Variation in the sugar yield in response to drying-off of sugarcane before harvest and the occurrence of low air temperatures

Abstract

The need to irrigate sugarcane in the Brazilian Savanna is due to the lack of rain from April to September. For efficient sugar accumulation, the crop needs water stress or heat stress at the maturation stage. However, when the water deficit is intense at this stage, it occurs the reduction in crop production. The objective of this study was: (i) to assess the quality of the raw material of sugarcane in different drying-off seasons before harvest; (ii) to evaluate the influence of heat stress on the culture. The experiment was conducted in Santo Antônio de Goiás (GO), Brazil, in Oxisol, with CTC4 variety in cane-plant cycle. A randomized block design in a split-plot array in time was used. The treatments of the plots were five drying-off times (90, 60, 30, 15 and 0 days before harvest) and, in the subplots, five seasons of the yield evaluation. Irrigation was carried out by surface drip method, which provided 50% of crop water requirement. The best results for sugar yield occurred 30 days before harvest, period in which the crop irrigation could be interrupted. The water deficit of 37.76 mm appears to be the critical limit of water shortage in the soil, from which the sugarcane yield starts to be reduced. The sugar concentration in the stalk was more influenced by low air temperatures than sugarcane yield.