MEASUREMENT OF NATURAL IRRADIANCE IN GREENHOUSES : THE EFFECT OF AVERAGING PERIOD AND NUMBER OF SENSORS ON MEASUREMENT RELIABILITY

概要

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Measurements of natural photosynthetic photon flux (PPF) at 1m above the floor in glass and polyethylene greenhouses obtained using a mobile sampling system are compared to data obtained by 6 stationary sensors at the same height. Analysis of the data shows that the use of multiple stationary sensors does not lead to an accurate value of the spatial average irradiance under sunny conditions in either glass or polyethylene greenhouses when integration times are short (1 to 3h). With longer integration times (up to 10h), these inaccuracies are insignificant under glass. Under polyethylene, systematic differences in PPF occur across the greenhouse. In our region, calculations using data from this experiment indicate that average differences in total radiation accumulations during February can be as large as those induced in typical supplemental irradiation experiments. These systematic gradients should be taken into account in experiments where the parameters being studied may be sensitive to radiation integrals.
九州大学の論文