Rubber Tire Pellet Mulch

(Question)

Hi!
We bought a house this past winter and just moved in a couple of weeks ago. This past weekend, we finally started working in our yard. To our horror, we realized that the landscaped garden was covered in brown rubber tire pellets, presumably put there to control weeds. The previous owner only lived there for two years, and said that she had the yard professionally landscaped, so the tire pellets may only have been there for two years.

We want to grow vegetables and we plan on extending the existing garden and planting the vegetables there, so they won’t be growing on soil that the pellets were on, but what do we do in the future? Once the pellets are removed, how safe would our topsoil be? Should we get the soil tested? Do we have to remove the soil and start over? This is our first house, and we are really not sure what to do about this. Any advice would be greatly appreciated.

 

(Answer)

Congratulations on your new home and I’m glad to hear that you are keen on gardening!

I agree that you should get rid of the rubber mulch. These mulches may look good and last for a long time, but are not considered as effective as other mulch types (e.g., organic matter like shredded bark, leaves) for controlling weeds. And unlike organic mulches, rubber mulches won’t add beneficial organic matter to the soil.  In addition, rubber mulch may attract insect pests, is flammable and may leach heavy metals (zinc in particular may be present at high levels) and other chemicals (contaminants) into the soil, which could persist for a long time.   Some rubber mulches may be made of steel-belted radial tires, and bits of steel wire can remain in the mulch, which can be an issue when handling these materials.

Plant health can be affected by metals like zinc; for example, zinc is more available for uptake by plants in acidic soil, so can be especially toxic under these conditions.

There is not much information in the literature about how best to remove the rubber mulch.  SF Gate’s How to remove rubber mulch provides basic information.  A caveat – this is a US resource, so their recommendations for disposal may not apply in Canada.  I suggest that you check with your municipality on how to properly dispose of the rubber mulch.

In any event, to get rid of the rubber mulch, you will have to remove some of the topsoil, as the rubber mulch pieces will have mixed in with the soil to some degree.  The level to which soil should be removed is something I cannot predict, as this would presumably include both soil that contains visible pieces of the mulch and underlying soil that may have been contaminated.  Soil tests may be a good idea, to give you some idea of soil contaminants, but you would need to ask the laboratory in advance if it can test for all likely contaminants seen with rubber mulch.

It is likely that the longer the mulch has been present, the more soil would be contaminated – I’d suggest confirming with the former owner that the pellets have only been there a couple of years.     Consider contacting a landscape company for additional advice.

Here are some helpful resources:

Lastly, as the health effects of metals and chemicals that rubber mulch may leach into the soil, caution is recommended when considering a vegetable garden, even once that mulch is removed.  The safest alternative is what you plan to do – plant the vegetables in a spot located away from where the rubber mulch was spread.

 

 

 

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