Philadelphia soil project signals largely positive findings for urban growers

UNIVERSITY PARK, Pa. — Initial findings from a soil testing project launched a year ago in Philadelphia indicate positive news for urban growers — low levels of contaminants and higher than expected levels of nutrients.

The project is aimed at helping to ensure safe and productive urban gardening, according to John Byrnes, Penn Sate community vitality extension educator in Philadelphia. With support from a $100,000 grant from the Pennsylvania Department of Agriculture, Penn State researchers are developing recommendations for site assessment, soil testing and management for gardening in urban settings. Stakeholders, including Penn State Extension educators and Master Gardeners, Philadelphia Parks and Recreation’s Farm Philly Program, and Temple University, are collaborating to provide site-specific assessments and soil testing guidance.

Patrick Drohan, team lead on the grant and professor of soil science and pedology in Penn State’s College of Agricultural Sciences, noted that the process of determining what soil test one needs begins with identifying how one’s gardening site was used in the past — perhaps even 100 years ago. Past uses, identified through what is called site assessment, can affect a soil’s fertility, potential contaminants and overall health.

Byrnes explained that the project focuses in part on how to make soils healthier — an area he said Penn State Extension can make a significant impact.

Last summer, the project took flight with a pilot group of about 15 managers of urban farms and gardens from across Philadelphia who volunteered to have their soil tested by Penn State Extension. The resulting reports include an integrated overview that provides all essential information in one place. Byrnes explained that soil test reports typically include two separate reports for soil fertility and heavy metals, which can be confusing for growers. The team aimed to create an integrated report that consolidated all information in an easily understandable format.

The initial findings were a pleasant surprise for the growers, with arsenic, cadmium and lead levels below any concerning thresholds in most of the locations sampled. However, the pilot sites often exhibited excessively high pH and concentrations of phosphorus, potassium, calcium, magnesium and soluble salts.

This discovery suggests, Byrnes said, that urban gardening organizations with limited budgets can reduce amendment application, which involves adding substances such as compost, manure or peat moss to boost soil fertility. The study’s findings indicate that using soil testing to guide decision making can prevent overfeeding with phosphorus and other minerals. As a result, urban farms can lower spending on compost and other amendments.

Over the past year, Raymond Balaguer Barbosa, Penn State urban agriculture extension educator and project collaborator, visited the growers, assessed their operations and offered tailored technical advice based on the soil test results.

Extension plans to develop educational materials, including short videos, fact sheets and workshops, Balaguer Barbosa said, to empower growers with the knowledge and skills for soil testing and interpretation. Temple University’s contributions to the project also aim to equip growers with a deeper understanding of the land, Byrnes said. 

Penny Retica, a Temple University student, focused on the ways the historical context of the land — particularly in relation to Philadelphia’s industrial past — can enrich the relationship a community gardener or farmer has to the land. Historical site assessments can allow growers to discover what existed on the land decades ago, such as a gas station, factory or even a thriving community garden.

Retica collaborated with Megan MacCall, special collections curator of maps at the Free Library of Philadelphia, to create educational materials, including a story map. This user-friendly, interactive tool integrates the extensive collection of historical maps of Philadelphia, freely available online, to reveal site histories that might inform growers’ decisions on how to use the land.

Byrnes said that knowing the site history can help gardeners scale their level of concern and take appropriate measures such as capping the soil, creating raised beds or bringing in clean soil from another source.

Looking ahead, Retica expressed interest in exploring the intersection between urban agriculture and public data.

“Both areas benefit from increased participation and collective efforts,” Retica said. “It would be exciting to see the development of interactive soil maps where people can contribute their own soil data and site histories.”

Ultimately, Balaguer Barbosa said, the project revolves around empowering growers.

“Our main goal is to get the information out to the growers as quickly as possible, especially since the growing season has already started,” he said, explaining that urban gardening can help reduce food insecurity, anxiety, depression and engage a variety of people. “Many new farmers are starting up with no prior experience, and we want to help them do something positive for their community.”

Team members on this project include Raymond Balaguer Barbosa, urban agriculture educator, Penn State Extension, Philadelphia; John Byrnes, community vitality educator, Penn State Extension, Philadelphia; Patrick Drohan, Department of Ecosystem Science and Management; John Spargo, Agricultural Analytical Laboratory and Department of Plant Science; Justine Lindemann, Department of Agricultural Economics, Sociology, and Education; Jessica Schweiger; Master Gardener coordinator, Penn State Extension, Philadelphia; Meghan Chawner, Penn State Extension educator in Lehigh and Northampton counties; and Beth Yount, Master Watershed Steward Coordinator, Penn State Extension, Philadelphia.