Moisture sensors control ventilation to prevent disease
TRIALS at Scottish Agricultural Colleges (SAC), Aberdeen, have shown there is a strong correlation between condensation and in-store potato disease problems, particularly silver scurf, black leg and, probably, skin spot.
To reduce the risk of tuber damage, a potato store ventilation control system has been introduced by Proctor Insulations of Blairgowrie which automatically shuts down a ventilation system when condensation is likely to occur. A sensor esatblsihes this point from dewpoint temperature, calculated from ambient air temperature and relative humidity.
"Condensation occurs when air comes into contact with a surface which is below dewpoint," explains Mike McLaughlin, Proctors managing director. "If the dewpoint of the ambient air is higher than the temperature of the tubers, any air that gets into the store will cause condensation. In the UKs maritime climate potatoes can be at risk for up to 50% of the time in store."
Any condensation in the crop is identified by a series of skin moisture sensors, four to six for a 1000-1500t store, located within the top layers of tubers, in the region of the stores air inlets.
"Now that we have the means of better understanding the problems of condensation, many existing ventilation systems can be upgraded relatively cheaply," says Mr McLaughlin.
He adds that the Dutch pre-packing, seed and processing trades have long recognised the importance of dewpoints and have persuaded their meteorological office to give farmers a daily dewpoint forecast in each region.
Price of the Proctor Dewpoint control for a new store is likely to be around £3000. *
Condensation in the potato store controlled with the Procter Dewpoint ventilation controller.