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Urban Ag Growing Food on Presumably Contaminated Soil
Citation:
Rock, S. Urban Ag Growing Food on Presumably Contaminated Soil. Presented at 14th International Phytotechnologies Conference, Montreal, CANADA, September 25 - 29, 2017.
Impact/Purpose:
To inform the public.
Description:
Urban lots are presumed to be contaminated. Urban soil retains contaminants from many years and different sources and is likely to contain atmospheric deposition from leaded gasoline, PAHs from soot deposition from historical neighborhood fires, and asbestos from building demolition. Don’t eat dirt. Despite this, contaminant testing in urban lots is unnecessary before building new gardens. Since we presume that the contaminants are in the soil, what is to be gained from testing? The level of contamination or absence of contaminants does not change the way urban gardens should be built. Good testing is expensive. Bad testing is useless. Neither is needed for two reasons. 1) Garden plants do not take up lead or other contaminants in dangerous quantities. Some plants can sparingly intake some contaminants but do not pose a health risk. Plants tend to ignore contaminants that are insoluble when the pH for growing is optimized, when there is plenty of water, and when the soil is fertile. If the soil is such that plants can grow well, there is little to no uptake. 2) Urban gardens almost always are built using raised beds with imported soil and compost. There is little or no contact with the presumably contaminated soil. Soil testing on urban lots prior to garden construction do not describe the soils in the final gardens. Lead poisoning is a real problem in many urban neighborhoods as people do ingest and inhale lead from dust. To prevent the transfer of lead the best practice for urban gardens is to cover the site with cardboard, build the beds on that covering, and fill in the pathways with woodchips. Mulching pathways and the non-growing areas of a garden (benches and tables) prevents direct contact with historical soils and suppresses dust movement.