ISHS Acta Horticulturae 148: III International Symposium on Energy in Protected Cultivation
QUANTIFICATION OF EFFECTS OF LIGHT REDUCTION IN GREENHOUSES ON YIELD. |
| Authors: | H. Challa, A.H.C.M. Schapendonk |
| DOI: | 10.17660/ActaHortic.1984.148.63 |
| Abstract:
In order to evaluate economically the benefit of technical measures that improve the thermal insulation of greenhouses it is important to consider the concomitant reduction in light transmission. From a plant physiological point of view it can be shown that there is no general rule describing quantitatively the relation between light reduction and reduction of yield: this relation is affected by the general light level (season) and by the stage of the crop. Two principally different situations may be distinguished: young, widely spaced plants as opposed to older plants growing in a closed canopy. With young plants the effect of light on growth rate is less than proportional and it will be reflected primarily in earliness of the production phase. The rate of production of older crops will be approximately proportional to light except for very low irradiances where production will be affected more than proportional. The mechanisms through which light effects are mediated are discussed and a general frame work will be given for an approximate quantitative analysis. | |
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