The substrate for orchids has an open structure, which consist of their own recipe of bark and 30% pieces of coconut fiber (= moist carrier). The growth manager: Before we grew phalaenopis on solely a coarse fraction bark. The disadvantage was that we had to use many liters of water to make the plant moist, because the substrate was like a sieve where the water just ran through. We had to water them with lots of water twice a week."
Water has a number of challenges when growing phalaenopsis. Orchids are sensitive to salt (NaCl) and does not absorb much sodium, which cases NaCl levels to rise rapidly. When recirculating the irrigation water the sodium level in the root environment has to be kept low (max 1 mmol/) to minimize take up by the crop.
Before reusing the water, it has to be properly (100%) decontaminated, to prevent the transfer of diseases, bacteria, fungi, and viruses to plants in the breeding phase (30 weeks at 28 to 29 degrees Celsius). Van Vliet: "Because younger plants are grown at a higher temperature, they are more prone to disease. In the cooling and growing phase the temperature is cooler, ranging from 19 to 22 degrees." Levoplant decontaminates the water with UV light (Vialux installation).
Before the finer substrate and the new pot were used, 70 to 80% of the irrigation water was returned. In spite of the reuse in the growing phase, still too much was left over. Now only 50 to 60% of the water is returned, which is now also used in the breeding phase. The growth manager: "Before reusing we want to ascertain whether the irrigation water has been properly decontaminated. Because we cannot measure things like EC and pH, we do not have sufficient data. That is why we have a monthly DNA Previscan for bacteria and fungi by an external company, but we only know whether the water was good in hindsight. This makes orchid growers reserved in the reuse of water, because it is precise balancing act. We still do it, because we assume the water to be disease-free. But we do not know for sure."
The location in Maasland is a potted plant nursery by origin, with a concrete floor for the ebb and flow system. At the other locations a closed floor by Erfgoed with drainage was installed prior to building the growing installations for the roll cages with wire mesh bottom. Van Vliet: "Because water is expensive we have always opted for collecting water to save on costs. In an existing situation the installation of a closed floor takes a lot of time, complicates working, and impacts the production negatively, which makes it more expensive."
"We also see that we are only using half the fertilizer at an average EC of 1.2. If we would drain all the return water, we have to use new water again and again and keep on adding fertilizer. The return water consists of 1.5 EC of usable fertilizer. We reuse 0.6 to 0.9 EC of this, and add 0.4 to 0.6 EC of fresh fertilizer. This saves on fertilizer."
At the location in Maasland the water circuit is almost close. At 4 hectare annually 260 m3 remains to be drained. For water purification they have joined the collective Oud Camp, of which the business plan has been approved. Van Vliet: "Because we hardly have anything to drain, we easily meet the nitrogen standard. In 2027 we want a completely closed system. If the water is reused, it is no longer drained to the collective. In that case we will invest in our own purification installation with the latest technology, which purifies to a level of 98%. We do not want an accumulation of pesticides in the irrigation water."
"The authorities have a different mindset than before, when it was reprimanding, condemning and fining. Now they help more, look at causes and how they can solve problems together with the grower. A grower just does not know where and how the tubes are running. Only when it is necessary you are trying to find out where the drain water, condensate water, CHP water and flushing water end up. If you know, you can keep the water in. The area focused approach also leads to improvement. Sharing information with other entrepreneurs and the cooperation with research (WUR greenhouse horticulture), district water board, and government are examples of what you can achieve together."