Application of Near Infrared Reflectance Spectroscopy (NIRS) for Macronutrients Analysis in Alfalfa (\u3ci\u3eMedicago sativa\u3c/i\u3e L.)

Near infrared reflectance spectroscopy was used to assess the mineral composition of alfalfa (Medicago sativa L.) as a tool for nutritional diagnosis. One hundred and ninety four (n = 194) samples of alfalfa from different locations representing a wide range of soils were used. Samples were reflectance scanned in a NIRS 6500 (NIRSystems, USA) instrument. The coefficients of determination (R2) of the regression estimate of the concentration of nitrogen, calcium, phosphorus, potassium, magnesium and sulphur and the errors in cross validation (SECV) were 0.93 (SECV: 1.6), 0.95 (SECV: 1.3), 0.93 (SECV: 1.9), 0.88 (SECV: 2.8), 0.82 (SECV: 1.9) and 0.75 (SECV: 4.7) respectively. The best NIRS predictions were obtained for calcium and nitrogen, meanwhile the poorest was obtained for sulphur