Climate change is expected to have a major effect on crop production in sub‐Saharan Africa. Crop models can help to guide crop management under future climate. The objective of the study was to investigate the possible effects of climate change on Ethiopian barley (Hordeum vulgare L.) production using the Decision Support System for Agrotechnology Transfer (DSSAT)‐Crop Environment Resource Synthesis (CERES)‐Barley model. The study included field data of two barley cultivars (Traveller and EH‐1493) and four climate study areas in Ethiopia over 5 yr. Climate change scenarios were set up over 60 yr using representative concentration pathways (RCP; RCP4.5 and RCP8.5) and five global climate models (GCM). The model results indicated that the prediction of days to anthesis and maturity, as well as final grain yield, was highly accurate for cultivar Traveller with normalized RMSE (nRMSE) of 2, 1, and 12%, respectively, and for cultivar EH‐1493 with nRMSE of 2, 4, and 11%. A consistent increase in average temperature up to 5 °C and a mixed pattern of rainfall (‐61 to +86%) were projected. Yield simulations showed a potential reduction in yield up to 98% for cultivar Traveller and 63% for cultivar EH‐1493 in the future. Within a sensitivity analysis, different sowing dates, sowing densities, and fertilizer rates were tested as potential adaptation approaches to climate change. The negative effects of climate change could be mitigated by early sowing, with an increased sowing density of 25% and fertilizer rate of 50% more than what is recommended. Overall, the results indicated the ability of the CERES‐Barley model to evaluate climate change effects and adaptation options on rainfed barley production in Ethiopia.

Aims: The general aim of this meta-analysis is to synthesize and summarize the mean response of barley yield variables to elevated CO₂ (eCO₂) and how temperature and nitrogen (N) affect the CO₂-induced yield responses of barley. Methods: A meta-analysis procedure was used to analyze five yield variables of barley extracted from 22 studies to determine the effect size and the magnitude concerning eCO₂ and its interaction with temperature and N. Results: CO₂ enrichment increased aboveground biomass (23.8%), grain number (24.8%), and grain yield (27.4%). The magnitude of the responses to eCO₂ was affected by genotype, temperature, nitrogen, and CO₂ exposure methods. Genotype “Anakin” shows the highest CO₂ response of aboveground biomass (47.1%), while “Bambina” had the highest grain number (58.4%). Grain yield response was observed to be higher for genotypes “Alexis” (38.1%) and “Atem” (33.7%) under eCO₂. The increase of aboveground biomass and grain yield was higher when plants were grown under eCO₂ in combination with higher N (151–200 kg ha⁻¹). The interaction between eCO₂ and three different temperature levels was analyzed to identify the impacts on barley yield components. The results revealed that the CO₂-induced increase in grain number and grain yield was higher in combination with a temperature level of 21–25 °C as compared to lower levels (< 15 and 16–20 ℃). The response of barley yield to eCO₂ was higher in growth chambers than in other CO₂ exposure methods. Moreover, a higher response of aboveground biomass and grain yield to eCO₂ was observed for pot-grown plants compared to field-grown. Conclusions: Overall, results suggest that the maximal barley production under eCO₂ will be obtained in combination with high N fertilizer and temperature levels (21–25 °C).

Barley (Hordeum vulgare L.) is an important food security crop due to its high-stress tolerance. This study explored the effects of CO₂ enrichment (eCO₂) on the growth, yield, and water-use efficiency of Ethiopian barley cultivars (15 landraces, 15 released). Cultivars were grown under two levels of CO₂ concentration (400 and 550 ppm) in climate chambers, and each level was replicated three times. A significant positive effect of eCO₂ enrichment was observed on plant height by 9.5 and 6.7%, vegetative biomass by 7.6 and 9.4%, and grain yield by 34.1 and 40.6% in landraces and released cultivars, respectively. The observed increment of grain yield mainly resulted from the significant positive effect of eCO₂ on grain number per plant. The water-use efficiency of vegetative biomass and grain yield significantly increased by 7.9 and 33.3% in landraces, with 9.5 and 42.9% improvement in released cultivars, respectively. Pearson’s correlation analysis revealed positive relationships between grain yield and grain number (r = 0.95), harvest index (r = 0.86), and ear biomass (r = 0.85). The response of barley to eCO₂ was cultivar dependent, i.e., the highest grain yield response to eCO₂ was observed for Lan_15 (122.3%) and Rel_10 (140.2%). However, Lan_13, Land_14, and Rel_3 showed reduced grain yield by 16, 25, and 42%, respectively, in response to eCO₂ enrichment. While the released cultivars benefited more from higher levels of CO₂ in relative terms, some landraces displayed better actual values. Under future climate conditions, i.e., future CO₂ concentrations, grain yield production could benefit from the promotion of landrace and released cultivars with higher grain numbers and higher levels of water-use efficiency of the grain. The superior cultivars that were identified in the present study represent valuable genetic resources for future barley breeding.

AimsThe general aim of this meta-analysis is to synthesize and summarise the mean response of barley yield variables to elevated CO₂ (eCO₂) and its interaction with temperature and N fertilization. Methods The present study quantitatively synthesized the response of barley to eCO₂ and its interaction with temperature, and Nitrogen (N). A meta-analysis procedure was used to analyse five yield variables of barley extracted from 76 articles to determine the effect size and the magnitude in relation to eCO₂ and its interaction with temperature and N. Results CO₂ enrichment increased biomass (23.8%), grain number (24.8%), grain yield (27.4%), and thousand-grain weight (5.6%). However, responses to eCO₂ were affected by genotype, additional stress, and experimental conditions. In comparison, genotype “Anakin” shows the highest response of biomass (47.1%), while “Genebank accessions” had a higher grain number (46.1%) and grain yield (57.1%) under eCO₂. The maximal enhancement of barley yield was observed when plants grow under a combination of eCO₂ and higher nitrogen fertilizer (>100 kg ha^-1). Nevertheless, biomass (-12%), and grain yield (-17%) responses were lower when eCO₂ is combined with high temperature (>25 °C). It was further noted the response of barley yield to eCO₂ was higher in the growth chamber than in other CO₂ exposure methods. Moreover, comparing pot-rooted versus field-rooted barley plants, a higher response of biomass and grain yield was observed for pot-rooted plants. ConclusionsOverall, results suggest that the maximal barley production under eCO₂ will be obtained in combination with high nitrogen fertilizer and optimal temperature (21-25 °C).