Healthy soils for food system resiliency

Urban gardens produce a growing portion of food consumed in U.S. cities and throughout the world. Spreading out food production means less reliance on centralized food industries, making the food system less vulnerable to external stresses brought about by climate change and other challenges. Yet, urban food production may occur in soils that need some revitalization before they produce safe, healthy food. Some urban soils contain a record of poor environmental practices in the form of accumulated toxins like heavy metals. Certain heavy metals can be toxic to plants, enter plant parts that people consume, or they can affect a person's health through direct ingestion, dermal contact, or breathing in contaminated dust or soil. Gardeners often seek solutions to problems proactively; the goal of this work is to provide the proactive gardener tools that can be used to assess the potential for toxins to be present, give suitable methods for detecting heavy metals, and provide guidance on making appropriate plans based on these findings. This work investigates whether land use and environmental histories for a garden plot scaled up to a region can predict which heavy metals are present in the garden plot. Case studies are presented for Lawrence, Kansas including a broad environmental history of the town and site specific land use histories for ten urban gardens. Soil samples were collected and elemental analyses were performed using x-ray fluorescence. These results were used to demonstrate that predictions based on Lawrence land use and environmental histories were effective for arsenic, copper, lead, and zinc, but cadmium, chromium, mercury, and nickel were difficult to predict. Soil organic carbon was determined for a portion of the samples and a model for estimating organic carbon based on soil color is provided. A discussion of the policy landscape for urban gardening in Lawrence, Kansas and Flint, Michigan provided material for a tool for determining what policy barriers may exist in any given city, and actions a gardener can take to address these barriers. Finally, a decision support tool was prepared based on lessons learned from the case study that will help gardeners gather relevant information, analyze the information, and make appropriate decisions in land management. Addition of organic matter is lauded as the simplest urban soil treatment that addresses many toxins as well as increasing soil tilth, nutrient status, and water holding capacity. Because urban gardening holds great potential for adding resiliency to the food system, urban soil health must be improved to protect public health