Understanding absolute humidity in greenhouse climate control
Source: HD.com
For example, air containing the same amount of moisture may measure 40% relative humidity at 29°C, but 100% relative humidity at 15°C. Your aspirated sensor box might be hanging 25 centimeters away from the crop, showing an RH of 85%.
However, inside that boundary layer, the humidity could be near 100%, creating a perfect breeding ground for fungi. Modern greenhouse climate control now favors vertical fans that use as little as 1 watt per square meter to achieve the same effect that 40 watts of pipe heat would provide.
If the difference is too low (below 0.2 kPa), transpiration slows down and the plant becomes less active. If the difference is too high (above 2.0 kPa), the stomata begin to close to reduce water loss, limiting transpiration and plant activity.
Why this matters: For operators, this is a water-management story. The useful signal is that direct substrate measurements can help cut drain loss materially without giving up yield or fruit quality, which is exactly the kind of controllable efficiency gain a facility can build on.
Frequently Asked Questions
Why does substrate sensing matter in free-drain strawberry systems?
Because drain percentage tells a grower what already happened, while substrate moisture and EC data show root-zone conditions directly. That makes it easier to cut water loss without guessing.
What is the operator takeaway from this trial?
If the thresholds are understood well enough, growers can reduce drain water materially while protecting yield and fruit quality, which makes sensing an operational tool instead of a reporting tool.
