CALIBRATION OF A NEAR-INFRARED REFLECTANCE MOISTURE METER FOR GRASS

In earlier work it was shown that the moisture content of grass samples could be inferred from the reflectance of the sample at two wavelengths in the near infrared. However, in that work it was noted that the relationship between sample reflectance and water content was dependent on the variety and maturity of the grass samples. This severely limited the usefulness of the device. The present paper investigates the reasons for the variation in calibrations and shows how the calibration obtained for one grass variety at a given stage of maturity can be applied to any grass sample provided that the dry matter of the standing crop is known. The overall accuracy of the instrument, using this calibration procedure, on 12 different grass types varied between ±3 and ±6% (wet basis). © 1993 Silsoe Research Institute.