her legumes there is
seldom need of using nitrogen in the fertilizer; the tubercles on the
pea or clover roots will furnish that. Hence, as a rule, only potash and
phosphoric acid will have to be purchased as plant food.

The farmer is assisted always by a study of his crop and by a knowledge
of how it grows. If he find the straw inferior and short, it means that
the soil is deficient in nitrogen; but on the other hand, if the straw
be luxuriant and the heads small and poorly filled, he may be sure that
his soil contains too little phosphoric acid and potash.

=EXERCISE=

Let the pupils secure several heads of wheat and thresh each
separately by hand. The grains should then be counted and their
plumpness and size observed. The practical importance of this is
obvious, for the larger the heads and the greater the number of
grains, the larger the yield per acre. Let them plant some of the
large and some of the small grains. A single test of this kind will
show the importance of careful seed-selection.

[Illustration: FIG. 198 A WIDELY GROWN CROP]

SECTION XXXVIII. CORN

When the white man came to this country he found the Indians using corn;
for this reason, in addition to its name _maize_, it is called _Indian
corn_. Before that time the civilized world did not know that there was
such a crop. The increase in the yield and the extension of the acres
planted in this strictly American crop have kept pace with the rapid
and wonderful growth of our country. Corn is king of the cereals and the
most important crop of American agriculture. It grows in almost every
section of America. There is hardly any limit to the uses to which its
grain and its stalks are now put. Animals of many kinds are fed on
rations into which it enters. Its grains in some form furnish food to
more people than does any other crop except possibly rice. Its stalk and
its cob are manufactured into many different and useful articles.

A soil rich in either decaying animal or vegetable matter, loose, warm,
and moist but not wet, will produce a better crop of corn than any
other. Corn soil should always be well tilled and cultivated.

The proper time to begin the cultivation of corn is before it is
planted. Plow well. A shallow, worn-out soil should not be used for
corn, but for cowpeas or rye. After thorough plowing, the harrow--either
the disk or spring-tooth--should be used to destroy all clods and leave