ISHS Acta Horticulturae 633: XXVI International Horticultural Congress: Protected Cultivation 2002: In Search of Structures, Systems and Plant Materials for Sustainable Greenhouse Production
CONTROL AND OPTIMIZATION OF THE GREENHOUSE ENVIRONMENT USING INFRA-RED SENSORS |
| Authors: | F.A. Langton, J.S. Horridge, M.D. Holdsworth, P.J.C. Hamer |
| Keywords: | speaking plant, canopy temperature, plant stress, environmental optimization, chrysanthemum, dieffenbachia, begonia |
| Abstract:
Wide-angle, infra-red (IR) sensors were linked directly to a greenhouse climate control computer, and were used successfully both to monitor plant canopy temperature (CT), and to control greenhouse heating and cooling on the basis of CT. Summer trials used pot chrysanthemums and dieffenbachias, and relationships between CT and air temperature (AT) under the trial conditions are given. Flowering crops typically showed high CT values in summer. IR monitoring on a commercial begonia nursery showed that CT at night was generally about 2°C below AT in summer, but that CT exceeded AT during the day by up to 7°C. Differences between CT and AT were found to mirror changes in photosynthetic photon flux density (PPFD). Allowing AT to fall at dawn to give compact plants (DROP) did not always result in comparable reductions in CT. This was because increasing irradiance at the start of day tended to nullify the effect of lowered AT on CT. Potential benefits of controlling greenhouse operation on the basis of CT include avoidance of plant stress in summer, improved environmental optimization, more precise crop scheduling and, possibly, energy savings. Control based on CT is an example of the ‘speaking plant’ approach to crop management, and commercial activity in the Netherlands suggests that this is at last becoming a reality. | |
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