Climate availability for apple trees in Vacaria, southern Brazil/Disponibilidades climaticas para macieira na regiao de Vacaria, RS

This study aimed to evaluate the variability and temporal tendency for the main climate parameters--air maximum, minimum and mean temperatures, chilling hours (bellow to 7°C), pluvial precipitation, and relative air humidity --in the 1983-2009 period, focusing to evaluate the climate conditions for Gala and Fuji apple groups, in Vacaria, Brazil. Daily weather data in the 1983-2009 series were compared to climate means of the 1931-1960 and 1961-1990 periods, for analyzing the temporal trends. The annual pluvial precipitation showed significant differences in comparing the 1983-2009 series to both the climate means, with increments of 479 and 256mm, respectively. There were no significant differences in monthly air temperatures among the analyzed periods. The pluvial precipitation in spring season and the annual mean of minimum air temperature showed significant tendencies for increasing. The mean number of 657chilling hours was from May to August. The minimum number of chilling hours defined zoning of agroclimatic is achieved in most of the years, in Vacaria, however, does not mean the natural breaking of bud dormancy the apple tree. Otherwise, the number of chilling hours had a significant tendency for reducing. Key words: Malus domestica, climate, temperature, chilling, pluvial precipitation, dormancy. O objetivo deste trabalho foi avaliar a variabilidade e as tendencias temporais das principais variaveis climaticas--temperaturas maxima, minima e media do ar, horas de frio (abaixo de 7°C), precipitacao pluvial e umidade relativa do ar--no periodo 1983-2009 e confronta-las com as necessidades de macieiras dos grupos Gala e Fuji, na regiao de Vacaria, RS. Foram utilizados dados diarios de estacao meteorologica da Embrapa, do periodo de 1983 a 2009, e comparados com as normais 1931-1960 e 1961-1990, para analise de tendencia temporal. A precipitacao pluvial apresentou diferencas significativas entre a media do periodo 1983-2009 e as normais, com aumentos de 479 e 256mm, respectivamente. Nao houve diferencas significativas na temperatura do ar mensal entre os periodos analisados. A precipitacao pluvial da primavera e a temperatura minima do ar mensal apresentaram tendencia significativa de aumento. O numero medio de horas de frio foi de 657 de maio-agosto. O numero minimo de horas de frio delimitado no zoneamento agroclimatico e atingido, na maioria dos anos, na regiao de Vacaria, no entanto, nao significa a superacao natural da dormencia de gemas de macieira