Abstract
PUEP and PUEL, photosynthetically active radiation (PAR) energy utilization efficiencies were calculated by dividing the chemical energy fixed in plants by the PAR energy measured at the top of plant populations and by the theoretical value of total PAR energy on lamp surfaces, respectively. EUE, electric energy utilization efficiency of a closed transplant production system, was also calculated using the total electric energy consumed in the system as a denominator. Tomato seedlings on plug trays were grown for 20 days in the closed system in which air current speed and CO2 concentration were controlled at 0.53±0.07ms-1 and 1040±50 μmol mol-1, respectively, and the effect of leaf area index (LAI) of tomato seedling populations on PUEP, FUEL and EUE were investigated. The maximal values of PUEP, FUEL, and EUE during the present study were 0.10, 0.075 and 0.015, respectively, which were obtained when the LAI reached the maximal value of 2.4. The maximal value of PUEP (0.10) obtained in the present study was greater than the theoretical maximal value that Beadle and Long (1985) reported for C3 plants grown under ambient CO2 concentration. Results suggest that a closed system is energy efficient for transplant production and the efficiency could be even higher with a greater planting density and optimized air current speed and CO2 concentration.
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