rse soon become too poor to
grow any crop. If, on the other hand, clover or alfalfa or corn or
cotton-seed meal is fed to stock, and the manure from the stock returned
to the soil, the land will be kept rich. Hence those farmers who do not
sell such raw products as cotton, corn, wheat, oats, and clover, but who
market articles made from these raw products, find it easier to keep
their land fertile. For illustration: if instead of selling hay, farmers
feed it to sheep and sell meat and wool; if instead of selling cotton
seed, they feed its meal to cows, and sell milk and butter; if instead
of selling stover, they feed it to beef cattle, they get a good price
for products and in addition have all the manure needed to keep their
land productive and increase its value each year.

[Illustration:FIG. 14. RELATION OF HUMUS TO GROWTH OF CORN
1, clay subsoil; 2, same, with fertilizer; 3, same, with humus]

If we wish to keep up the fertility of our lands we should not allow
anything to be lost from our farms. All the manures, straw, roots,
stubble, healthy vines--in fact everything decomposable--should be
plowed under or used as a top-dressing. Especial care should be taken in
storing manure. It should be watchfully protected from sun and rain. If
a farmer has no shed under which to keep his manure, he should scatter
it on his fields as fast as it is made.

[Illustration: FIG. 15. THE COTTON PLANT WITH AND WITHOUT FOOD
In left top pot, no plant food; in left bottom pot, plant food scanty;
in both right pots, all elements of plant food present]

He should understand also that liquid manure is of more value than
solid, because that important plant food, nitrogen, is found almost
wholly in the liquid portion. Some of the phosphoric acid and
considerable amounts of the potash are also found in the liquid manure.
Hence economy requires that none of this escape either by leakage or by
fermentation. Sometimes one can detect the smell of ammonia in the
stable. This ammonia is formed by the decomposition of the liquid
manure, and its loss should be checked by sprinkling some floats, acid
phosphate, or muck over the stable floor.

Many farmers find it desirable to buy fertilizers to use with the manure
made on the farm. In this case it is helpful to understand the
composition, source, and availability of the various substances
composing commercial fertilizers. The three most valuable things in
commercial fertilizers are nitrogen, pot