EVALUATING THE EFFECT OF IRRIGATION ON PADDY RICE YIELD BY APPLYING THE AQUACROP MODEL IN NORTHERN GHANA

Abstract

The yield of lowland paddy rice (Oryza sativa L.) is sensitive to water application regimes, which can be affected by irrigation management. This study assessed the impacts of different irrigation applications on rice yield using the AquaCrop model. Experiments were conducted at two sites (On-station and On-farm) during the 2012/2013 and 2013/2014 dry seasons using five different irrigation treatments: field capacity (FC) moisture content (W1), saturated soil moisture content (SC; W2), continuous flooding (CF; W3), 10ETc (crop water requirement) (W4), and 15ETc (W5). A 115-day rice variety, Gbewaa (Jasmine 85), was transplanted with a spacing of 20 cm × 20 cm for the experiments. The AquaCrop model was calibrated in terms of green canopy cover (CC), aboveground dry biomass, harvest index (HI), and paddy rice yield. The model was validated using various efficiency criteria (coefficient of determination, root mean square error (RMSE), RMSE–observations, standard deviation ratio, index of agreement, and Nash– Sutcliffe efficiency), and satisfactory simulation results were obtained for biomass, HI, yield, and green CC. The AquaCrop model proved to be robust and applicable for paddy rice under various irrigation methods, although it underestimated dry biomass and grain yield for all treatments except FC. The simulated rice yield was highly sensitive to the maximum CC. This study represents the first site-specific application of the AquaCrop model to paddy rice in Northern Ghana; therefore, the model should be further tested for different climatic conditions, soil types, and crop varieties in Ghana.