ISHS Acta Horticulturae 711: V International Symposium on Artificial Lighting in Horticulture
INTERLIGHT AND PLANT DENSITY IN YEAR-ROUND PRODUCTION OF TOMATO AT NORTHERN LATITUDES |
| Authors: | B. Gunnlaugsson, S. Adalsteinsson |
| Keywords: | Artificial light, interlight, tomato, plant density |
| Abstract:
When applying artificial light in greenhouse cultivation, lamps are traditionally mounted only above the plants giving limited light to the lower leaves in the canopy. Recent experimental work in Finland and Norway implies that the lower leaves of tomato and cucumber plants are able to assimilate quite actively, suggesting that a better utilization of the energy used for the lighting could be obtained by giving part of the radiation to the lower parts of the canopy. A set of experiments was conducted to compare three different strategies for mounting of HPS-lamps for artificial lighting in tomato cultivation. The total installed effect of 238 W/m2 was either applied as toplight with 400W or 600W lamps mounted horizontally over the aisles or as 22% and 45% interlight respectively, applied with 250W lamps mounted vertically within the double plant rows. Light was generally provided for 18 hrs (0400-2200 hrs) but the lamps where automatically turned off when incoming radiation was above the desired set-point. In the first experiment, conducted in the winter season, the average saleable yield of tomatoes cv. 'Espero' and ‘Geysir’ ranged between 33.0–39.9 kg/m2 when harvested for 19 weeks. The amount of interlight given did not affect the yield of cv. 'Geysir' whereas cv. ‘Espero’ gave the highest yield when illuminated with 45% interlight and the lowest when lit by toplight only. The results indicate that some cultivars of tomato grow equally well whether they are lit by toplight only or partially by interlight. Toplight is easier to install in the greenhouses and presumably, growers would prefer such an installation, if suitable cultivars can be found. In the second experiment, conducted in the summer season of 2004, cv. 'Espero' was cultivated at two plant densities, i.e. 2.5 tops/m2 and 3.3 tops/m2 with the same lamp installation. Again cv. 'Espero' gave highest yield at 45% interlight, and the lowest when lit by toplight only. Increased plant density from 2.5 tops/m2 to 3.3 tops/m2 gave 10% more average yield. | |
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