate.
  • The pH buffering capacity of the substrate.
  • The sensitivity of the crop and for example the crop stadium.


In addition, the interactions that can occur between all these aspects are important. The interaction between these aspects can reinforce or weaken each other. Interactions that can occur are for example:
the amount of organic Nitrogen that ammonifies in a short time
and the presence of nitrifying bacteria
and the start pH
and pH buffering
and the temperature
and crop sensitivity and development
and the stage of the mineralization process.

RHP meeting World Horti Center
RHP meeting World Horti Center


Next year, RHP wants to set up a procedure and a standard for RHP Bio substrates with the Product Group Horticulture. Organic growers and organizations will be involved.

Sharing knowledge

With this meeting, a first step was taken in sharing the knowledge to the RHP certified substrate producers. With the new insights, they can also inform the users about all the points of attention in the application of organic fertilizers.


Didn’t you have the opportunity to attend this meeting or would you like to download the handouts of the presentations and all the information digitally? Employees of RHP certified companies can do this at My RHP > RHP presentations.

RHP meeting World Horti Center
RHP meeting World Horti Center

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