高垣 美智子

Harvest time is one of the key factors for obtaining high-quality cherry tomatoes. This parameter depends on environmental conditions and tomato variety. In plant factories with artificial lighting (PFALs), it is possible to control environmental conditions to enhance tomato production and quality. Since the ripening status of tomato fruit is correlated with cumulative temperature (CT), and the temperature inside PFALs can be easily controlled, CT could be used as an alternative method to predict tomato harvest time. In this study, three experiments were conducted to determine the optimal CT for harvesting high-quality cherry tomatoes in a PFAL. The experiments aimed to (1) evaluate the yield and quality of cherry tomatoes as affected by different harvest times based on CT (ranging from 900 to 1400 °C), (2) comparatively evaluate the yield and quality of cherry tomatoes that were still on the plant and off the plant (in storage) based on the same CT levels (i.e., 1100, 1200, and 1300 °C), and (3) investigate the fruit-cracking percentage during the ripening stage based on CT levels. The results showed that the fruit harvested at lower CTs exhibited higher hardness values, while those harvested at higher CTs had a higher sugar content. The on-the-plan treatment resulted in a higher yield and sugar content compared with the off-the-plan treatment, indicating that harvesting tomatoes early would come at the expense of a certain yield and sweetness. Moreover, the fruit-cracking percentage tended to increase with increasing CT, possibly due to the fast fruit growth rate and increased internal turgor pressure. These results indicated that producers can use CT as an index to predict the harvest time, thereby optimizing profits in cherry tomato production.

Calendula is an edible flower with highly beneficial bioactive compounds for human health. Environmental factors such as light influence flower yield and quality. Calendula is cultivated under controlled environments in plant factories with artificial lighting (PFALs), which enhance its productivity. However, electricity is the main operating cost, with fees based on the time of use in some countries. This study aimed to investigate the effects of lighting patterns on calendula growth and yield. Two varieties of calendula seedlings were cultivated in a PFAL and subjected to six different lighting patterns, i.e., 6 h/6 h, 12 h/12 h, 6 h/2 h, and 18 h/6 h (light/dark) and two continuous lighting patterns with varying light intensities (24 h-200 and 24 h-400). The results indicated that plants cultivated under the 6 h/2 h, 18 h/6 h, 24 h-200, and 24 h-400 conditions showed a more rapid appearance of the first flower bud than those cultivated under the 6 h/6 h and 12 h/12 h conditions. The number of flowers and the fresh and dried weights tended to increase with a longer photoperiod. Interestingly, the total carotenoid content (TCC) of “Citrus Orange” increased under 6 h/6 h and 12 h/12 h conditions compared with the others. For “Orange Gem”, continuous lighting (24 h) increased the total phenolic content (TPC) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity in flowers compared with the 6 h/6 h 12 h/12 h, and 6 h/2 h treatments. The energy use efficiency (EUE) under the 24 h-200 condition was the highest in terms of flower yield and secondary metabolite production. These results suggest that lighting patterns can be used to modulate the growth and flowering of calendula and to maximize EUE.

This study explores organic hydroponic cultivation as a sustainable alternative to chemical fertilizers amid global supply challenges. With rising costs and the depletion of conventional nitrogen sources, organic liquid fertilizers are gaining attention for their microbial enrichment processes (MEP) that convert organic matter into plant-accessible nutrients. This experiment focuses on lettuce cultivation using two organic liquid fertilizers, Power Fish and POF vol. 2, in controlled environments. The results show that there are significant differences in plant growth parameters such as leaf number, fresh weight, chlorophyll content, and root length across different fertilizer treatments. Key findings include that effective management practices, including pH control and regular nutrient application, are crucial for maintaining microbial activity and optimizing nutrient uptake efficiency. Additionally, Bacillus sp. and Xanthomonas sp. were isolated from these fertilizers and dual-cultured with rot fungi, Pythium sp. and Fusarium sp. This dual cultivation demonstrated inhibitory activity against these pathogens, showcasing the potential of these microorganisms in promoting biofilm-mediated disease resistance in organic hydroponic systems. The study also emphasizes the phosphate solubilization capabilities of isolated bacteria, essential for sustainable nutrient cycling. Overall, organic hydroponic systems present a promising strategy for sustainable agriculture, reducing dependency on chemical inputs while enhancing crop productivity and resilience to environmental stressors.