Effect of blended (NPSB) fertilizer rate on growth and yield of onion (Allium cepa. L.) varieties at Gubalafto district, North-Eastern Ethiopia

Onion (Allium cepa, L) is one of the most important vegetable crops produced as a condiment for home consumption and income sources for many smallholder farmers in Ethiopia. However, the productivity of onion is low at national as well as regional levels; due to various limiting factors such as low soil fertility and lack of improved varieties. Therefore, a field experiment was conducted to determine the effect of blended (NPSB) fertilizer rates on growth and yield of onion varieties at Gubalafto district from September 2017 to March 2018 under irrigation conditions. Two onion varieties (Bombay Red and Adama Red) were evaluated using six levels of NPSB blended fertilizer rates (0.00, 81.34, 162.68, 244.02, 325.36, and 406.70 kg ha-1) and laid out using the factorial arrangement in randomized complete block design with three replications. Data on growth and yield parameters were recorded and subjected to analysis of variance. Results revealed that days to maturity, leaf length, plant height, and the number of leaves, were significantly (p≤0.05) influenced by the main effect of NPSB blended fertilizer rate and varieties. The highest plant height (68.78 cm) was obtained from Adama Red variety when NPSB blended fertilizer was applied at a rate of 325.34 kg ha-1. Higher total bulb yield (29.58 t ha-1) was obtained from Bombay Red variety, while lower total bulb yield (25.27 t ha-1) was recorded from Adama Red variety. Since this result is based on one season and location, it is suggested to repeat the experiment at the study district, different locations, and seasons by including other onion variety. The inclusion of organic fertilizer and cost-benefit analysis also is suggested as a future line of work to make a conclusive recommendation.