Abstract
The present research work was conducted at the Spices Research Sub-Centre (SRSC), Bangladesh Agricultural Research Institute, Lalmonirhat during the period 2014 – 2016 to develop improve package for successfully summer onion bulb production. Seven experiments were conducted in the study. Results revealed that soil test basis fertilizer combination of N₁₀₀, P₃₀, K₉₀, S₃₀ & B₃ kgha⁻¹ gave the highest performance in growth, quality and bulb yield followed by recommended practices of Spices Research Centre (SRC). Rice straw mulch (3.0 tha⁻¹) conserved ideal soil moisture which enhanced the better growth and development, which gave the highest bulb yield and longer shelf life and bulb quality during different days after storage. In another experiments of fertilizer, nitrogen applied at 100 kgha⁻¹, sulfur 30 kgha⁻¹ and boron 3.0 kgha⁻¹ were observed the higher growth as well as bulb yield. Application of lime (2.0 tha⁻¹) was the best for quality onion bulb production. Maturity indices/harvest stage as 75 % leaf top fall showed positive effect on quality bulb, longer shelf life and percentage of marketable bulb. Studied long time curing (20 days under shade) showed that reduced the sprout length, sprouting, rotting, weight loss, black mould and moisture content and increased marketability, total soluble solids and dry matter of bulbs. Growth suppressant hormone Malice Hydrazaide (3000 ppm) sprayed before 15 days of harvesting reduced the sprouting, rotting and black mould resulted increase percentage of marketable bulb. The maximum yield and quality obtained from the early planting of Kharif-1 (14 February) and late planting of Kharif-2 (28 August. The maximum bulb yield was obtained from the highest plant density (10 cm × 10 cm) and the lowest bulb yield from the lower density (20 cm × 10 cm). However, from the economic point of view, 15 cm × 10 cm row-spacing was the best for summer onion bulb production which was about SRC recommended spacing (10 cm × 10 cm). Based on the results of the experiments, an improve technology for summer onion production has been suggested. The suggested package technology includes: soil test basis fertilizer combination (N₁₀₀, P₃₀, K₉₀, S₃₀ & B₃ kgha⁻¹) + 2.0 tha⁻¹ lime application + planting time (February 14 or August 28) + spacing (15 cm × 10 cm) + 3.0 tha⁻¹ rice straw mulch + 3000 ppm Malice Hydrazide (MH) before 15 days of harvesting + 75% leaf top fall of onion leaf + 20 days curing at shade house was the best treatment combination for summer onion cultivation which was superior to the SRC recommended package and the farmer's practice.