Research plots in Puyallup include a long-term organic farming experiment initiated in 2003. Because soil properties have been influenced by nine years of differing organic practices, the researchers expect to see differences in gas exchange from the soils over the next three years of their project.

Together with their colleague Ron Turco at Purdue University, who is studying the same thing in plots transitioning to organic status, they will not only measure emissions but also develop a series of "best practices" that farmers can use to minimize nutrient loss from their soils.

The researchers plan to measure the cycling of gases through the soil over several years because a single measurement is just a snapshot of the system at a given moment - not an accurate inventory of its behavior over the year-long cycle of growth, decay and renewal.

"Long-term data sets are few and far between in organic agriculture but are very much needed," said Fortuna.

Many factors affect soil, emissions

"Any time you are adding nutrients to a system and building them up, you need to be concerned about where the nutrients are going," Fortuna said.

In organic agriculture, nutrients are added via organic matter, including animal manure, residual plant matter after vegetables and grains are harvested, cover crops and compost. These materials are recycled by soil microorganisms, which releases the nutritional building blocks the next generation of plants needs to grow and thrive.

Soil is a complex, living system, so its fertility ebbs and flows with the rise and fall of temperature, the availability of moisture and other factors.

"All systems are leaky," Fortuna said. "Just because you have more organic inputs doesn't mean you are creating more greenhouse gases. There is probably a difference in the way the gases cycle.

"But you do need to have proper cropping and management systems in place to keep nutrients from escaping and becoming pollutants or contributors to greenhouse emissions," she said.