EFFECT OF CLIMATE CHANGE ON WHEAT CROPLAND SUITABILITY AND CROP YIELDIN FINCHAA WATERSHED, ETHIOPIA.

Abstract

Climate change on land suitability and crop growth and yield for wheat is evaluated in the Finchawatershed. To assess land suitability, slope, soil property, the distance between watershed and land, rainfall deficit, and the crop growing period temperature was used. The weighting of factors was done by using a pairwise comparison method. Climate change effect on wheat growing period and yield was simulated and projected by Crop Environment Resource Synthesis (CERES) wheat of Agro-technology Transfer (DSSAT) model for the current (1990 to 2020) and future (2021 to 2080) years. Coupled Model Inter-Comparision Project Phase 5 (CMIP5) of Global Circulation Models (GCMs) was used for future time climate data. Representative Concentration Pathway (RCP) 4.5 was used for the future projections, and GCMs data were downscaled to station level by delta method downscaling. Due to temperature rise in the watershed, Potential Evapotranspiration (PET) increases, which leads to increased rainfall deficits in the 2030s and 2060s. In the 2060s, rainfall decline is another factor to increase deficits, which leads to more reduction of land suitability for surface irrigation than in the 2030s. Under climate change scenarios, rising temperature is shortening anthesis days and the growing period of the wheat. The increasing temperature during the crop maturity stage affects the crop yield negatively, and increasing carbon dioxide (CO2) increases crop yield. In the watershed, anthesis days are 75, 70, and 67 days, maturity days are 118, 110, and 107 days, crop yield is 42.5 qt/ha, 41.0 qt/ha, and 41.4 qt/ha for wheat in baseline, the 2030s, and 2060s, respectively. In general, the crop's growing time is shortened, and the crop yield is reduced due to the temperature rise. However, crop yield is not exclusively reduced when the temperature rises because rising CO2 positively affects wheat crop yield under climate change. Furthermore, rising temperatures have a direct impact on increasing evapotranspiration. As a result, an increase in evapotranspiration and a decrease in rainfall results in deficits that affect the crop's land suitability. The water deficit must be managed by irrigation to control the potential effects of climate change on land suitability. The negative impact of rising temperature on a wheat crop yield may be mitigated by sowing earlier to escape the maturity period of the crop from the heat stress.