NUTRITIONAL EVALUATION OF CROP RESIDUES USING NEAR INFRARED REFLECTANCE SPECTROSCOPY

Abstract

Traditionally, the nutritional constituents of forages were determined by tedious wet-chemistry methods which did not match with current analytical requirements in terms of quickness, easiness, cheapness, effectiveness and accuracy offered by the near infrared reflectance spectroscopy (NIRS). Two studies were carried out to the use of NIRS for evaluating the nutritional composition (CP, IVOMD and NDF) of crop residues. In the first study, 561 samples of sorghum and 1010 samples of groundnut residues with already determined wet-chemistry values were subjected to NIRS scan to determine the prediction power and analytical efficiency of the NIRS technique in relation to the routine methods. The results showed higher R2 of 0.89 and 0.86 for CP and NDF respectively and a moderate R2 of 0.36 for IVOMD. The 1010 groundnut samples analysed with NIRS produced more consistent values (CV% of 15.88, 7.54 and 11.19 for CP, IVOMD and NDF respectively) than values obtained by the wet-chemistry methods (CV% of 18.18, 8.68 and 13.35 for CP, IVOMD and NDF respectively). There was a higher correlation (r = 0.89, 0.88 and 0.82 for CP, IVOMD and NDF respectively) between values measured with both techniques (p˂0.05). In the second study, comparative review was done with NIRS and routine methods viz., accuracy, speed and cost. The results showed that the routine methods are not only time-consuming, they are expensive and also less consistent than NIRS method. In conclusion, the study indicates that NIR spectroscopy calibrated properly for groundnut haulms and sorghum stover and thus has potential for effectively quantifying the nutritional components of sorghum and groundnuts residues with acceptable accuracy, precision and repeatability.