The production of temperate climate fruits, such as apples, has its “secrets”. One of them is the accumulation of cold hours recorded between April 1 and September 30 each year. This is a very important measurement for guiding orchard management.
Between late autumn and early winter, fruit trees enter a state of dormancy, when there is a drastic reduction in their metabolic activity. Each fruit tree needs a minimum amount of cold to come out of this state.
Two methods are used to measure the amount of cold required to break dormancy. The cold hours represent the sum of temperatures recorded below or equal to 7,2°C. The cold units are calculated using the Modified North Carolina Method. Both methods consider the interval between the beginning of April and the end of September.
The Cold Monitoring available on the website of the Agricultural Research and Rural Extension Company of Santa Catarina (Epagri/Ciram) provides this information to producers and technicians working in the area. To improve the service, the page was updated and now provides more information, which is especially valuable for regions of the state where there are few automatic weather stations.
According to Angelo Massignam, a researcher at Epagri/Ciram and one of those responsible for the changes, seven new maps were added to the cold monitoring system. The innovations provide more detailed information about areas that have fewer automatic weather stations. The technology does this by interpolating information generated by the surrounding stations.
New graphs have also been added to the tool. They show the average air temperature for the current year and the average climatological air temperature for decades, between 1993 and 2023. “This detail helps fruit growers, technicians and students linked to the sector to monitor the evolution of this year's temperatures compared to the average temperatures of the last 30 years”, explains Ângelo.
Another way to follow the cold monitoring is through the monthly bulletins available on the page. The September bulletin reports that the accumulated cold hours from April 1 to August 31, 2024 were below the historical average in all monitored locations, with the exception of São Joaquim, which was slightly above average. The document also reports that the accumulation of cold units in the period was below the historical average in all monitored locations.
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