TODOS SANTOS, Bolivia » There is nothing clandestine about Julian Rojas’ coca plot, which is tucked deep within acres of banana groves. It has been mapped with satellite imagery, cataloged in a government database, cross-referenced with his personal information, and checked and rechecked by the local coca growers’ union. The same goes for the plots worked by Rojas’ neighbors and thousands of other farmers in this torrid region east of the Andes who are licensed by the Bolivian government to grow coca, the plant used to make cocaine.

President Evo Morales, who first came to prominence as a leader of coca growers, kicked out the Drug Enforcement Administration in 2009. That ouster, together with events like the arrest last year of the former head of the Bolivian anti-narcotics police on trafficking charges, led Washington to conclude that Bolivia was not meeting its international obligations to fight narcotics.

But despite the rift with the United States, Bolivia, the world’s third-largest cocaine producer, has advanced its own unorthodox approach toward controlling the growing of coca, which veers markedly from the wider war on drugs and includes high-tech monitoring of thousands of legal coca patches intended to produce coca leaf for traditional uses.

To the surprise of many, this experiment has led to a significant drop in coca plantings in Morales’ Bolivia, an accomplishment that has largely occurred without the murders and other violence that have become the bloody byproduct of American-led measures to control trafficking in Colombia, Mexico and other parts of the region.

Yet there are also worrisome signs that such gains are being undercut as traffickers use more efficient methods to produce cocaine and outmaneuver Bolivian law enforcement to keep drugs flowing out of the country.

In one key sign of progress in Bolivia’s approach toward coca, the total acres planted with coca dropped 12 to 13 percent last year, according to separate reports by the United Nations Office on Drugs and Crime and the White House Office of National Drug Control Policy. At the same time, the Bolivian government stepped up efforts to rip out unauthorized coca plantings and reported an increase in seizures of cocaine and cocaine base.

"It’s fascinating to look at a country that kicked out the United States ambassador and the DEA, and the expectation on the part of the United States is that drug war efforts would fall apart," said Kathryn Ledebur, director of the Andean Information Network, a Bolivian research group. Instead, she said, Bolivia’s approach is "showing results."

Still, there is skepticism. "Our perspective is they’ve made real advances, and they’re a long way from where we’d like to see them," said Larry Memmott, charge d’affaires of the U.S. Embassy in La Paz. "In terms of law enforcement, a lot remains to be done."

Although Bolivia outlaws cocaine, it permits the growing of coca for traditional uses. Bolivians chew coca leaf as a mild stimulant and use it as a medicine, a tea and, particularly among the majority indigenous population, in religious rituals.

On a recent afternoon, Rojas placed a few dried leaves into his mouth and watched the sun set over his coca field, slightly less than two-fifths of an acre, the maximum allowed per farmer here in this region, known as the Chapare.

"This is a way to keep it under control," he said, spitting a stream of green juice. "Everyone should have the same amount."

Rojas is a face of a changing region. He makes far more money growing bananas for export on about 74 acres than he does growing coca. But he has no intention of giving up his tiny coca plot.

"What happens if a disease attacks the bananas?" he asked. "Then we still have the coca to save us."

The Bolivian government has convinced growers that by limiting the amount of plantings, coca prices will remain high. And it has largely focused eradication efforts, of the kind that once spurred strong popular resistance, outside the areas controlled by growers’ unions, like in national parks.

The registration of thousands of Chapare growers, completed this year, is part of an enforcement system that relies on growers to police one another. If registered growers are found to have plantings above the maximum allowed, soldiers are called in to remove the excess. If growers violate the limit a second time, their entire crop is cut down and they lose the right to grow coca.

Growers’ unions can also be punished if there are multiple violations among their members.

"We have to be constantly vigilant," said Nelson Sejas, a Chapare grower who was part of a team that checked coca plots to make sure they did not exceed the limit.

But there is still plenty of cheating. Officials say they are going over the registry of about 43,000 Chapare growers to find those who may have multiple plots or who may violate other rules.

"The results speak for themselves," said Carlos Romero, the minister of government. "We have demonstrated that you can objectively do eradication work without violating human rights, without polemicizing the topic and with clear results."

He said that the government was on pace to eradicate more acres of coca this year than it did last year, without the violence of years past. A government report said 60 people were killed and more than 700 were wounded in the Chapare from 1998 to 2002 in violence related to eradication.

But even as Bolivia shows progress, grave concerns remain.

The White House drug office estimated that despite the decrease in total coca acreage last year, the amount of cocaine that could potentially be produced from the coca grown in Bolivia jumped by more than a quarter. That is because a large amount of recent plantings began to mature and reach higher yields; new plantings with higher yields replaced older, less productive fields; and traffickers switched to more efficient processing methods.

Yet the glaring paradox of Bolivia’s monitoring program is that vast amounts of the legally grown coca ultimately wind up in the hands of drug traffickers and are converted into cocaine and other drugs. Most of those drugs go to Brazil, considered the world’s second-largest cocaine market. Virtually no Bolivian cocaine ends up in the United States.

Cesar Guedes, the representative in Bolivia of the U.N. drugs office, said that roughly half of the country’s coca acreage produces coca that goes to the drug trade. By some estimates, more than 90 percent of the coca in Chapare, one of two main producing regions, goes to drugs.

Two Chapare farmers said they generally sell one 50-pound bag of coca leaf from each harvest to the government-regulated market. The rest, often 200 pounds or more, is sold to buyers who work with traffickers and pay a premium over the government-authorized price. One of the growers said he recently delivered coca leaf directly to a lab where it would be turned into drugs.

The central question is how much coca is needed to supply traditional needs. Government policy permits about 50,000 acres of legal coca plantings, although the actual area in cultivation is much higher. The United Nations estimated there were about 67,000 acres of coca last year.

Whatever the exact figure, most analysts agree that far more is produced than is needed to supply the traditional market.

The European Union financed a study several years ago to estimate how much coca was needed for traditional uses, but the Bolivian government has refused to release it, saying that more research is needed.

The push to reduce coca acreage comes as the Morales government is lobbying other countries to amend a U.N. convention on narcotics to recognize the legality of traditional uses of coca leaf in Bolivia. A decision is expected in January.

On a recent morning just after dawn, a squad of uniformed soldiers used machetes to cut down a plot of coca plants near the town of Ivirgarzama.

They had come to chop down an old coca patch that had passed its prime and measure a replacement plot planted by the farmer. The soldiers determined that the new plot was slightly over the limit and removed about two rows of plants before going on their way.

"Before, there was more tension, more conflict, more people injured," Lt. Col. Willy Pozo said. "This is no longer a war."

© 2012 The New York Times Company