Blankets may be opened and closed manually or
set automatically with a photocell or time clock.
Light activated operation is most desirable for crop
production, and requires no change in settings with
the seasons. A light level of 50 fc is a good threshold
point. At this level, blankets will remain open even
on dark, cloudy days. Time clocks are the most
common method of control, even though growers
must change the clock settings as seasons change