GROWTH AND YIELD OF ONION (Allium cepa L.) AS AFFECTED BY VARIABLE RATES OF POULTRY MANURE AND MINERAL NITROGEN FERTILIZER AT ALAGE, CENTRAL RIFT VALLEY OF ETHIOPIA

Abstract

Onion is one of the important vegetable crops produced in many home gardens and in some extent commercially in different parts of Ethiopia. However, the average yield of the crop is low compared with the world average yield. Declining soil fertility and lack of information on appropriate fertilizer type and rates are the most important factors attributing for the low yield of onion in Ethiopia. Therefore, the field experiment was carried out at Alage Central Rift Valley of Ethiopia, during 2018/19 cropping season, with the objectives of assessing the growth, yield and quality response of onion to the variable rates of poultry manure and mineral nitrogen fertilizer. The experiment comprising of three nitrogen levels (0, 46 and 92 kg ha -1 ) and four levels of poultry manure (0, 5, 10 and 15 t ha -1 ) were laid out in randomize complete block design with three replications. Data on plant growth, yield and quality components were collected and subjected to ANOVA using SAS (9.2 version) software. The main effects of poultry manure and nitrogen fertilizer significantly affected the leaf length, leaf number, days to maturity, bulb length, unmarketable bulb yield and bulb dry matter content, except total bulb yield and marketable bulb yield. Plant height, bulb diameter and harvest index were significantly affected by the interaction of poultry manure and nitrogen fertilizer levels. Application of poultry manure at the rate of 15 t ha -1 recorded the highest total bulb yield (63.33 t ha -1 ) and marketable bulb yield (62.52 t ha -1 ), but statistically there were no x significant difference between 15t ha -1 and 10t ha -1 poultry manure application. Lower amount of total bulb yield (53.44 t ha -1 ) and marketable bulb yield (52.40 t ha -1 ) were obtained from the control plot as compared to the maximum yields obtained from other treatments. Marketable bulb yield was positively and significantly correlated with most of the growth parameters. The results of partial budget analysis showed that 15 t ha -1 poultry manure application gave the highest marginal rate of returns. Since, the highest bulb yield and maximum marginal rate of returns are obtained at 15 t ha -1 poultry manure application, this rate can be recommended for onion production in the researched area, and areas having similar agro-ecologies. However, as the research is conducted for a single season and location, repeating the experiment over location and year will be required to give a conclusive recommendation.