Why humidity is crucial in climate control

Greenhouse climate control involves optimising the elements to maximise yield at the lowest possible cost, and to do this properly, growers need to understand the effect of vapour pressure deficit (VPD) on plant growth. This is according to Deon van Rooyen, commercial manager at Vegtech Netafim and a speaker at a Netafim South Africa seminar held in Stellenbosch in November.

VPD, explains Van Rooyen, is the difference between the amount of moisture within a plant’s leaves and the air surrounding the plant. It drives various plant processes, such as transpiration, the opening of stomata, and the uptake of carbon dioxide (CO₂) and nutrients.

“By managing respiration rate through VPD, one cannot only optimise plant growth, but ensure that plants stay stress-free and thus healthier. The process further optimises nutrient uptake, resulting in better yields,” he says.

TEMPERATURE PLUS HUMIDITY

Optimal VPD is achieved through the management of the humidity and temperature in greenhouse or tunnel structures.