Effect of planting time on growth, yield components, seed yield and quality of onion (Allium cepa L.) at Tehuledere district, northeastern Ethiopia

Abstract Background Onion (Allium cepa L.) is member of the family Alliaceae and the most widely grown herbaceous biennial vegetable crop. Quality planting material is one of the major inputs to successful vegetable production. However, it is one of the major constraints in Ethiopia. Northeastern Ethiopia has suitable agro-climatic condition for onion seed production. However, onion seed production packages, including its appropriate planting time, are not yet determined. Evidences on effects of the different planting time on quality and yield level are not well explored. Therefore, this experiment was conducted at Jari small-scale irrigation scheme from September 2015 to April 2016 to determine an appropriate planting time for a better plant growth, yield components, seed yield and quality of Adama red onion variety. Methods The experiment was laid out in randomized complete block design with three replications. Treatments were nine planting dates: September 1st, September 16th, October 1st, October 16th, October 31st, November 15th, November 30th, December 15th and December 30th. Data were collected on growth, yield components, seed yield and quality parameters and analyzed using SAS version 9.2 statistical software. Results Analysis of variance revealed that plant height, number of leaves per plant, number of scapes per plant, scape diameter, scape height, days to 50% flowering and maturity, umbel diameter, number of seeds per umbel, 1000-seed weight, seed yield and germination percentage were significantly influenced by planting time. The highest seed yield (1032.7 kg/ha) and the highest germination percentage (94.3%) were recorded from bulbs planted early (September 1st). On the other hand, the lowest seed yield (29.7 kg/ha) and germination percentage (15.3%) recorded from bulb planted late (December). The correlation values explain the apparent association of the planting time parameters with each other and clearly indicated the magnitude and directions of the association and relationships. Conclusion The September 1st is recommended as appropriate planting time for onion seed production at Jari, northeastern Ethiopia