Agricultural Research Institute of Cyprus - Closed system for soilless culture adapted to the conditions of Cyprus
Scarcity of water combined with high cost of collection and use of the limited surface rainwater have become constrains for irrigated agriculture in Cyprus. The open system of soilless culture (open hydroponic systems, see figure below) is at present most favoured commercially in the country due to its simplicity, mainly in managing the nutrient solution.
However, such systems are linked with environmental pollution problems, such as depletion of underground water and creation of fertiliser waste and of wastewater. The leachate, collected in a reservoir and used for the fertilisation of open cultures or greenhouse cultivations, results in approximately 30% loss of fertilisers and loss of water from the system.
The project is carried out at the ARI research station in Zygi village, on tomato cultivation in a modern greenhouse of 600m2 ground area. The climatic conditions during the day are adjusted by natural ventilation using automatic side and roof ventilation openings or at higher temperatures by the use of a fan and pad cooling system. During the night an automatic humidity control system is put in operation.
The Agricultural Research Institute of Cyprus (ARI) initiated a project to address these problems bu developing a locally adapted closed hydroponic system. This system uses inert substrates (soilless mixtures) in various blends, such as, 70% perlite and 30% expanded clay; 70% gravel, 20% perlite and 10% expanded clay; 100% rock wool. The leachate from the substrates is collected in a tank and is re-circulated after being sterilised passing through a UV lamp. The EC and pH of the water are regulated by the use of an automatic fertiliser-mixing unit (see figure below).
− The system requires water of very good quality, which is difficult to find in Cyprus. At the coastal areas where greenhouse cultivation has developed due to the favourable climatic conditions, the ground water salinity ranges from 1.5 to 4 dS/m, whilst the salinity of water coming from dams is around 1 dS/m.
− The relatively high cost of imported inert materials (such as rock wool). The use of locally available inert fertilisers (such as perlite, coarse sand and crashed gravel) is still under research.
− Environmental pollution is avoided
− Water and fertiliser loss from the system is minimal
The system is easily adaptable to the skills of local growers. In Mediterranean countries, where water is limited and of high cost, protected cultivation and soilless culture are promising alternative and innovative approaches: the water consumption of a well managed closed system is nearly zero, being reduced to the evaporisation level of the plants.
and Polycarpou et.al
picture source: Polycarpou et.al