THERMAL CONDITIONS FOR CUCUMBER IN THE TAQUARI VALLEY REGION, RS. 2 - MAXIMUM TEMPERATURE AND THERMAL TIME

Abstract

The probabilities of maximum temperatures harmful to the growth and development of cucumber crop and the thermal time occurring from transplanting to end of harvest of this crop were calculated for the "Baixo Vale do Taquari" Region, Rio Grande do Sul State, Brazil. Maximum and minimum temperature data during the period 20 January 1963 through 31 March 1999 measured in a meteorological station at Taquari (29°48' S Latitude, 51 °49' W Longitude and 75 m altitude) were used in this study. For the analysis of maximum temperature, the probabilities of occurring values greater or equal to 30°C, 32°C, 34°C, 36°C and 38 °C were calculated. It was assumed that temperatures greater than 30°C are harmful to the plant. In order to determine a planting date schedule for the crop, the thermal time above 12°C during the phenological phase from transplanting to end of harvest period was used in the calculations. Results showed that temperatures greater than 30°C may occur even during the winter months, when growing cucumber is not recommended in this region due to the risk of low lethal temperatures. Also, it was found that there is a probability of occurring temperatures greater than 32°C from the third decade of August to the third decade April, greater or equal to 34°C from the third decade of August to the first decade of April, greater or equal to 36°C from the third decade of September to the third decade of March and greater or equal to 38°C from the second decade of November to the second decade of February. Based on thermal time, the duration of the phenological phase from transplanting to end of harvest period was shorter during January and February (as short as 45 days) and longer during August, September and March (as long as 100 days).