Abstract:
Onion (Allium cepa L.) is an important vegetable crop in Ethiopia. However, the yields of
the bulb crop as well as seed are often constrained by low and imbalanced nutrient supply
in soil particularly nitrogen and phosphorus. Therefore, a field experiment was conducted
at the research station of Shire-Maitsebri Agricultural Research Center (SMARC), located
in Tselemti Woreda to study the effect of inorganic NP fertilizers and vermicompost on
growth, seed yield and seed quality of onion (Allium cepa L.) during 2016/17 dry season
under irrigation. Bombay Red onion variety was used for the study. The treatments
consisted of five NP fertilizer rates {0, 17.25 N: 23 P2O5 (25 %), 34.5 N: 46 P2O5 (50 %),
51.75 N: 69 P2O5 kg ha-1 (75 %) and 100 % of recommended NP rates (69 N: 92 P2O5 kg
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. Data were collected on phenology and plant growth, seed yield, and seed
quality. The results revealed that days to bolting, days to 50 % flowering, stand count
percentage, number of umbels per plant, umbel diameter, number of seeds per umbel, seed
weight per umbel and thousand seed weight were significantly affected by the main effect
of NP fertilizer rates and vermicompost. Days to maturity was highly significantly
influenced by the main effects of NP fertilizers (P<0.01) but, not significantly influenced
by the main effect of vermicompost. The interaction effect of NP fertilizers and
vermicompost had significant (P<0.05) effect on plant height. The highest seed yield per
hectare (1462.5 kg ha-1) was obtained from the plants grown at 51.75 N: 69 P2O5 kg ha-1
with vermicompost at 2.5 t ha-1 which was about 263% higher than seed yield from
unfertilized control plot. Purity seed test was significantly (P<0.05) improved by NP
fertilizers and vermicompost. The interaction effect NP fertilizers and vermicompost also
improved germination percentage, speed germination, seed vigour I and II. The highest net
benefit (Birr 443693.5 ha-1) was recorded from application of 51.75 N: 69 P2O5 kg ha-1
with 2.5 t ha-1 vermicompost. It can, thus, be concluded that the combined application of
51.75 N: 69 P2O5 kg ha-1with vermicompost at 2.5 t ha-1can improve growth, yield, and
quality of seed of Bombay Red onion variety in the study area.
