Articles
POTTING SUBSTRATES IN THE NETHERLANDS
In vegetable growing the composts consisted of peat moss, low moor peat, sand, farm yard manure and additions of fertilizers.
In floriculture the major components were of local origine, like lake dredgings in Aalsmeer, clayloam in the river area and leafmold in the more woody regions.
Because of insufficient insight into the physical and chemical requirements of composts for growing plants, errors were not uncommon, jeopardizing the growing results.
Vegetable growers started using factory made compost about 1945, flower growers not until 15 years later.
Causes for the growers to switch to factory made composts were the increasing labour costs, labour scarcity and the growing awareness that compost making is a highly specialized operation.
The first compost factory was set up in 1942; (Roorda van Eysinga, 1965) since then the number of factories has increased to over a thirty.
Figure 1 shows the sites of these factories in the Netherlands.
The present total potting compost production might be estimated at 700 000 m3 per year.
Table 1 gives data on the trade of factory made composts.
As can be seen over 40% of the total compost produced is used in vegetable growing.
With 5 000 ha under glass the yearly need of this industry amounts to 60 m3 per ha.
Over 10% is sold to amateurs.
A fairly large quantity is exported, mainly to France, Germany and Belgium; to a minor extend to England and Switzerland.
Miscellaneous refers to the compost used for instance in bulb growing for potting purposes and in fruit growing for filling up plant holes.
Table 2 presents production figures for the various compost manufacturing firms.
It appears that of the 32 firms 18 produce less than 25 000, three between 50 000 and 75 000 and only one over 75 000 m3 per year.
It should be noted that not all the firms solely produce compost.
Several of them, especially among the smaller ones, are, in addition, involved in other business activities such as the exploitation and processing of peat, the trade of farm yard manure and the selling of various other horticultural commodities.