In organic agriculture, nutritional building blocks like nitrogen, carbon and phosphorous are introduced via organic matter to improve soil over time. But when these nutrients are released as gases into the air or in stormwater runoff, they can pollute water sources and contribute to greenhouse gas buildup.

For farmers, the loss of valuable nutrients affects the bottom line because they must be replaced with more costly inputs.

Comparing various farming systems

Washington State University scientists Ann-Marie Fortuna, Craig Cogger and Doug Collins are developing a series of experiments to determine the types and amounts of gases emitted by organic cropping systems.

"We are going to work out a set of practices that give growers a way to manage inputs that give plants the nutrition they need while not creating pollution," said Cogger, a soil scientist and extension specialist based at WSU's Research and Extension Center in Puyallup.

"To that end, we are comparing how different organic farming systems with a history of different amendments and tillage frequency affect releases of carbon dioxide and nitrous oxide, two major greenhouse gases," he said.

Microbes the focus of research

"We know that both tillage and type of amendment affect the soil ecosystem, but we want to know how the microbes in these different ecosystems affect the release of greenhouse gases from the soil," Cogger said.

"This research will improve our understanding of how carbon and nitrogen cycle between land, air and water in vegetable and row crop farming systems in the Pacific Northwest and Midwest," said Fortuna, an assistant professor of soil science at WSU and director of the project.

While a great deal is known about crop production and nitrogen fertilizers, she said, knowledge of the way soil microorganisms regulate the cycling of nutrients is limited.

"We need to learn how agronomic management practices alter the microbiology controlling these reactions," she said.

Video, guidelines, info to aid growers

The team plans to communicate the research results to growers via a video on climate change and soil microbiology.

The direct impact of the research will be a set of management practices for farmers, as well as information about the availability of nutrients in soils, Fortuna said.

The research has an additional potential bonus in that the team may be able to quantify a way to tell growers what their carbon footprints are, which growers could use in marketing.