Articles
THE RADIATION SPECTRUM THROUGH ORNAMENTAL NET HOUSES AND ITS IMPACT ON THE CLIMATE GENERATED
Article number
719_73
Pages
631 – 636
Language
English
Abstract
The net house is a simple and cheap structure that can provide an interesting climatic environment for the crop, especially during the summer conditions in the Mediterranean area.
The main climatic parameter influenced by this structure is the solar radiation which depends on the cover material.
Solar radiation provides the main energy input to the plants and the internal environment, with much of this energy being converted to heat and driving other radiation exchanges.
Shade cloths are mainly used to reduce internal energy levels.
Shade cloths permit the entry of pests, and for this reason an anti-pest mesh was used to provide an insect proof barrier.
The trial was based on the comparison of the climate generated under two kinds of nets in a 540 m² house.
The covering material of the whole net house was an anti-pest mesh of 20×10 threads (APM) and an aluminised thermal screen with 40% shading was additionally placed (APM+ATS) over a tunnel inside the same net house.
Values of global external radiation, air temperature, substrate temperature and relative humidity were measured every 15 minutes during the whole experiment, and the light quality was measured in the middle of the experimental period at 12 solar hours.
The results showed transmission factors for global radiation under the two treatments were 0.70 and 0.36 for APM and APM+ATS respectively. Measurements were made of the transmission of thermal radiation between 800 and 1100 nm, the radiation intensity and the transmission coefficient through the spectrum.
The differences between air and substrate temperatures were not significant between treatments but the air temperature was 2.2 ºC higher than the external temperature, this effect being more pronounced during the daytime, especially at midday (6 ºC). The VPD was lower under APM than APM+ATS and both presented significant and important differences with respect to the external VPD. The average daily values of VPD were -0.68 (external), -1.15 (APM+ATS) and -1.62 (APM) kPa.
The main climatic parameter influenced by this structure is the solar radiation which depends on the cover material.
Solar radiation provides the main energy input to the plants and the internal environment, with much of this energy being converted to heat and driving other radiation exchanges.
Shade cloths are mainly used to reduce internal energy levels.
Shade cloths permit the entry of pests, and for this reason an anti-pest mesh was used to provide an insect proof barrier.
The trial was based on the comparison of the climate generated under two kinds of nets in a 540 m² house.
The covering material of the whole net house was an anti-pest mesh of 20×10 threads (APM) and an aluminised thermal screen with 40% shading was additionally placed (APM+ATS) over a tunnel inside the same net house.
Values of global external radiation, air temperature, substrate temperature and relative humidity were measured every 15 minutes during the whole experiment, and the light quality was measured in the middle of the experimental period at 12 solar hours.
The results showed transmission factors for global radiation under the two treatments were 0.70 and 0.36 for APM and APM+ATS respectively. Measurements were made of the transmission of thermal radiation between 800 and 1100 nm, the radiation intensity and the transmission coefficient through the spectrum.
The differences between air and substrate temperatures were not significant between treatments but the air temperature was 2.2 ºC higher than the external temperature, this effect being more pronounced during the daytime, especially at midday (6 ºC). The VPD was lower under APM than APM+ATS and both presented significant and important differences with respect to the external VPD. The average daily values of VPD were -0.68 (external), -1.15 (APM+ATS) and -1.62 (APM) kPa.
Publication
Authors
M. Pérez, B.M. Plaza, S. Jiménez, M.T. Lao, J. Barbero, J.L. Bosch
Keywords
Temperature, VPD, transmission coefficient, relative humidity, ornamental crops, anti-pest mesh and aluminised thermal screen
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