Comparing the effects of growing conditions on simulated Ethiopian tef and wheat yields

Abstract

Tef and wheat are staple grains in Ethiopia and are an important part of Ethiopian food security. The DSSAT NWheat and DSSAT Tef models were used to examine the effects of nitrogen fertilizer, planting date, and atmospheric CO2 on tef and wheat grain yields across four locations in Ethiopia and a 30-year time period.Observed wheat yields were consistently higher than observed tef yields, but the models showed that tef could outproduce wheat in some low yielding scenarios. Wheat yields were more responsive to N fertilizer than tef, due to a higher harvest index causing more of the additional biomass to be allocated to grain yields. Frequently, high rainfall increased N leaching, exacerbated N stress, and reduced yields for both crops. Early planting was often detrimental to yields, except for regions and years with terminal drought and heat stress. With continuously increasing atmospheric CO2 concentrations, wheat, as a C3 crop, will further outperform tef, a C4 crop, in the future, as long as N is not limiting. Breeding for lodging resistance and a higher harvest index could significantly improve future tef yields, while higher N applications and the use of split fertilizer applications to avoid leaching would improve both tef and wheat yields. As wheat has a higher N response than tef, is more responsive to future elevated atmospheric CO2 levels, and is generally higher yielding, wheat could add more to food security in Ethiopia. However, under low input, low yielding conditions, growing tef will likely remain the preferred cereal in Ethiopia due to its higher cultural, nutritional and economic value.