Measure and display transpiration with ProDrain

In order for crops to be healthy, sufficient moisture needs to evaporate through the leaves. This process is known as "transpiration". During sunny weather, transpiration is necessary to cool the crops. Transpiration is also needed, however, to stimulate the uptake of water from the roots, so nutrients are transported to the growing parts of the plant above the ground.

HortiMaX has succeeded in developing an accurate way of measuring crop transpiration. After receiving the measurement data from the ProDrain weighing tray, the software mathematically filters out any disturbances and then calculates the transpiration. These calculations give a minute-by-minute representation of how the crop’s transpiration is reacting to the greenhouse climate. ProDrain therefore offers extremely useful information for precision climate control. The transpiration rate measured by ProDrain is also sent to the climate computer. This enables the computer to control the greenhouse systems based on the measured transpiration. If the transpiration is too low, the computer can be programmed to automatically increase the minimum pipe temperature, for example.
Since the plants in the ProDrain weighing tray cover a few square metres of the greenhouse area, they are sufficiently representative of the whole crop. ProDrain can be used for any hydroponics-grown crop. In addition to transpiration, ProDrain also measures the irrigation volume, the drain quantity and the drain percentage achieved. ProDrain can even measure the growth rate of hanging crops such as cucumbers and tomatoes.

The ProDrain measurements are displayed in graphs under Synopta. The graph above clearly shows how the solar radiation (red line) affects the transpiration (black line). In this case, the transpiration in the morning slowly rises in relation to the radiation. The crop growth (pink line), however, slows down as the transpiration increases, but recovers once the transpiration starts to drop in the afternoon.
The graph also clearly illustrates how the humidity (green line) follows the same pattern as the transpiration; if the transpiration is high, so is the humidity and vice versa. This proves once more that a low transpiration rate is not necessarily the result of high humidity. Transpiration is therefore a much more useful measurement for control actions aimed at stimulating transpiration (known as ‘activating the crop’) than humidity. More...