“With Svensson's newest climate screen, Harmony 1315 O FR, lighting tomato growers can get through the worst of climates, even a record hot summer like in 2018,” says greenhouse climate consultant Joost Haenen.

The major challenge in every crop lies in the realization of a good assimilate balance. In other words, the production of assimilates (controlled by irradiation) and the consumption of assimilates (depending on temperature) must be in balance. During a heat wave such as our past summer, the temperature is high, and therefore the consumption of assimilates is high. Too high consumption of assimilates comes at the expense of the roots. Weak or uneven root growth can lead to quality problems and water stress during a heat wave with a lot of radiation, causing high evaporation. This will close the stomata. However, open stomata are necessary for CO2 absorption. As a result, not only growth comes to a halt, but also less moisture enters the greenhouse air. This can easily be avoided with the right ventilation strategy but preventing plant stress is even better. The Harmony 1315 O FR summer screen has been developed for this purpose.

Specially for exposed tomato cultivation

High light levels and air permeability are unique to the Harmony 1315 O FR summer screen. When closed, it provides a slight shadow effect (13% in direct light) and a very high diffusivity. The screen has been specially developed for illuminated tomato growing. Tomatoes can have a lot of light, but at some point, they can't handle it anymore. This climate screen has been developed to remove the sharp edges. Especially in the scarce warm months, April to July, when the plant is old and has long stems.

“Tests at the Improvement Center have shown that the plant does not have to evaporate as much on an extremely sunny day with the new screen. The water consumption is then approximately 20% lower, which means that the root quality remains better due to oxygen retention in the mat. The open structure is also unique, ensuring that there is more than enough air exchange. That's why it's a perfect screen for the summer," says climate consultant Joost Haenen. “Moreover, the cultivation plan changes from tomato. Lighting growers are planting plants earlier and earlier, sometimes in August or even in July. Small plants then have a hard time due to the high radiation and temperature. During this period, the climate screen can easily be used to keep the plant in balance."

Flexible fencing

“The summer screen has so far been tested at the Improvement Center in departments with Son-T, hybrid and full-LED lighting. There is also a practical test of more than 3 hectares with a tomato grower and there are already several growers who will install the screen in new construction projects,” Haenen continues.

He mentions the advantage over a layer of chalk or a coating is that no light is lost on dark days and during the day, because the screen can then remain open. “You are flexible with screens and only help the plants when the plant really needs them. On hot sunny days, plant stress and quality problems can occur. At the same time, the working climate is improving.” Although the summer of 2018 was exceptionally hot, climate experts warn that extreme summers will occur more frequently, which justifies the extra investment in the longer term.

Screens in the night

In addition to tempering hot summer days, the summer cloth can also perform well at night. During a hot period, the nights are often crystal clear, so the appearance is very high. This makes the greenhouse cover cool much faster than the outside air. As a result, the crop head radiates towards the deck and thus becomes colder. This seems positive, but it also has risks. Because of reduced evaporation, young leaves and fruits can be deprived of calcium, which leads to weaker plants. This is at the expense of leaf and fruit quality. In combination with a high root temperature, this can lead to problems such as Mycosphaerella, inner rot and nasal rot. The plants can also be wet due to condensation in the head of the crop, which in turn gives the chance of Botrytis or Fusarium. With the new Harmony 1315 O FR screen, excessive cooling of the head at night can be prevented, while cooling of the greenhouse is not inhibited.

Quality from Sweden

The Svensson Harmony 1315 O FR summer screen is produced in Sweden, which means that it meets the highest quality and safety requirements. The summer screen is flame-retardant, and the diffuse strap in the canvas is patented. "All of this makes it a unique climate screen," says greenhouse climate consultant Joost Haenen.

Kas Magazine - March 2019

www.kasmagazine.com