Have you ever wondered if the soil is safe in urban garden plots? A study at the University of Illinois titled “Testing and educating on urban soil lead: A Case of Chicago Community Gardens” in the Journal of Agriculture, Food Systems and Community Development (January 2011) may give you some insight on this topic.
The study goals were to learn how much lead is present in participating gardens in the study; to determine if lead levels vary in different types of garden areas and to inform participants and urban gardeners about soil quality and how to deal with urban gardening issues such as lead, soil fertility and soil pH.
Ten gardens participated in the study and soil cores were taken from raised and non-raised beds used to grow food and also in areas such a playgrounds and pathways. Then the researchers grew lettuce on the soils and tested the crops for quantity of lead.
Lead levels in most gardens were not a concern. Most of the garden plots contained excessive fertility with raised beds containing more phosphorus and potassium than non raised garden spaces. The lack of soil testing among the 10 gardens in the study is likely a contributing factor to the over fertilization of the gardens. Use of raised beds significantly reduced lead levels and therefore less potential risk of lead ingestions from plant uptake. Higher lead levels in soil from adjacent areas supported the notion that areas with bare soil adjacent to gardens may be an equal or greater source of risk. None of the lettuce shoots in this study exceeded the World Health Organization recommendations.
Additionally, a training program about urban garden safety with live and online options was created and evaluated by questionnaires given to Master Gardeners. Both live-trained and online trained groups’ quiz scores improved significantly after the trainings, demonstrating that education about urban soil management can be effective.
By Monica David, University of Illinois Extension Master Gardener Coordinator