ISHS Acta Horticulturae 633: XXVI International Horticultural Congress: Protected Cultivation 2002: In Search of Structures, Systems and Plant Materials for Sustainable Greenhouse Production
THE DESIGN AND EVALUATION OF A SHADE SCREEN TO OVERCOME WITHIN-ROW VARIABILITY OF TOMATO CROPS GROWN IN SMALL EXPERIMENTAL GLASSHOUSE COMPARTMENTS |
| Authors: | P.J.C. Hamer, S.R. Adams, V.M. Valdés |
| Keywords: | light interception, model, fruit size, fruit quality, numerical integration, yield, uneven ripening |
| Abstract:
Long season tomato plants at the ends of rows intercept more light, particularly at the south end of rows that are orientated north-south where they are in direct sunlight for much of the day. The use of extra guard plants to minimise the within-row variability is not always practical. A light interception model was developed and used to design a screen for an experimental facility at HRI, where tomato crops were grown in double rows with a north-south orientation. The effectiveness of this screen in reducing the end of row effects was investigated. For the model, the canopy was assumed to be a solid cuboid of horizontally parallel rows rectangular in cross-section and of finite length. Shading was provided by a vertical screen at the south wall with the same height as the crop canopy. Numerical integration techniques simulated the distribution of light on each cuboid face for the months March to August with a range of screen transmissions. The model predicted that a screen would considerably improve the uniformity of light distribution. A nominal ‘50%’ shade screen was positioned on the south wall of a compartment and adjusted with the height of a tomato crop. Each double row was split into four sections SW, NW, SE and NE and crop performance compared with compartments without shade. In unshaded compartments there was considerable within-row variability, with significant effects both on the mean fruit size and the proportion of class 1 fruits. The screen had a significant effect on the pattern of yield within the compartments resulting in a more uniform distribution in mean fruit size. Furthermore, the screen reduced the incidence of gold marbling and uneven ripening, and increased the percentage of class 1 fruit from plants that had been on the south ends of the rows. | |
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