New useful method determining CRF dosage directly after substrate production 

30 september 2019

The existing method to objectively determine the dosage of CRF fertilizers in a substrate is quite a time-consuming, manual job. The RHP certified company ICL Specialty Fertilizers developed a new separation method. RHP tested this on CRF products of several producers and concludes that the method is ready to be used directly after substrate production, not after storage or cultivation.

Controlled Release Fertilisers (CRF) are an important tool in achieving the desired nutritional level for plants over a longer period. This applies to different cultures and cultivation methods. For the intended effect in a pot it is important that the desired CRF dosage and a uniform distribution is achieved.

Why this research?

The RHP research aimed to test to what extent the CRF granules could be retrieved in substrates using this new separation method, directly after production, after storage and after cultivation. There lacked a standard research method to objectively determine the dosage of CRF fertilizers in a substrate. Presently the substrate is dried and then the CRF granules are retrieved manually, counted and weighted. A time-consuming job. ICL therefore developed a separation method, which RHP has now tested on several CRF products.

The research

RHP examined six CRF products of different producers, each with an effective period of 6 months. Substrates were made from fine peat with a set number of CRF granules in a dosage of 5,0 grams per litre of peat. After bringing the substrates to a normal moisture level (such as during delivery at a grower), the separation method was executed at three moments: directly after the mixing of the substrate, after 4 months of storage and after 4 months in a culture simulation in a greenhouse of 20 up to 35 °C.

The separation method follows these principle steps:

  •  Drying of the sample.
  •  Scattering of the dry matter in a container of water. The CRF granules then sink to the bottom of the container.
  •  Then drying them and subsequently weighing and counting.

Research results

The tested separation method works well on a substrate that is tested directly after production. Then practically all granules are found back and the CRF dosage can be determined meticulously. For storage samples and samples from culture situations the method failed. In those cases a certain level of release took place, causing a share of the granules to no longer sink and therefore cannot be separated anymore from the substrate sample using the tested method. Drying of a substrate directly after its production can stop the CRF release in storage samples, so that also after storage the separation method can be applied successfully. However, it is uncertain whether this is practically manageable. The existing, manual method seems to remain the most reliable one for counter samples and culture situations. For this it is however necessary to know the weight of the granules of the CRF (number of granules per gram).

More about this research?

Certified companies can download the complete research report and work instruction for the separation method soon through My RHP.

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