Effect of farmyard manure and nitrogen fertilizer rates on growth, yield and quality of onion (Allium cepa. L.) At jimma, southwest Ethiopia

Abstract

Onion is one of the most important vegetable crops produced in Ethiopia. Among different varieties ‘Bombey Red’ is the most widely accepted by farmers for its earliness. Onion is heavy feeder and requires more fertilizer than other vegetable crops. However, study on combined application of organic and inorganic fertilization to improve the yield of onion bulb is scarce. Therefore, a field experiment was conducted at Jimma University College of Agriculture and Veterinary Medicine research field from October 2011 to March 2012 under irrigation to assess the response of onion to farmyard manure and nitrogen fertilizer rates. The study consists of four levels of FYM (0, 15, 30 and 45 ton FYM ha-1 ) and four levels of nitrogen (0, 50, 100 and 150 kg N ha-1 ). The experiment was conducted in 4 × 4 factorial arrangements in a randomized complete block design with three replications. Data on growth, yield, and quality parameters were recorded and analyzed using SAS Computer Software version 9.2. Results revealed that interaction of FYM and N fertilizer significantly (P < 0.05) influenced Plant height, number of leaves, leaf lengh, maturity, average bulb weight, total yield, marketable yield, harvest index, bulb dry matter, TSS and split bulbs. However, leaf diameter, bulb length, bulb diameter and unmarketable yield were not affected by the combined application of FYM and N fertilizer. The findings highlighted that the performance of onion at Jimma area can be enhanced through application of FYM and N fertilizers. The highest bulb yield of onion (36.85 ton ha-1 ) was obtained when the plots received combined application of 100 kg ha-1 of N and 45 ton ha-1 of FYM which significantly increased the total bulb yield by about 53% as compared to the unfertilized plot (17.45 ton ha-1 ). This however was statistically similar with the combination of 150 kg ha-1 of N and 30 ton ha-1 of FYM and also150 kg ha-1 of N and 45 ton ha-1 of FYM. In this study, maximum dry bulb yield of onion (33.30 ton ha-1 ) was obtained when the plots received combined application of 150 kg ha-1 of N and 30 ton ha-1 of FYM. The highest organic carbon, organic matter, N, P and K were recorded from highest dose of farmyard manure. It can be concluded that organic fertilizer (FYM) can significantly increase the soil nutrient content. Based on these result it can be concluded that farmyard manure improves the soil organic matter, adds soil nutrients, improves soil physical properties and increases the productivity. The above findings indicated that the growth and productivity of onion at Jimma can be improved by using increased farmyard manure and nitrogen fertilizer combination. Therefore, from statistical point of view and labour requirements to prepare and apply FYM, a farmyard manure application at a rate of 30 ton ha-1 and nitrogen fertilizer at a rate of 150 kg ha-1 can be used as a recommended fertilizer combination for onion production around Jimma area. To develop robust recommendation, it will be good to repeat the experiment on soils of different characteristics, agro-ecological conditions and cost benefit analysis should be done.