Print version ISSN 0365-2807
ORTEGA-FARIAS, Samuel; FLORES, Luis and LORENZO, León. Elaboration of a predictive table of apple diameter cv. Granny Smith using growing degree days. Agric. Téc. [online]. 2002, vol.62, n.4, pp. 624-632. ISSN 0365-2807. doi: 10.4067/S0365-28072002000400014.
A study was performed in three orchards of San Fernando, VI Region, Chile, in order to develop a predictive table of apple size (Malus domestica Borkh.) using a logistical equation, whose main variable was accumulated degree days (GDA). To this end, data were collected on fruit equatorial diameter and air temperature for the 1989/90 and 1992/93 seasons in three apple orchards cv. Granny Smith. Sampling was carried out from 80 GDA until harvest, selecting 5 trees in each orchard, in which 40 fruit/tree were chosen, covering all the size ranges, at a height approximately 1.0 to 2.0 meters about the soil. At harvest, the evaluated fruit was grouped according to four ranges of diameter (63-68, 69-74, 75-80, and 81-86 mm), to develop the logistic growth models as a function of GDA. The results of this study indicated that the implemented models were able to estimate apple sizes with a coefficient of determination (r2), absolute error (Ea) and standard error of estimate (SEE) ranging from 0.91 to 0.94; 5.8 and 6.7%; and 3.0 to 3.6 mm, respectively. Based on these statistical results a predictive table able to predict apple size as a function of GDA was constructed, which presented an Ea of 5% starting at 600 GDA.
Keywords : logistic model; fruit size; apple growth; pome fruit.