Spectral response of grapevine (Vitis vinifera L.) cultivar Riesling to foliar applications

Bodor-Pesti, Péter and Váradi, Gyula and Hüvely, Attila and Pető, Judit and Nyitrainé Sárdy, Diána and Deák, Tamás and Varga, Zsuzsanna and Masiero, Luca and Németh, Erzsébet Krisztina (2025) Spectral response of grapevine (Vitis vinifera L.) cultivar Riesling to foliar applications. PROGRESS IN AGRICULTURAL ENGINEERING SCIENCES, 21 (1). pp. 425-441. ISSN 1786-335X

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Abstract

This study investigates the effects of different foliar applications on the spectral characteristics of grapevine ( Vitis vinifera L.) cv. Riesling leaves. In addition to untreated control plants, experimental plots were treated with natural bioactivator extracts and microelements. Leaf samples were collected at the beginning of July and September 2024, referring to E-L33-34 and E-L38 Eichhorn-Lorenz phenological stages. Reflectance measurements were performed on leaf discs of uniform size ( r = 10 mm; A = 314.2 mm 2 ) using a CI-710 Leaf Spectrometer. Spectral data were analyzed using principal component analysis (PCA), and selected wavebands were utilized to compute vegetation indices, including NDVI (Normalized Difference Vegetation Index), EVI (Enhanced Vegetation Index), CI-G (Chlorophyll Index Green), MCARI (Modified Chlorophyll Absorption Ratio Index), NDRE (Red-Edge Normalized Difference Vegetation Index), VARI (Visible Atmospherically Resistant Index), and PRI (Photochemical Reflectance Index). PCA revealed that the first principal component (PC1) accounted for 54.3% of the total variance, while PC2 and PC3 explained 35.5 and 5.5%, respectively. The highest loading for PC1 was observed at 725 nm, whereas for PC2, it was at 505 nm. Analysis of variance (ANOVA) indicated that the applied treatments had a statistically significant effect on the vegetation indices. These findings highlight the impact of foliar applications and corroborate previous results demonstrating that leaf chlorophyll content and morphology are influenced by different treatments.

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