Is asphalt harmful to plants

[mrrick]

I recently removed a section of my asphalt driveway to make way for a small garden. My plan was to remove about a foot or two of the very poor looking dirt under the section of drivway and replace with topsoil.

This dirt is mostly rocks, clay and sand, but contains small pieces of asphalt and asphalt dust. I thought I might spread it over a section of lawn that I was planning on turning into a raised bed. I would then cover it with topsoil.

My question is, will this layer of "stuff" hurt the plants that will grow above and though it? Could it hurt the rest of the world below it? Is this a bad thing to do?

-Rick

[Travis]

Would you eat the asphalt?

[Alan Sung]

I wouldn't eat most stuff that goes into the garden soil (compost, manure, loam, perlite, worms). The small amount of asphalt shouldn't be harmful/toxic to your plants. Just add something to the soil so that it doesn't become compacted.

-al sung Hopkinton, MA Zone 6a

[Mike Prager]

What is the asphalt made of? I have no idea, but I wonder if (e.g.) used motor oil is a constituent, or anything else rich in metallic compounds? That could be an issue if the plan is to grow vegetables above.

Mike Prager On the North Carolina coast - Zone 8a (Remove spam traps from email address to reply.)

[Snooze]

Asphalt is made from tar and rocks/sand. Tar is the left over stuff from processing crude oil and coal, some tar is extracted from the ground as well. If some asphalt gets mixed into the soil as you remove the driveway, no harm done. There isn't anything inherently nutrient rich in asphalt that would make me want to intentionally add it.

-S