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How The Plant Feeds From The Soil
Manuring The Soil


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You have perhaps observed the regularity of arrangement in the twigs and
branches of trees. Now pull up the roots of a plant, as, for example,
sheep sorrel, Jimson weed, or some other plant. Note the branching of
the roots. In these there is no such regularity as is seen in the twig.
Trace the rootlets to their finest tips. How small, slender, and
delicate they are! Still we do not see the finest of them, for in taking
the plant from the ground we tore the most delicate away. In order to
see the real construction of a root we must grow one so that we may
examine it uninjured. To do this, sprout some oats in a germinator or in
any box in which one glass side has been arranged and allow the oats to
grow till they are two or more inches high. Now examine the roots and
you will see very fine hairs, similar to those shown in the accompanying
figure, forming a fuzz over the surface of the roots near the tips. This
fuzz is made of small hairs standing so close together that there are
often as many as 38,200 on a single square inch. Fig. 17 shows how a
root looks when it has been cut crosswise into what is known as a cross
section. The figure is much increased in size. You can see how the
root-hairs extend from the root in every direction. Fig. 18 shows a
single root-hair very greatly enlarged, with particles of sand sticking
to it.

Highly magnified]

These hairs are the feeding-organs of the roots, and they are formed
only near the tips of the finest roots. You see that the large, coarse
roots that you are familiar with have nothing to do with _absorbing_
plant food from the soil. They serve merely to _conduct_ the sap and
nourishment from the root-hairs to the tree.

When you apply manure or other fertilizer to a tree, remember that it is
far better to supply the fertilizer to the roots that are at some
distance from the trunk, for such roots are the real feeders. The plant
food in the manure soaks into the soil and immediately reaches the
root-hairs. You can understand this better by studying the distribution
of the roots of an orchard tree, shown in Fig. 19. There you can see
that the fine tips are found at a long distance from the main trunk.


You can now readily see why it is that plants usually wilt when they are
transplanted. The fine, delicate root-hairs are then broken off, and the
plant can but poorly keep up its food and water supply until new hairs
have been formed. While these are forming, water has been evaporating
from the leaves, and consequently the plant does not get enough moisture
and therefore droops.

Would you not conclude that it is very poor farming to till deeply any
crop after the roots have extended between the rows far enough to be cut
by the plow or cultivator? In cultivating between corn rows, for
example, if you find that you are disturbing fine roots, you may be sure
that you are breaking off millions of root-hairs from each plant and
hence are doing harm rather than good. Fig. 20 shows how the roots from
one corn row intertangle with those of another. You see at a glance how
many of these roots would be destroyed by deep cultivation. Stirring
the upper inch of soil when the plants are well grown is sufficient
tillage and does no injury to the roots.

A deep soil is much better than a shallow soil, as its depth makes it
just so much easier for the roots to seek deep food. Fig. 21 illustrates
well how far down into the soil the alfalfa roots go.


Dig up the roots of several cultivated plants and weeds and compare
them. Do you find some that are fine or fibrous? some fleshy like
the carrot? The dandelion is a good example of a tap-root.
Tap-roots are deep feeders. Examine very carefully the roots of a
medium-sized corn plant. Sift the dirt away gently so as to loosen
as few roots as possible. How do the roots compare in area with the
part above the ground? Try to trace a single root of the corn plant
from the stalk to its very tip. How long are the roots of mature
plants? Are they deep or shallow feeders? Germinate some oats or
beans in a glass-sided box, as suggested, and observe the

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