Tef [Eragrotis tef] is a major staple cereal crop in Ethiopia but yields are low due to inadequate nutrient supply and other constraints. A field study was conducted in 2014 and 2015 in Jamma district of South Wollo Zone of Amhara Region to determine the economic optimum rate of fertilizer-N for tef. Fertilizer-N rates of 0, 23, 46, 69, 92, 115 and 138 kg ha-1 were evaluated. The randomized complete block design with three replications was used. The fertilizer-N rate means fit a quadratic yield response function with R2=0.25**. The maximum mean grain and straw yields were recorded with 138 kg N ha-1 which was not statistically different from the 92 and 115 kg ha-1 N rates. The net economic returns to N were optimized with the 115 and 92 kg ha-1 N rates with respective net benefits of Ethiopian Birr 30508 and 28971 ha-1 and with marginal rate returns of 236 and 288%, respectively. The highest value to cost ratio (VCR) and highest benefit to cost ratio (BCR) of 10.9 and 5.2, respectively were obtained with 46 kg N ha-1. Using the yield response function determined, the profit-maximizing optimal rate of N was found to be 117 kg N ha-1. Therefore, for financially constrained farmers 46 kg N ha-1 is recommended, while for farmers without financial constraints 92 to 117 kg N ha-1 can be recommended for economic optimum return from tef production on the Vertisols in Jamma District and similar agroecologies.
Key words: Economic optimum, Jamma district, nitrogen fertilizer, yields response of tef.
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