The American, 28, hit eight birdies in a bogey-free 64 to lead Sung Kang, with Stewart Cink, Jhonattan Vegas and Kyle Stanley another shot back on six under.
England's Justin Rose shot a five-under 67, with 2015 Masters champion Jordan Spieth two more shots adrift.
England's Luke Donald carded a one-under 71, while compatriots Chris Wood and Andrew Johnston are one over.
"They've done a great job here with conditions around the greens and making it as similar as possible to next week," said Fowler, who will be aiming to win his first major at Augusta.
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The chairman of the House intelligence committee, Devin Nunes, told reporters that Paul Manafort had voluntarily offered to speak to the panel.
Mr Nunes also contradicted Mr Trump's claim that Barack Obama had wiretapped him before the US elections.
"There was no wiretapping at Trump Tower, that didn't happen," he said.
However, Mr Nunes said he was concerned that the names of members of Mr Trump's transition team were "unmasked" during the surveillance of foreign individuals.
Earlier this week, AP news agency reported that Mr Manafort had worked for a Russian billionaire to assist Russian President Vladimir Putin.
Mr Manafort has insisted that he never worked for Russian interests.
He had worked as Mr Trump's unpaid campaign chairman from March until August last year.
He resigned after AP revealed that he had co-ordinated a secret Washington lobbying operation on behalf of Ukraine's ruling pro-Russian political party until 2014.
The Trump administration has denied any collusion with Moscow, while Russia has always denied attempting to influence the US presidential election.
Speaking to reporters on Friday, Mr Nunes said that he had invited FBI director James Comey and National Security Agency (NSA) chief Adm Mike Rogers to provide further testimony at a closed intelligence committee session.
On Monday, Mr Comey told an open hearing that the FBI was investigating alleged Russian interference in the 2016 election, and said he saw no evidence that Mr Trump had been wiretapped by the Obama administration.
Mr Nunes said there were questions that Mr Comey and Adm Rogers "could not answer in a public setting", so he was asking them to return for a closed session.
However, Democrats have criticised Mr Nunes after he delayed a planned open hearing with ex Director of National Intelligence James Clapper, former CIA director John Brennan, and ex deputy Attorney General Sally Yates.
The top Democrat on the committee, Adam Schiff, said that was an attempt to "choke off" information to the public.

He said William McNeilly's allegations were either factually incorrect or the result of misunderstanding or partial understanding.
The Royal Navy submariner has claimed missile programme system on the Clyde was a "disaster waiting to happen".
He wrote a report, detailing "serious security and safety breaches".
In a statement addressing the 25-year-old's concerns, Mr Fallon insisted that neither the "operational effectiveness" of the fleet "nor the safety of our submariners or public have been compromised".

Most of the churches affected had predominantly African-American congregations.
"We believe that this fire-setting activity is meant to send a message," said John Ham of the Bureau of Alcohol, Tobacco, Firearms and Explosives.
The most recent fire broke out early on Thursday morning.
"It was really disheartening to see what you worked so hard for brought down in a matter of minutes," said Pastor David Triggs of the United Believers in Christ Church, which was heavily damaged on 17 October.
The fires have all been set at the front or side doors of buildings, usually without causing serious structural damage.
This was not the case for Pastor Triggs, who said his church's building is likely unsalvageable.
That leaves his roughly 70 active congregants without a house of worship.
He is holding services on the lawn this coming Sunday while trying to determine next steps.
"We're kind of at a cross road," he said. "I have no doubt that God is going to provide for us."
Rickie Fowler warmed up for next week's Masters by taking a one-shot lead after the first round of the Houston Open.
[NEXT_CONCEPT]
US President Donald Trump's ex-campaign chief has agreed to be interviewed by a panel investigating alleged links between the Trump team and Russia.
[NEXT_CONCEPT]
The UK's Defence Secretary Michael Fallon has said a whistleblower's concerns about Trident nuclear submarine safety have not been proved.
[NEXT_CONCEPT]
Police in the US state of Missouri are searching for arsonist who set fire to seven churches in the St Louis area in the past two weeks.