At this price they might certainly defy the
competition of the United States. It is one thing, however, to grow
crops in a lecture room, and quite another to grow them in a field. In
dealing with artificial manures, furnishing phosphoric acid, potash, and
nitrogen, we have substances which act upon the soil in very different
ways. Phosphate of lime is a very insoluble substance, and requires an
enormous amount of water to dissolve it. Salts of potash, on the other
hand, are very soluble in water, but form very insoluble compounds with
the soil. Salts of ammonia and nitrate of soda are perfectly soluble in
water. When applied to the land, the ammonia of the former substance
forms an insoluble compound with the soil, but in a very short time is
converted into nitrate of lime; and with this salt and nitrate of soda,
remains in solution in the soil water until they are either taken up by
the plant or are washed away into the drains or rivers.

Crops evaporate a very large amount of water, and with this water they
attract the soluble nitrate from all parts of the soil. Very favorable
seasons are therefore those in which the soil is neither too dry nor too
wet; as in one case the solution of nitrate becomes dried up in the
soil, in the other it is either washed away, or the soil remains so wet
that the plant cannot evaporate the water sufficiently to draw up the
nitrates which it contains.

The amount of potash and phosphoric acid dissolved in the water is far
too small to supply the requirements of the plant, and it is probable
that what is required for this purpose is dissolved by some direct
action of the roots of the plant on coming in contact with the insoluble
phosphoric acid and potash in the soil.

In support of this view, I may mention that we have clear evidence in
some of our experiments of the wheat crop taking up both phosphates and
potash that were applied to the land thirty years ago.

To suppose, therefore, that, if the ingredients which exist in twenty
bushels of wheat and its straw, are simply applied to a barren soil, the
crop will be able to come in contact with, and take up these substances,
is to assume what certainly will not take place.

I have often expressed an opinion that arable land, could not be
cultivated profitably by means of artificial manures, unless the soil
was capable of producing, from its own resources, a considerable amount
of produce; still the question had never up to this time c