Baixas temperaturas nas características agronômicas, produtividade e qualidade em genótipos de cana-de-açúcar, no estado do Rio Grande do Sul

Abstract

Brazil is the world's largest producer of sugarcane, and this crop is one of the most important for Brazilian agribusiness. In the state of Rio Grande do Sul, the area cultivated with this species is considered small compared to the main producing states, representing less than 0.5% of the planted area of the country. However, the culture is of great importance because it is associated to the activities developed in family agriculture, related to the processing of derivatives and animal feed, being an important source of income for many gaucho families. Actually one of the great challenges faced by researchers and producers of sugarcane in the RS is to achieve greater productive stability coupled with varieties more adapted to the climate of the region. In view of this scenario, the objective of this work was to identify the effect of low temperatures on sugarcane genotypes in the state of Rio Grande do Sul. The experiments were conducted in Pelotas, with evaluation of 20 sugarcane genotypes and in Salto do Jacuí, São Borja and Santa Rosa, with evaluation of 10 genotypes, during two agricultural years. The quality of the broth was evaluated through the hydrogenation potential (pH), titratable acidity (TA) and total soluble solids (TSS), the cold damage level (NDF) in a visual way, assigning grades from 1 to 5, the yield of stalks (TCH) and sugar (TSSTH) and the efficiency of conversion of solar energy into production (Ef Es). The results show that there is variability for cold tolerance, broth quality, productivity and conversion efficiency of solar energy in production in the evaluated genotypes. In Pelotas/RS, the minimum air temperature recorded during the two evaluated agricultural years was -1.8 ° C, in the 2016/17 harvest, with no severe damage to the genotypes studied, with NDF scores ranging from 1 to 3, not compromising quality and final productivity. In the other environments during the two years of evaluation, minimum air temperatures of -3.0 ° C and -3.7 ° C were recorded in Salto do Jacuí / RS, in the 2015/16 and 2016/17 crops, respectively, causing damages to the genotypes, with NDF scores varying between 4 and 5, and in the last evaluation period, reducing the quality of the broth and the probable decrease in productivity. Among the evaluated genotypes are RB006996, RB016916, RB931003 and RB92579, which presented the best performances in the different meteorological conditions to which they were exposed in the different study environments.