When Obdulia Salinas is picking grapes, she goes by the name “abuelita,” or granny. It’s partly because she is the oldest on her field crew and has 35 grandchildren, and partly because she sets the bar for know-how and stamina among her cohorts.

But even as the 65-year-old Santa Rosa resident, originally from Mexico, pushes long hours in the vineyards of Sonoma County, often outlasting her younger peers, she struggles to pay the bills — a reality facing many of California’s 800,000 farmworkers who have little choice but to seize the low-wage jobs forged by the brutal economics of agriculture.

“We’re not making enough, especially with rents being so high,” Salinas said in Spanish, through an interpreter, after finishing an overnight harvest of white wine grapes at 5 a.m. one day this week.

Field hands like Salinas, from Wine Country to the Central Valley, are welcoming news that they might be in line for a pay increase. The state Legislature approved a bill Monday that would grant farmworkers, who have long been exempt from many employee protections, the same overtime pay that other Californians enjoy — time-and-a-half if a shift exceeds eight hours or a work week exceeds 40 hours.

The legislation, which has touched off a fierce debate between farm interests worried about rising costs and organized labor looking after its own, awaits action from Gov. Jerry Brown. The governor has not indicated whether he will sign it into law.

“It’s not necessarily the group of workers that people are clamoring to take big risks for,” said the bill’s author, Assemblywoman Lorena Gonzalez, D-San Diego. “Farmworkers, for the most part, don’t vote. They don’t have a political voice … (but) we’re engaging with the governor’s office in this discussion and hoping this will establish his legacy of creating true equality for workers.”

Current state law requires farms to pay time-and-a-half only if an employee works more than 10 hours in a day or 60 hours in a week.

For Salinas, who makes $12.50 an hour working for a winery, the legislation could mean the difference between having to cut back on groceries and putting a few dollars in the bank. The $1,500 rent that she and her husband pay for their two-bedroom apartment, which is sparsely furnished and decorated with family pictures, can be a stretch — even with another couple living with them to defray costs.

“The extra money would pay for necessities,” Salinas said, estimating that she’d make the higher hourly wage for at least seven hours most weeks. “And what’s left over I will save until the day I can no longer work.”

The push to expand overtime pay is the latest effort by the United Farm Workers of America, the union traced to activists Cesar Chavez and Dolores Huerta that has long fought for those toiling in agriculture.

On the other side of the overtime battle is a coalition supporting agricultural employers, which contends that the pay requirement is shortsighted for a low-margin industry in which the workload varies from season to season and a 40-hour work week just doesn’t make sense.

The legislation, opponents say, would heap another financial strain on farmers already burdened by minimum-wage hikes, increased environmental regulations and water shortages caused by the historic drought.

“I absolutely agree that farmworkers need to make more money,” said Assemblyman Jim Patterson, R-Fresno, who voted against the proposal. “I think everybody in California needs to make more money. (But) the answer isn’t to drive out the small businesses that employ people.”

Patterson, like other opponents, said requiring higher wages after eight hours would backfire on workers because farmers would be forced to cut hours or switch to crops that allow greater automation, resulting in smaller paychecks for field crews.

Exactly what the proposal would mean for the finances of farms and farmworkers, however, remains to be seen, said Jeffrey Michael, an environmental economist and director of the University of the Pacific’s Center for Business and Policy Research in Stockton.

“It’s definitely going to hurt the bottom line of farmers,” he said. “But we’re talking about the most impoverished group of workers. There’s a long way to go before you eliminate poverty and economic distress in this community.”

Michael doesn’t think most agricultural employers would slash worker hours to avoid paying overtime, since the work still needs to get done and the labor supply is limited. He said that after years of record-setting revenues in farming — though those receipts dipped last year due to the drought — it may be a good time for the state’s $47 billion industry to absorb a pay hike.

Farmers have been getting a break on what they pay employees for nearly eight decades. The Federal Labor Standards Act in 1938 excluded most agricultural workers from overtime benefits, and to this day no state, according to Gonzalez’s office, mandates that farms or ranches provide a higher wage after eight hours.

During Brown’s first stint as governor in the 1970s, his administration issued a directive requiring additional pay for farmworkers after a 10-hour day or 60-hour work week. The standard hasn’t changed since.

The new legislation, Assembly Bill 1066, would require that hourly workers receive one-and-a-half times their pay after eight hours of work in a day or 40 hours in a week, and double pay after 12 hours in a day. The increases would be phased in between 2019 and 2022, and the governor would retain the ability to suspend the law in the case of economic problems.

Salinas and her fellow vineyard workers are nervously awaiting the fate of the bill. Angela Espinoza Chavez, 40, just saw her rent go up for the $600 Santa Rosa room she lives in with her 12-year-old daughter.

“Farmwork is hard and we deserve to make more money,” she said in Spanish.

Espinoza Chavez, who emigrated from Mexico many years ago, has dabbled in restaurant jobs and housecleaning, but says she most enjoys working in the fields, even when overnight shifts throw off her sleep cycle.

“I feel free,” she said. “It’s more liberating than working indoors.”

Salinas agreed: “If God gives me permission, I will work as long as I’m physically able.”

Kurtis Alexander is a San Francisco Chronicle staff writer. Email: kalexander@sfchronicle.com Twitter: @kurtisalexander