Effects of a shading screen on microclimate and crop water requirements |
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Authors: | Markus Möller Shmuel Assouline |
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Institution: | (1) Department of Environmental Physics and Irrigation, Institute of Soil, Water and Environmental Sciences, ARO-Volcani Center, P.O. Box 6, 50250 Bet Dagan, Israel |
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Abstract: | Despite the steadily increasing area under protected agriculture there is a current lack of knowledge about the effects of
the 30% black shading screen on microclimate and crop water requirements. Meteorological and lysimeter measurements inside
a screenhouse planted with sweet pepper were compared to external reference data. Irrigation water use efficiency (IWUE) was
calculated from yield records Y and water meter readings I
applied. Shading reduced mean global radiation R
G
by more than 40%, and the screen transmissivity τ
screen was shown to vary with solar elevation angle β. Wind speed inside the screenhouse u
in was reduced by more than 50%. Crop water requirements ET
c
were 38% lower than estimates for an open field crop, suggesting a significant water saving potential when using screenhouses.
However, the screen did not significantly modify maximum temperature T
max and daily vapor pressure deficit. The FAO-Penman–Monteith approach based on meteorological measurements in the screenhouse
accurately predicted daily crop evapotranspiration, and was in close agreement with lysimeter measurements. IWUE was relatively
high (10.7 kg m−3 in 2004 and 13.5 kg m−3 in 2005), but additional research is required to quantify the effect of shading on yield as well as to determine the water
saving potential of other commonly used screens.
Contribution no. 603/06 from the Agricultural Research Organization
An erratum to this article can be found at |
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Keywords: | Shading screens Radiation Wind speed Reference evapotranspiration Sweet pepper Crop water requirements Irrigation water use efficiency |
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