Measurement of grapevine canopy leaf area by using an ultrasonic-based method.

Aim: Measurement of leaf area in grapevine has always been a critical point in researches focused on irrigation management, training systems, source-sink interrelationships and efficiency of spray application to canopies. In this work, we propose the use of ultrasonic sensors as a fast and accurate tool for the estimation of large portions of leaf canopy area. Methods and results: Through outputs of ultrasonic sensors installed on a tractor moving along vineyard rows, we calculated an ultrasonic-based leaf density index that we correlated with three measurements or estimates of canopy area: I) direct measurement of the area of a canopy portion (LAØ), assessed by summing the areas of all the leaves, where each single-leaf area was assessed by regressing the leaf diameter (the maximum width perpendicular to the main rip) against the related leaf area calculated on the basis of a relation between the leaf diameter and the leaf area, previously assessed through an area meter on a 20-leaf sample; II) the point quadrat output (LApq); and III) the canopy leaf area index (LAI) obtained through LAI-2000 (Li-Cor) technology. The measurements were assessed on six cultivars in three replicate rows (8-12 plants per cultivar per row) in a vineyard trained to a vertical trellis system. Conclusion: When we correlated the three independent control parameters with each other, we obtained highly significant correlations between LApq and LAØ, but less significant correlations between these two and LAI-2000 outputs. Also, the correlations between ultrasonic outputsoutputs and LAØ and LApq were significant, with R2 ranging between 0.84 and 0.85. On the contrary, no significant correlation was found between ultrasonic outputs and LAI-2000 outputs. These results were obtained by averaging all the values belonging to each replicated cultivar (10.5 m along the row, i.e., twelve contiguous vines); on the contrary, when the analysis was done over a shorter distance (3.5 m, i.e., four contiguous vines), the reliability of the ultrasonic-based method decreased. Significance and impact of the study: These results point to the ultrasonic technology as a powerful tool to estimate large-scale leaf canopy area, with potential applications in precision farming. At the moment, however, the limitation of this approach is the requirement of reference values for leaf area (e.g., assessed by point quadrat) to obtain absolute and not only relative outputs. With this application we can quantify, in a few hours, the canopy of a whole vineyard, in order to analyze different vegetation zones or to follow canopy development

MACSUR Project – The case study of vineyards. Eco-physiological and biophysical modeling applied to the growth and productivity of vineyards in northwestern Italy.

Viticulture in Italy is one of the economically most important agricultural sectors. Recent research allows eco-physiological and biophysical models to develop tools able to provide support to the crop management, in terms of optimizing production performance and limiting environmental impacts. The ability to check on a daily basis the activities of vegetative and productive phases of vines is certainly a fundamental tool for the vineyard organization and management, and for linking the trends of growth and productivity with the quality of the final product: the wine. Since some years, some researches are taking place in the vineyards of northwestern Italy, with the aim of modeling the eco-physiological behavior of the vines, using and valorizing all available historical field data related to the vegetative and productive behavior of the vines, as well as laboratory qualitative data. At the same time, our team is evaluating two different modeling approaches: one biophysical, using the land surface scheme UTOPIA (University of TOrino land Process Interaction in Atmosphere), and another one eco-physiological. The case-study vineyards, referred to the northwestern Italian territory, is part of a wider working program involving several integrated teams from Italy, Spain and Germany. The objectives are: to improve the use of the models used by different groups; to compare the results obtained by different modeling tools; to create a common database of field measurements; to study the relationships between vegetative-productive behaviors and quality of productions