(Adds latest exchange rate, context of policy changes)
BUENOS AIRES, Jan 5 (Reuters) - Argentina's peso weakened more than 5 percent against the dollar on Tuesday due to weak dollar inflows from exports, currency traders said.
At 1138 ET (1638 GMT) the peso traded at 13.770 pesos per dollar against an opening price for the session of 13.240.
"Exporters aren't selling their dollars to the central bank at the same rate seen in past days, while there is demand for greenbacks from importers and holiday-makers traveling abroad," one currency trader said.
President Mauricio Macri, a free-markets advocate who took office last month, has lifted capital controls that were imposed by his leftist predecessor and said the central bank will allow the peso's rate to be determined by the market.
The peso has now fallen 29 percent since the controls were lifted on Dec. 16.
Macri's center-right government said on Monday it was disappointed by the volume of soy stocks sold by farmers in the three weeks export taxes had been cut. Soy is a key cash crop for the Argentine economy and the government is counting on dollars from grains exports to help bolster weak currency reserves.
The removal of currency controls has greatly reduced a previously gaping margin between the official rate and black market peso rate.
Traders said the peso was trading at 14.080 on the black market on Tuesday, only a touch weaker than the official rate. (Reporting by Jorge Otaola; Writing by Richard Lough; Editing by David Gregorio)