Web edition: July 17, 2008
A number of speakers at this
morning’s media preview of the Smithsonian’s soils exhibit acknowledged how
they initially didn’t know that soil and dirt were not synonymous. Of course,
none went on to explain the difference either. So when the Q&A period
opened, my hand shot up with the first question: “What IS the difference
between dirt and soil?”
Elizabeth Duggal, associate
director of the museum, demurred — and then turned to Pat Megonigal for the
answer. A good choice since he’s the exhibit’s curator and one of some 6,000
dues-paying members of the Soil Science Society of America. In a nutshell, he explained
that “Dirt is displaced soil.”
Uh, what? Like when it’s on my
shoe it’s dirt, and when it’s on the ground it isn’t? This simplistic answer
didn’t quite satisfy.
So when I was able to corner
Megonigal, a half hour later, I asked for some clarification. As he described
it, soil is the compilation of minerals, air, water, animals and other living
matter (and their wastes or decaying bodies) that accumulate in layers and
become compacted over time. Indeed, soils are laid down in discrete horizons (his
name for those layers) and whose compositions vary over time and space.
When particles of that soil
erode or are dug up, they lose the “history” of their place, he says —
essentially their associations with particles that might have been above,
below, and to their sides.
It sounds like he’s saying
soil is the diverse but integrated community of living and inanimate things
that make up the ground beneath our feet. And dirt? It’s a group of runaways or
kidnapped individuals that can’t easily be associated with where they were born
and grew up. In a sense, they’re particles that have been rendered anonymous.
As my toxins rant indicated,
a few days ago, I think people should use words carefully and appropriately. If,
however, the distinction is all but moot, let’s not get too silly about this. When
I got back to my office, this afternoon, I did look up both terms in my trusty desk
dictionary (a reporter’s best friend) and found one definition of dirt as
“loose or packed soil or sand: EARTH.” And a definition for soil was “firm
If one of you agronomists or soil scientists out there cares to weigh in, please be my guest.