The aim of this study was to determine four biometeorological indexes approach: Primault (P), Heliothermic Huglin Index (HHI), Heliothermic Geslin Index (HGI) and Photothermal Units (PU) for 'Niagara Rosada' cultivar pruned in the winter and summer seasons. The experiment was carried out on 13-year-old plants in Piracicaba, state of São Paulo-Brazil, evaluating 24 production cycles, 12 from the winter pruning and 12 from the summer pruning. The statistical design was comprised of randomized blocks, using the pruning dates as treatment: July 20th, August 4th, August 19th, and September 3rd (winter); February 1st, February15th, March 2nd, and March 16th (summer). Comparison of the mean values of P, HHI, HGI and PU among pruning dates was evaluated by the Tukey test, and comparison between pruning seasons was made by the F test for orthogonal contrasts, both at the 5% probability level. The results show that the inclusion of the meteorological element insolation and the photoperiod factor on thermal sum requirement is not proved effective in determining an average value for cycle prediction in vines pruned in different seasons; none of the biometeorological indexes are efficient for harvest prediction in vines pruned in different seasons; independent of the time when the cycle starts, the average of 120 days can be used to estimate the harvest date of vines in climate region Cwa.
grape; biometeorological index; heliothermal index; photothermal units
