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