king off crops. All you have to do is to cultivate
your soil, when part of the nitrogen becomes soluble in water and is
carried down by the rain into the water-table unless you have plants
growing with roots to take it up; a large part escapes into the air. So
when your black prairie soil has been under cultivation for twenty
years, as an orchard, usually from one-half to one-third of the
original nitrogen has escaped, most of it into the air, only the smaller
part being carried off in the crops. That is the one thing that
orchardists and horticulturists have to concern themselves about first
of all, so far as soil fertility is concerned.

I see that the first of the questions for me to answer deals with that.
"What crop do you consider the best green manure?" There are two kinds
of green manures. One is represented by rye. Rye takes up the nitrogen
that is in the soil, and when it dies leaves behind what it took out of
the soil; the next crop can get this. By plowing under the rye crop you
do not increase the amount of nitrogen, the most important element of
fertility in the soil.

We have a better green manure than that, better than rye or oats or
barley or any of those plants that properly belong to the grass family;
namely, the members of the clover, bean or pea family--all of these
plants which are called legumes, which have pods and which have flowers
shaped like butterflies.

As these grow they take up nitrogen from the air; the bacteria which
make their home on the roots of those plants take the nitrogen from the
air and give it to their host plants. The plants receive this nitrogen,
store it in themselves, and when the crop is plowed under you have a
great amount of nitrogen added to the soil. Now, a clover crop of an
acre growing from spring until the freeze-up in the fall may take out of
the air as much as 120 pounds of nitrogen. One hundred and twenty pounds
of nitrogen, bought in the form of commercial fertilizer from Swift &
Company, or Northrup, King & Company, would cost you $24.00. The clover
has taken that much out of the air. If the crop were pastured off, the
greater part of this nitrogen would be returned to the soil; when you
plow the clover under still more nitrogen is taken from the air by
bacteria that live upon the decaying plant material, and you may have
$48.00 worth of nitrogen per acre added to the soil by simply growing
clover for one year.

Any kind of green manure crop that bears pod