computation will show that the gross receipts from an 80-bushel crop
will pay $7.20 an acre for soil enrichment, $4 for raising the crop,
$4 for harvesting and marketing, $1.53 for taxes and 5 per cent
interest on a valuation of $305.45 an acre.

The average yield of corn in the United States is only 25 bushels an
acre, and the average net returns even from the farms of the Corn
Belt will not pay 4 per cent interest on their present market value.
But the intelligent investment of $2 an acre annually in positive
soil enrichment will increase the crop yield by two bushels of corn
each year--or by equivalent amounts of other crops grown in the
rotation--and will maintain this increase for at least a dozen years
on the average land now under cultivation in the United States; and
no other safe investment can be named that will pay so great
returns. Of course, the cost is $1 a bushel for the first year's
increase, and even the second year the 4 bushels of corn cost $2;
but what is the cost per bushel of the increase the tenth year? It
is 10 cents; and the twelfth year the 24 bushels of increase cost
only 8-1/3 cents a bushel, with a return of nearly 500 per cent on
the annual investment in soil improvement.

And this is not based on mere theoretical considerations. The
average Corn-Belt land is producing only 40 bushels of corn to the
acre; while a six-year average yield of 90 bushels has been produced
on the common Corn-Belt land with proper and profitable soil
treatment. Thus is it too much for any farmer to adopt a definite
system based upon established practical scientific information which
makes it possible for his yield to increase from 40 bushels to an
average of 64 bushels an acre? But let him make sure that the system
he adopts is cumulative and truly permanent, and not merely