Project tests introduction of chickens in organic fields

In an effort to quantify the potential for chickens to be part of safe and sustainable commercial organic vegetable production, University of California Cooperative Extension researchers have joined a nationwide project to diversify organic farms with chickens.

Project coordinator Faye Duan, a UC Davis graduate student, acknowledged that using chickens to contribute to soil fertility on farms isn't a new idea. But, she said, "there is currently little scientific information for using chickens on a bigger scale, especially in terms of food safety concerns."

The California project fits into a national effort, funded by the U.S. Department of Agriculture, that also involves researchers from Iowa State University and the University of Kentucky.

In the trials, chickens are introduced as part of a rotation that includes cover crops and a variety of vegetable crops. In California, chickens were placed on research plots in April, following a winter cover crop of vetch, peas, fava beans and oat grass.

Duan said the chickens are contained in "chicken tractors," to protect them from predators.

Each 50-square-foot tractor—described as a floorless chicken coop on wheels—can accommodate 29 birds. Built by two UC Davis students, the tractors consist of wood frames covered with mesh and plywood. Each day, researchers move the tractors to a different part of the plot, where the birds can graze on cover crop residue and deposit manure.

"The first day, the chickens were confused," Duan said. "We had to go slowly. It's a learning process for the chickens and us."

But ultimately, she said, the chickens appeared "excited to move to a new spot where they have fresh food to graze on."

Once the chickens have done their part on the plots, researchers plant vegetables amid the leftover cover crop residue and chicken manure.

This summer, UC said, the experiment in California will grow processing tomatoes. Subsequently, melons, eggplant, spinach and broccoli will be part of the vegetable rotation in California or the other states involved in the project.

Other replications of the trial will have the chickens immediately follow the vegetable harvest, so they can graze on the crop leftovers before the cover crop is planted. Comparing the soil health, fertilizer needs, chicken quality and other factors will help the scientists optimize the rotation, Duan said.

"Vegetable yield will be an important indicator of success," she said.

UC Cooperative Extension specialist Maurice Pitesky, a poultry specialist and a project lead, said soil samples will be tested to determine the presence or absence of Salmonella bacteria after the chickens have been removed.

Salmonella is a bacterium that can be part of poultry's microbiome. If the bacterium contaminates human food, it can cause illness.

"Since Salmonella lives in the chicken gastrointestinal system, when it gets into the soil, it will eventually be out-competed by bacteria more adapted to soil than the gut of a chicken," Pitesky said.

Noting that there are many different types of Salmonella, he said only "a select few" found in birds prove harmful to humans.

"Nevertheless," Pitesky said, "it is very important to test and use various practices to mitigate the presence of Salmonella on land that will be used for crop production following poultry."

Early results of soil tests in Iowa and Kentucky detected Salmonella in the soil where chickens grazed, but the bacteria disappeared very quickly, he said.

After 24 days on pasture, the chickens become part of the project's meat study.

"We have broiler chickens that are raised for meat," Duan said. "Some people believe chickens that graze and eat grass taste better and are more nutritious. It will be part of the study to look at the chickens' meat quality."