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USE OF BARK, AND OF SOD AND CUTTINGS FROM MOORLAND VEGETATION IN POTTING MIXTURES
In one-year experiments, composted and non-composted conifer bark, and sod and cuttings from moorland, in combination with different rates of nitrogen, were compared as substrates with a standard potting soil.
The standard soil consisted of "frozen black peat" (i.e. improved by freezing and shredding), white peat and sand.
The moorland materials released a small amount of nitrogen to the plants; there was no distinct difference between composted and non-composted material.
Without additional nitrogen, growth was poor on all substrates.
At optimum rates of nitrogen application, differences in growth of plants on the various substrates were generally small.
Different methods to predict the amount of nitrogen released by a material were tested.
The most promising index was the C/N-ratio determined according to a modification of the method of Walkley and Black.
Growth of plants on potting soils with a limited water-holding capacity was found to be reduced.