When it comes to groceries, "organic" and "sustainable" usually mean "expensive."

But the supposed productivity gaps between organic and conventional farming may be a lot smaller than thought—and organic farming may be especially competitive during droughts like the one currently crushing California's massive agricultural sector.

A new analysis of more than 100 studies conducted by researchers at the University of California, Berkeley, concluded organic farming created a unique mix of biodiversity in the soil and surrounding environment that is difficult to mimic with synthetic chemicals. The researchers analyzed what they say is the largest data set ever compiled on organic and conventional methods across an index of about 50 common crops.

The findings were published Tuesday in the journal the Proceedings of the Royal Society of London.

They did find a productivity gap—organic farms are almost 20 percent less productive than conventional ones, a number still lower than conclusions drawn by many previous studies. The group also thinks that that gap could be reduced or even totally eliminated by further investment in organic farming research, education and seed breeding.



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"With global food needs predicted to greatly increase in the next 50 years, it's critical to look more closely at organic farming because, aside from the environmental impacts of industrial agriculture, the ability of synthetic fertilizers to increase crop yields has been declining," said Claire Kremen, one of the researchers who worked on the report.

The assertion that organic farms can compete with conventional ones—especially during droughts or other adverse weather—is not new.

Separately, the Farming Systems Trial at the Rodale Institute in Pennsylvania has been comparing the productivity of organic and conventional farms since 1981. The institute uses common organic farming methods in some plots and farms more conventionally in others, using popular pesticides and growing genetically modified organisms in its conventionally farmed plots. It found that the organic plots on its own property outperformed the conventional ones, especially when things turned tough.

The organic plots were especially more resilient to droughts, and other weather events such as frost and flooding.



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Much of the difference comes down to what is in the soil, said Kristine Nichols, who is the chief scientist for the Rodale Institute. The microbes, fungi and other organisms that build up in organically farmed soil and the immediate environment create mutually dependent relationships with plants—fungi provide channels that carry nutrients and water through soil, for example.

As a result, organic field soil absorbed more water and needed less water overall. The organic soil also seemed to store water better and do a better job of replenishing groundwater supplies. So there is much more water in the soil for plants to draw on when dry spells strike. Plants without these kinds of networks—such as those found in conventional farming plots—actually secrete water into surrounding soil to mimic these channels.



"I like to say that microorganisms are like little engineers," Nichols said. "They build out these systems and engineer the environment to be beneficial for the plants so that the plants will feed them in turn."

Using technology to mimic these natural methods would be incredibly difficult and expensive, Nichols said. "The only way we could do this more efficiently is if we took needles and injected nutrients right into the plants."

But of course, the notion that organic farming can feed the world has its skeptics.

"Such claims are absurd," molecular biologist Henry I. Miller told CNBC in an email. Miller was the founding director of the FDA's Office of Biotechnology and a supporter of genetically modified foods. He is now a fellow at Stanford's Hoover Institution.

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Miller contends that genetic modification techniques have already given us drought-resistant crops, and argues that farmers have turned to conventional methods precisely because they are more efficient. "That's why genetically engineered crops were grown last year by 18 million farmers in 27 countries and why there is an extremely high 'repeat index,' the percentage of farmers who are repeat customers for genetically engineered seeds" such as those produced by Monsanto, said Miller in a report he wrote and forwarded to CNBC.

Some farmers are also skeptical, especially on the water issue. "Organic HAS NOTHING to do with water usage," Joel Nelson, a California citrus grower and president of the California Citrus Mutual growers association, wrote in an email to CNBC. "Our organic producers achieve a yield, generally 40 percent less than conventional producers, but all of them require the same amount of water," he said.



Even if a plot of land can produce using organic methods, other questions remain. The Rodale farm is about 12 acres, and Miller cited research in his report doubting whether such results could scale up to larger farms.

Another big question is whether it is feasible or even possible to begin converting the entire U.S. food system—or even California's system alone—to a primarily organic one. Kremen said it could be difficult, without even factoring the higher labor costs that would be involved. It would require vast economic, political and structural changes. But she also said the "true price" of conventional agriculture is not reflected in the grocery store, but comes in hidden costs in the form of taxes for subsidies, environmental damage and health problems. Currently, less than 2 percent of all government funding for agriculture goes to organics, according to Kremen.

"The surprising finding here that conventional agriculture pulls ahead so slightly despite all of this extra investment," she said.