hes. But perhaps it would be better yet to add manure with
a lot of straw in it. This is the easiest kind of thing for country boys
and girls to get, because the bedding swept out of horses' stalls is
just the thing.

"When I speak of clay's horrid habit of tight squeezing, I always have
to stop and talk about the two great needs of all soils. One is the need
for water; the other, for air. A soil cannot exist without these two
things any more than we can. Without these, or poorly supplied with
them, a soil is as if it were half-starved.

"That trouble always comes from a lack of one or the other is quite
sufficient to prove to us that these are essential. Just see how sand
lacks water, as does lime soil too! But there is plenty of air space,
unless these soils are too finely powdered. Now look at clay! plenty of
water, but how about the air? When clay begins its packing, then air is
excluded.

"So one of the questions to be asked in soil improvement concerns the
water and air problem. We must have air spaces, and we must have
water-holding capacity.

"Before we go home I must just speak of soil and subsoil. When you
strike your spade down into the earth and lay bare a section of the soil
this is what you see: on top is the plant growth, the soil beneath this,
dark in texture and about our locality of a depth of from six to eight
inches. This layer is called the topsoil. In sections of the West it is
several feet in depth. Now below the topsoil is a lighter coloured, less
fertile, more rocky layer, the subsoil. Beneath comes a layer of rock.

"And finally you may be a bit confused by the word loam. It is often
given as one of the classes of soils. By loam we mean clay, sand and
humus. You will often hear people speaking of a sandy loam or a clayey
loam according as there is a greater percentage of sand or clay in the
soil.

"Next Friday I shall talk about soil fertility. So trot home lively
now!"

II

PLANT FOOD

A soil, as I have said before to the boys, may contain all the food
necessary for plant growth and still not support any good growth at all.
That means then we ought to be able in some way or other so to
understand the soil that it will be possible to unlock these good things
for the plants to live on.

"I see a question in Josephine's and Miriam's faces. I guess that this
question is concerning what the plant food is in soils. That is right,
is it not?

"Well, I'll take that up first, th