SANTIAGO (Reuters) - Chilean President Michelle Bachelet's approval rating ticked higher in September, breaking a recent downward trend that had pushed her ratings to an historical low a month earlier, pollster Gfk Adimark said on Thursday.

Center-left Bachelet, who ruled in 2006-2010 and then returned for another four years in 2014, had enjoyed sky-high ratings after her first term.

But those numbers plummeted as her ambitious second-term reform agenda to tackle inequality and education of the poor stalled after a sharp drop in the price of Chile's top export copper hurt investment and the economy at large. Her ratings were also hit by a series of high-profile scandals involving corrupt or dubious practices by politicians across the spectrum.

Bachelet's approval ratings rose to 23 percent in September from an all-time low of 19 percent in August, while her disapproval ratings fell to 72 percent from 77 percent the prior month.

"An approval rating of 23 percent in September can hardly be called positive but it certainly leaves behind an especially harsh (Southern Hemisphere) winter for the president," said Adimark.

Bachelet's image got a boost as the public's attention turned to Chile's 2017 presidential election, and the start of Spring and the Sept. 18 national independence day holiday boosted the public's morale. People were also encouraged by the appearance of more unity among her cabinet members than in previous months, according to the pollster.

The Socialist president secured tax reforms in the first year of her second term that have helped pay for changes to education, and also tweaked the electoral system. However, other aspects of her pledged reform drive, that would have been ambitious at the best of times, have struggled.

The Adimark survey interviewed 1,070 people between Sept. 5 and 29, and had a margin of error of 3 percentage points.

(Reporting by Anthony Esposito; Editing by Bernadette Baum)