Uso de reguladores de crescimento como potencializadores do perfilhamento e da produtividade em cana-soca

The use of plant growth regulators as ripeners in sugarcane has been an agronomic practice with well solidified results. However, the residual effect of these products over the next ratoon is still not very well studied. This research aimed to evaluate the residual effect of two plant growth regulators, applied before the harvest, in the stool regrowth and productivity of three sugarcane genotypes. The experiment was carried out near Jaú (SP). The experimental design was a randomized complete block, in split-plot, with four repetitions, constituted by the genotypes IAC87-3396, IAC91-2195 and IAC91-5155, and by three crop management: 20 g ha^-1 sulfomethuron-methyl; 480 g a.i. ha^-1 ethephon and control. The growth regulators were applied 126 days before harvest. To quantify the action of growth regulators the following variables were evaluated: the number of tillers m^-1 at 0, 90, 180, 270 and 360 days after the harvest; the final percentage of stalk number by meter in relation to the initial percentage; the mass of 10 stalks, the length and the diameter of stalks; the pol and the fiber% cane, the reducing and total recoverable sugars, and the productivity of stalks and sugar. It was concluded that there was stimulating effect on the emergency of tillering up to six months after the harvest. The ethephon promoted larger productivities of stalks and sugar. There were differences among genotypes in relation to growth regulators for stalk length. There was no effect on the technological quality over the subsequent ratoon crop.