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Recirculation may cause a too high sodium concentration in pot orchids
Pot orchids are very salt sensitive. This may cause growth problems if the drainage water is fully recirculated, as is mandatory in The Netherlands from 2027. That is why the Greenhouse Horticulture & Flower Bulbs Business Unit of Wageningen University & Research is investigating the limiting sodium value for pot orchids.
Pot orchids (or phalaenopsis) originate from the tropics where they grow on trees: they are so-called epiphytes. Consequence is that they don't get water through the soil, but only through the rain, which contains hardly any nutrients. As a result, the plants have a low tolerance for sodium. In practice this means that If the concentration is too high, the plant has to use more energy for water uptake, which reduce growth. In addition, sodium hinder the uptake of other nutritional elements such as calcium and potassium.
Pot orchids are fertilized much lower compared to other crops and growers of pot orchids are therefore exempted from the recirculation obligation. However, in view of the target of zero emissions in 2027, this exemption has ended and these growers must recycle drained off water also. However, the exact consequences of this are not yet known. This is because it is not yet clear from what level of sodium the plant growth will be affected.
WUR is therefore investigating the effects on the growth and development of different sodium levels (up to a maximum of 10 mmol per liter) in a five-month preliminary study. The results of this trial determine the bandwidth of treatments for a larger trial that will start this summer: then the effect of sodium growth and the flowering of the pot orchid will be investigated in a fullcropping cycle.
The 'Sodium limiting values for pot orchids' research is funded by the Topsector Tuinbouw & UItgangsmaterialen, Stichting Kennis in je kas (KijK), Yara Benelux en Elektravon Haket.