Application of the AquaCrop model to simulate the biomass of Miscanthus x giganteus under different nutrient supply conditions

Abstract

There are conflicting opinions about the need to fertilize Miscanthus and, also, the question has been raised whether Miscanthus should be irrigated, especially if water resources are limited. Crop growth modeling can help answer such questions. In this article the FAO AquaCrop water-driven model was selected to simulate Miscanthus biomass under different nutrient and water supply conditions. The article reports the outcomes of 6-year experiments with Miscanthus on two locations in Serbia: Zemun, where three fertilizer treatments were applied (Nl - 100 kg ha-1, Nopt 50 kg ha-1 and Nf nonfertilized), and Ralja, where only Nl 100 kg ha-1 was applied. Model calibration focused on the measured data (root depth, crop phenology, and the above-ground biomass by year of growth. Calibration results showed a very good match between measured and simulated values. The largest and only significant difference was noted in 2008, when the crop was establishing and exhibited uneven radication. The simulation results for the next 5 years showed a variance from -4 to 5.7%, believed to be a very good match. A high coefficient of determination (R2 = 0.995) and high Willmott index of agreement (0.998) were also indicative of a good match between simulated and recorded biomass yields. The measured and simulated results for validated datasets at both locations were good. The average RMSE was 2.89 Mg ha-1; when compared to the deviations noted at the test site itself, it was apparent that they were smaller in all the years of research except the first year. The index of agreement was 0.97 and the coefficient of determination R2 0.947. The AquaCrop model can be used with a high degree of reliability in strategic planning of Miscanthus cultivation in new areas, under different nutrient and water supply and local weather and soil conditions.