Optimizing mechanical transplanting in intermediate-day onions: impacts of mulching and winter cover on yield and quality

Abstract:

This study was conducted to evaluate the effects of mechanical transplanting, mulching/covering methods, and cultivar selection on the growth and bulb yield of intermediate-day onions (Allium cepa L.). Field trials were performed during 2018/2019 and 2019/2020 growing seasons. The growing methods included mechanical transplanting under polyethylene mulch (MTPEM), mechanical transplanting under no mulch and nonwoven polypropylene covering in winter (MTNWPPC), mechanical transplanting under no mulch (MTNM), and hand transplanting under polyethylene mulch (HTPEM). Ten cultivars widely grown in major onion-producing areas were selected for this study. Stand reduction of ten cultivars in the seedling tray ranged from 6.9% to 23.2%. MTPEM significantly enhanced bulb weight and marketable yield compared to other growing methods, despite a significant stand reduction of 23.5% in the main field. MTNWPPC achieved 82.0% of the bulb yield obtained under MTPEM, while simultaneously improving scale quality- including the number of intact rings and centers, and enhancing storage stability. Among the cultivars, ‘Powerball’, ‘Bigbang’, and ‘Bridger’ produced marketable yields exceeding 100.0 Mg ha^-1 under MTPEM. However, ‘Honors’ and ‘Daehwang’ performed best under MTNWPPC, yielding over 85 Mg ha^-1. Additionally, ‘Healthy Q’ and ‘Bridger’ showed higher number of scales, number of intact rings and dry matter content, resulting in lower storage loss. These results suggest that mechanical transplanting without mulching, combined with NWPP covering during winter, is an effective onion production system for ensuring stable productivity, superior bulb and storage quality and potential for reduced labor inputs. Future cultivar selection should prioritize high emergence rates and high yields for mechanical transplanting under non-mulched conditions.

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