Date: January 31, 2014

Title: Predicting Key Phenological Stages for Grapevines: A Simple but Scientific Approach for Management and Site Selection

Principal Investigator(s): Gerrit Hoogenboom, Melba Salazar, and Markus Keller
Organization: AgWeatherNet Program and Viticulture & Enology Program, Washington State University
Address: 24106 North Bunn Road, Prosser, WA 99350
Phone: 509-786-9371 (Hoogenboom); 509-786-2226 (Salazar); 509-786-9263 (Keller)

Collaborator(s): Diana Zapata, Graduate Student
Organization: Department of Biological Systems Engineering, AgWeatherNet Program, WSU, Prosser, WA 99350

Project Budget Number: 10A-3096-0786

I. Project Summary:

Temperature is one of the most important and controlling factors in grapevine development. The base temperature (Tb) defined as the temperature threshold below which plant growth ceases varies depending on the cultivar. In general, cultivars with a lower Tb have earlier bud break than those with a higher Tb. Grapevine growth and development is proportional to biological time, or thermal time, which can be defined as the integral of time and temperature above a certain threshold. This constitutes the concept of growing degree days (GDD). The objectives of this study were (i) to determine the Tb of key phenological stages for grapevine and (ii) determine the duration for the key development stages as a function of grapevine cultivar. We used three phenological stages including budbreak, full bloom and veraison for four cultivars, including Cabernet Sauvignon, Chardonnay, Merlot, and Riesling. Different methods were used for determining Tb.

In general, we found an increase in Tb during grapevine development from first swell until veraison. Cabernet Sauvignon and Riesling had the highest values for Tb for all the phenological stages that were considered. GDD required from bud burst to veraison varied from 2010.6°F to 2284.2°F for Riesling and Merlot, respectively. The results of this study provided valuable information for determining the development of grapevine from available local weather data. Any delay in the initial developmental stages such as budbreak has an impact on the entire cycle. It is, therefore, a critical factor in the selection of a cultivar based on its precocity for vineyard establishment. Initial parameters were obtained for the development of a growing-degree day model for different grape cultivars that can ultimately be implemented on the AgWeatherNet web site as a decision support tool.

Read more by downloading the full report above.

Viticulture //