Research update: combining multiple components into one substrate

6 april 2020

The extensive RHP research in combining multiple components into one substrate in a conscious way has now been running for a few years. We previously reported on the progress in this multiannual, complex research. Another interim update…

This RHP research is based on the increasing demand for alternative substrate components. These are now also used in substrates that often have a peat base, but for the RHP quality mark in a safe, limited dosage. Peat is a predictable raw material that is easy to adjust thanks to its large buffer capacity. Partly for this reason, peat has so far had a large content in substrates. Alternative raw materials have a variation in properties and because of the numerous possible combinations many variables change, including pH or available nutrients for the plant. This makes it a challenge to make statements about plant safety of these raw materials, individually and especially in combination. Everything in this research aims to clarify this. Everything will be different, that is clear. For producers in producing the substrates. And for growers in the fertilization and the adjustments they make during the culture.

Worked on research methods

In the past period RHP has mainly worked a lot on research methods. For example, steps have been taken in fine-tuning the standard test EN 16086-1 for various raw materials. A new nitrogen immobilization test has also been developed. To get a good idea of a raw material, first it is important to be able to compare it honestly with the reference material. All factors that can inhibit growth on a plant must first be eliminated for a correct analysis. One factor is unbalanced nutrients in raw materials. For example, tree bark naturally contains a lot of manganese and compost usually contains a lot of potassium. In order to achieve a better nutritional balance, nutritional compensation must first be carried out for a bio assay. Another growth inhibiting factor can be physical properties of substrate components. In this research, work has been done on how to exclude these growth inhibiting factors in the analyses.

EN 16086-1 test fine-tuned

In order to determine the safety of substrate components in terms of plant compatibility, the standard test EN 16086-1 has been further examined. One possibility in this analysis is to test an extract of a raw material (comparable to the current RHP growth test). In the EN test, a standard extract is made which is added to a pot with fine perlite. In this way, on very coarse raw materials can also be sown and be tested. In this research, this test has been further refined in compensating the nutrition in the first extract and in fertilizing during the test. The next step involves testing plant compatibility and growth with other percentages of substrate components in various combinations. In this way we will really test with combinations of substrate components and thus analyse what are safe dosages and combinations.

New nitrogen immobilization test developed

RHP has also designed a new nitrogen immobilisation test. Bacteria take up nitrogen when decomposing organic matter, but for the plant nitrogen is an important nutrient that it needs for growth. Lack of nitrogen inhibits growth or results in damage. New raw materials sometimes immobilise much more nitrogen than peat. Peat has long gone through these decomposing processes by bacteria during its formation in thousands of years. Compared to the old nitrogen immobilisation test, there are now more measuring points over a longer period and the test can indicate more precise at higher immobilisation rates. In the old nitrogen immobilisation test, nitrogen was only measured at one moment, after 21 days. This did not give a complete picture of the course of the, often higher, nitrogen fixations in some raw materials. In this new test, a weekly measurement takes place for 6 weeks. The whole dynamics of immobilisation and release of nitrogen can be better evaluated with this new test.

For the new nitrogen immobilisation test, we incubate materials to be tested in this cabinet for a long time and we follow the dynamics of nitrogen immobilisation and release.

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