Effects of CO2 Enrichment on the Cut Flower Quality and Economic Efficiency of Eustoma grandiflorum (Raf.) Shinn. During the Winter Season Production in a Mild Climate Region with High Sunshine in Japan

Abstract

We investigated the effect of CO2 enrichment on the cut flower quality and profitability during the winter season production of Eustoma grandiflorum (Raf.) Shinn. in a mild climate region with a long sunshine duration in Japan. This study aimed to elucidate the benefits of CO2 enrichment in the area, where plants are grown in a greenhouse with high ventilation frequency owing to the mild weather conditions. Plants were cultivated under two greenhouse conditions: one was subjected to CO2 enrichment, and the other was control (without CO2 enrichment). CO2 was supplied during the day (from 8:00 to 15:00). The CO2 concentration setting in the CO2-enriched greenhouse was switched by closing and opening the ventilating windows; the concentration was 700 nmol mol when the windows were closed and 430 nmol mol when the windows were open. The average CO2 concentration in January with strong solar radiation from 10:00 to 15:00 was about 200 nmol mol higher in the CO2-enriched greenhouse than in the control greenhouse. Similarly, in March, the average CO2 concentration in the CO2-enriched greenhouse was 100 nmol mol higher than that in the control. CO2 enrichment improved the cut flower quality: the fresh weight of plants and diameter of main stem were increased. Therefore, the incidence of obtaining the highest-grade cut flower increased. CO2 enrichment also improved the shipping rate. Even after the production cost was considered, CO2 enrichment provided remarkable profit increase. The extent of profit depends on the cultivar and transplantation date. Thus, CO2 enrichment under a winter culture regime was effective for improving profitability in the mild climate region with a long sunshine duration in Japan.