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"Controlling based on plant activity rather than conditions"

Don't control your crop based on the conditions in the greenhouse, but on the activity of the plant. That's what's happening with Priva TopCrop Monitor. Peter Kamp explains how the system translates the plant activity into a workable figure and what the grower can do with this.

What is already being used in greenhouse horticulture in order to control cultivation? The conditions of the plant: the solar radiation, temperature, moisture deficit, the airflow - to name but a few. At Priva, they've decided to do it in a different way. Plant physiologist and innovator Peter Kamp has carried out research into what affects the crop. This is what Priva TopCrop Monitor is based on. After extensive testing with twelve growers, the system is now widely available.

Importance of water
The water in the plant is partly used for evaporation and partly used for the development of the plant and the crop. According to Peter Kamp, the best quality plant development occurs when water intake is constant. "Photosynthesis is of enormous importance to the growth of the plant. The water intake affects the quality of the growth," he says. "For example, a disruption in water intake causes missetting, or tears in the plant. The measurement shows what you can eventually see in the plants. And in this way, you can trace the source of the problem." Therefore, proper control of water intake and evaporation not only gives a better yield, but also results in less losses.

Measuring with a camera
The TopCrop Monitor therefore measures evaporation activity. This is done with an infrared camera. The temperature of the plant is compared to the temperature of the surroundings. In this way, it can be studied how the plant responds to environmental conditions: can the plant follow the temperature of the environment? To that ratio, a scale is applied from 0 to 100. At 0, the plant hardly evaporates, there is generative growth. At 100, the evaporation is in full swing: an active crop results in a more vegetative crop cultivation. At 50, the plant is continuously using 10% of the water supply for plant development and the plant is in balance.

The evaporation measurement is, in this sense, independent of conditions such as temperature, solar radiation and humidity. "Even at a relative humidity of 95%, the evaporation can still be optimal. You don't want that because it could cause fungus cultivation, but it can be done. It's about relationships," says Kamp. "With lots of sunshine, you have a lot more evaporation. But because we assess the measurement relative to the 0-100% scale, this effect is removed and you can always strive for the same value."

No fluctuations
According to Kamp, the cultivation is optimal when there are minimal fluctuations in the evaporation activity. Therefore, the Priva TopCrop Monitor changes the evaporation activity in the target cultivation. The cultivation conditions are factors by which the evaporation can be optimized. This leads to unorthodox measures. Indeed, it shows that irrigation is the biggest disruption to the continuity of evaporation.

Kamp highlighted how water is used in a plant: mainly for evaporation, but also to carry out other processes: root, stem and leaf development, but also flower and fruit development. This is done partly due to the cell pressure, which is brought about to a certain extent via irrigation. The research shows that the plant gets used to a schedule of irrigation. Skipping a watering disrupts the process and the required cell pressure is not reached. That's why he sometimes advises growers to go against their instincts and based on the Monitor not to skip watering, but to reduce it. "Your irrigation does not need to equal the evaporation. Even if there is no evaporation, the water dosage may be needed in order to kick start other plant processes." He points out the opening of a flower: something that only happens in the morning. "And only happens if the cell pressure is high enough. If water is not given before, the flower will not open. Therefore it is important not to skip watering." In order to follow this kind of action, the system is combined with cultivation guidance.

Heating pipes
There are more ways in which the TopCrop Monitor changes the choices in cultivation. Kamp refers to the opening of the vents and heating up the pipes. "If the vents are opened, we are afraid of the cold. Therefore, the pipes are heated up. But with higher temperatures in the pipes, the plant will evaporate more. This ultimately results in a lower plant temperature." It would be better to increase the temperature uniformly in order to allow the evaporation to increase gradually and to allow the plant to come to the same temperature as the ambient temperature. "Then you get no disturbance in your evaporation."

The cultivation advice is determined in consultation with the grower based on the data. One way or the other, however, a constant rate of evaporation is ultimately not achieveable, acknowledges Kamp. "When it rains, you have to close the vents, even when you are actually airing to optimize your evaporation." And what about the sharpening up of your plants? Sometimes you just need to bother them - to get the production back on track? This also varies by crop, acknowledges Kamp. "By measuring the evaporation rate, you can also measure the bothering. If you see that the plant has grown vegetatively, you can then consciously manipulate for a generative growth. But you should know how the crop responds. You can only do that by measuring it."

Missed the seminar? Another seminar about Priva TopCrop Monitor is being organised on 12 November. Sign up here. 

For more information:
Priva (e-mail)
Zijlweg 3
2678 LC De Lier
T +31 (0)174 522 600
F +31 (0)174 522 700
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