Disponibilidade de frio para o cultivo de espécies frutíferas na metade sul do Rio Grande do Sul

Abstract

The production of temperate fruit trees plays an important role in Brazil, and Rio Grande do Sul has stood out in the production of some of these fruits such as grape, plum, apple, peach, fig, persimmon, kiwi, among others. And with that, the need arises to assess regional climatic conditions for better planning and introduction of new cultivars in the southern half of Rio Grande do Sul. Thus, this work comes with the purposal to quantify the availability of chiling hours below 7.2°C for the southern half of Rio Grande do Sul, as well as to estimate the accumulation of chiling hours and cold units based on methodology that allows the use of data from meteorological stations and establish the probability of occurrence of these Hours of Chiling and at the end determine the annual variation of hours of cold and their possible relations with the ENOS phenomena. For this, historical data from 1980 to 2019 from May to August were used. To determine the Number of Hours of Chiling, direct thermogram counting was used for Pelotas, and the NHF was estimated for the locations of Pelotas, Bagé, Uruguaiana, Santa Vitória do Palmar, Santana do Livramento and Encruzilhada do Sul a from the methodology proposed by Angelocci et al. (1979). The probability was used to verify the occurrence of cold over the years. In addition to NHF, Cold Units were estimated using the Utah, North Carolina and Modified Utah and North Carolina methods. And to verify the relationship between the ENOS phenomena and the NHF, the years were classified into La Niña, El Niño and Neutro according to the occurrence of the phenomenon in the coldest months of the year. From this it was possible to conclude that the model proposed by Angelocci et al. (1979) is effective for estimating the Number of Cold Hours and can be used safely for this purpose. The average availability of cold hours for the 6 municipalities in the Southern region studied is 375.7, 273.4, 323, 429, 198.7, and 261.9 NHF for Bagé, Uruguaiana, Santa Vitória do Palmar, Santana do Livramento, Encruzilhada do Sul and Pelotas respectively, presenting great annual variability. The South Region of Rio Grande do Sul does not have enough cold hours to cultivate cryophilic species that have a high requirement for cold hours, however, using less requeriment varieties and cultivars, there may be the possibility of cultivation. The use of cold units did not show satisfactory results for the region, and the model of cold hours estimates proposed by Angelocci et al. (1979) the best option. Regarding the ENOS phenomena, it was observed that in El Niño years there is a lower number of cold hours and in La Niña years there is a decrease in temperatures during autumn and winter and, consequently, there is a greater accumulation of chiling hours.