Yield and postharvest performance of green onion (Allium fistulosum L.) as influenced by planting distance and fertilizer application

Green onion (Allium fistulosum L.) is known throughout the world by its culinary and medicinal properties. Its production, therefore, must be maximized through appropriate cultural management practices, including the use of optimum population density per unit area and appropriate fertilizer management. This study was conducted to evaluate the performance of green onion in response to plant density, to determine suitable fertilizer material that would optimize growth and productivity per unit area, and also to assess its postharvest quality. The experiment was laid out in a split-plot design in RCBD with three replications. The main plot consisted of the type of fertilizer material (no application of fertilizer, organic fertilizer, vermicast, and inorganic fertilizer at recommended rate) and the sub-plots were four different planting distances using a single row planting of 25×15, 15×15, 10×15 and a double-row 10×15×15 cm planting as practiced by farmers. Results revealed that the population density that maximized onion grown was a 10×15 cm spacing. This had a significantly increased plant height, number of suckers per hill and total yield ha^‑1. Application of vermicast resulted in a significant increase in, weight of bunch per hill and yield compared with other fertilizer materials. However, postharvest quality assessments showed that application of organic fertilizers significantly increased percent weight loss six days after harvest compared to plants applied with either inorganic fertilizer or with no fertilizer application, both of which had significantly lower percent weight loss. Highest return on investment (ROI) was found at the combined use of recommended dose of synthetic fertilizer and 15×15 cm planting distance to obtained an ROI of 2.59 pesos per 1-peso investment.