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The quantum sensor approximates PAR light, the
radiation between 400 and 700 nanometers. These are the
most influential wavelengths for optimum plant growth.
PAR light is necessary for the plant to function properly.
Light requirements differ between crops, but the rule of
thumb is to allow the maximum amount of light possible.
Growers commonly apply shade to decrease temperature
and improve foliage. In some crops, such as tomatoes, the
yield has been shown to be directly proportional to the
amount of light. Limiting light may cause the stomates to
close which prevents the leaves from cooling off. The da-
ta logger monitors the light available and records it as
moles/day (Peet, 2002).
Moles/day is the unit for the Daily Light Integral (DLI);
the amount of light present during a day. The DLI varies
with the seasons, increasing in the spring and decreasing
in the fall. The greenhouse film and structure allow 35-
70% of the light to reach the plants. Environmental fac-
tors like dust and dew can also block light. Light transfer
is hard to assess using the human eye because it adjusts
immediately to the current light level. The only way to
verify light quantity is to use a light meter (Faust, 2002).
Installation of light sensors
- Position the sensor in an appropriate area to monitor
plant conditions.
- Make sure the quantum sensor is not being shadowed or
blocked.
- Use the bubble level to ensure the sensor is horizontal.
- Inspect the sensors frequently to make certain they are
clear of obstructions.
Contact your cooperative extension agricultural agent for
further suggestions on field placement.
Light
