Abstract
The dynamic nature of soil fertility status across different landscapes attracted research attention in Ethiopia and the globe. Teff [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 2020 and 2021 in the Habru district of Amhara Region to determine teff yield response to fertilizer-N and -P at hillslope, midslope, and footslope positions with slopes of >15%, 5-15%, and 0-5%, respectively. N and P fertilizer rates were factorially combined in randomized complete block design with three replications in each farmer's field. A linear mixed modeling framework was used to determine effects on grain yield due to N rate, P rate, slope, study sites, and years. Model fit was examined using Akaike's Information Criterion and Bayesian Information Criterion. Economic analysis was done with a quadratic response function to determine the economics of fertilizer. Yield response to fertilizer-P was affected by slope but the response to fertilizer-N was not affected. Teff yield increase with fertilizer-N application up to 92 kg ha(-1) the economic optimum rate based on the yield response function for nitrogen fertilizer was 85.4 kg ha(-1) to obtain maximum profit (86878.8 birr ha-1). Similarly, the optimum phosphorus fertilizer rate at the hill slope was 39.7 kg ha(-1 to) obtain a maximum profit of (96847.8 birr ha(-1)). But there was not a profitable response at the midslope and foot slope positions. Therefore, for Habru district and similar agroecologies85.4 kg ha(-1) N and 39.7 kg ha(-1) P in hillslopes and only 85.4 N kg ha(-1) for midslopes and foot slopes are expected to give the most profitable returns to fertilizer applied for tef production.