The objectives of this study were to evaluate the yield of different types of cucumbers from the perspective of yield components. The yield and yield components of nine cucumber cultivars (Beit Alpha, Greenhouse, and Japanese) grown hydroponically in a greenhouse were investigated. Fruit yield fresh weight in the Beit Alpha type was higher than that of the Japanese type, and the fruit yield fresh weight was significantly correlated with fruit yield dry weight, total dry matter (TDM), fraction of fruits, and number of fruits. However, the fruit yield fresh weight was not significantly correlated with intercepted light, light use efficiency (LUE), leaf area index, light extinction coefficient, and fruit dry matter content. High fruit yield dry weight was associated with a high TDM and the fraction of fruits. Moreover, the high TDM and fraction of fruits were associated with LUE and the number of fruits, respectively.

In this study, we aimed to estimate dry matter (DM) production and fresh fruit yield in “Fresco-dash” (FD) and “Project X” (PX) cucumber cultivars using an empirical model developed for tomatoes. First, we cultivated the two cucumber cultivars under a hydroponic system for about six months. Also, parameters related to DM production such as light use efficiency (LUE), light extinction coefficient (k), DM distribution of fruits (DMD), and fruit dry matter content (DMC) were measured via destructive measurements. The k, DMD and DMC values were 0.99 and 0.93, 46.0 and 45.2, 3.84 and 3.78 in “Fresco Dash” and “Project X”, respectively. Second, we cultivated cucumbers to estimate DM production and fruit fresh yield using the model without destructive measurement for about eight months and validated the model’s effectiveness. The predicted DM fell within the range of the observed DM ± standard error at 51 and 132 d after transplantation (DAT) in PX as well as 51 (DAT) in FD. The predicted and observed DM at 163 DAT were 2.08 and 1.82 kg m⁻², 2.09 and 1.87 kg m⁻² in “Fresco Dash” and “Project X”, respectively. The predicted and observed fruit yield at 200 DAT were 30.3 and 31.7, 30.5 and 29.1 in “Fresco Dash” and “Project X”, respectively, which were 4.4% lower than the observed fruit yield in FD and 4.9% higher than that in PX. These results suggest that the model applies to cucumbers in predicting dry matter production and fresh fruit yield.

In Japan, greenhouse cucumber production is generally conducted as either a long-term, one cropping system or a short-term, two cropping system; short-term cultivation requires time for crop replacement, which may result in lower yields. It is important to increase plants’ intercepted light to increase yield, which requires maintaining a high leaf area index. In this study, a new training method (separating method), in which the sink and source are separated, was developed for the short-term cultivation of cucumber (Cucumis sativus L.) under greenhouse conditions. In the separating method, the main stem had only leaves and the lateral branch had only fruits. The main stem was trained vertically and pinched when it reached a 1.8 m high training wire, while the lateral branch continued to grow horizontally at approximately 40 cm above the floor. A hydroponic system was used from October 2020 to February 2021. During this period, we assessed the yield productivity of the new training method and compared it with that of the lowering method (training method for growing the main stem without pinching) based on yield components. We observed that the fresh yield of the separating method was lower than that of the lowering method owing to a decrease in the number of fruits as result of fruit picking from the main stem. Conversely, total dry matter under the separating method was higher than that under the lowering method, and this could be attributed to the greater increase in leaf area index under the separating method. In terms of photosynthetic rate, values for the upper leaves were lower than those for the lowering method in the separating method approximately one month after pinching. These results suggested that the separating method could produce yields comparable to those of the lowering method in short-term cultivation. In addition, this method may contribute to mechanical harvesting because the fruit is always in a fixed location.