Rethinking the WOFOST model to simulate growth and development of Chinese cabbage (Brassica rapa L. ssp. Pekinensis)

Chinese cabbage ( Brassica rapa L. ssp. Pekinensis ) is a leading open-field leafy vegetable crop in China, with known shallow roots, short lifespan and high nutritional content. To ensure its precise field management in a changing world, an accurate leafy vegetable model is urgently needed to enhance decision-making. We modified the WOrld FOod STudies ( WOFOST ) crop model to create a version specifically for Chinese cabbage ( WOFOST-Chinese cabbage ) that quantifies its daily dynamic growth based on fertilizer management, climate, and soil conditions. We conducted field experiments in southwestern China from 2019 to 2021 to collect extensive site-specific soil data and specific crop data relevant to eco-physiological processes of Chinese cabbage. We used 2021 field trail observations under optimal growing conditions to parameterize and calibrate the model with integrated image data in a stepwise procedure. The datasets from 2019 and 2020 were used for model validation, while the no-fertilizer dataset was used to test model performance under nutrient-limited conditions. Overall, the developed WOFOST-Chinese cabbage is reliable in simulating biomass (rRMSE = 0.13 for total aboveground production), leaf area index (rRMSE = 0.34), and nutrient uptake (rRMSE = 0.15). Additionally, model robustness is increased by the sensitivity analysis of biomass-relevant and nutrient-uptake-relevant parameters. However, this good performance is constrained by a less effective differentiation between functional and non-functional leaves. Besides, model validation provides further improvement directions of model structure under nutrient-limited conditions. This study provides the first set of comprehensively calibrated parameters for applying WOFOST to Chinese cabbage in open cropland. The outcome of this study will aid in fertilizer management for open-field Chinese cabbage production across diverse climate and soil conditions. Additionally, it will contribute a new model for comparative multi-model studies of leafy vegetables, addressing climate change impacts at regional, national, and global scales. • WOFOST was adapted for Chinese cabbage simulation for the first time. • A novel stepwise parameterization process integrating image data was applied. • Model calibration and validation used a continuous 3-year dataset from field trial. • Model robustness was evaluated under both potential and nutrient-limited growth.