On the allotment site in Northern England where I grow food, there’s a fashion for rockdust. Some of my neighbours swear by it. I’m not tempted, and my plot’s the envy of the site (well it was so, until my worsening disability put a kibosh, but that’s another story).
I’m not tempted by rockdust partly because I distrust any claim about ‘soil remineralisation’ that doesn’t involve naming minerals, appropriate to particular sites. You can find a list of what’s in the rockdust online, but I’ve seen nothing about what that means in practice.
There’s plenty of calcium and magnesium in there. Calcium carbonate is also known as lime, used by many gardeners (including me) to raise soil pH. It’s often used with magnesium sulphate, also known as Epsom salt. Epsom salt can be made from magnesium oxide. Here’s what the European Commission says about the lime, magnesium oxide and…
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