Where 86 pounds of nitrogen was applied in sodium nitrate the
average yield was 79 bushels; but where the nitrogen, phosphorus and
other minerals were all applied the average yield for the twenty-six
years was 203 bushels.

At 50 cents a bushel for potatoes, the investment in phosphorus
alone paid 600 per cent net profit; and even the complete
fertilizer, including 392 pounds of acid phosphate, 550 pounds of
sodium nitrate and 500 pounds of alkali salts, aggregating 1442
pounds, and costing at moderate prices $24.28 an acre per annum,
paid back $76 a year as a twenty-six year average, thus making 300
per cent even on an investment of nearly $25 an acre a year.

Phosphorus Helps Good Farming

There is also but one place in the world where we can learn the
results secured from the application of phosphorus for a period of
thirty-six years in a good system of farming; and again this place
is Rothamsted.

In 1848 Sir John Lawes and Sir Henry Gilbert began investigations on
Agdell Field. The Norfolk rotation, already known at that time as
one of the best rotation systems, was turnips, barley, clover, and
wheat; and in these practical field experiments the turnips were fed
on the land and the animal fertilizer thus produced was returned to
the soil, which was well supplied with limestone.

During the next thirty-six years $29.52 worth of phosphorus per acre
was applied to one part of the field; and in comparison with another
part of the same field cropped and managed similarly, except that no