Measurements by field radiometry on a Brazilian vineyard

Abstract

Spectral parameters as the NDVI (Normalized Difference Vegetation Index) are helpful to monitor developing stages in vegetation, including the detection of water stress in vineyards. Even if other indices can be advantageous to observe vegetation, the NDVI is popular among those which join precision viticulture, since the red and infrared bands, which define this index, usually carry low noise, compared with the blue band in many products from radiometric devices and even from orbital sensors. Vegetation indices are valuable to map a terrain’s aptitude to grow crops, and in vineyards, have been helpful in the so-called “precision viticulture” to define which parcels would produce the best grapes. In this paper, we report NDVI measurements of a 2.1 hectares Chardonnay vineyard in the Serra Gaúcha region in south Brazil. Field data were acquired through a radiometer, with hyperspectral measurements of about 45 individual plants, which were used to derive the NDVI index. Spatial resolution of the grid was about 15 m x 20 m. Ground data were compared, through satellite images, with field information on spatial distribution of soil depth and fruit quality. Qualitative analysis show that there is an effective correlation between NDVI, soil depth and reported grape quality, indicating that radiometric measurements are instrumental to precision viticulture techniques.