plants,
it must be furnished with the materials required in the formation of
_all kinds of vegetable ashes_.

It is not absolutely necessary to have the soil analyzed before it can
be cultivated with success, but it is the _cheapest_ way.

[How is the fertility of the soil to be maintained, if the
crops are _sold_?

What rule is given for general treatment?

Give an instance of matters in the soil that are to be rendered
available by mineral manures?]

We might proceed from an analysis of the plant required (which will be
found in Section V.), and apply to the soil in the form of manure every
thing that is necessary for the formation of the ash of that plant. This
would give a good crop on _any_ soil that was in the proper _mechanical_
condition, and contained enough organic matter; but a moment's
reflection will show that, if the soil contained a large amount of
potash, or of phosphate of lime, it would not be necessary to make an
application of more of these ingredients--at an expense of perhaps three
times the cost of an analysis. It is true that, if the crop is _sold_,
and it is desired to maintain the fertility of the soil, the full amount
of the ash must be applied, either before or after the crop is grown;
but, in the ordinary use of crops for feeding purposes, a large part of
the ash will exist in the excrements of the animals; so that the
judicious farmer will be able to manure his land with more economy than
if he had to apply to each crop the whole amount and variety required
for its ash. The best rule for practical manuring is probably to
_strengthen the soil in its weaker points, and prevent the stronger ones
from becoming weaker_. In this way, the soil may be raised to the
highest state of fertility, and be fully maintained in its productive
powers.

2d. Those manures which render available matter already contained in the
soil.

[How may silica be developed?

How does lime affect soils containing coarse particles?

How do mineral manures sometimes improve the mechanical texture of the
soil?]

Silica (or sand), it will be recollected, exists in all soils; but, in
its pure state, is not capable of being dissolved, and therefore cannot
be used by plants. The alkalies (as has been stated), have the power of
combining with this silica, making compounds, which are called
_silicates_. These are readily dissolved by water, and are available in
vegetable growth. Now, if a soil is deficient in these so