On-line optimization of intensity and configuration of supplementary lighting using fluorescence sensor technology

To estimate the impact of different applications of supplemental light in greenhouses, laborious and time consuming experiments are required to measure and verify differences in crop productivity. Especially when the expected differences are small, it will be difficult to prove that a given lighting application outperforms others in that test. Random variation and interaction of numerous environmental factors in a greenhouse environment limit differences that can be determined accurately enough to 5%, at least in an experimental setup. Still effects of less than 5% are of very high economic importance and it would be a big advantage if these small effects could be made visible in an earlier stage than at the time of harvest. Therefore it is important, that effects are not only made visible by comparison of integrated yield, but also by comparison of the dynamics of the responses at different developmental stages and seasons. We tested a modulated fluorescence monitoring system that was specially adapted for horticultural practice, in combination with a sensor system (Growlab) to study photosynthesis responses under 2 different lighting configurations in roses. Comparison of the yield data, based on fluorescence measurements with data based on photosynthesis measurements gave strong support that fluorescence signals, after species-specific calibration, are a sound basis for optimization of light intensity and lamp configuration in roses, with good perspectives for application in other horticultural crops.