ISHS Acta Horticulturae 184: I International Symposium on Computer Modelling in Fruit Research and Orchard Management
FIRST EXPERIENCES WITH CHILL-UNIT MODELS IN SOUTHERN BRAZIL |
| Authors: | A. Ebert, J.L. Petri, R.J. Bender, H.J. Braga |
| Abstract:
The Utah and North Carolina chill-unit models were tested at three locations in Santa Catarina and compared with the model of chilling hours below 7.2°C. At São Joaquim (1415 m elevation) the number of estimated chilling hours was very low during 1982, bud break of apple trees, however, was normal. Apparently temperatures above 7.2°C and fluctuating temperatures affected chilling. The chill-unit models considering a broader temperature range with positive or negative chill-unit contribution accumulated during 1982 a similar amount of chill-units in comparison with the other years. In general, the chill-unit models showed better agreement with bud break data than did the number of hours below 7.2°C. Modifications of both models concerning cycle lenght of high temperature influxes resulted in notable increase in accumulated chill-units with the Utah model at the lower elevations. The North Carolina model seems to be better suited for the conditions of Southern Brazil than the Utah Model. | |
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