Dynamic temperature integration with temperature drop to improve early fruit yield and energy efficiency in greenhouse cucumber production

High early yield is important in greenhouse cucumber production due to shortage of fresh produce and high price in the market. High temperature may increase plant growth and early fruit production. However, it is not feasible in commercial greenhouse production because it also increases heating energy costs. A large experiment was conducted in 2011 for improving cucumber fruit yield while conserving energy. Two temperature integration (TI) regimes, one without (Regular TI) and the other with a pre-night or pre-morning temperature drop (TI-Drop), were applied in 6 greenhouses, 3 replications for each regime. The plants of 5 cucumber cultivars were planted into the greenhouses in late January. For TI-Drop, air temperature was allowed to drop to 12°C during pre-night period (6 to 9 pm) from March 6 to April 20 (stage one of the greenhouse trial) and to 13°C during pre-morning period (3 to 6 am) from April 27 to May 27 (stage two) while it was maintained at 19°C (stage 1) or 18°C (stage 2) for Regular TI. The 24-h average temperature or temperature sum was the same for both TI regimes. TI-Drop increased marketable fruit yield over Regular TI in both stages of the greenhouse trial on most of the cultivars tested in this research without additional (even slightly less) energy use. Therefore, the new dynamic temperature integration regime with a pre-night or pre-morning temperature drop (TI-Drop) is an energy efficient climate control strategy for greenhouse cucumber production.