y soils
and opens the clay, thus helping the sand to soak up and hold more
moisture and lessening excessive ventilation, and at the same time
helping the roots to take a firmer hold. It helps the clay to absorb
rain, helps it to pump water faster, helps it to hold water longer in
dry weather, increases ventilation, favors root penetration and
increases heat absorption. We can increase the amount of organic
matter in the soil by plowing in stable manure, leaves and other
organic refuse of the farm, or we can plow under crops of clover,
grass, grain or other crops grown for that purpose.

CHAPTER VIII

PLANT FOOD IN THE SOIL

We learned in previous paragraphs that the roots of plants take food
from the soil, and that a condition necessary for the root to do its
work for the plant was the presence of available plant food in
sufficient quantities.

What is plant food? For answer let us go to the plant and ask it what
it is made of.

=Experiment.=--Take some newly ripened cotton or cotton wadding, a
tree branch, a cornstalk, and some straw or grass. Pull the cotton
apart, then twist some of it and pull apart; in turn break the branch,
the cornstalk and the straw. The cotton does not pull apart readily
nor do the others break easily; this is because they all contain long,
tough fibres. These fibres are called woody fibre or cellulose. The
cotton fibre is nearly pure cellulose.

=Experiment.=--Get together some slices of white potato, sweet potato,
parsnip, broken kernels of corn, wheat and oats, a piece of laundry
starch and some tincture of iodine diluted to about the color of weak
tea. Rub a few drops of the iodine on the cut surfaces of the
potatoes, parsnip, and the broken surfaces of the grains. Notice that
it turns them purple. Now drop a drop of the iodine on the laundry
starch. It turns that purple also. This experiment tells us that
plants contain starch.

=Experiment.=--Chew a piece of sorghum cane, sugar cane, cornstalk,
beet root, turnip root, apple or cabbage. They all taste sweet and
must therefore contain sugar.

Examine a number of peach and cherry trees. You will find on the trunk
and branches more or less of a sticky substance called gum.

=Experiment.=--Crush on paper seeds of cotton, castor-oil bean,
peanuts, Brazil nuts, hickory nuts, butternuts, etc. They make grease
spots; they contain fat and oil.

=Experiment.=--Chew whole grains of wheat and find a gummy
mucilaginous substance