On the back porch of her Brighton Heights home, Suzy Meyer squeezes juice from a Golden Honey Bunch cherry tomato onto the glass plate of a refractometer. Holding the instrument to her eye, she says, "A seven" -- a nutrient density rating between average and good.
She washes the glass, cuts a scarlet wedge from a Tiffen Mennonite heirloom and squeezes a drop of juice that registers an 8.
Eight is good but not enough. According to an index of crop juice readings that are tied to an endeavor called high-brix (or Brix) farming, the best tomato is a 12. But only one commercial tomato that Ms. Meyer tested this summer was richer in nutrients than her own Tiffen Mennonite.
To the layman, the difference between a 4 and an 8 is the astonishingly sweeter taste of the 8. But to critics of high-brix agriculture, the interpretation is short on science.
The brix rating system, which has detractors in agriculture schools and is largely ignored by industrial farmers, was named after Adolph Brix, a 19th-century German chemist who first measured the sugar density of plant juice. Carey Reams, described by different sources as either an agronomist or a physicist, devised the refractive test in the 1970s and founded International Ag Labs, a Minnesota company whose business was built on enhancing the biological systems of soil for nutrient density.
The mantra is: High brix means higher sugar, mineral and protein content, a lower freezing point, longer shelf life and better pest resistance.
A refractometer, which looks like a tiny telescope and has a prism that bends light, measures the density of sugar, minerals and proteins in the juice of any crop specimen, from alfalfa to apples, parsley to papaya. The more total suspended solids in the juice, the more the light will bend and yield higher readings.
Vintners have used the brix scale for years to determine when grapes are ready, but the nutritional application has lagged.
Several things may explain this.
One, agriculture schools largely reject the reasons behind the claims of farmers and other adherents, some of whose websites have a tint of the New Age about them -- i.e. "the Path to High Brix" from highbrixgardens.com.
Two, the high-brix movement depends on comparisons, such as the tests Ms. Meyer has been doing. Jon Frank, an owner of International Ag Labs, said that until results are presented to more consumers, they will be content "to eat a C-grade tomato and say 'this is good.' "
Ms. Meyer is among "less than one percent" of crop growers who strive for high brix, said Mr. Frank.
Three, gardeners have been led to believe that composting is the height of soil conditioning. Mr. Frank said a garden's soil might have too much potassium from previous applications. Tomatoes love potassium, but they also love calcium, he said, "and excessive applications of compost almost always lead to a calcium deficiency. Compost is just one tool."
Mr. Frank said his company has had "some major pooh-poohing," citing Washington State University Extension officials who "think we're scam artists. I didn't respond because it's our customers that count."
Indeed, a full-scale argument earlier this year pitted an extension specialist in urban horticulture against numerous growers on a Washington State Extension blog. After several exchanges about International Ag Labs, the site was basically hijacked by soil experts, farmers and others weighing in to defend the high-brix method, taking on Linda Chalker-Scott, the horticultural scientist, who had argued that Ag Labs uses "bad science."
Responding on the blog, Michael Astera, author of "The Ideal Soil," wrote that "the hard science was done between 1920 and 1950 under the direction of Dr. Firman Bear at Rutgers and Dr. William A. Albrecht at the University of Missouri." He described their research as "seminal work in soil mineral balance." After 1950, college agriculture departments began receiving funding from chemical corporations and Dr. Bear's work was "diverted" and Dr. Albrecht was "forced into retirement in 1959."
Most respondents on the blog scattered scorn on academicians for not investigating results.
A farmer named Dave wrote, "My peers -- real farmers -- are seeing improved yield, flavor and quality by using a weak acid soil test. If organic farmers had waited for consensus from the scientific world, we would be stuck with conventional ag. Good luck with your blog."
The high-brix community favors a weak acid test over the strong acid test that university extension agencies use. A strong acid test identifies all the nutrients in the soil. The high-brix argument is that plants exude weak acids that microbes feed on and then feed back to the plants. A weak acid test identifies soil components the plant can absorb.
For instance, said Mr. Frank, "you can add bone meal to your soil but it takes microbial activity and time to break down enough" for a plant to take it up. And it won't be this year.
He suggested that people who go high-brix should strive first for average, then work toward good.
"You don't offload a truck of food to a baby and say, 'Eat boy, I want you to be a man.' Soil takes time."
Ms. Chalker-Scott wrote of her concerns that high-brix advocates are overmineralizing soil and contributing to harmful runoff. International Ag Labs promotes commercial fertilizers, but high-brix farming can be done organically, said Dan Kittredge, director of the organic Real Food Campaign in New England.
"It is unnecessary to use synthetic materials," he said. "You can use calcium nitrate from a bag or you can make calcium nitrate out of limestone and grass clippings."
He said 5 percent of the farmers he knew five years ago had heard of high-brix growing. "Now it's 80 percent. It's the leading edge in farming and it is going to be much bigger news in the next two years."
Ms. Meyer, a landscape architect, became interested after her association with the Pennsylvania Association for Sustainable Agriculture as a consultant four years ago. She began her high-brix conversion by researching online. She sent soil away for a weak-acid test and bought customized soil amendments. This summer, she began measuring the refractive index of juices of commercial tomatoes against her own.
"Most of the tomatoes in my sampling experiment came in around 4," she says. She bought at four supermarket chains, independent stores and farmers markets. Spokesmen at several supermarkets said they had never heard of brix.
"If I pay $4 for an heirloom tomato," said Ms. Meyer, "I want it to be superior, and I haven't had any."
Ms. Meyer said the only tomatoes she bought that made it out of the 5s were orange cherry tomatoes from Blackberry Meadows Farms, a vendor from Fawn at the Farmers@Firehouse market in the Strip District. They were an 8 and an 8.4.
Greg Boulos, an owner of Blackberry Meadows, said he and his wife strive for high-brix organically but do not test every specimen. When they do, they test in the mornings. They have found that their brix readings "can vary a lot" depending on sun, temperature and rain.
More important, he said, is their goal of growing "the most nutrient-dense foods" by keeping their soil in balance. "I don't know if science explains a lot about living systems," he said. "These are not static situations replicated in a lab. We are dealing with living organisms, completely unpredictable, with their own personalities and their own lives. The best thing we can do is give them the best conditions, then they're going to do the work."
Ms. Meyer's own tomatoes were consistently above 5, with two spikes -- a 9.2 Roma in August and a 10.5 Big Beef in September.
"A 12 is going to knock your socks off," she said. "That is a tomato that has reached its DNA potential. It has all the minerals, sugars and proteins we have evolved with as a species."
When foods rank that high, she said, they will sell themselves as an alternative to junk food. "Kids will eat this stuff willingly. And what's great is that any home gardener can do this."
Soil tests can be ordered from state university extension services or by researching high-brix online. This website offers numerous sources of soil consultation: http://home.roadrunner.com/~krisjohnson/Garden/SoilTesting.htm.
To reach Suzy Meyer, e-mail her at firstname.lastname@example.org or call 412-860-8606.