Multispectral survey for precision viticulture

 

The strategic goal of precision viticulture is to know the vine in the detail of the individual plant and to adapt cultivation techniques to its specific needs.

The vineyards present high variability in their biophysical properties, and the many factors that define them can be classified as “static”, such as climate and some properties that describe soil properties (eg weaving, pH, carbonate content, depth, etc …), and “dynamic”, such as the thermal and water values of the soil, the nutrient content and the annual climatic trend. From this, it is clear that the fundamental question on achieving predetermined results is the need to measure the variability.

 

Multispectral survey is the fundamental tool for having agronomic knowledge of the agricultural resource because it allows a series of comparisons between the vegetative health conditions of the crop:

  • in the different vegetative stages expected during the seasons;

  • before treatment for targeted intervention;

  • after treatment for an assessment of the consequences;

  • in different plots to understand different reactions to equal interventions;

  • in different seasons to monitor growth and health.

 

Below you can view a dataset of orthophotos in the 8 different bands of a multispectral survey conducted with MAIA on a wineyard in the Franciacorta district, in the north of Italy, famous for the fine quality of grapes and wines. Please open images in a new tab to appreciate them in big size:

And then here below you can view the same portion of vineyard in orthphoto of different indexes and views calculated on the raster products shown above:

From multispectral data, it is possible to obtain a series of indexes capable of describing precisely the characteristics of the vegetation present on the soil. Among these vegetation indices, the best known is the Normalized Difference Vegetation Index (NDVI), which is based on a normalized difference between the near and red infrared bands. As evidenced by countless studies, the NDVI proves very reliable in describing the magnitude of photosynthetic active biomass present on the investigated surface. The NDVI index is in fact correlated positively with the amount of plant biomass per unit of surface (LAI, leaf area index) and, therefore, the vigor of culture. The index assumes values between +1 and -1: in particular, from 0.1 to 0.3 we usually find a naked or slightly inert soil, while in the case of plant biomass there is an index higher than 0.5, and it increases to identify a different vegetative state of the plant, and an increasing production of chlorophyll.

The contribution of specific vegetative indices to viticulture has been extensively studied and demonstrated, but it should be remembered that other interesting thematic maps for viticulturists can cover crop yields, acidity, sugars, polyphenols, anthocyanins.