Heat and the Piece Rate: Work-Rest Design for Harvest Labour That Does Not Quietly Tax the Worker's Pay

SIMULATED, NOT MEASURED; nothing was built or field-tested. Manual sugarcane cutting (414 W, heavy work) is modelled under hourly WBGT on a hot day peaking at 32.0 C. The safe work-rest schedule for a conventional 07:00-15:00 shift leaves 2.25 work hours and piece-rate earnings of $20.25 against $72.00 unsafe reference, a 71.9 percent loss. A split shift recovers output to 4.5 tonnes and $45.00. Shade-and-water stations cost $0.227-$0.504 per tonne, schedule shifting $1.046-$1.556 per tonne, and full rest compensation $6.00 per tonne on the split schedule (combined package $7.78 per tonne extra, total labour $17.78 per tonne). Above 30.0 C WBGT (acclimatised) or 27.5 C (unacclimatised) no work-rest schedule protects and work must stop.