ASSESSMENT OF CLIMATE CHANGE AND VARIABILTY EFFECTS ON CROP YIELD: A CASE STUDY IN WOLAYTA ZONE SNNPR, ETHIOPIA.

Abstract

This study reviews the impact of climate change and variability on crop production mainly on rain fed agriculture in Wolayta Zone. In all nine stations daily climate data were collected from NMSA and aggregated to monthly. The monthly rainfall was varied and distributed moderately on annual and seasonal basis in all stations. The occasion of onset dates are slightly increasing (delaying) for both stations toward the recent years. The end dates of the growing season were decreasing at Wolayta station and very slightly increasing at Bilate station. The interannual variability of length of growing season for both the stations was low. In both the stations, the dry spell length probability of longer than 5, 7 and 10 days were decreasing from the starting date of the growing season to the middle of Belg season and increasing towards the end of Belg Season. SDSM is applied in order to downscale the climate variables at the station level. Under A2 scenario, SDSM indicates an increase in the mean monthly precipitation by 2%, 6%, and 15% in 2020s, 2050s and 2080s respectively, while under B2 scenario it indicates by 3%, 5% and 11% in 2020s, 2050s and 2080s respectively. Under A2 scenario, the monthly maximum temperature is projected to increase by 1.4°C, 1.8°C and 3.7°C in 2020s, 2050s and 2080s respectively, while under B2 scenario the increase will be 0.1°C, 1.0°C and 2.6°C in 2020s, 2050s and 2080s relative to baseline period. Agricultural model AquaCrop was used to model the effect of changing climate. The simulated yield of the selected crops in study area under projected climate showed a decrease from baseline without considering the effect of CO2 fertilization and increase from baseline by considering the effect of CO2 fertilization. The average reduction in the yield of Maize under changing climate elements (i.e. temperature and precipitation) were noticed as 15% and 12% for A2 and B2 scenarios respectively. Similarly the Barley average yield reduction perceived in the same aspect of climate under A2 and B2 scenarios are 18% and 15% respectively in the future tri-thirty (90 years) time period. On the other hand under the combined effect of changing climate and CO2 fertilization the simulated yield of selected crops showed an increase from baseline. The average increments of Maize and Barley yield over the total period of 90 years, with CO2 fertilization effect under both A2 and B2 scenarios was evaluated as 3.3% and 2.3% , and 3.6% and 2.2% for investigated crops and scenarios respectively.