Hydroponics is defined as “any method of growing plants without the use of soil as a rooting medium, in which all inorganic elements that are required for plant nutrition (except carbon which is fixed in the leaves through the process of photosynthesis) are supplied to the root system via the irrigation water”. The fertilizers used as sources of the nutrients to be supplied to the crop are dissolved to the irrigation water at proper concentrations and the resultant solution is termed “nutrient solution”. The proposed Best Practice is the establishment of a closed-cycle hydroponic cultivation system, in which the nutrient solution will be constantly recirculating. The cultivation of plants in closed hydroponic systems can substantially reduce the pollution of water resources by nitrates and phosphates originating from fertilizer residues, while contributing to an appreciable reduction in water and fertilizer consumption.
The hydroponic school garden proposed as one of the Best Practices will be a simple closed-loop hydroponic unit, consisted of:
- A trough continuously supplied with flowing nutrient solution that will be used to accommodate the plant roots,
- A supply tank that will serve both as a reservoir of nutrient solution to be supplied to the plants and as catchment tank of the returning solution to be reused,
- A replenishment tank that will be used to automatically replenish the consumed nutrient solution in the supply tank via a floating valve,
- A small pump that will be used to supply nutrient solution to the plants
- Irrigation pipes to supply nutrient solution to the upper edge of the trough and collect the remainder solution after flowing through the plant roots at the lower edge of the trough.
The supply of nutrient solution to the plants and its recirculation within the hydroponic unit will be continuous. No water or nutrients will be discharged. Standard water-soluble fertilizers will be used to prepare concentrated stock solutions which will be diluted at a ratio of 1:100 to prepare the final nutrient solution whenever needed. The latter will be regularly added to the replenishment solution tank (e.g. every two or three days) to compensate for nutrient and water uptake by plants. No other operations are needed for fertilization and irrigation of the plants, since both nutrients and water will be automatically provided through the recirculating nutrient solution.