Billet samples for measuring sugar content in variety trials

Sugarcane breeding and research programs use hand-cut sound whole-stalk samples for determination of commercial cane sugar (CCS) and other quality components. Whole stalks provide a biased sample of the material harvested for milling from experimental plots, as they are free from extraneous matter and inferior quality cane. The small mill has low efficiency of juice extraction from whole stalks and this leads to bias. Bias for whole-stalk samples was quantified and compared with samples of commercially harvested cane in selection experiments at Broadwater and Tully. A bias of more than seven units of CCS was measured in badly lodged, heavily suckered and deteriorated cane harvested green at Tully. A bias of three units of CCS was found in burnt cane at Broadwater. Despite these biases and the inaccurate over-estimation of sugar content of harvested cane from experimental plots, sound whole-stalk samples arc usually adequate for ranking of clones for selection purposes. However, billet samples provide a far more accurate estimate of commercial CCS and are preferable for predicting the true responses of commercial varieties to various agronomic treatments.