A Prototype Sensor for Estimating Light Interception by Plants in a Greenhouse

Light interception is one of the most important factors for plant growth. The intercepted amount depends on the incoming radiation in the greenhouse and the percentage of interception by the crop and is directly related to the leaf area. Proper crop management requires the measurement of the most important growing factors. In case of application of crop growing models the simulation of the leaf area is one of the major uncertainties in the results of the models. Automatic calibration of the model based on radiation interception increases the accuracy of the model results. For the determination of the crop¿s light interception in a greenhouse, a radiation sensor was used which determines the ratio of the incoming radiation from the upper side and the reflection at a specific wavelength from the lower side. The ratio of reflected radiation versus intercepted radiation can be used to estimate light interception as well as leaf area. However, the measurement of this fraction can only be used after filtering out erroneous data due to technical errors, insufficient diffuseness, insufficient solar height, etc. This paper describes the boundary conditions to be taken into account for proper measurement of reflected radiation. Time series measurements of incoming, reflected and global radiation are used, to filter the data acquired by the sensor. The sensor functioned well during tests on a cucumber crop in a commercial greenhouse

Dynamic control system (DCS) for apples (Malus domestica Borkh. cv 'Elstar'): optimal quality through storage based on product response

Dynamic control system (DCS) is an interactive, patented storage concept, which can be regarded as the successor of traditional controlled atmosphere (CA) storage for some commodities. Instead of using static, fixed set-points for gas conditions like in CA, the oxygen concentration in the DCS storage facility is controlled upon product response. When applying DCS, the oxygen concentration is slowly lowered until the product emits a stress-signal. More specific, DCS uses ethanol, the final product of fermentation, to establish the lowest possible oxygen concentration under which a product can be stored. DCS was applied for the storage of apples (cv `Elstar¿). Experiments with this cultivar, as presented here, show that apples are firmer after DCS storage, especially after shelf life, and have a better colour retention compared with traditional CA. Furthermore, apples tend to develop less skin spots under DCS, a major storage disorder of `Elstar¿