Examples

Open or closed circuit „

• Installations with "lost solution" or "open circuit": the excess nutrient solution is eliminated by drainage and then discharged outside the culture system. But this solution can be recycled on crops in the open ground.

• “Recycled solution” or “closed circuit” installations: the nutrient solution is recovered, recycled (disinfected, analyzed and reconstituted) and returned to the plants.

With or without substrate „

• Systems "with substrate" (the most widely used to date): the substrate provides a reserve of water and nutrients while maintaining good oxygenation of the root system between two irrigations. On the other hand, they have numerous drawbacks as regards the handling of the substrates used, their recycling (or their destruction) and their cost.

• Culture "without substrate" (little developed in the tropics): the nutrient solution is contained in a container or distributed in gutters. This may require additional oxygenation of the nutrient solution to prevent root suffocation and plant dieback. It avoids the constraints related to the recycling of the support and the disinfection of the installation is easier. The problem of warming the nutrient solution may arise. The lack of water reserve at plant level represents a risk in the event of pump failure.

• Choice of substrate: It must have both good water and air availability (high micro- and macro-porosity). The substrate is also chosen according to its purchase price (transport included), its ease of installation in the greenhouse, its ease of storage without forgetting the cost and the constraints of elimination. In Réunion, the substrates that can be used are blond peat and coconut fibres.