Effect of inorganic NP fertilizers and vermicompost on growth, seed yield and yield components of onion (Allium cepa L.) at Maitsebri, northern Ethiopia

The NP fertilizer or organic resources alone may not provide sufficient amounts or may be unsuitable for alleviating specific constraints to crop production. Therefore, a field experiment was conducted at Maitsebri Research Station of Shire-Maitsebri Agricultural Research Center (SMARC) to study the effect of inorganic NP fertilizers and vermicompost on growth, seed yield and yield components of red onion (Allium cepa L.) variety during 2016/17 dry season under irrigation. The treatments consisted of five NP fertilizer rates {0, 25, 50, 75 and 100% of recommended NP rates (69 kg N and 92 kg P2O5 ha-1)} and four rates of vermicompost (0, 2.5, 5.0, 7.5 t ha-1). The experiment was laid out in a factorial arrangement using randomized complete block design (RCBD) with three replications. Results of the analysis revealed that the interaction effects on inorganic NP fertilizer and vermicompost significantly (P<0.05) affected plant height. Days to bolting, days to 50% flowering, flower stalk diameter and days to maturity were significantly (P<0.05) affected by the main effect of NP fertilizer rates and vermicompost. Similarly, numbers of umbels per plant, umbel diameter, number of seeds per umbel and seed weight per umbel were significantly affected by the main effect of NP fertilizer rates and vermicompost. The highest seed yield per hectare (1462.5 kg ha-1) was obtained from the plants grown at 75% of RDF with vermicompost at 2.5 t ha-1 which was about 263% higher than seed yield from unfertilized control plot. It can, thus, be concluded that the combined application of 75% of RDF with vermicompost at 2.5 t ha-1can improve growth, seed yield and yield components of Bombay red onion variety in the study area. Key words: Growth, onion, NP fertilizers, parameters, seed yield, vermicompost.