his adoption. Still,
while he has confined his remarks to the more simple improvements on the
present system of management, he would say, briefly, that _no manuring
can be strictly economical that is not based on an analysis of the soil,
and a knowledge of the best means of overcoming the deficiencies
indicated, together with the most scrupulous care of every ounce of
evaporating or soluble manure_.

FOOTNOTES:

[AG] Marl is earth containing lime, but its use is not to be recommended
in this country, except where it can be obtained at little cost, as the
expenses of carting the _earth_ would often be more than the value of
the _lime_.

[AH] The straw producing the grain and the turnip and potato tops
contain more lime than the grain and roots.

[AI] See Working Farmer, vol. 2, p. 278.

[AJ] Glycerine, etc.

CHAPTER X.

ATMOSPHERIC FERTILIZERS.

[Are the gases in the atmosphere manures?

What would be the result if they were not so?]

It is not common to look on the gases in the atmosphere in the light of
manures, but they are decidedly so. Indeed, they are almost the only
organic manure ever received by the uncultivated parts of the earth, as
well as a large portion of that which is occupied in the production of
food for man.

If these gases were not manures; if there were no means by which they
could be used by plants, the fertility of the soil would long since have
ceased, and the earth would now be in an unfertile condition. That this
must be true, will be proved by a few moments' reflection on the facts
stated in the first part of this book. The fertilizing gases in the
atmosphere being composed of the constituents of decayed plants and
animals, it is as necessary that they should be again returned to the
form of organized matter, as it is that constituents taken from the
_soil_ should not be put out of existence.

AMMONIA.

[How is ammonia used by plants?

How may it be carried to the soil?

How may the value of organic manures be estimated?

What effects has ammonia beside supplying food to plants?]

The _ammonia_ in the atmosphere probably cannot be appropriated by the
leaves of plants, and must, therefore, enter the soil to be assimilated
by roots. It reaches the soil in two ways. It is either arrested from
the air circulating through the soil, or it is absorbed by rains in the
atmosphere, and thus carried to the earth, where it is retained by clay
and carbon, for the uses of p