Abstract
The grapevine vegetative cycle, which is morphologically described by its phenological stages, is strongly determined by weather conditions. Phenological models are widely applied in viticulture and are based on the assumption that air temperature is the preponderant environmental factor which determines vine development. In this study, phenological development models (PDMs) were calibrated and validated to simulate several intermediate stages between budbreak and veraison for cv. Touriga Nacional (TN) and cv. Encruzado (EN) winegrape varieties, which are widely grown in the Dao Wine Region, Portugal. These are thermal models, with which the daily sum of the rate of forcing (R) was calculated using a sigmoid function. For this purpose, a high-quality and comprehensive dataset was used which combines phenology data and weather station data in several vineyard sites spread over the region. The model showed an overall high performance (global RMSE of 5.4 days for EN and 5.0 days for TN), although it depended on the phenological stage and variety. The RMSE ranged from 3.2 to 6.2 for TN, and from 3.9 to 6.8 for EN. For both varieties and in all phenological stages, the RMSE was significantly lower than the standard deviation of the phenological observations. For TN, the model efficiency was greater than 0.71 for all phenological stages. In future studies, these models will be combined with specific models that simulate the evolution of winegrape berry quality indicators commonly used for harvest decision support. The relatively low complexity of the selected PDMs enables their use as a crop management and decision support tool. To our knowledge, no previous studies have been carried out on either of these two varieties and their intermediate phenological timings. The present study is an illustration of conceivable model development under diverse environmental conditions, thus allowing similar approaches to be adopted in other wine regions on a worldwide scale.
Highlights
The Dão winegrowing region is located on a plateau in the central part of northern Portugal
If the models are to be used as a vineyard management support tool, it will be necessary to determine whether the accuracy of the models can be significantly improved via one-off readjustments in the F* values when an intermediate phenological dates are available
A phenological development model (PDM) for predicting several intermediate stages between budbreak and veraison of two grapevine Portuguese varieties (Touriga Nacional and Encruzado) growing in the Dão wine region was developed in this study
Summary
The Dão winegrowing region is located on a plateau in the central part of northern Portugal It is surrounded by mountains and is protected from both the Atlantic moist winds and the continental influence from inner Iberia. Ninety‐seven percent of vineyard soils are derived from granite (Dias, 1995), and are classified as Humic or as Dystric Cambisols according to the FAO Soil Classification (FAO, 2015). These are coarse-textured soils, which have a slightly acid reaction and low organic matter content, but they are reasonably enriched with phosphorus (Almeida, 2005)
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