Soil for Sustainability: Impacts of Urban Agriculture on Soil Health

Abstract

Urban agriculture (UA) is growing in popularity around the world, transforming vacant parcels into flourishing farms and gardens. While UA is typically associated with positive environmental, social, and economic benefits, multiple challenges and barriers to UA exist. In many post-industrial landscapes, soil lead contamination poses a real threat to agriculture, with potential implications for human health as well as impacts on other aspects of soil health, such as fertility and microbial activity. The addition of compost, use of cover crops, or other management practices in urban gardens has the potential to reduce lead bioavailability and can simultaneously improve soil fertility; however, little is known about the impact of these management practices on urban soil health. This suggests that risks, such as lead contamination, should be considered within a broader soil health framework to ensure a healthy and sustainable future for UA practices. To advance these goals, this study investigated how a range of management practices within UA impact urban soil health. Soil samples were collected from 13 UA sites in Detroit, Michigan, and analyzed for a suite of biological, chemical, and physical soil health components. Results show that lead levels were lower in managed areas than in unmanaged areas of the farms and gardens sampled (p= 0.006), suggesting that management practices have a significant impact on lead bioavailability. Further, multiple soil health variables were significant predictors of reduced lead bioavailability throughout garden sites. While management practices such as compost addition have the ability to reduce lead bioavailability, tradeoffs exist for excess levels of soil phosphorus and potassium on UA sites. This study also analyzed urban growers’ motivations for participating in UA and the challenges growers face in advancing UA goals. Specifically, farmers and gardeners identified that economic factors present the greatest barriers sustainable management practices. To fully understand the impacts of UA, and its contribution to city sustainability, both environmental and social components of urban gardens must be considered.