Calibration and Evaluation of the SIMPLE Crop Model for Chili Pepper Growth and Yield Simulation under Korean Field Conditions

This study investigated the growth characteristics and yield of chili pepper cultivars at production sites in Andong and Yeongyang, Gyeongsangbuk-do Province, and evaluated the predictive performance of the SIMPLE crop model.Seven cultivars, comprising two existing and five newly released varieties, were tested and categorized into adaptive and resilience groups based on breeder-provided performance data.Temperature analysis from 2019 to 2023 revealed minimal climatic differences between regions, with both sites accumulating approximately 1,800Cday GDD by season end.Adaptive cultivars exhibited compact canopy architecture and greater vegetative biomass, while resilience cultivars displayed an open canopy structure with elongated internodes.Regional differences were apparent in reproductive efficiency: in Andong, both groups achieved comparable final yields, whereas in Yeongyang, adaptive cultivars produced significantly higher yields.The SIMPLE model was modified to incorporate a first-order decay term to account for late-season biomass decline attributable to leaf senescence and assimilate redistribution toward maturing fruits.Calibration yielded distinct regional parameter sets: Andong was characterized by rapid early growth, high radiation use efficiency, and low heat tolerance, while Yeongyang showed gradual growth, high heat tolerance, and an elevated harvest index.Model performance varied considerably across site-cultivar combinations, indicating that predictive accuracy is governed by interactions between cultivar traits and microenvironmental conditions.Region-specific calibration and mechanistically improved senescence modules are essential for enhancing model robustness and transferability across diverse Korean chili pepper production environments.Multi-year, multi-site validation and uncertainty analysis are identified as priorities for future work.