The PLS-CV model for the determination of total crude protein content of forages harvested in May from a permanent meadow (Grădinari; Caraş-Severin), using NIR spectroscopy

Abstract

This paper presents our studies regarding the determination of total crude protein content (%) from forages, using NIR Spectroscopy. The forage samples were harvested in the middle of May 2008 from a permanent meadow situated in Caraş-Severin County, near Grădinari. The permanent meadow was organized in ten trials with different doses of organic and mineral fertilizations and five replicates for each trial. The fertilization of permanent meadow was made using: GP1 - unfertilized variant, GP2 - 20 t sheep manure, GP3 - 40 t sheep manure, GP4 - 60 t sheep manure, GP5 - 20 t sheep manure + 50 P2O5, GP6 - 20 t sheep manure + 50 P2O5 + 50 K2O, GP7 - 20 t sheep manure + 50 N + 50 P2O5 + 50 K2O, GP8 - 100 N + 50 P2O5 + 50 K2O, GP9 - 150 N + 50 P2O5 + 50 K2O, GP10 – (100 + 100) N + 50 P2O5 + 50 K2O. The main species founded on the permanent meadow from Grădinari were: Festuca rupicola and Calamagrostis epigeios. Other species were Antohoxanthum odoratum, Briza media, Poa pratensis, Trifolium arvense, Trifolium medium, Lotus corniculatus and Filipendula vulgaris. The mathematical model (PLSCross Validation model) for the determination of total crude protein content (%) by NIR method was performed using the values of reflectance from NIR spectra and those obtained with chemical Kjeldahl method. For the statistical interpretation we used UNSCRAMBLE software. The external calibration was made using forage samples harvested from the same permanent meadow, but in March 2008.