Potential use of visible and near infrared reflectance spectroscopy for the estimation of nitrogen fractions in forages harvested from permanent meadows

One‐hundred and ninety‐two herbage samples from permanent meadows located in the mountains of León (NW Spain) were analyzed for total nitrogen (total N), nitrogen in trichloroacetic acid precipitated matter (TCAN), borate–phosphate buffer insoluble nitrogen (BPBN), neutral‐detergent insoluble nitrogen (NDIN) and acid‐detergent insoluble nitrogen (ADIN). These data were used to calculate the partition of nitrogen fractions proposed by the Cornell Net Carbohydrate and Protein System (CNCPS): A (total N ? TCAN), B₁ (TCAN ? BPBN), B₂ (BPBN ? NDIN), B₃ (NDIN ? ADIN) and C (ADIN). Near‐infrared reflectance spectroscopy (NIRS) technology accurately predicted total N, TCAN and NDIN, as judged by coefficient of determination (R²) and ratio performance deviation (RPD) values greater than 0.90 and 2.5, respectively. The rest of the insoluble N fractions (BPBN and ADIN) were predicted with less accuracy by NIRS. Estimations of CNCPS N fractions (A, B₁, B₂, B₃ and C) using visible–NIR spectra of forage samples did not allow accurate predictions (R² < 0.90; RPD < 2.5). Copyright © 2005 Society of Chemical Industry