Ask G

Ask G: Can I add polystyrene to soil?

Is it possible to lighten clay soils with polystyrene bits?

I have very clay soil and was wondering if I could add polystyrene bits (plenty to be had at the rubbish dump) to lighten the texture and help drainage. I can successfully break it into small pieces in my compost shredder.
-Lynne Harris, South Africa

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Polystyrene doesn’t break down in soil, landfill or the digestive systems of small animals. But stockpiles at waste facilities might one day be recycled. It’s far harder to remove tiny bits of plastic from the environment.

Remember that soil is an ecosystem. Adding bits of polystyrene to it runs the risk of them being ingested by wildlife.

It’s far better to dig in some gypsum, which makes the fine clay particles clump together. This creates a more aerated, crumb-like texture, providing room to move for air, growing plant roots and beneficial creepy-crawlies.

Over time, dig in compost and other organic matter. I’ve done this in my own garden. What was once relatively lifeless clay is now thriving, teaming with earthworms and producing roses and tomatoes!