Crop biomass evaluation using radiometric measurements

Abstract

Crop biomass can be evaluated from radiometric measurements either by relating biomass to instantaneous measurements or by relating an integral of biomass to a radiometric value integrated over the corresponding portion of the growth period.

In this study, the success obtained by using these two methods is discussed. A simple radiative transfer model was used in conjunction with experimental results to demonstrate the universality of the relationship between the normalized difference vegetation index (ND) and leaf area index (LAI) or the photosynthetically active radiation (PAR) absorbed by the crop. It shows that the relationship between ND and absorbed PAR is less dependent on leaf orientation than the relationship between ND and LAI. A remaining problem is the sensitivity of those two relationships to soil optical properties. Nevertheless, temporal integration of radiometric data using the absorbed PAR concept appears to be a more promising approach than one-time measurements.