Main subjects collective research RHP known

30 may 2017

Organic fertilizers and the stacking of raw materials. Those are the two main subjects on the programme of RHP’s collective research for the next period.

Organic fertilizers

How do organic fertilizer behave in substrate mixtures? This research will give insight in the matter. The focus is on the dynamics of nitrogen and its interaction with the substrate. In the first - up until now executed - part of the research it became clear that the pH can change more strongly in substrates with a small pH buffer. In this the pH can increase to very high levels. At a high pH ammonia can develop. Is this harmful for the plants? That is currently researched further. To prevent appearance of ammonia, it is important that during the mineralisation of the nitrogen, nitrification also starts. That’s why the research will also try to find out under which circumstances the nitrification can proceed optimally.

Stacking of raw materials

Nowadays more different raw materials are used in recipes for substrate mixtures. For a number of raw materials under the RHP quality mark there is a maximum quantity allowed in substrates. In substrate mixtures more raw materials with a maximum quantity limit are combined. The combined (negative) effect on the below mentioned aspects is not taken into account then. The limit for the quantity of a raw material is determined by:

  • the growth and development of the crops in the cultivation trial (what are the growing achievements on the substrate mixture?);
  • the nitrogen fixation of the substrate mixture (for example with bark, wood fibre and rice hulls);
  • the level of (nutrition) elements in the substrate mixture (for example with compost and coir fibre);
  • the carbonate level of the mixture (with clay).

The research focuses on the following questions:

  • What risks develop when stacking raw materials?
  • Can the risk of stacking raw materials with a quantity limit be estimated?
  • Can the risks be distinguished through analysis?
  • Can the risks be eliminated by changing the recipe of the mixture?
  • In how far can N-fixation really be compensated?

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