Abstract:
Onion (Allium cepa, L.) is one of the most important vegetable crops grown in Ethiopia for
consumption and sources of income for many small and large scale farmers. However, due to
Nutrient management, lack of improved varieties, poor agronomic practices and pests are
the most critical causes of low production and productivity of onion in Gamo Zone.
Therefore, field experiment was carried out to the effect of blended (NPSB) fertilizer rates on
the growth and yield of onion varieties in the Mirab Abaya district from December 2021 to
June 2022 under irrigation. The experiment was laid out in randomized complete block
design (RCBD) with three replications in 3x5 factorial arrangements: three onion varieties
(Bombay Red, Red Creole and Melkam) and five levels of blended NPSB fertilizer rates (0,
150, 250, 350, and 450 kg ha-1). The data on growth and yield characteristics were collected
for two rounds. The growth data was taken after four months and yield data was collected at
time of harvest. The result revealed that the two main factors, variety and blended NPSB
fertilizer rates had significant effect on all parameters considered in this study. The
interaction of variety and blended NPSB fertilizer rates had significant effect on growth
parameters (plant height, leaf length and leaf number), and yield parameters (bulb weight,
marketable, unmarketable and total bulb yield). However, the interaction of two factors had
non-significant effect on bulb length in yield parameter. Melkam variety was the beast one
compere to Bombay Red and Red Creole variety in our growth and yield parameters. The
application of 350 kgha-1 blended NPSB fertilizer rate was the beast in our growth and yield
parameters. On the other hand, Melkam variety with the application of 350kg ha-1 blended
NPSB rate fertilizer showed the highest marketable bulb yields and total bulb yields was
42.33tha-1 and 42.35tha-1 respectively. Furthermore, economic analysis indicated that
Melkam variety with the application of 350kg ha-1 blended NPSB fertilizer rate resulted in
the highest net benefit with acceptable marginal rate of return. Generally, application of
350kgha-1 blended NPSB fertilizer rate over Melkam onion variety would promote the growth
and yield components of onion in the study area. However, the result of this study is from one
season work and further specific field studies need to be conducted in different seasons
across multi location for sound recommendation.
