It is important that this distinction should be well understood by the learner, as the words "mechanical" and "chemical" in connection with manures will be made use of throughout the following pages.

What are absorbents?

What kind of manure is charcoal?

There is another class of manures which we shall call absorbents. These comprise those substances which have the power of taking up fertilizing matters, and retaining them for the use of plants. For instance, charcoal is an absorbent. As was stated in the section on soils, this substance is a retainer of all fertilizing gases and many minerals. Other matters made use of in agriculture have the same effect. These absorbents will be spoken of more fully in their proper places.

TABLE.

Mechanical Manuresare those which improve the mechanical condition of soils.
Chemical "are those which serve as food for plants.
Absorbentsare those substances which absorb and retain fertilizing matters.

Into what classes may manures be divided?

What are organic manures?

Inorganic? Atmospheric?

Manures may be divided into three classes, viz.: organic, inorganic, and atmospheric.