Paper Title
Sensitivity Analysis of Apsim Model using Gem-Sa Software: Emulator Accuracy Assessment

Abstract
Global sensitivity analysis of process-based crop models is laborious and computationally expensive. Hence, less computationally expensive and reliable approach is required. Gaussian Emulator Machine for Sensitivity Analysis (GEM-SA) use an emulator-based approach to conduct sensitivity analysis, hence it is computationally less expensive way to conduct global sensitivity analysis. It is tested with some process-based models, however rarely tested for crop models. This study aimed to assess the applicability of GEM-SA to conduct sensitivity analysis of APSIM crop model. Above ground biomass, fresh cane yield and sucrose weight of sugarcane were simulated for 300 input combinations using apsimr package of R 3.5 software. Thirty emulators (10 years x 3 outputs) were developed to estimate parameter sensitivity of 26 plant parameters using GEM-SA software. Results revealed that, the developed emulators are accurate, hence emulator-based approach is confident enough to conduct the sensitivity analysis of APSIM. GEM-SA provide a computationally less expensive and reliable platform to conduct sensitivity analysis of APSIM crop model. Keywords - Apsimr, Emulator, GEM-SA, Global sensitivity analysis, Sugarcane.