Abstract:
Farmers of Hararghe highland practice rain-fed onion cultivation, which is suffering from poor soil fertility caused by undulating topography that is prone to erosion and sub-optimal chemical fertilizers resulted for low yields of crop. Therefore, this research was designed with the objectives of assessing the effects of planting method and integrated nutrient management (VC and RDF) on growth, yield and yield attribute of onion at Oda Bultum University, West Hararghe, Ethiopia during 2022 main cropping season. The experiment consisted six levels of nutrients (control, 100% recommended fertilizer (RDF), 2.5 and 5 t ha-1 VC combined with 50% or 75% RDF) and three methods of planting (flat, raised and ridge-furrow). The treatment combinations were arranged using split plot design by considering planting method as main plot and the fertilizers as subplot. The analysis of variance revealed that most of the studied parameters were significantly (P<0.05) influenced by main effects of planting method whilst integrated nutrient management showed highly significant (P<0.01) effects. The highest plant height (66 cm, and lowest bolter plants (1.06%) were recorded from plant grown on ridge-furrow and treated with 5 t ha-1 VC and 50% RDF whereas the highest above ground (4.23 g) and total dry biomass (23.96 g) per plant were obtained from ridge-furrow supplied with 5 t ha-1 VC and 75% RDF. On the other hand, the highest leaf length (47.63 cm), leaf number per plant (10.6), bulb diameter (6.2 cm), bulb length (7.072 cm), mean bulb weight (77.3 g), days to maturity (115.78), bulb dry matter (18.63%), harvest index (HI) (80%), marketable yield (27.12 t ha-1) and total bulb yield (28.59 t ha-1) were recorded from ridge-furrow whereas the highest unmarketable bulb yield (1.89 t ha-1) was recorded from raised planting method. Similarly, longest leaf (46.33 cm), leaf number (10.9), days to maturity (118.56), bulb diameter (6.1cm), mean bulb weight (78.9 g), HI (81.25) and marketable yield (27.64 t ha-1) were recorded from plants that received 5 t ha-1 VC and 50% RDF. The highest adjusted marketable bulb yield (24.4 t ha-1) and highest net benefit (329632.6 Birr) with acceptable MRR (883.65%) obtained from ridge-furrow whereas net benefit 260987.37Birr with 9537.36% MRR was obtained from integration of 5 t ha-1 VC plus 50% RDF. Thus, it is inferred that ridge-furrow planting method with application of 5 t ha-1 VC and 50% RDF seems be appropriate for Bombay Red onion producing farmers in the studied area as well as other areas having similar agro-ecologies.
