Physiological demands and working efficiency of sugarcane cutters in harvesting burnt and unburnt cane

Harvesting burnt and unburnt sugarcane has various implications for the farmer and the cutters. The primary focus of this study was to investigate in situ the differences in energy expenditure and working efficiency of sugarcane cutters with regard to harvesting burnt and unburnt sugarcane. Heart rate was measured telemetrically by means of a Polar Pacer heart rate monitor. Metabolic measurements were done by means of the portable MetaMax Ergospirometry System. Data per subject (n=15) were collected on two consecutive occasions, separated by at least 1 day, harvesting burnt and unburnt cane. The short handle Okapi curved blade cane knife was used. After a warm up period of 5 min to reach steady rate, data were collected for 30 min per subject. Each day, four subjects were measured in the cane field between 05:00 and 09:00 h. Cane cutters used significantly more kilojoules (11.11%) and worked at a higher percentage of their maximum aerobic capacity (11.96%) while cutting unburnt as opposed to burnt cane. This was achieved with a slightly higher (+3.23%) increase in mean heart rate. Ratings of perceived exertion (RPE) values recorded during harvesting burnt (11.71) and unburnt (11.13) cane did not differ significantly. It was less cost effective (−24.22%) to harvest unburnt cane as less cane was cut per time unit. Burnt cane required significantly more cutting strokes per minute than unburnt cane.Relevance to industrySouth African farmers are under increasing pressure to change harvesting practices from burnt to unburnt cane. The results of this study can encourage farmers to also consider physiological stress on cutters when making decisions on harvesting practices.