ISHS Acta Horticulturae 148: III International Symposium on Energy in Protected Cultivation
LOWERING HEATING COSTS PER ROSE THROUGH INCREASED PRODUCTION BY USE OF MOVABLE BENCHES |
| Author: | G.A. van den Berg |
| Abstract:
Glasshouse roses are the most important cutflowers in the Netherlands. In 1982 the area was 756 ha with a total auction value of about 420 million Dutch guilders. The roses are grown on a rootstock in glasshouse soil. The common planting scheme includes beds of 105 cm wide, alternated by walking paths of 55 cm wide. The plant density is 6–8 shrubs per bruto square meter glasshouse soil surface. To keep the walking paths free from overhanging shoots, wires are stretched a longside the beds. With this system about 64% of the bruto soil surface is covered by the canopy. The restricting factor for the winter production is the low daily radiation. Thus it is obvious that a maximal light interception by photosynthetic active green leaves is of the greatest importance. The light interception is influenced by the cultivar, the planting scheme and cultural methods. If most of the walking paths are to be left away, which is possible by growing on movable tables or benches, an increase of 64% up to 90% of the surface covered by the canopy can be reached. Compared with the first situation this means an increase of 41%. This does not mean that the total amount of light intercepted by green leaves also rises 41%. This depends on the distribution of light throughout the glasshouse and the canopy. Models which describe this, are being developed (Nederhoff, 1983). However it is clear, that growing on movable tables or benches intercepts more light. This can lead to a higher production. An increase in production per bruto square meter means a decrease in energy costs per unit product. This is the main reason we started experiments at our research station with the cultivation of roses on movable benches. There are more reasons, however. The benches can be constructed in such a way that they contain their own heating system (Van Weel, 1983). Depending on the layout a heated surface can be made, which encloses more than 50% of the soilsurface. Such a large heated surface gives the possibility to use water with a low temperature for at least a part of the necessary heating capacity. This fact gives possibilities to use heat sources with a low temperature for heating the glasshouse. Besides the energy aspects movable benches also have some attendant profits. The labour productivity during cut increases (Van den Burg, 1980). Also problems with "bad" soil, which can be caused by physical problems or by soilborne diseases can be overcome. If we use movable benches instead of soil, we must choose for a substrate other than the glasshouse soil. In our experiments we have chosen for rockwool. With this substrate a lot of experiments have been carried out during the last ten years. As a fact at the moment more than 1000 ha of vegetables are grown in this substrate in the Netherlands. This paper covers a number of first experiments with roses on movable benches grown in rockwool, which were carried out at our research station. | |
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