"And Avimelekh fought against the city, all that day, and he took the city, and slew the people that were in it, and pulled down the city, and sowed it with salt." This Avimelekh was clearly not a bloke to be trifled with, but my question is about the sowing part. Did anyone really get bags of salt and plow it into the ground just to prove what total conquerors they were? Salt was a rare and valuable commodity for most of history, so this would have been an expensive way to make a symbolic point, no?
— Sam, Singapore
I learned in elementary school that when the Romans sacked Carthage during the final Punic war, they "salted the earth," so that nothing could ever grow there again. However, here in Vermont we dump literally tons of salt all over the roads every winter in the name of ice control. This salt goes somewhere, washed by the spring rains into the soil by the roadside, eventually into rivers, lakes, and ponds and the water table. Yet every spring Vermont explodes into lush greenery, even right by the side of the road. So how effective is salt as a herbicide?
Mark Z, via e-mail
We’ll start with the easy question. How effective is salt as a herbicide? If you use enough of it, real effective. I refer you to a book I’ve mentioned before, Jared Diamond’s Collapse: How Societies Choose to Fail or Succeed (2005). A major environmental problem in Australia, Diamond informs us, is soil salinization due in part to sea salt carried inland by winds and inundation and then brought to the surface by land clearance and irrigation. Looming result: in 20 years a third of Australia’s wheat belt may be sterilized by salt. Some Australian soil holds more than 200 pounds of salt per square yard of surface, which is surely more than you’ll find by the roadside in Vermont, but knowing the level of eco awareness in the average highway department, my feeling is: give it time.
Did people actually sow fields with salt in ancient times? Hard to say. The earliest nonbiblical account of salt sowing dates from the eighth century BC, and several sources speak of Jewish, Hittite, and Assyrian cities being sown with salt or other minerals. In Deuteronomy, Moses warns the Jewish people that if they turn away from the Lord their land will be destroyed, “all its soil devastated by sulfur and salt, beyond sowing and producing, no grass growing in it, just like the upheaval of Sodom and Gomorrah.” In Judges we read about the above-cited Avimelekh, who was upset with the city of Shechem. But we have no evidence that any of these saltings actually occurred.
As for Carthage, we need to take that story with a pinch of salt too. When Scipio sacked Carthage at the end of the Third Punic War in 146 BC, it’s not out of the question that he salted the ground. Salt was readily available at salt works and brine springs all over Italy, and the Romans had conquered Carthaginian salt works in north Africa. However, no ancient account says anything about salting the ground — that twist may have originated with the 19th-century German historian Ferdinand Gregorovius, who mentions it in his History of the City of Rome in the Middle Ages. Gregorovius’s contemporary Theodor Mommsen says the Roman senate ordered the site of Carthage to be plowed under, but even that’s debatable. Whatever fearsome measures may have been adopted, they didn’t take; the site was reinhabited within a century and developed into a thriving Roman city.
One claimed salting for which there’s at least some evidence took place following the Tavora affair in mid-18th-century Portugal, when several nobles from the house of Tavora were accused of attempting to assassinate King Joseph I. Most of the Tavoras were tortured and killed as punishment; the family’s palace in Lisbon was razed and the ground allegedly salted. The spot on which the palace stood, now a Lisbon courtyard marked with a stone memorial, is called Beco do Chao Salgado, which loosely translates as “alley of the salty ground.”
However expensive it may have been in antiquity, salting the earth today is surprisingly affordable. Making certain assumptions (75 percent yield reduction = crop failure, salt sown to a depth of one foot, etc), you’d need 31 tons of salt per acre. Rock salt can be had for under $50 a ton, so figure $1,500 per acre for materials, pretty cheap for the satisfaction of expunging all trace of your enemies from the face of the earth. Be aware, however, that rain readily leaches salt out of soil, meaning that in a well-watered climate salted ground might be recoverable in a few years. Also, let’s face it: biblical extermination of those who cross you has a way of ensuring their names are remembered at least as long as yours.
Send questions to Cecil via firstname.lastname@example.org.