Effects of Different Nitrogen and Sulfur Fertilizer Rates on Growth, Yield, Quality and Nutrient Uptake of Onion (Allium cepa L.) at Shewa Robit, North Shewa, Ethiopia

Abstract

Onion is one of the most important crops widely cultivated throughout the world, including Ethiopia. The production of onion is mainly affected by the inadequate application of inorganic fertilizer types and rates. A field experiment was conducted to evaluate the effect of nitrogen and sulfur fertilizers on the growth, yield, quality, and nutrient uptake of onion at Shewa Robit in 2018/19 under irrigation. The experiment consisted of four nitrogen rates (100, 150, 200, and 250 kg N /ha) and five sulfur rates (0, 15, 30, 45, and 60kg S/ha). The treatments were laid out in a factorial arrangement with three replications using randomized complete block design (RCBD). Bombay Red was used as a testing onion variety. The interaction effect of nitrogen and sulfur significantly increased plant height, leaf length, leaf diameter, leaf area index, neck diameter, shoot dry weight, bulb fresh weight and bulb dry weight, percent dry matter content, yield, and quality parameters. The application of 200kg N/ha and 45 kg S/ha resulted in the highest yield (42.6 t ha-1), the average weight of bulb (193.6g), and a marketable bulb (99.8%). The highest N uptake (243.3 kg ha-1) and S uptake (31.9kg ha-1) were obtained by the combined application of 200 kgN/ha and 45kg S/ha. The application of 200 kgN/ha and 45kgS/ha can be recommended for high yield and quality onion production in the study area.