Procedure for obtaining NIR spectra in sugarcane stalks using a portable instrument under field conditions

Abstract

Obtaining near-infrared spectra (NIR) directly from the sugarcane stalks in the field requires additional care due to the presence of wax on their surface. This study investigated the best cleaning procedure to be applied in sugarcane studies to obtain NIR spectra with reduced noise. NIR spectra were obtained from two sugarcane varieties using three cleaning methods (wax not removed, polyurethane abrasive sponge, and stainless steel sponge), and the sample sizes ranged from 2 to 8 stalk. Different pre-treatments were compared by principal components analysis (PCA). The p-value associated with the Mahalanobis distance measure was used to choose the best number of stalks to be sampled. PCA results demonstrated that the stainless steel sponge method is the most efficient procedure for distinguishing between the different sugarcane varieties once all wax is removed from the surface. Four stalks are necessary to obtain the average spectrum (p-value < 0.05).