RHP nitrogen immobilisation test on growing media constituents

Nowadays nitrogen immobilisation is a major topic in growing media, especially whereas peat is replaced by other organic secondary or waste materials. Often constituents do show a high biological breakdown. In this process nitrogen is taken up by microorganisms. Thus, immobilised nitrogen is not available anymore for plant growth until it is mineralized later on. Mineralization will occur when breakdown decreases. Especially in pot and container cultures this could result in nitrogen deficiency for the crop. To overcome nitrogen deficiency in a culture it’s important to know upfront, when producing a growing medium, what level of nitrogen immobilisation can be expected. Often used methods like the VDLUFA test and the NDI by Handreck are not applicable on the broad variety of growing media constituents. For this reason, a new test was developed by RHP which provides an insight into the development of nitrogen immobilisation and eventual nitrogen mineralisation for a period of nine weeks. The test is suitable to test immobilisation of nitrogen and mineralisation over a period of nine weeks and shows differences in immobilisation rates. Results of the test can be used as a tool to determine suitable combinations of materials in growing mixtures and to come to an adaptive fertilisation for growing medium at production and during cultivation.