Estimation of the Amounts of Supplemental Carbon Dioxide (CO2) when Considering Night Respiration for a Hydroponics Tomato Greenhouse

초록

This study aimed to estimate amount of carbon dioxide (CO2) supplementation necessary for tomato hydroponic cultivation by considering nighttime respiration using model-based equations. Experiment 1 was conducted in a commercial tomato hydroponic greenhouse during the spring growing season. Experiment 2 was conducted in an experimental greenhouse during the autumn growing season, with the predicted and measured CO2 increases due to plant respiration during the nighttime also compared. In experiment 1, the supply rate of CO2 fertilizer with LPG was a set to 600 mu mol<middle dot>mol-1 from 7:30 to 11:00 in a commercial tomato hydroponics greenhouse, and in experiment 2, CO2 was supplied at a set rate of 600 mu mol<middle dot>mol-1 from 9:00 to 11:00 using a liquefied CO2 generator in the experimental greenhouse. The estimation of the CO2 concentration prior to the first supplement of the day was calculated by adding the CO2 concentration about the time of sunset (lower than 50W solar radiation) on the last day to the integrated respiratory CO2 concentrations during the nighttime. In experiment 1, the estimated amount of CO2 supplement ranged from 3.24 to 36.9 g CO2<middle dot>m-2<middle dot>h-1 when the nighttime temperature was between 16 and 19 degrees C, while in experiment 2, the estimated amount of CO2 supplement ranged from 4.21 to 52.6 g CO2<middle dot>m-2<middle dot>h-1 when the lowest nighttime temperature was 13 degrees C. These results suggest that the night respiratory CO2 was affected by the night temperature of the greenhouse and therefore has an impact on the CO2 supplementation amount. Therefore, it suggests that the new model equation that introduces night respiration into the estimation of supplemental CO2 amounts can be used to precisely control greenhouse CO2 supplement.

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