In following the bits and pieces relating to the story about lead in the White House Garden from sewage sludge applied years ago, I learned 2 things about lead in the soil.
One is that when the soil pH is adjusted to between 6.5 and 7, any lead in the soil is unavailable to plants. Secondly, I learned that adding 1/3 by volume of organic matter to the WH Garden before planting this year, they were able to reduce the lead amounts from 93 ppm to 14 ppm. Even the 93 ppm was well below what the EPA allows as safe, 400 ppm.
The amendments added to the WH garden were greensand, crab meal, compost from the National Park Service, and lime.
Other organic amendments to use on home gardens are composted leaves, non-acid peat, and well-rotted manure. Leaves should not be gathered from along highways and city streets in order to prevent lead contamination.
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