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Main Index > Markets > Horticultural Applications > Perlite Plant Guides > Cultivation of Spruce Seedlings Cultivation
of Spruce Seedlings in Mixture of Perlite and Sphagnum Peat in Norway Norwegian forest plant nurseries began to change from bare root transplant production to plugplant productions in 1971. This trend will continue until virtually all forest plants grown in Norway will be produced in some form of container with a growth substrate which is more or less artificial.
Perlite as a Seedcover In commercial plugplant production in greenhouses, spruce seed is initially sown on the surface of 100% sphagnum peat of the least degraded type. A perlite seedcover is applied over the sown seed. This procedure is particularly effective with spring seedlings because of the sharp sun with high radiant energy and high daytime temperatures.
Indirect Effect of Perlite Seedcovers In areas of Norway with moist and cold weather, a common problem in the development of mosses and algae on the surface of growth substrates. This can create a poor growing environment for seedlings - especially in the initial stages of plant development as the algae seal the substrate surface and do not allow water to penetrate nor gas exchange to occur. Seedlings are not as adversely affected when perlite seedcovers are used.
Perlite in the Growth Substrate A great disadvantage of using peat as a growth substrate since the latter part of the 70's has been the tremendous variations in peat quality. These variations in quality have caused inconsistencies in the amount of air that peat can retain at full water saturation. In addition, as seedling growth usually takes place through two seasons, there is additional degradation of peat which leads to further reduction of the substrate quality. This is particularly important as the second year of growth is outdoors and is of decisive importance.
Effect of Perlite Growth substrates used today in Norway contain 25-30% perlite. Previous studies indicate that peat alone is a risky growth substrate and that a mixture of 75% peat and 25% perlite reduces this risk to an acceptable level. Properties of several peat/perlite substrates are summarized in the Table.
Side Effects of Perlite Work by the Norwegian Forestry Society with 75% peat, 25% perlite substrates indicates that the filling of containers is much more predictable than when peat alone is used. Filling is less dependent on the water content of the peat and the peat particle size. In the latter stages of seedling growth it is also clear that peat/perlite substrates do not sink in the container as does peat alone. Other Materials Studied Polystyrene Beads - Our studies have indicated
that polystyrene beads do reduce the water content in growth substrates but that they do
not increase air content. Rockwool - Another material studied was granulated
rockwool. This material provides good air content but, with 100% rockwool, total water
content is less than satisfactory during transport, storage in the forest and after
planting. In addition, mixtures of peat and rockwool do not permit consistent container
filling with equipment available today. Another consideration with rockwool is that Ca
cations may be leached out during production. This can have two distinct effects on the
growing substrate. Firstly, pre-treatment with dolomite limestone can be avoided if few Ca
cations are leached, the spruce seedlings may suffer from nutrient deficiency. In
addition, excess calcium will speed up the degradation of the peat. |
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Information given herein is from sources considered
reliable, but no guarantee of accuracy can be made or liability assumed. Your
supplier may be able to provide you with more precise data. Certain compositions or
processes involving perlite may be the subject of patents. |
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