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Growth Regulators in Orchard Management
University of California
Growth Regulators in Orchard Management

Dynamic Model & Chill Accumulation

An illustrated step-by-step guide for calculating Chill Portions (CP) using weather data collected from personal data loggers and the Dynamic Model. Available here: The guide, a PowerPoint presentation: Dynamic Model & Chill Accumulation Guide - Glozer (pdf) and The Dynamic Model, an Excel file: Dynamic Model (excel file)

  • California often provides too little chilling for optimum dormancy and rest-breaking for some chill-requiring crops. Research to overcome lack of chilling includes developing methods to measure chill accumulation under California’s conditions. 
  • Chill accumulation can be calculated using various mathematical models. UC Davis researchers, with the cooperation of many growers, have tested the Dynamic Model as a way of calculating chill accumulation. The model calculates chilling accumulation as ‘chill portions’ using a range of temperatures from ~35-55°F, and accounts for chill cancellation due to fluctuating warm temperatures.

Hourly data is needed for Dynamic Model calculations. For those who collect temperature data every 1-0 minutes is provided: Information and calculation instructions are provided here: Sorting Temperature Data to Get Hourly Data 

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