ISHS Acta Horticulturae 588: II International Symposium on Cucurbits
LIGHT INTERCEPTION OF A GREENHOUSE CUCUMBER CROP: MEASUREMENTS AND MODELLING RESULTS |
| Authors: | R.M. Peil, M.M. González-Real, J. López-Gálvez |
| Keywords: | Cucumis sativus, Photosynthetic Active Radiation, light extinction coefficient, LAI, growth, row crop, shading screen |
| Abstract:
Light interception of a cucumber row crop was investigated under greenhouse conditions during two growth periods (spring and summer). Measurements of the photosynthetic active radiation (PAR) were performed throughout the growth periods at the top (PARo) and at the bottom (PARt) of the crop. A shading screen inducing conditions of diffuse light was used in summer, leading to a reduction of the integral of the incoming PAR (ΣPARo) of 33% (1036 and 691 mol m-2 in spring and summer, respectively). The contrasting conditions of ΣPARo induced changes in the geometric characteristics of the crop (height, row width and leaf area), which influenced the amount of intercepted light. The intercepted PAR (ΣPARi = ΣPARo-ΣPARt) experienced a higher reduction than the one observed in ΣPARo, which was calculated to be 37% (684 and 429 mol m-2 in spring and summer, respectively). Maximum values of the light interception efficiency (  i = PARi/PARt) were relatively high (0.90 and 0.87 in spring and summer, respectively). In order to estimate the intercepted light by the crop, an existing model of canopy light interception (M1) by a row crop was used along with a simple estimation approach based on the Lambert-Beer's law (M2). Models validation was performed using experimental data, assuming that all PARo in summer was diffuse.
Validation results showed that both approaches were able to correctly estimate the daily intercepted PAR under contrasting conditions of PARo, tending to overestimate at high LAI values, although only the M1 model was able to simulate daily variations of PARi.
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