we apply a light manure as we would to clay, it is
comparatively useless; it adds no firmness to the texture of the soil,
and hence does not increase its capacity for controlling water. On such
land, the only good that manure does, is while decomposition is taking
place in the soil, it renders it more moist, and hence more productive.
Apply clay to such a soil, and it will increase its firmness and
consequent capacity of retaining and appropriating moisture, and thus
render it highly valuable. Dry straw manure is sometimes said to dry up
land, and ruin crops. So of turf in a dry season. In a wet season they
greatly increase the growth of crops. Now they contain just as much food
for plants in one season as another. Hence a soil too easily impervious
to the atmosphere, will be a poor soil, that is, will produce poorly,
simply because it has no power to retain the necessary moisture.

We suppose these facts and reasons to establish our theory, that the
principal benefit of manures, and of mixing different soils, is in the
control they give over the moisture and the atmosphere. Hence the
greatly increased crop of clover from the application of three quarters
of a bushel of plaster to an acre. The increased weight of clover on
five square rods, would outweigh the plaster applied, and still that
plaster remains, in almost its full weight, on the soil. This principle
explains the benefit of mulching trees, plants, or vegetables. This is
the best means of preserving trees, the first year after transplanting,
and of securing a great growth, of any kind of shrubs or plants. This
may be done with common straw or leaves. Now wherein is their utility?
Not in the nourishment they afford the plants, but in the fact that
mulching so covers the surface as to prevent rapid evaporation. In such
cases, it is the more abundant moisture that secures the greater
growth.

Hence the first study of a soil culturist should be to ascertain how he
shall so mix and manage the materials at his command, as to cause them
to retain moisture for the longest time, without leaving water to stand
about the roots of his plants. On this depends the whole importance of
deep plowing and ditching. On this theory we may also account for the
fact that certain plants prefer a certain kind of manure to all others.
It is that those plants act in a certain manner on the soil requiring a
specific action of manure to enable it to appropriate moisture and tax
the atmos