NEAR-INFRARED REFLECTANCE SPECTROSCOPY FOR ANALYSIS OF SUGARCANE FROM CLONAL EVALUATION TRIALS .1. FIBRATED CANE

Determination of quality components is important in assessing the economic merit of clones in sugarcane (Saccharum spp. hybrids) evaluation trials. Laboratory throughput is limiting and analytical costs are high. This research aimed to assess near infrared reflectance (NIR) spectroscopy for analyzing fibrated cane to resolve these problems. A replicated trial provided samples of cane. Quality components were analyzed by routine laboratory methods. Samples of fibrated cane were scanned using a Technicon 450R NIR spectrophotometer to provide reflectance data (log 1/R). Sampling analyses indicated all routine lab determinations were performed with high accuracy relative to plot-to-plot variation and subsampling was unnecessary. Correlation coefficients (r) obtained for the prediction test for fibrated cane were: Brix (0.91), commercial cane sugar (0.91), conductivity (0.20), fiber (0.89), moisture (0.92), polarimetry (pol) reading (0.96), and purity (0.60). Regressions for moisture and pol reading were significantly skewed. The NIR and routine lab analyses did not differ significantly for any component. Precision of NIR analysis compared with routine lab analysis was inferior for all components except purity. Error ratios ranged from 1.3 to 3.4. Sampling analyses of spectrophotometer readings (as log 1/R) revealed inadequate sample fibration, mixing, and presentation as potential major sources of error. Analysis of fibrated cane is promising, but insufficiently accurate for advanced selection stages. The substantial operational advantages of fibrated cane analysis warrant further research to resolve the problems described.