Scheduling operations for the harvesting of renewable resources

We discuss the harvesting of renewable resources from an operations research scheduling viewpoint. We report on two practical harvesting case studies arising in agricultural contexts, based on practical data from commercial enterprises, involving minimum and maximum time lags and resource constraints. One of the case studies is concerned with the harvesting of rape seed in Australia and the other with hay harvesting in New Zealand. It appears that the scheduling of harvesting operations is a significantly different scenario from those represented by the scheduling models available in the literature. The differences come about because: the duration of each operation is dependent upon the combination of constrained resources allocated to it, individual worker-equipment allocation is restricted, and minimum or maximum time lags can be imposed. We report on harvesting operations scheduling models and solution procedures, designed specifically for the case studies. The results represent significant improvements over the schedules that were traditionally used. The computational times experienced in solving general instances of the model of practical size by a commercial integer programming package are encouraging.