in which it possesses these three ingredients.
The more sandy a soil is, the less will its power be of absorbing water;
and this, there is little doubt, is one of the reasons why a sandy soil
is, as a rule, an unfertile soil. Of course there are other and even
more important reasons; but that this absorptive power has an important
bearing on the question is conclusively proved by the fact that sandy
soils are more fertile in a climate where rain is frequent than in one
where much dry weather prevails. The incapacity of a sandy soil to
absorb a large quantity of moisture is not fraught with such evil
effects to the crops in the former case, because it is counteracted by
the climatic conditions, which obviate the necessity, in a soil, of
possessing great absorptive powers.

The converse, of course, we may mention in passing, holds good of clayey
soils.

_Fineness of Soil-particles._

The second quality in a soil on which its absorptive power depends is
the fineness of its particles. The great benefit which a soil derives
from a good tilth, in this respect, was one of the reasons why Tull's
system of horse-hoeing husbandry was so successful in its results.[35]
The finer the soil-particles, it may be said generally, the greater is
the absorptive power of the soil.

_Limit to Fineness._

There is, however, a limit to the fineness to which the particles of a
soil ought to be reduced; for it has been found by experiment that when
a certain degree of fineness is reached, the absorptive power decreases
with any further pulverisation. A German experimenter found, for
example, that a garden loam, capable of absorbing 114 per cent of water
in its natural state, when pulverised very fine was able to absorb only
62 per cent of water. Here, clearly, the limit to which it is advisable
to pulverise a soil had been exceeded.

_Reason of the above._

It is not difficult to see why this should be so. The amount of water
that a soil can soak up is due to the number of pores, or air-spaces, it
contains of a certain size. If these pores are large and few in number,
the amount of water absorbed will be naturally less than when they are
numerous and smaller in size. Up to a certain extent, the more a soil is
broken the greater will be the number of pores created, of a size to
permit the water to soak in. Beyond that point the pores become too
minute, and the soil becomes too compact, each particle clinging
together too closely.