"There are five plots in each of four different fields that have
received no applications of plant food from the beginning. Thus,
every year the crops are carefully harvested and weighed from twenty
measured plots of ground that receive no treatment except the
rotation of crops. The difference between the average of the first
twelve years and the average of the second twelve years should
represent the actual change in productive power during a period of
twelve years. These averages show that the yield of corn has
decreased from forty-one and seven-tenths bushels to twenty-seven
and seven-tenths bushels; that the yield of oats has decreased from
thirty-six and seven-tenths bushels to twenty-five bushels; that the
yield of wheat has decreased only from thirteen and three-tenths
bushels to twelve and eight-tenths bushels; and that the yield of
hay has decreased from three thousand seventy pounds to two thousand
one hundred and eighty pounds.

"As a general average of these four crops the annual value of
produce from one acre has decreased from $11.05 to $8.18. Here we
have information which is almost if not quite equal in value to that
from the Agdell rotation field at Rothamsted. While the Rothamsted
experiments cover a period of sixty years, each crop was grown but
once in four years; whereas, in the Pennsylvania experiments, there
have been four different series of plots, so that in twenty-four
years there have been twenty-four crops of corn, twenty-four crops
of oats, twenty-four crops of wheat, and twenty-four crops of hay.

"Under this four-year rotation the value of the crops produced has
decreased twenty-six per cent. in twelve years. What influence will
impress that fact upon the minds of American landowners? A loss