Deliverable 8. A blueprint for optimal management of multiple-quality water-resources (IMAG)

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Closed system is a definition that applies to all growing systems, whereby the water drained from the root zone can be recollected and [partly] re-used for irrigation of the same crop. However, even with total re-utilisation of drain, such systems have an outlet (the water and nutrients uptake by the crop) and an inlet (the water and fertilisers that are injected to balance losses, and non useful salts that may come with the water).

Such systems differ according to the way fertilisers are added to the loop, as shown in the scheme below. The “Dutch” system (that is sometime applied in the Mediterranean region as well) requires on-line control of EC and ph, and automated injection of chemicals to meet pre-set targets of both. The “Mediterranean” system is suitable for manual operation: an amount of nutrient solution is prepared and then used to refill the system until it runs up. Either way, when the water used for refill contains salts that are not fully absorbed by the plants, these will accumulate in the substrate-mixing tank loop, and make it necessary to refresh (leaching) at some time.