Fig. 1.

Three process-based approaches to modelling weed dynamics in an agricultural system. In Approach 1, the processes influencing the system are represented at the field scale, and so the model is more transparent, but less realistic; in Approach 2, the processes influencing the system are represented directly at the individual-plant or individual-seed scale, and so the model is less transparent, but more realistic; in Approach 3, the processes influencing the system are represented at the field scale, but these field-scale sub-models are built using models that represent processes at the individual-plant or individual-seed scale or lower, and so the model of the agricultural system is more transparent, and more realistic.