Acta Scientiarum Polonorum: Hortorum Cultus (Dec 2012)
THE SUM OF ACTIVE TEMPERATURES AS A METHOD OF DETERMINING THE OPTIMUM HARVEST DATE OF ’ŠAMPION’ AND ‘LIGOL’ APPLE CULTIVARS
Abstract
The harvest date is crucial for the storability of autumn apple cultivars like ’Šampion’ and winter apples cultivars like ‘Ligol’ intended for long storage. Only apples picked at the optimum maturity stage are suitable for storage over 3 months because of better storage potential and organoleptic quality. The research was conducted in the cold storage facility and laboratory of the Department of Pomology of the Poznan University of Life Sciences between 1999 and 2006 and was designed to evaluate and determine the sum of accumulative temperatures for both cultivars. Fruits were collected every 4–5 days starting some weeks before the estimated OHD. Maturity at harvest was evaluated in terms of firmness, TSS, starch disintegration, ground colour and titrable acidity. There were 3–4 main harvests from which fruits were stored in a cold storage facility for 3 months. The storability of apples was evaluated after an equal number of days of storage respectively to their harvest date. The evaluation was based on subjective quality judgments and measurements made after storage. The air temperatures in the orchard were measured every 2 hours. The results obtained from the four loggers provided the basis for the calculation of (a) the average day temperature and (b) the cumulative temperature, for which the values of 0.0°C, 4.0°C, 5.0°C, 10.0°C, and 15.0°C were taken respectively as reference. After eight years of study the optimal value of the SAT for ’Šampion’ was determined at 2550 degrees and for ‘Ligol’ at 2600 degrees with 0°C as the base temperature. The OHD was determined most accurately for both cultivars taking 0°C as the base temperature. The SAT method was recognized as the basis for determining the harvest date of the apple cultivar ‘Šampion’ and ‘Ligol’.
