From: jmc@SAIL.Stanford.EDU (John McCarthy)
Subject: Topsoil as a commodity
Reply-To: jmc@cs.Stanford.EDU
Organization: Computer Science Department, Stanford University
Date: 16 Nov 92 00:02:46

Some time ago, in the newsgroup sci.environment, I suggested that
farmers would be more motivated to take good care of their topsoil
if it were a commodity.  Thus a farmer with deep topsoil could sell
some to a farmer with inadequate topsoil.  Land with very deep
topsoil, e.g. in river valleys, would become more valuable than it
is today.  Land with barely adequate topsoil would become somewhat
less valuable than it is today.  Land with no or inadequate topsoil
would become more valuable, because it could be restored.  Of course,
quality of topsoil is not the only component of the price of agricultural
land.  Thus where rainfall is suboptimal, water rights may be even
more important.

The feasibility of this idea depends on the cost of moving topsoil.
My intuition that it probably would be feasible was based on the
fact that land is often leveled to make irrigation work better,
and this requires moving most of the topsoil around, often on
a multi-acre field.  We have the figure that land with good
topsoil in Idaho near Boise is worth $4000 per acre and land
with bad topsoil is worth $1000 per acre.

When I posted the idea some said it was ridiculous, and one said that
if it were economical it would already be in use, although he later
took it back.  Others said it was necessary to determine the costs.
This I undertook to do, but just got around to making the necessary
telephone calls.

Relevant facts:

Amount of topsoil: 1,000,000 pounds per acre - Encyclopedia Britannica
article on soil.

Cost of moving dirt: $1.00 to $1.50 per cubic yard - Caterpillar Performance
Handbook.  This includes the digging, loading and unloading but refers
to short distances.

Weight of dirt: 2500 lbs per cubic yard.

Our million pounds is 400 cubic yards, 500 when swelling is taken into
account.  Therefore, it costs $750 per acre to move it short distances.
However, the handbook in question is for construction contractors, and
maybe topsoil has to be treated more gently than is customary for
contractors.

A standard dump truck carries 10 cubic yards, the driver costs
$30 to $40 per hour including benefits, and the truck costs $30 to $40
per hour including rented wet, i.e. including fuel, etc.  A double
trailer could carry 20 yards, might cost twice as much to rent but
would cost no more per driver.  It could go 40 miles per hour loaded
and somewhat faster on the way back.

Using the bigger truck, there being a weight limit of 10 tons per axle
including the vehicle itself on U.S. highways, we get a cost of $2400
per acre-hour, assuming the higher cost figures above.  This tells us
that the limit of profitability is about 20 miles.

I suppose there is a fair amount of eroded upland within 20 miles
of river valleys with deep topsoil.

Of course, rail transportation is a lot cheaper, and barge transportation
is a lot cheaper than that.  Still the differential in price of land
with good and bad topsoil will have to get somewhat larger, before it
will be profitable to dig up the Mississipi delta, which largely consists
of topsoil washed down the river and barge it back up the river.
--
John McCarthy, Computer Science Department, Stanford, CA 94305
*
He who refuses to do arithmetic is doomed to talk nonsense.

Newsgroups: sci.environment