S06 - Session O7 - Keynote: Developments in recirculation of drainage solution for crops on growing media

Authors: Chris Blok *, Tommaso Barbagli, Dimitrios Savvas

Growing media offer the technical possibility to collect and re-use all drainage water as well as all nutrients in the drainage water. Recirculation makes it possible for most places on earth to increase water use efficiency with 50% and, nutrient use efficiency with over 50%. It will be argued drainage water is an inevitable consequence of the natural property of plant roots to take in some elements more readily than others. Furthermore, when recirculating, the amount of nutrients added to the system must carefully match the amount of nutrients leaving the system, predominantly by plant uptake, otherwise accumulation or depletion of one or more elements will occur. A short history of nutrient recommendation systems and a version currently in use in the Netherlands will be discussed. Practical problems and current solutions will be shown for 1) various water qualities; 2) accumulation and management of sodium; 3) the unequal distribution of irrigation solution in supply pipes; 4) dealing with fluctuations in both, the amount of drainage water and the amount of nutrients in the drain; 5) further automation including the use of ion specific meters. The consequences of new developments will be discussed, ending with suggested lines of research.