WHAT HAPPENS FROM FIELD TO MILL? CROP-FRACTION AND CCS CONSIDERATIONS

Sugar content (CCS) of sugarcane grown on the northeast tropical coast has plummeted in the seasons from 1995 to 2000. Increased proportions of extraneous matter and sucker-culm billets have been blamed. The research reported here quantified the proportion and quality of crop fractions pre- and post-harvest. Pre- and post-harvest sub-samples were taken from 54 sites in the 1999 and 2000 harvest seasons. These were dissected into basic crop fractions and analysed for five quality components using conventional and near infra-red spectroscopic techniques. Each sampled site produced a discrete mill rake. Potential CCS (mature stalk or billet) was high in both years. Average, weighted mill-realised CCS compared poorly with pre-harvest potential CCS (75.9 and 85.1%, for 1999 and 2000, respectively) and post-harvest potential CCS (82.9 and 87%). In 1999 and 2000, mill-realised CCS was only marginally above the average, weighted, whole-crop, pre-harvest CCS, but was almost equal to the post harvest CCS, in 1999, and just below in 2000. In 1999, harvesting did not reduce the proportion of extraneous matter from the in-field value (18.9%). In 2000, the proportion changed from 18.9 to 13.1%. Data presented severely questions the efficacy, or use, of current harvesting technology. Implications for harvesting and crop improvement are discussed.