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Fig. 32: Sugar content of tomatoes
4.3.4 Interior quality of yield – sugar content
Sugar content of tomatoes was measured two times during the harvest period. Completo had a sugar content of 3,2-3,6°BRIX. The sugar content was independent of the light treatment. However, the sugar content seems to be tendentially higher under HPS lights than under Hybrid lights (Fig. 32).
Fig. 32: Sugar content of tomatoes.
Letters indicate significant differences (HSD, p ≤ 0,05).
4.4 Economics
4.4.1 Used energy
The number of lighting hours is contributing to high annual costs and needs therefore special consideration to consider decreasing lighting costs per kg “yield”. The total hours of lighting and the used kWh’s during the growth period after transplanting were measured with dataloggers.
Production of tomatoes resulted in the “HPS” chamber in a daily usage of 235,9 kWh, in the “Hybrid high” chamber in a daily usage of 237,8 kWh and in the “Hybrid” chamber in a daily usage of 241,1 kWh (Tab. 7). This means that the costs for growing tomatoes were in all the light treatments comparable (Tab. 7).
