MODELLING THE POTENTIAL IMPACTS OF CLIMATE CHANGE ON FABA BEAN (Vicia faba L.) PRODUCTION IN WELMERA DISTRICT, OROMIA REGIONAL STATE, CENTRAL ETHIOPIA

Abstract

Studying climate change and variability at a local scale is curial for devising proper strategies that enhance adaptive capacity. In view of this, this study was conducted in Welmera District, to assess; the potential impacts of climate change on faba bean (Vicia faba L.) production. Historical climate and crop yield data were obtained from National Meteorological Agency of Ethiopia and Holeta Agricultural Research Center respectively. After quality control, consistency check and homogeneity test on rainfall and temperature data; trend, variability, correlation and regression analysis were carried out by statistical software InStat_v3.36, XLSTAT2014 and SPSS_v20 were used. Future climate data was downscaled using the output of ensemble by four GCMs climate models (BSS-CSM1-1, HadGEM2-ES, MIROC-ESM and NorESM1-M) under RCP4.5 and RCP8.5. The time period centered 2030s and 2050s were considered. Besides this, soil and crop data of two faba bean varieties (Gora and Tumsa) were used to assess future climate impacts in the study area. The results indicated that the mean start of main rainy season (JJAS) for Holeta station started on the 3rd decade of May. The annual, kiremt, belg and bega seasonal rainfall amount were found to be decreased by a factor of 8.53, 4.7, 2.32 and 0.8 mm/year respectively. The mean maximum and minimum temperature revealed an increasing trend by 0.005 and 0.06 0C changes/year. Moreover, the correlation of kiremt start of rain and kiremt rainy day had negative impact on Gora yield with (r=-0.407 and -0.369) respectively. Similarly, kiremt start of rainy season and mean air temperature had negative impacts (r=-0.482 and r=-0.605) where moderate and strong correlated with Tumsa yields and statistically significant at p- value levels (0.01 and 0.05) in the study area. The coefficient of determination was analyzed with (R2 =56.0% and 74.4%) of total variance in Gora and Tumsa yields respectively were explained jointly by climatic events. The future projection of highest mean monthly rainfall and air temperature changes occur during faba bean growing season will in July (147.3%) mm/months and August (0.24 0C/month) under RCP8.5. However, in August and September mean monthly rainfall will be dramatically decrease by 50.85 % and 31.05% mm/month in the 2020 up to 2079 under RCP 8.5 and RCP 4.5 respectively. This could negatively affect faba bean yield in the area, because this months are the critical stages (flowering, grain filling and harvesting period). Tumsa yield will significantly decline by 24.19% under RCP8.5 mid- century. If future study consider using different climate and crop models with more appropriate adaptation management options incorporate is better for further study