Mapping of the Evolution of Soil Suitability for Wheat and Sugar Beet Under Climate Change in the Tadla Irrigated Plain - Central Morocco

Agricultural soils are interfaces for various climate change effects which they translate into changes in suitability for different crops. In this work, we studied the climate change impact on the agricultural soil suitability for wheat and sugar beet, for the four main soil types of the Tadla irrigated plain in Central Morocco: Kastanozems, Vertisols, Calcaric Chernozems, and Chromic Luvisols. This impact was assessed through mapping of the actual suitability and modeling of its future spatial distribution. Soil suitability evolution was considered as a manifestation of the impact of changes in temperature and rainfall on yields of wheat and sugar beet, between a reference period (1986-2005) and a future period (2041-2050). The actual soil suitability for the two crops was mapped using a dataset of chemical, physical and hydrodynamic characteristics of the soil units of the study area. The soil potential was scored using the guidelines of the FAO GAEZ (Global AgroEcological Zoning) framework, using data of soil characteristics that are known to impact its behavior under irrigation in Central Morocco. Daily precipitation and temperature data for reference, future and calibration periods were extracted from the bias-corrected RICCAR dataset. The climate scenario considered is RCP 8.5. Mapping of the actual soil suitability for the two crops was followed by the crop model calibration, then yield series for reference and future were simulated and the suitability evolution for each soil type was determined accordingly. The results showed projected yield reductions for the two crops and the four soil types of the study area, with higher decrease rates for sugar beet. Overall, a soil suitability downgrade from high to medium class was indicated for 68% of the perimeter’s soils for the case of wheat and for 86% for the case of sugar beet. Student’s t test showed that the yield reduction was significant for sugar beet across the the four soil types, while significant decrease for wheat was observed only on Kastanozems. The study showcased the characteristic variability of the response to climate change, ranging from vulnerability to resilience, as manifested by the main soil types in the agricultural perimeters of Central Morocco.