Predicting Soluble Nitrogen and Fibrous Fractions in Crested Wheatgrass with Near-Infrared-Reflectance Spectroscopy

Abstract

A near-infrared-reflectance (IR) spectroscopic method was evaluated for potential usage in predicting soluble N, total N and some fibrous fractions in crested wheatgrass, Agropyron cristatum (L.) Gaertn., A. desertorum (Fisch. ex Link), et al. The correlation coefficients (r) between IR and total N, soluble N in 0.15N NaCl (N Sal), soluble N in 10% Burroughs Mineral Mixture solution (NBMM), neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) for 84 samples were 0.95, 0.90, 0.70, 0.90, 0.82, and 0.72, respectively. The IR technique provided a closer estimation of total N and N Sal than of NBMM in the calibration data. The mean solubility of N Sal was higher than that of NBMM. High variation occurred between the duplicate determinations of NBMM. The predictions on 30 unknown samples by the equation developed using 84 calibration samples for mean, SED (standard error of difference), and r were: total N, 1.01, 0.04, 0.98; N Sal, 0.43, 0.04, 0.90; NDF, 64.1, 0.96, 0.93, ADF, 36.2, 1.01, 0.91; and ADL, 5.24, 0.53, 0.62. Predictions of fibrous fractions were highly satisfactory even though the correlations were low. Correlations between chemical determinations of total N and N Sal, NBMM, NDF, ADF, ADL were 0.89, 0.53, -0.13, -0.33, -0.08, respectively. Significant differences (P<0.01) were found among crested wheatgrass species for all nitrogenous and fibrous fractions measured. Differences among clonal lines within species were also significant (P<0.05 or 0.01) for all determinations indicating that opportunities are available to improve the nutritional value of crested wheatgrass through selection.