Home Gardens and Lead – University of California Cooperative Extension
What You Should Know about Growing Plants in Lead-Contaminated Soil
By Arthur Craigmill, University of California Cooperative Extension Environmental Toxicology Specialist, UC Davis; Ali Harivandi, University of California Cooperative Extension Environmental Horticulture Advisor, San Francisco Bay Area.
Can I do anything to reduce the amount of lead my vegetables take up from the soil?
Yes, you can! You can reduce the amount of lead uptake by plants by providing amendments that promote binding of the lead with other components of the soil, and also manage the soil acidity (pH).
Organic matter has been proven to bind and hold lead effectively, making it less available to plants. However, organic matter eventually breaks down, so the soil should be frequently amended with organic matter (compost, decomposing leaves, or well-rotted manure).
Composts rich in phosphorus are especially able to lower lead uptake into the edible parts of plants. Applying additional phosphorus using any garden fertilizer containing phosphate to the soil surface when adding organic matter increases the phosphorus content and does not hurt the plants even if the compost is already rich in phosphorus.
For vegetable gardening, maintain the soil pH in a range close to neutral (pH 6.5 to 7.5). You may need to add limestone to increase the pH in acidic soil. Generally, plants take up less lead as the soil pH increases. However, the soil pH should not be raised beyond 7.5, otherwise elements necessary for healthy plant growth and development will also become unavailable to the plants. Although garden pH meters are readily available at garden centers, it may be more accurate to have the soil tested for pH at a local commercial soil laboratory (see below for more information on soil testing).