Dry-farmed tomatoes can thrive in proper conditions

Dry-farming organic tomatoes is not as simple as putting the plants in the ground and walking away. Farmers and advisors say several factors go into successful production of dry-farmed, fresh-market tomatoes.

Jim Leap, retired manager of the University of California, Santa Cruz, farm, currently works as an agricultural advisor/educator in San Benito County. He said his introduction to dry farming was from Molino Creek Farming Collective in Davenport. They had learned dry-farming techniques from some of the old Italian growers in the region, who began dry-farming tomatoes because they had limited water, Leap said.

"I hooked up with those guys, and they kind of encouraged me to do dry farming at UC Santa Cruz," Leap said.

He started raising dry-farmed tomatoes, then added beans and winter squash.

"It was just incredible what we did, and what we were able to grow, and the actual revenue that we were able to generate from a crop that doesn't receive any water," Leap said.

There are several benefits to dry-farming tomatoes, he said: less disease, minimal soil compaction, healthier soils and improved weed management.

But there are also problems in growing tomatoes without irrigation.

Leap said dry-farmed tomatoes are susceptible to a physiological condition known as blossom end rot, which relates to the plants' inability to move calcium to the blossom end of the fruit. The symptom is a black, sunken spot on the blossom end of the fruit that is prone to rot, depending on the severity of the symptom. Fruit showing symptoms are not marketable, Leap said, adding that the Early Girl variety is less susceptible to blossom end rot.

Cultivation is also critical in successfully growing dry-farmed tomatoes, according to Joe Schirmer, owner of Dirty Girl Produce in Santa Cruz. Ripping down the middle allows the tomato to deep-root quickly, he said; by doing this, moisture is trapped in the soil and allows the plants to access all the water.

"If you don't rip and soil mulch, then you're going to have a really low production and low success rate," Schirmer said. "The soil mulch is key. You don't dry-farm without that. It is probably the single most important thing."

Leap said he has done trial work, comparing fresh-tomato varieties.

"I've trialed hundreds of varieties, and I know of three other farmers here in the region who have trialed probably hundreds of varieties, but nothing comes close to Early Girl," he said.

Schirmer created a Dirty Girl variety out of the hybrid Early Girl that is open-pollinated.

"It's a good tomato," he said. "It's solid, it's really good. It doesn't get blossom end rot that the Early Girl does, but it's also not as consistently high in the acid. It's often as sweet as the Early Girl, but doesn't quite have the same acid as the Early Girl."

Schirmer said he likes to have both varieties in the field because they go back and forth.

"One tastes good, one's not ready, one is. One's easy to wholesale because it's clean, and then one isn't," he said.

Leap also conducted trials on rotation of tomatoes at the UCSC farm. He tried growing tomatoes in the same ground for three years in a row. By the third year, he said, there were problems with symphylan (garden centipede), a root-feeding arthropod that can be devastating to dry-farmed tomatoes because their roots have to go deep for moisture.

If the symphylan is near the surface eating the roots, it prevents the plant from going deep for moisture—a necessity for dry-farmed tomatoes, Leap said.

When dry-farming tomatoes, there are minimal opportunities to create soil compaction, he said.

"You have a very loose, friable, open soil," Leap said. "You can go to the field, run a harvest crew or pick up bins or load winter squash or whatever with a tractor, and you're not compacting anything because there's minimal moisture in the soil."

In many "regenerative" systems, farmers strive for continual irrigation and continual production so the soil never dries down—the premise being that moisture is necessary for enhanced soil microbial growth, Leap said. But he said he thinks that's a misconception of how soil microbes work.

It isn't necessary for microbes to be alive all the time to have a healthy soil, he said; they can go through a dormant phase, then when it starts raining in the fall, they come back to life.

Leap dry-farms with 15 inches of rain per year.

"We have the perfect conditions. We have maritime influence, fog in the summer in the mornings and evenings, we get a cool breeze off the ocean, we have a loam soil that goes right to clay, and the clay is deep," he said, adding that most growers that are successful at dry farming have the same situation.

Schirmer agreed climate was important to dry-farmed tomatoes. He said he farms in a microclimate around the Santa Cruz Mountains and Monterey Bay that's unique. Proper cultivation of the tomato and the bed prep is also critical to growing an aggressive tomato where the rooting system will go deep for water, he added.

The Early Girl is a good dry-farmed tomato, Schirmer said, because it puts all its energy into the fruit. It adapts to dry farming by dropping its leaves, especially the lower leaves. The first fruit will be big and beautiful, he said, but as the plant continues to grow, the fruit "gets better and better."

"The fruit will get smaller, it'll get a thicker, stronger skin, and then it will have a sharper acid and sugar content," Schirmer said. "There's really not another tomato that's at all like it."

(Kathy Coatney is a reporter in Bend, Oregon. She may be contacted at kacoatney@gmail.com.)