A functional–structural plant model for climbing bean: simulating light capture in maize/bean polycultures

Abstract A novel functional–structural plant (FSP) model for climbing common bean has been developed, encompassing twining behaviour and physical plant–plant interactions. The model enabled simulation of maize/bean polycultures, where common bean climbed upwards around the maize stalk, elucidating how plant architecture facilitates light capture in such polycultures. Employing sensitivity analysis, parameters have been identified that have the most influence on key outputs such as leaf area index and aboveground biomass. Simulations revealed limited maize growth impact but significant bean growth reduction in the polyculture compared to monocultures. Considering three different environmental conditions, the model suggested that the environment greatly affects model outputs in both the monocultures and polyculture, predicting that, within the polyculture, there would be very little bean growth in Dutch and French conditions. In contrast, the polyculture developed in Mexican conditions, with bean growth influenced by the magnitude of the time delay between maize and bean germination. Simulations in Mexican conditions predicted an increase in total peak biomass of up to 60%, in agreement with experimental observations of overyielding in polycultures. This indicates that aboveground processes (specifically light capture; in addition to root system complementarity) play an important role in the phenomenon of overyielding. In addition, it confirms that such agricultural systems may play a role in sustainable agricultural intensification. The maize/bean model presented in this work is one of the first examples of an aboveground FSP model of a polyculture with complex plant–plant interaction. Our results suggest that FSP modelling could be a valuable tool to investigate such agricultural systems.