Effect of Transplanting Date and Harvesting Period on Bulb Production of Winter Onion (Allium cepa L.)

Climate change has brought about unpredictable temperature fluctuations and altered rainfall patterns, which directly impact onion cultivation. Adjustment in planting and harvesting schedules in the context of changing climate and environmental factors is not only academically significant but also holds practical implications for agriculture, resource management, climate adaptation, economic development, and food security in Bangladesh. The present study was carried out to observe the influence of the transplanting and harvesting time on maximizing onion production. The experiment followed a RCB design with three replications, involving the cultivation of BARI Piaz-1 as the test crop with varying transplanting dates on November 1st, November 15th, and December 1st, and harvesting periods at 120, 130, and 140 days after planting (DAP). The study's results indicated that the choice of transplanting date and harvesting period had significantly influenced onion yield and yield attributes. Improved performances, including increase in plant height, number of leaves per plant, neck diameter, bulb diameter, bulb length, bulb weight, and overall yield were observed when onions were transplanted on November 15th and harvested after 130 days from planting. The highest yields, specifically 10.32 t/ha in 2018 and 11.33 /ha in 2019, were achieved under this conditions. Conversely, the lowest yields 6.28 t/ha in 2018 and 6.70 /ha in 2019 were obtained when onions were transplanted on December 1st and harvested after 120 days from planting. Additionaly, early planting (November 1st) exhibited a higher incidence of bolting, while late planting (December 1st) showed a higher disease incidence. Therefore, optimizing transplanting dates to align with November 15th and a 130-day harvesting period proved to be the most effective strategy for maximizing onion yield and other attributes, while late planting and early harvesting adversely affected these key attributes.