In history class they teach the military strategy Scorched Earth: "burn the villages and forests, salt the fields, come back next year to fight a starving enemy".

What is the chemical process by which salt is harmful for plants? How much salt is needed to render one cubic meter of soil infertile? How long does that persist in the face of rain/watering?

A practical application is as follows. When I grill, sometimes I salt the food after putting it on the grill. So some salt falls in the fire. I then use the embers and ash as a carbon source for my compost*. Is the salt destroyed by fire? By composting?

* - the word "compost" was used because the aim of the final substance is to enrich potted soil. In reality it's several bucket of kitchen scraps, very carbon-poor


Very few plants can tolerate much salt in the soil. There are some exceptions in costal areas like mangrove. But it requires a lot of salt ; the amount you put on food will have no effect. If a large amount of salt is used, plants will not grow, or grow poorly until rain rinses the salt away, which may take years ; depending on the relative amounts of salt and rain.

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