Article ID: SZD-042
Large head production systems, mainly for autumn, winter, and spring cropping, have been examined to reduce the cost of broccoli production for processing. To ensure year-round supply, the adaptability of this system in regions with summer cropping should be evaluated. Therefore, in this study, we selected cultivars suitable for producing large heads and examined the effects of harvest size, fertilizer, plant spacing, and mulching on their growth and yield in Shiojiri City, Nagano Prefecture, which is a summer cropping region for broccoli. Spring-sown cropping (harvested from June to July) and summer-sown cropping (harvested from September to November) were investigated from 2019 to 2022. Broccoli heads were enlarged even at a conventional plant spacing of 37.5 cm (planting density: 59,260 plants per ha), and mulching advanced the harvest period. However, effect of fertilizer on yield was relatively small. Among the 23 cultivars tested, ‘SK9-099’ was found to be the most suitable. The average temperature during cultivation should be below 18°C for spring-sown crops and below 22°C for summer-sown crops for best growth. Moreover, harvesting heads 20 cm in diameter yielded up to 35,000 kg per ha of florets. However, the risk of yellowing increased with increasing size; therefore, the practical harvest size should be approximately 16 cm in diameter (20,000 kg per ha), which yielded approximately three times the national average yield of 6,000–7,000 kg per ha. We also analyzed the temperature changes during transportation using different packaging methods; Styrofoam boxes with ice (SB) and two types of functional films: Pal Fresh (PF) and Xtend (XT) and investigated the quality retention period after arrival at different states (head or florets). SB transport consistently maintained the quality for over 14 days, even for larger sizes, but film packaging showed instability in terms of its cooling effect during transport, with mold observed upon arrival in some cases. Moreover, transport and storage of florets can cause serious problems, such as browning at the cut edges, making them impractical for commercial use.
