Can Solar-Powered Irrigation Systems Naturally Meet Crop Water Requirements? Proof of Concept From a Case Study in Sub-Saharan Africa

Irrigation scheduling is crucial for ensuring precise water delivery to crops. However, in many sub-Saharan African irrigation schemes, water is applied without considering crop water needs, resulting in low crop water productivity and low yields. Solar-powered irrigation systems can automatically meet these needs by utilizing solar radiation, which drives both evapotranspiration and solar panel power production for pumping. This study aimed to integrate irrigation scheduling into a solar-driven irrigation system and assess the impact of meteorological variables on reference evapotranspiration (ET_o) in Ghana. A 50-watt solar panel powered a 12-V submersible pump, with a flow meter installed on the outlet pipe for hourly volume of water pumped (VWP) data readings. These data were used to examine correlations between solar radiation (R_s) and ET_o, as well as between R_s and VWP. Partial correlation analyses were used to assess the relative influences of R_s, wind speed (U₂), relative humidity (RH) and air temperature (T_air) on ET_o across 10 locations in Ghana's agroecological zones. The study revealed a strong linear correlation between the hourly R_s and ET_o (R² > 0.9) and between the hourly R_s and VWP (R² = 0.8). The VWP was sufficient to meet crop-water demand year-round. Solar radiation was consistently the primary meteorological factor influencing ET_o in Ghana.