Influence of yield and other cane characteristics on cane loss and product quality

Field and crop conditions affect cane loss, cane-supply quality and the amount of extraneous matter that is mixed with cane billets supplied to the mill. The size of the crop produced also impacts on machine performance and cane loss during harvest. Crop physical properties and the composition of the sugarcane stalk are driven by a wide range of agronomic practices, including nutrition. The objective of this study was to investigate the impact of different crop conditions on sugar loss during harvest, with in-field nutrient practises being the primary driver of the changing cutting pour rates when the ground speed is fixed. The physical properties of the sugarcane (stalk length and diameter, population density and yield) were measured in the experimental plots in Bundaberg in 2014 and Macknade in 2015 that had received a range of different nitrogen (N) application rates before being cut by a chopper harvester. Cane loss during cutting was then determined at harvest by collecting all material (leaves, tops, stalks, etc.) discarded from the harvester. This procedure was performed using a standard ‘tarp test’ combined with a loss-assessment method based on measuring juice loss on trash to evaluate cane loss, juice loss, etc. The residue samples gathered from the tarp were shredded and frozen for determination of sugar loss by colorimetric method, using a Glucose and Sucrose Colorimetric Assay Kit. Different N rates resulted in a range of stalk physical properties (stalks per unit area, billet size and stalk weight) and cane yields (t/ha). With the harvester operating at a constant ground speed (and set fan speed) the pour rate was driven by the N applied. As pour rate increased, the ability of the extractor fan to efficiently differentiate trash from billets decreased, resulting in greater sugar loss. Sugarcane sizing influenced by the varying N rates led to the sugar loss differences occurring during the cutting by the harvester