The use of near infra-red reflectance spectroscopy for the determination of plant nitrogen.

Abstract

A Near Infra-Red Reflectance Spectrophotometer was calibrated to analyse Italian ryegrass for protein nitrogen (N). Ryegrass samples having a wide range in N content were analysed by standard "wet" chemistry techniques and the resulting data used to calibrate the Near Infra-Red Spectrophotometer for ryegrass N analysis. A correlation (r) of 0, 99 and standard error of calibration (SEC) of 0, 209 resulted from the initial regression analysis between the Near Infra-Red Spectroscopy (NIRS) estimated and "wet" chemistry data. In order to further evaluate the accuracy of the NIRS calibration a separate set of ryegrass samples were analysed for N content, by both the "wet" chemistry and NIRS methods, resulting in a correlation (r) of 0, 98 and standards error of prediction (SEP) of 0, 235. The applicability of the NIRS ryegrass calibration to other species was briefly examined by estimating the N content of Kikuyu (Penisetum clandestinum) (r = 0, 97 and SEP = 0, 277).

Keywords: italian ryegrass; kikuyu; lolium multiflorum; near infra-red spectroscopy; nitrogen; plant physiology; protein; regression analysis; ryegrass; south africa; spectroscopy; technique