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In a semi-arid environment, the main challenge for crop production is water deficit. FAO’s AquaCrop model, which simulates yield response to water, has been calibrated to explore alternative water management strategies in teff crop. To calibrate and evaluate this model, we used independent data sets of the cropping season 2008 and 2009 in the northern Ethiopia. The teff crop cover, biomass and soil water simulated by the model agreed well with the observed data. The model revealed that the grain-water use efficiency of teff increased when supplementary irrigation after start of flowering was increased from 0 to 95 mm. The biomass-water use efficiency showed the opposite trend: it decreased. The implication of these results is that if land is not a constraint, and if the intention is to grow teff for its biomass, the best option is to use the available water to grow teff with deficit irrigation. But when the major intention is to produce grain, the best option is an optimum irrigation application. It is concluded that the AquaCrop model can be used to explore management options to improve teff water productivity in the area. (C) 2009 Elsevier B.V. All rights reserved.