Leopold Center Funds Research to Guide the Way

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Posted: Monday, February 17, 2014 6:41 pm

AMES, Iowa -- With the rising popularity of local foods the spotlight is now on cities and the health of the soil underfoot.

Increasingly, sustainable agriculture practitioners and researchers view cities as places of potential. A green space like an urban garden or farm can revitalize a neighborhood by making abandoned or underutilized land productive again. It also reduces the distance, and disconnect, between people and produce.

“But the soils in these areas have been so altered by prior land use that they could pose some challenges for cultivation,” cautions Mark Rasmussen, director of the Leopold Center for Sustainable Agriculture at Iowa State University.

Soils in brownfields, the former sites of factories, gas stations and other industrial or commercial zones, may show signs of past land use in the form of residual chemicals, oils, pest control poisons, detergents or heavy metals. Lead, in particular, may even be present in residential areas from chips of old lead-based house paint. Soils near highways or railways also may accumulate petrochemical residues, including leaded gasoline.

These are not just on-site issues, Rasmussen says, since wind and rain may carry contaminants from other locations. For example, floodplain areas collect soil displaced upstream. Meanwhile, foot and vehicle traffic may have compacted the soil so it holds little moisture and no room for roots to grow. And since only a few hardy plants can eke out a living on uncultivated urban land, there may be very little organic matter built into the soil by plant roots.

Rasmussen suggests that if you are planning to convert an urban lot into a green space, “Start from the ground up, and revitalize the soil first.”

He cautions that soil remediation efforts involve time, effort, financial investment and expertise. Contact a local extension office, agronomist or soil scientist first, since options will vary based on existing soil conditions, the types and levels of contaminants present, the kinds of plants to be grown and municipal restrictions on land use. Some information also may be found through city records showing past land use, or soil tests through a lab.

Based on the site’s conditions, soil in the urban lot may need to be excavated and replaced, a barrier laid between old and new soil for building raised beds, or the existing soil treated to remove or reduce contaminant levels. Other work could include tilling or aerating the soil, constructing mechanisms to improve drainage and infiltration, or adding compost or lime to reduce heavy metal concentrations.

But urban farmers are not alone in these tasks. An extension agent may be able to offer other resources such as toward toolkits, cost-reduction schemes and partner organizations.

“Many organizations and city planning groups are eager to increase the number of small farms and gardens in the city,” said Craig Chase, the Leopold Center’s Marketing and Food Systems Initiative program manager. “They might consider the cost to be an appealing investment for the future of local foods in their community.”

To pave the way for this type of green development, the Leopold Center is funding three new urban agriculture projects this year. A policy initiative grant supports the creation of a guidebook for city officials that covers municipal zoning regulations on urban food production and sales. Two grants from the marketing initiative will support research on an agricultural urbanism toolkit to reduce barriers to local food access, and community-based research to find existing and future opportunities for expanding food networks in the city.

SOURCE: Leopold Center for Sustainable Agriculture

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