Abstract
Phenological models applied to grapevines are valuable tools to assist in the decision of cultural practices related to winegrowers and winemakers. The two-parameter sigmoid phenological model was used to estimate the three main phenological stages of the grapevine development, i.e., budburst, flowering, and veraison. This model was calibrated and validated with phenology data for 51 grapevine varieties distributed in four wine regions in Portugal (Lisboa, Douro, Dão, and Vinhos Verdes). Meteorological data for the selected sites were also used. Hence, 153 model calibrations (51 varieties × 3 phenological stages) and corresponding parameter estimations were carried out based on an unprecedented comprehensive and systematized dataset of phenology in Portugal. For each phenological stage, the centroid of the estimated parameters was subsequently used, and three generalized sigmoid models (GSM) were constructed (budburst: d = −0.6, e = 8.6; flowering: d = −0.6, e = 13.7; veraison: d = −0.5, e = 13.2). Centroid parameters show high performance for approximately 90% of the varieties and can thereby be used instead of variety-specific parameters. Overall, the RMSE (root-mean-squared-error) is < 7 days, while the EF (efficiency coefficient) is > 0.5. Additionally, according to other studies, the predictive capacity of the models for budburst remains lower than for flowering or veraison. Furthermore, the F-forcing parameter (thermal accumulation) was evaluated for the Lisboa wine region, where the sample size is larger, and for the varieties with model efficiency equal to or greater than 0.5. A ranking and categorization of the varieties in early, intermediate, and late varieties was subsequently undertaken on the basis of F values. These results can be used to more accurately monitor and predict grapevine phenology during a given season, thus supporting decision making in the Portuguese wine sector.
Highlights
Phenology can be understood as the study of the phenological events, or the stages of plant development that occur during their active lifecycle, in response to climatic conditions [1]
The main objective of the present study is to develop tools to support the winegrower’s decision in Portugal
In the analysis of the average values of the different phenological stages, the grapevine varieties were split into early, intermediate, and late, which correspond to Quartile 1 (≤ 25%), Quartile 2 + Quartile 3
Summary
Phenology can be understood as the study of the phenological events, or the stages of plant development that occur during their active lifecycle, in response to climatic conditions [1] Sci. 2020, 10, 3708 important in agriculture, as crops are subject to continuously evolving environmental conditions. For a specific site and year, the farmer may vary strategies, such as irrigation, to adapt a particular crop to the current environmental conditions [2], aiming to maintain or even improve the annual productivity and income. The development of grapevines is mainly influenced by climatic elements [3], such as temperature, solar radiation, and precipitation, which influence the production and the quality of grape berries [4,5]. Temperature is the main forcing element on the phenology of grapevines [6,7]
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