Soil scientists in the spotlight at World Congress of Soil Science

Soil scientists from the University of Wisconsin–Madison will have international attention this week at the 18th World Congress of Soil Science on July 9-15 in Philadelphia.

They will present research in many different areas, including interactions between antimicrobial agents and soil; efforts to improve climate change models by better understanding the response of soil to climate warming; and how water can be used more efficiently in potato crops grown in sandy soil.

Given the quantity of antibiotics used in both human medicine and animal production, it’s inevitable that some of them wind up in the environment, says Joel Pedersen, a professor of soil science and one of the UW–Madison’s presenters at the World Congress of Soil Science. Compounds like sulfonamide antimicrobials – used to treat urinary tract infections in humans, as well as illness in cattle, swine and poultry – are not always eliminated as waste is processed, and the resulting material is often applied to agricultural fields to add nitrogen or amend the soil.

“The question is, are we promoting antibiotic resistance when we introduce these agents into the environment by increasing selective pressure to favor resistant microorganisms?” explains Pedersen, who conducted his research with graduate student Juan Gao. Long a concern in hospitals and clinical settings, antibiotic-resistant bacteria defy conventional methods of treatment and can be deadly to people with compromised immune systems.

“We’re trying to understand how antibiotics interact with soil, which is a mix of organic and inorganic components. How readily do they move through the material and leach to groundwater or run off into streams? What is their bioavailability to microorganisms?”

In general, Pedersen says that sulfonamide antimicrobial agents are mobile in soils. The organic matter content of soils strong influences this mobility, a finding that will be important as researchers try to understand antimicrobial bioavailablity and movement.

Other UW–Madison research that will be presented at the World Congress of Soil Science includes:

• In order to help improve current global-scale models of climate change, Teri Balser is exploring some of the simplifying assumptions that are included in the models by investigating the response of soil communities to climate change. With more than a billion bacterial cells in a gram of soil, microbes pack an important punch. In effect, they act as a valve between the carbon that’s locked in soil and carbon dioxide gas in the atmosphere. And as temperatures rise, their population decreases and the structure of their community changes. “I want to know how that impacts the larger picture,” she says. “The current models predict carbon release based on simple kinetics, when in fact the ecological community interacts with and responds to the environment.”
• Potatoes are a major crop in Wisconsin, and are grown primarily in the sandy soil of the central part of the state. However, as the sand in the potato row dries it becomes hydrophobic – meaning that water from rain or irrigation tends not to enter it and move downward between the crop rows, says Birl Lowery. In addition to stressing the plant, this also contributes to problems with nutrients leaching to groundwater, particularly for nitrate. Lowery and his colleagues have found that using a surfactant – a chemical that improves the ability of soil to take on moisture – from the golf course industry can increase soil water content by as much as 50 percent following irrigation or a rainfall.