Effects of Different Levels of Nitrogen, Phosphorus and Potassium Fertilization on Growth and Yield of Onion (Allium cepa L.) at Jimma, South Western Ethiopia

Abstract

Onion (Allium cepa L.) is one of the most important vegetable crops produced in Ethiopia. Yield and productivity of the crop has been far below the regional and national standards owing to several factors; absence of location specific fertilizer recommendation being the major among others. Thus, a field experiment was conducted at Jimma University College of Agriculture and Veterinary Medicine Research field in dry season to study the effects of Nitrogen (N), Phosphorus (P) and Potassium (K) fertilizer on growth and yield of irrigated onion under Jimma condition, South Western Ethiopia. The treatments consisted of factorial combinations of four levels of Nitrogen (0, 50, 100 and 150 kg N ha^-1), three levels of Phosphorus (0, 46, and 92 kg P₂O₅ ha^-1) and four levels of Potassium (0, 40, 80, and 120 kg K₂O ha^-1) laid out in Randomized Incomplete Block Design with three replications. Data on growth and yield parameters were recorded and analyzed using GenStat 12.1 version computer soft ware packages. Results of the study revealed that; N, P and K had shown a highly significant effect on growth, yield and yield parameters like plant height, leaf diameter, leaf length, number leaves per plants, leaf sheath length, harvest index, mean bulb weight, bulb length, bulb diameter and on quality parameters like TSS (^oBrix), DMC (%) and bulb shape index. The higher total bulb yield per hectare (18.78 ton) was recorded with combined application of 150:92:120 kg of N-P-K ha^-1 and it is statistically the same with the results obtained in the combined applications of 150:46:120 and 150:46:80 kg of N-P-K ha^-1 which were significantly superior over the rest of other treatments. This can be recommended for use by potential onion investors or farmers with high initial capital in the study area. Nevertheless, more researches are needed in different locations and on different soils to come up on general recommendation.

Keywords: Growth, Nitrogen, Onion, Phosphorus, Potassium, Yield