Developing a broccoli crop model to guide growers with sustainable decision-making

Abstract

Broccoli (Brassica oleracea var. italica) has emerged as a key crop for diversification in southeastern U.S. vegetable systems, driven by regional market demand and strategic efforts to reduce reliance on imports. However, its sensitivity to climatic conditions, particularly air temperature leads to significant challenges in its production. This dissertation addressed two complementary approaches to optimizing broccoli cultivation in the region: cultivar evaluation and climate-resilient crop modeling. Field trial using commercial cultivars (Castle Dome, Eastern Crown, Emerald Crown, Green Magic, Gipsy, Imperial, and Belstar) were conducted over two consecutive years (2022 and 2023) during spring and fall seasons in Alabama. Cultivars were assessed for yield performance, canopy development, and biomass accumulation. Results showed consistent yield advantages among early-maturing cultivars under warmer conditions, while late maturing were more susceptible to seasonal variability. An air temperature-driven broccoli crop model was adapted from the SIMPLE crop model and was calibrated using field data from the cultivar trial. The model simulated daily biomass accumulation and final yield based on air temperature, incorporating cultivar-specific coefficients for radiation use efficiency (RUE), harvest index (HI), and LAI dynamics. A seasonal sensitivity analysis was performed using 20 years of historical weather data adjusted under seven air temperature scenarios (−6°C to +6°C), with outputs generated through bootstrap simulation. The model successfully captured genotype by-environment interactions, simulated yield responses under varying air temperature conditions, and identified critical thresholds for reduction in yield. Validation against 2023 field data demonstrated high simulated accuracy across cultivars. The results presented here offered practical tools for broccoli production planning in the southeastern U.S.