Abstract:
Onion (Allium cepa L.) is one of the most predominantly produced bulb crops in East Hararghe. The productivity of onion in the study area was mainly below the national average due to a number of production constraints, including a lack of specific fertilizer recommendations, depletion of soil fertility, improper agronomic practices, a lack of improved onion varieties and a lack to access seed, are generally to blamed for reduced bulb yields. To create management plans that maximize fertilizer use of the crop and boost returns with quality bulb characteristics to the producer, a better understanding of the nutrient requirements of improved onion varieties is necessary. Therefore, this research was conducted to determine the effect of blended NPS fertilizer rates on growth, yield components, yield and bulb quality traits of onion varieties and to estimate economically feasible blended NPS fertilizer rates for onion production at Haramaya, East Hararghe. The experiment was arranged in factorial combination of six rates of NPS fertilizer (0, 50, 100, 150, 200, 250 kg ha-1) and three onion varieties (Nasik Red, Sirius F1 and Red coach F1) in a Randomized Complete Block Design with three replications. Data were collected and analyzed using Genstat software (18th edition). The analysis of variance revealed that variety and NPS fertilizer had significant effect on crop phenology, growth, and yield components such as plant height ,leaf number per plant, leaf length, days to physiological maturity, above ground dry biomass, bulb length, bulb diameter and harvest index(HI). The interaction of variety and blended NPS fertilizer showed significantly differences on bulb neck thickness, mean bulb weight, total dry biomass yield, marketable, unmarketable and total bulb yield, TSS and percentage of bulb dry matter. The highest mean bulb weight (219.93 g),bulb dry matter percentage (16.42% ),marketable bulb yield (57.23 t ha-1) and total bulb yield(58.35 t ha-1) were obtained from Red coach F1 at rate of 200kg ha-1 NPS fertilizer. The highest total soluble solids (TSS) 12.8oBrix were recorded from Nasik variety at the application rate of 250 kgha-1 of NPS fertilizer. The maximum net benefit Birr 739,658.5 was obtained from Red coach F1 with the acceptable MRR of 2435 at 200 kg ha-1 NPS fertilizer application rate. Therefore, production of Red Coach F1 with application of 200 kgha-1 NPS fertilizer could be recommend for producers at Haramaya as well as other areas having similar agro-ecologies. It is suggested that the experiment to be repeated over seasons and locations to recommend and use the output sustainably. The experiment could be combined with organic fertilizer and other improved variety in different agro-ecological condition may reflect the yield performance