Researchers look for best ways to prepare the soil

Central Coast growers, University of California Cooperative Extension farm advisors from five counties, researchers from both UC Davis and UC Santa Cruz, as well as two California State University campuses, are working together to test and discuss promising organic farming methods.

Most recently, the Collaborative Organic Research and Extension Network completed a four-year strawberry trial on the Santa Cruz campus and in growers' fields of compost, cover crops and anaerobic soil disinfestation, a promising organic method of ridding the soil of diseases.

"It's likely we'll adopt ASD in part if not all of our berries," said Stephen Pedersen, who has been growing organic vegetables and berries with his wife Jeanne Byrne on their farm overlooking Harkins Slough outside Watsonville for 15 years.

"We go five years between strawberry crops, but ASD may let us shorten the rotation," he said.

The chance to regularly discuss the trial with the researchers and other farmers lets Pedersen come away hopeful about the disease control technique, even though mistakes in execution led to mixed results.

"The people in this project are still learning," said Pedersen, who markets his harvest under the High Ground Organics name. "Researchers have tried disinfestation with six tons of rice bran, instead of nine, but it was right on the bed. We did six, but it was on the ground before the beds were listed."

The rice bran provides a source of carbon essential to the disinfestation process. Researchers learned that too low a rate in the recent trials led to inconsistent disease-control results.

"All of the trials used rice bran at six tons an acre broadcasting method," said Joji Muramoto, UC Santa Cruz associate researcher at the Center for Agroecology and Sustainable Food Systems. "That was one of the mistakes we made for the ASD; it should have been nine tons an acre."

The ambitious attempt to save money by using a lower rate of rice bran came after one Central Coast grower got good results incorporating just six tons after the beds were made.

"Another small trial with a bed-top application suggested that six tons an acre works as well as nine tons an acre," Muramoto said. "However, that was only for the bed-top application. We were too excited about the results and misinterpreted it, applying six tons an acre of rice bran for the broadcast application: a big mistake."

There was also a learning experience in seeing that the ground must be saturated right after the carbon source is incorporated, rather than waiting, if ASD is to be most effective.

"We should have sprinkled first, waited for the perfect moisture for bed listing, and then broadcast rice bran, incorporated it and listed the beds right away," Muramoto said. "We learned this the hard way. So basically, all the trials did not create sufficient anaerobic conditions to control verticillium wilt. Some growers are doing a much better job in ASD application on a commercial scale than we did. We were not used to doing ASD in a larger scale trial just yet."

Pedersen said he believes waiting too long before saturating the soil was another lesson on the ASD learning curve at his farm.

"If we were to do it again, we would create the anaerobic conditions right after we incorporated the rice bran," Pedersen said. "It may also be harder to do disinfestation on heavy soil, because the water drops through the cracks rather than saturates the soil. It remains to be seen how the ASD plots will do. I don't think all the conclusions are in yet. There's still a couple months left in the season, and the ASD plots with less disease may yield better."

Regular interaction with the researchers helped sort out how to make the system work better.

"One of the benefits of being part of the program is access to the information," Pedersen said. "I'm into my fifth year in the program, and they have meetings every year."

The regular communication between the researchers and farmers was particularly beneficial at the Agriculture and Land-Based Training Association, a Salinas agency that helps farmworkers learn to become farmers.

"One of the benefits was having the researchers and investigators interact with our farmers," said Nathan Harkleroad, agricultural education program manager at ALBA. "It was good for them to have a chance to talk with researchers who are on the cutting edge."

Disinfestation produced the best strawberry yields in the ground at ALBA, which apparently had strong pressure from the soil-borne disease verticillium wilt.

"It's definitely an approach that could have some benefit to organic strawberry growers," Harkleroad said. "We will probably use it at ALBA, especially if UC Santa Cruz can get funds to continue the trial."

The four-year study also produced highly detailed information on other subjects, including the contribution compost and cover crops make to fertility.

"We learned how quickly the nitrogen is available after incorporating the cover crop," Harkleroad said. "Some of the nitrogen was available in the first few weeks; it was quicker than I thought."

The standard program at High Ground produced the best strawberry yields in the most recent trial, and Pedersen said he suspects the credit goes to his ambitious and expensive fertility program.

"We go with a heavier pre-plant application of organic fertilizer," Pedersen said. "We use 750 pounds of 10 percent nitrogen before planting, then we do a supplementary feeding every couple weeks during the long season."

The in-season fertilizer applications alone cost almost $50 an acre every two weeks, but it is worth the cost, he said.

"It's not huge considering the potential yields," Pedersen said. "Fertility is probably a bigger issue than disease because the plants are in the ground so long. We plant them in December, and they are in the ground all the way until the next October. We're still probably around half of what a high-yielding conventional field would be."

Pedersen and Byrne have to find organic answers to the challenge of fertility as one of the conditions of buying their land next to Harkins Slough.

"This land used to be one of the last dairies on the Central Coast before it was purchased by the Open Space Alliance," Pedersen said. "They sold it to us in 2000 with a conservation easement that calls for restoration of the hillside going down to Harkins Slough, and an agricultural easement on the farming portion of it. It has to be farmed organically."

This high ground is about half the 40 acres the couple farms, and the easement made it possible to purchase affordable land in the Watsonville area.

"The Open Space Alliance bought this land and sold it to us with the easements in 2000 for about half off," Pedersen said. "Flat farm ground around here can go for $60,000 an acre now."

(Bob Johnson is a reporter in Santa Cruz. He may be contacted at bjohn11135@aol.com.)