RECOMMENDATIONS FOR GREENHOUSE CROP

For fruit vegetables multi-year rockwool slabs, perlite or coir enveloped in polyethene foil lying in a profiled coated steel or polypropene trough is recommended to get a sustainable system (Van Os et al., 2008). In north-west Europe, commercial firms mostly use single-year rockwool of several qualities (water content, density) and of several brands. Main reasons are the quick change of crops in winter and the clean restart. After the cultivation period rockwool might be collected and recycled by the manufacturer. In southern Europe there is more variety in the use of substrates. Especially perlite, delivered in bags, and locally found pumice are used very much. In these countries rockwool is used to a lesser extend because of its transportation costs.

For collecting the drain water growers try to find the cheapest way. Not only sustainable metal troughs are used but also the so-called drain profiles of polypropene or poly vinyl chloride (PVC). Drain profiles are not self-supporting and are laid down partly into the soil, because they do not have a flat bottom. Often you see a system where the trough is being made of foil in which a drain pipe is laid and upon which slabs or bags are placed. This system is also in use in the Mediterranean countries, it is the cheapest option, but not very sustainable. The foil has not a very long lifespan and must be renewed every year. Besides, the risk of leakages caused by sharp stones or mice is rather big. However, in the Mediterranean countries most of the systems are still open.

For cut flowers to be harvested more than once, e.g. roses and carnations, similar systems and substrates as used in vegetable production are recommended. In some cases it is economic to use rolling benches to increase the utilisation of space. Gerbera is grown on stages, because of labour efficiency. In that case only self-supporting troughs can be used. Crops growing span-wide with many plants per m2, such as chrysanthemums, lettuce and radishes, it is recommended to dig in a polyethene foil with pumice stone, flugsand or sand as a substrate. In the Netherlands these crops are not grown hydroponically, mainly because of economic reasons. In Belgium and Scandinavian countries there is an NFT-system for lettuce and herbs, at which the troughs can be spaced automatically. Instead of a span-wide system a bed system with aisles consisting of polyethene foil and concrete or aluminium side supports filled with a loose substrate can be used for freesia, alstroemeria and amaryllis. An additional demand of the latter group of crops is that of planting and yielding of the bulbs or tubers. At this moment there are only some small scale experiments.

Other aspects of soil less culture systems contain the control of the nutrient solution (Gieling et al.,1997). The total amount of ions resulting in a certain EC (Electric Conductivity) and pH has to be controlled depending the crop, climate and growing season.

For further information, you can visit the Soil Less Culture (or Hydroponic) page of the Alternatives section.

Writing Date : 2008-06-12
Latest update Date : 2008-06-12