Carla and Hans Houben are growing high-wire, FitQ mini-cucumbers 4,7 hectare greenhouse in Sevenum, a village in the south-east of the Netherlands. About six years ago they first started with implementing ‘Next Generation Growing’ in their operation. Throughout the years they gained more experience with this new growing method and nowadays they can be called experienced ‘Growing by Plant Empowerment’ (‘GPE’) advocates.
"By focusing on the optimal growth circumstances for the cucumber plants and keeping the plants in balance, the desired energy savings came as a side bonus!"
Hans Houben Fit-Q
Put the cucumber first
“When we started with Plant Empowerment it was out of a quest for extra energy savings, but looking back that should not have been our main objective. You need to put the cucumber crop first!” Hans says. Implementing ‘GPE’ has resulted in growing at a higher speed with higher 24 hour average temperatures in combination with a lower fruit load, in allowing higher temperatures and humidity levels at higher natural light conditions and, in not using the climate screen only for energy saving.
Screening hours increased enourmously
Hans: “The amount of screening hours have increased enormously. Keeping the LUXOUS climate screen fully shut in combination with venting on both lee- and wind-side results in a more even greenhouse climate and you can control your humidity level much easier. We are not only using the LUXOUS climate screen to save energy, but also to protect the heads of the plant and the young fruits against an excess of heat emission. Protecting your crop against the negative impact of heat emission is in fact very easy: when there is more outgoing than incoming radiation, the screen should at least be partially closed to ‘cover the crop like a cloud’. Even after a warm summer day.”
To control the climate screen in relation to heat emission additional sensors are being used: a Pyrgeo-sensor (measures outging longwave radiation in W/m2) on the weather station and a Thermographic ‘Thermoview’ camera inside the greenhouse to get an good idea of the temperatures of different parts of the plant.
Covering the crop
Hans continues: “An excess of heat emission of the plant does not only occur with clear skies. For example from experience with using both sensors I know that due to rain showers the head, flower and young fruit temperatures can fall down 5 to 6 degrees Celsius, although the Pyrgeo-sensor does not show a lot of outgoing longwave radiation. The cold rain drops will cool down the greenhouse roof rapidly, and this increases the heat emission of the different parts of the plant. So while you want an active crop, instead you get cold heads. By covering the crop for 90%, using the climate screen to limit the heat emission, the plant temperature will rise again rapidly and within 10 minutes the temperature of the heads will increase with 4 to 5 degrees.”
Weather forecast linked to climate computer
Nowadays Hans has linked the weather forecast to his climate computer. With a predicted rain shower of a certain intensity, the LUXOUS 1347 FR climate screen will already be steered to cover the crop, even before the shower has arrived at the greenhouse. Ones the shower has left, the climate screen will remain in the same position for at least 10 minutes before it will be steered opened again. This is because often the sun comes through directly after the rain shower. “By keeping the climate screen in the same position for a little longer the crop is less sensitive for sun burn and cold stripes”. This approach prevents temperature shocks in the cucumber crop and this results in a faster growth, a more resilient crop, no more “dark heads” and less diseases in the fruit like Mycosphaerella.
Hans concludes: ”by focusing on the optimal growth circumstances for the cucumber plants and keeping the plants in balance, the desired energy savings came as a side bonus!”