In order to adapt the wheat model for tef, changes were made to the phenology, photoperiod response, radiation use efficiency, and transpiration efficiency for both standard and elevated atmospheric CO 2 based on published research for tef and other C4 crops, such as sorghum, maize, and millet. The major differences between tef and wheat are that tef is a short-day C4 crop, while wheat is a long-day C3 crop. The parameters and structures of DSSAT-NWheat were preserved unless the literature suggested a significant difference between tef and wheat. The NWheat model was selected, instead of a C4 crop model like DSSAT-Sorghum, as a starting point, because of its robust model structure, which has been successfully applied to many different growing conditions around the world. The tef crop model was created using the DSSAT-NWheat model as a basis. In addition, the AquaCrop tef model was not developed to take differences in daylength into account, limiting its application to low latitudes. This limits its application in Ethiopia, where soil degradation and low levels of fertilizer use cause nutrient limited growing conditions. The AquaCrop tef model was designed for water limited growing scenarios and therefore does not directly take soil nutrients and fertilizer management practices into account. A crop specific harvest index is then used to calculate the grain yield based on the simulated biomass production. The second tef model, the FAO’s AquaCrop model, simulates biomass production using the daily crop transpiration and the normalized crop water productivity. The FAO-AEZ model also only produces yields at maturity, and not the dynamic daily changes in yields, which restricts its applications. As growing season length is treated as an input, the model cannot simulate the effects of temperature, or day length, on phenology. The FAO-AEZ model has certain limitations. Each yield is calculated based on the yield of the previous step. First, the model calculates the radiation limited yield, then the water limited yield, and finally, the yield affected by soil and management limitations. The Food and Agriculture Organization (FAO)-AEZ crop growth simulation model estimates yields using a three step process. Two published crop models currently exist for tef. While more data from contrasting environments are needed for further model testing, DSSAT-Tef can be used to assess the performance of crop management strategies, the suitability of tef for cultivation across growing environments, and food security. Less data were available for N uptake, and the model simulated crop N uptake with an RMSE of 45 kg N/ha (46.2%) and 15 kg N/ha (37.3%) for grain N. Simulation-observation comparisons resulted in an RMSE of 2.5 days for anthesis, 4.4 days for maturity, 2624 kg/ha (49.6%) for biomass, and 475 kg/ha (41.0%) for grain yield. DSSAT-Tef accurately simulated phenology and responded to changes in N supply and irrigation, but overestimated growth and occasionally yields. The new DSSAT-Tef model was compared with tef field experiments. A tef model was calibrated based on the Decision Support System for Agrotechnology Transfer’s (DSSAT) NWheat model and included parameter changes in phenology, photoperiod response, radiation use efficiency, and transpiration efficiency for both standard and elevated atmospheric CO 2, based on published literature for tef and other C4 species. As tef is nutritious and gluten free, it is also gaining popularity as a health food. Tef is an Ethiopian staple grain that provides both food security and income for smallholders.
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