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Leo Oprel, Sr. policy officer Ministry of Agriculture, Nature and Food Quality

"Water technology, a difficult subject with different facets"

Water technology is an up-to-date and multifaceted subject and moreover with the necessary interfaces with other greenhouse horticulture issues, such as greenhouse climate and new, fossil-free energy sources. Leo Oprel, Sr. policy officer at the Dutch Ministry of Agriculture, Nature and Food Quality (LNV), deals with the areas of energy, water and fertilization and observes that up close there is increasingly more interlocking of these issues and that is in line with the LNV vision. He will comment on various developments.

"A summer like 2018 makes us once again aware of the usefulness of the various aspects in the field of water technology", says Oprel. "Long-term lack of precipitation increases the importance of storing rainwater in the subsoil, in aquifers. This is not only a good storage place, but also desirable in the context of combating salinization. Especially if more is stored than finally used.

Therefore in this case it is possible to mix business with pleasure. A kind of social contribution from the sector. It can also contribute to the drainage of rainwater, as well as preventing that in dry summers your basin lacks good irrigation water and thus reverse osmosis or poorer surface water - which is also scarce, has to be used. In any case, reverse osmosis on saline groundwater is something that has to be phased out for years."

Less ventilation
According to Oprel, this also should be an item in restructuring. "It's not only about what happens above ground, but also underground. And for the western part of the Netherlands this is good against salinization, but in the east groundwater is also an issue. This year a lot of groundwater was extracted in the east. And that has yet to be replenished. In short, an important issue for both the greenhouse horticulture sector and for other sectors."

He also mentions atomization as an issue in water technology. "You need very pure water for it because it requires a very fine drop. After all, the crop must not get wet. With atomization you can control the heat load with minimum ventilation. That gives a better greenhouse climate and is part of Next Generation Growing.”

The fineness of the drop may differ depending on the equipment, but is important for the usage. The finer the better. Although I do not know what the technical limitation is. In any case, less ventilation is good again to limit the total water consumption and of course for CO2. Also more efficient use of good water for greenhouse horticulture is, not only elsewhere in the world, but also with us, of importance."

Precision irrigation
With the use of heat recovery from greenhouse air, you also win back water. This reduces the need for water for growth. Here, an energy-saving greenhouse climate and more efficient water management go hand in hand. "You can use different methods to that purpose, as various studies show. The question is whether we have already reached the limit or whether it still can be done better or differently."

At the tomato cultivation at the Improvement Center also a different substrate is looked at, Oprel continues. "It is very little substrate and that gives new attention to precision irrigation. When do you have to start the drip? Do you first need to reduce the moisture (and see the stem shrink) or learn from it that you have to drip x minutes earlier before the stem shrinks? That leads to great discussions with the researchers. In that trial, fertilizer is also well looked at. So underground in relation to above ground. And although it has advantages to irrigate precisely, it does require more attention from the certainty that everything is performing well."

Of vital importance for more than just plant growth
Water technology also affects geothermal energy and ATES (Aquifer Thermal Energy Storage). There, according to the policy officer, still a number of things have to be settled. "In geothermal energy you have to deal with aggressive water and at ATES it is usually not too bad. But the efficiency must be as high as possible with a high reliability of optimum heat utilization. There is still an improvement step to be made with suppliers."

Although the efficiency of ATES in greenhouse horticulture is generally better than outside the sector, there are always still some improvements and lowering of the costs possible.

"So water and water technology has more facets and interfaces with climate and energy when you think about it", says Oprel in conclusion. "Water is of vital importance, but not only for plant growth. It has become much wider in modern greenhouse horticulture."

Source: Glastuinbouw Waterproof

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