ISHS Acta Horticulturae 517: XXV International Horticultural Congress, Part 7: Quality of Horticultural Products
MEASUREMENT OF REPRESENTATIVE VOLUMES OF SUBSTRATES: WHICH METHOD, IN WHICH OBJECTIVE? |
| Authors: | Ph. Morel, L.M. Rivière, C. Julien |
| Keywords: | bulk density, growing media, substrate, volume |
| Abstract:
It has been generally admitted for years by growers and industries that the most suitable expression for substrate quantity is volume and not mass. This practice emerged because products used for growing media show a great range of bulk densities and water retention. But volume measurement presents an important difficulty which is the choice of a representative sample; substrates which are mainly organic often show a very weak mechanical resistance to settling and can also expand when manipulated. Numerous methods have been tested out in several countries, but generally they are complicated and time consuming; moreover, they use small samples because they are used to express analytical results. Therefore they are not adapted to estimate commercial volume in bulk or in bag. To meet this requirement, two methods, one proposed by CEN, the other by German industry (DIN) were tested on several peat and bark substrates, packaged in bulk and in bag on palettes, for three sampling levels and two stocking periods. The CEN method is very reproducible since the measured density variations remain comprised between 0 and 5.8%; the least satisfying results were obtained with mixtures of very different products about particles sizes and texture. The evaluation of the volume from bulk density measurement was also very precise and reproducible. A comparison between CEN and DIN methods showed a slight but significant difference; the CEN method gave a higher density. However differences were always inferior to 3.1% | |
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