Pay Attention to Vapor-Pressure
Deficit for Healthier Crops
Understanding vapor-pressure deficit can help growers more accurately predict plant water loss.
Image credit: iStockPhoto
Growers know it's important to pay attention to humidity in the greenhouse, but a more appropriate measurement -- vapor-pressure deficit (VPD) -- is often overlooked.
"VPD is the difference between the amount of moisture in the air and how much moisture the air could potentially hold when it is saturated," explains Michigan State University Extension Educator Heidi Wollaeger.
Relative humidity, which is more commonly used when considering the greenhouse environment, is dependent on temperature. "For every increase of 20° F, the water holding capacity doubles," says Wollaeger.
But, VPD can tell a grower a lot more about the greenhouse environment than relative humidity can.