GiESCO 2019 banner
IVES 9 IVES Conference Series 9 GiESCO 9 GiESCO 2019 9 Sensitivity of vis‐nir spectral indices to detect nitrogen deficiency and canopy function in cv. Barbera (Vitis vinifera L.) Grapevines

Sensitivity of vis‐nir spectral indices to detect nitrogen deficiency and canopy function in cv. Barbera (Vitis vinifera L.) Grapevines

Abstract

Context and purpose of the study ‐ Precision nutrient management in viticulture can be addressed on the basis of a spatial characterization of within‐vineyard vine nutritional status derived from proximal or remote spectral observations. However, a key challenge is the discrimination between mineral deficiencies and water stress related issues, often coexisting under low vigor conditions. In addition several mineral disorders are associated to a decrease in chlorophyll concentration in leaves resulting in a wide array of symptoms classified as chlorosis. Despite clearly associated to their origin, visible symptoms appear too late for supporting an efficient mineral management; thus, non‐destructive early detection of either asymptomatic excess or deficient status become a challenging task of precision viticulture. This work evaluates the Vis‐NIR reflectance spectra and the sensitivity of the derived‐spectral indices to detect nitrogen deficiency in grapevines.

Material and methods ‐ Well N‐fertilized vs. unfertilized vines were compared over two seasons (2016 and 2017) on Vitis vinifera L. cv. Barbera potted vines. For each treatment, 24 leaves from eight representative vines were tagged in order to collect, at different phenological stages, contact Vis‐NIR spectra and perform physiological measurements. The performance of several spectral vegetation indices sensitive to different biophysical (i.e. chlorophyll and carotenoids content, leaf area index) and physiological parameters (light use efficiency) was measured by means of a sensitivity (signal to noise ratio) analysis. Leaf greenness index was monitored with a handheld chlorophyll meter SPAD 502 whilst single‐leaf gas exchanges were assessed by using a handheld analyzer. Multispectral analysis was associated to a rigorous ground‐truthing as it concerns shoot growth, yield, fruit composition and pruning weight.

Results – In both years the differential fertilization increased leaf N concentration of N+ vines at veraison. Vine performance varied according to plant vigor and nutritional status. N+ increased canopy growth, vine productivity, and bunch compactness whilst N0 enhanced the proportion of shot berries and reduced titratable acidity and malate in juice. N deficiency resulted in lower SPAD readings and assimilation rates as compared to well N‐fertilized vines. N0 vs N+ contact Vis‐NIR spectra differed in Green and Red‐edge regions with faster responses on basal leaves. Data were associated to a different sensitivity of Vis‐NIR spectral indices specially when based on the Red‐edge bands showing higher efficiency in detecting leaf N concentration since early stages of canopy growth.

DOI:

Publication date: June 22, 2020

Issue: GiESCO 2019

Type: Article

Authors

Matteo GATTI (1,2), Alessandra GARAVANI (1,2), Alberto VERCESI (1), Cecilia SQUERI (1), Michele CROCI (1,2), Ferdinando CALEGARI (2), Massimo VINCINI (2), Stefano PONI (1,2)

(1) DIPROVES Università Cattolica del Sacro Cuore, Via E. Parmense 84, I-29122 Piacenza, Italy
(2) CRAST Università Cattolica del Sacro Cuore, Via E. Parmense 84, I-29122 Piacenza, Italy

Contact the author

Keywords

Mineral nutrition, Visual symptoms, Leaf age, Assimilation, Yield components, Phenotyping

Tags

GiESCO 2019 | IVES Conference Series

Citation

Related articles…

Aromatic stability of Syrah and Petit Verdot tropical wines from Brazil

The production of fine wines in the Sub-middle of the São Francisco River Valley, Northeast of Brazil, is relatively recent, about twenty-five years ago. This region presents different characteristics

MODULATION OF YEAST-DERIVED AROMA COMPOUNDS IN CHARDONNAY WINES USING ENCAPSULATED DIAMMONIUM PHOSPHATE TO CONTROL NUTRIENT RELEASE

Yeast-derived aroma compounds are the result of different and complex biochemical pathways that mainly occur during alcoholic fermentation. Many of them are related -but not limited- to the availability of nutrients in the fermentation medium and linked to nitrogen metabolism and biomass produced. Besides, the metabolic phase of yeast also regulates the expression of many enzymes involved in the formation of aroma active compounds. The work investigates the overall effect of continuous supplementation of nutrients during alcoholic fermentation of a grape must on the volatile composition of wines.

Comparison of imputation methods in long and varied phenological series. Application to the Conegliano dataset, including observations from 1964 over 400 grape varieties

A large varietal collection including over 1700 varieties was maintained in Conegliano, ITA, since the 1950s. Phenological data on a subset of 400 grape varieties including wine grapes, table grapes, and raisins were acquired at bud break, flowering, veraison, and ripening since 1964. Despite the efforts in maintaining and acquiring data over such an extensive collection, the data set has varying degrees of missing cases depending on the variety and the year. This is ubiquitous in phenology datasets with significant size and length. In this work, we evaluated four state-of-the-art methods to estimate missing values in this phenological series: k-Nearest Neighbour (kNN), Multivariate Imputation by Chained Equations (mice), MissForest, and Bidirectional Recurrent Imputation for Time Series (BRITS). For each phenological stage, we evaluated the performance of the methods in two ways. 1) On the full dataset, we randomly hold-out 10% of the true values for use as a test set and repeated the process 1000 times (Monte Carlo cross-validation). 2) On a reduced and almost complete subset of varieties, we varied the percentage of missing values from 10% to 70% by random deletion. In all cases, we evaluated the performance on the original values using normalized root mean squared error. For the full dataset we also obtained performance statistics by variety and by year. MissForest provided average errors of 17% (3 days) at budbreak, 14% (4 days) at flowering, 14.5% (7 days) at veraison, and 17% (3 days) at maturity. We completed the imputations of the Conegliano dataset, one of the world’s most extensive and varied phenological time series and a steppingstone for future climate change studies in grapes. The dataset is now ready for further analysis, and a rigorous evaluation of imputation errors is included.

Cordon height and deficit irrigation practices interact to affect yield and fruit quality of Cabernet Sauvignon and petite Sirah grown in a hot climate

Cabernet Sauvignon and Petite Sirah are the top red wine cultivars in CA, however, the hot climate in Fresno is not ideal for red Vitis Vinifera, particularly for berry color development. Mechanical pruning and irrigation were studied previously to significantly affect grapevine yield performance and berry quality. But there is lack of studies on cordon height and irrigation on mechanical pruned vineyard system.

Vinhos de talha: to pitch or not to pitch

In Alentejo, south of Portugal there is a traditional way of fermenting wines in clay vessels, known as “Vinhos de Talha”. Clay vessels were traditionally impermeabilized using pine pitch, creating a barrier between the fermenting must and the clay. Due to this unusual production technology that uses of clay vessels, instead of inox or wood vessels, “Vinhos de Talha” present unique characteristics increasingly appreciated by national and international consumers when compared with wine obtained by the said traditional methods of winemaking. Although the positive consumers feedback, there is little literature about the physical-chemical characteristics of these wines (Martins et al, 2018; Cabrita et al, 2018). This work aims to characterize the volatile composition of white wines produced in clay vessels with different coatings and to contribute to the knowledge and preservation of these wines that are a unique cultural heritage. Wine samples were produced during 2019 vintage from white grapes, using the traditional technology associated to these wines.