Characterization of vine vigor by ground based NDVI measurements

Many farming operations aim at controlling the leaf area of the vine according to its load. There are several techniques, direct and indirect, of estimate of this leaf area in a specific way, but impossible to implement at great scales. These last years, research in airborne and satellite remote sensing made it possible to show that a multispectral index of vegetation, computed from measurements of reflectances (red and near infrared), the « Normalised Difference Vegetation Index » (NDVI), is well correlated to the « Leaf Area Index » (leaf area per unit of ground) of the vine. Nevertheless these methods of acquisition and processing data are rather constraining and complex. Recently, N-Tech Industries in collaboration with Oklahoma State University developed a ground sensing apparatus, the GreenSeekerTM, which measures the NDVI.
In this study, the GreenSeekerTM, active sensor, is shown to function independently of the climatic conditions when it is used with a screen. The NDVI delivered by the GreenSeekerTM is mainly sensitive to the variations of porosity of the foliage. However, it can be used to carry out a follow-up of the foliar growth of the vine, but with much of precautions. Linked to a GPS, it makes it ple to chart relative variations of vigor at an intraplot level.