Use of canopy- and leaf-reflectance indices for the detection of quality variables of Vicia species

Abstract

Laboratory determinations of plant-nutrient contents are time consuming and costly. Measurements of reflectance may provide a rapid and accurate means of estimating plant quality variables. This study was conducted to determine relationships between nitrogen (N), phosphorus (P), potassium (K), acid detergent fibre (ADF) and neutral detergent fibre (NDF) contents of Vicia sativa, Vicia pannonica and Vicia villosa and their canopy- and leaf-reflectance indices. Canopy- and leaf-reflectance measurements were made by using a portable spectroradiometer and a plant probe. Linear equations between each forage quality variable and the simple ratio of reflectances in the near-infrared (R _NIR) to red regions (R _Red) of the electromagnetic spectrum, R _NIR/R _Red, or the normalized difference vegetation index, NDVI, had coefficients of determination, R ², of 0.45 ≤ R ² ≤ 0.80 and 0.49 ≤ R ² ≤ 0.85 at wavelengths of 760 and 640 nm, respectively. Validation of developed equations indicated that all quality parameters could be predicted by either NDVI or R _NIR/R _Red. Our results suggest that N, P, K, ADF and NDF contents of vetch species can be estimated at the beginning of the flowering stage and throughout the seed-filling stage using remote-sensing data of both canopy- and leaf-reflectance indices.

Acknowledgement

This work was supported financially by TUBITAK (Scientific and Technological Research Council of Turkey, project no. 106O554).