Agronomic and Economic Evaluation of Nitrogen Fertilizer Rates and Intra Row Spacing on Growth and Bulb Yield of Onion (Allium cepa L.) under Rainfall Condition

Abstract

A field experiment was conducted at Shire,  Lemlem demonstration farm under rainfall condition to study the impact of nitrogen (N) fertilizer rates and intra row spacing on growth bulb yields and profitability of onion (Allium cepa L.). Treatments consisted of factorial combination of four rates of N fertilizer (0, 50, 100 and 150 kg ha^-1) and four intra row spacing (4, 6, 8, and 10 cm). The experiment was laid out as a Randomized Complete Block Design with three replications. The result of this study revealed that the interaction effect of N and spacing affected days to maturity and plant height. The main effect of N significantly affected most of the studied parameters while spacing affected number of leaves and yield. Days to maturity of onions were prolonged in response to the increased rate of nitrogen application. Increasing nitrogen from the nil to 150 kg N ha^-1 decreased bolting percentage by 62%. Increasing the rate of nitrogen from 50 to 100 kg N ha^-1 increased the total bulb yield and leaf number by about 26.7% and 29% respectively. However, increasing the rate of N further from 100 to 150 kg N ha^-1 tended to decrease total bulb yield by 5.3 %. Higher marketable yield of 31.455 t ha^{- 1} were obtained at 100 kg N ha^.-1. The result of partial Budget analysis showed that 100 kg N ha^-1 combined with 6 cm intra row spacing was found the best treatment than others in relation to bulb yield and economic benefits under the condition of Shire, northern Ethiopia.

Keywords: Nitrogen, Intra row spacing, Onion Bombay Red, Growth and Yield