* Santos has support in war zones, Zuluaga in pacified areas
* Candidates running neck-and-neck ahead of Sunday's vote
* Some farmers fear return of paramilitaries
By Helen Murphy
PUERTO ASIS, Colombia, June 11 (Reuters) - Two camouflaged military helicopters dot the sky as Silvio Mora sweeps up remains of a freshly killed chicken at his backyard slaughter house in Colombia's southern conflict zone of Putumayo.
"At least peace may end that," he says, pointing toward the troop carriers as vultures pick at the bloody slop he brushed into the jungle behind his concrete shack. "Look at how we live. The war has brought only misery, we need peace talks to work."
Mora, 45, turned to subsistence farming in the regional capital Puerto Asis after his 20 hectares (49 acres) of coca were fumigated during former President Alvaro Uribe's hardline rule to stop Marxist rebels using the crop to produce cocaine.
The father-of-four is among hundreds of thousands of Colombians in frontline areas who want President Juan Manuel Santos re-elected on Sunday so he can continue negotiating an end to five decades of war with guerrilla leaders of the Revolutionary Armed Forces of Colombia (FARC).
Yet many other voters, living in once-violent regions that were pacified during Uribe's U.S.-backed military offensives against the FARC, oppose the negotiations with rebel leaders and instead support Uribe's candidate, right-wing opposition leader Oscar Ivan Zuluaga.
Polls show the men neck-and-neck ahead of the runoff vote in Colombia's closest presidential race for two decades.
Zuluaga says any peace deal must include prison terms for rebel leaders and a ban on entering politics. That could sink the talks and force an escalation of the military solution that Uribe favors.
Santos would allow the rebels into politics and likely impose alternative sentences like community service.
The two visions of how to end the war have split Colombia and turned the election on Sunday into a choice between making concessions to end Latin America's longest-running insurgency or seeking the rebels' surrender, on or off the battlefield.
Voting patterns in the first round of the election last month showed strong support for center-right Santos in coastal and border areas where the conflict continues, like Putumayo, which once produced most of Colombia's illegal coca leaves.
Zuluaga won in provinces that benefited from Uribe's relentless military push during his 2002-2010 rule, like rice-growing central Tolima and cattle-ranching Meta, where residents live in relative peace and their economies have improved.
"Santos hasn't been the best president, but he's far less bloodthirsty than Uribe and that's who we will elect if Zuluaga wins," says Alfonso Riascos, 82, sitting on his ramshackle porch down the road from Mora's farm.
Many in Putumayo struggle to recall Zuluaga's name and refer to Uribe when talking of the presidential hopeful. Some worry right-wing paramilitary death squads will re-emerge if Zuluaga wins, peace talks fade and the FARC steps up its attacks.
Uribe negotiated a deal with paramilitaries in 2006 that gave them soft sentences for serious crimes as long as they confessed and repaid their victims. The effort was broadly seen as a failure as many formed new crime gangs.
TOO MANY CONCESSIONS
In a pacified mountainous zone of central Colombia, villagers in Fomeque accuse Santos of giving the rebels an easy ride and squandering Uribe's security gains.
Fomeque was once overrun by rebels smuggling arms and hostages through canyons and planning attacks on nearby Bogota.
Uribe, whose father was killed in a FARC kidnapping, put the rebels onto the back foot and the local economy boomed. But residents feel they are regrouping and could menace again.
"It's clear to us, in the eight years of Uribe, we were safer, no doubt. Santos has let security slide and now we are seeing the FARC again," says Ernesto Zabogal, 50, a farmer debating politics with friends in Fomeque's central square.
"We see them more and more on patrol in the mountains and extortion has started again," adds Alvaro Rojas, 57.
Down the road in Choachi, residents fear a Santos win may mean demobilized FARC rebels morph into crime gangs just as the paramilitaries did.
Choachi suffered many rebel attacks before Uribe's troops pushed them out. Now tourists from Bogota flock to its springs and waterfalls, pouring money into local businesses and even buying property.
"We are packed. We have to buy dozens more pigs than before and now we have six people working instead of two a decade ago," says Evelia Amortegui, 54, whose family-run restaurant opened 30 years ago. "With Zuluaga, we are asking for Uribe back."
Trying to win over waverers in the final stretch, Zuluaga has slightly softened his previously militant line against the peace talks, while Santos has raised the specter of more war if he does not win a second term.
In one new campaign spot, the president asks a mother if she is willing to send her son to war. She replies no, to which the president cries over-and-over "No more war!"
But he has struggled to persuade residents of more peaceful areas there is much to be gained from negotiating with the FARC.
In Bogota and Medellin, Zuluaga had the edge in the first round, largely because voters in big cities feel far removed from a war playing out in rural areas.
"For people in cities, it's like the conflict in Crimea or the Ukraine, something they see on TV," said Alejo Vargas, political scientist at the National University of Colombia. (Additional reporting by Julia Symmes Cobb in Bogota; Editing by Andrew Cawthorne and Kieran Murray)