The progressive farmer. [volume] (Winston, N.C.) 1886-1904, 1902-08-05
Agriculture.
THE NATURE OF PLANT FOOD.

So much has ben written and spoken
on the subject of plant food and it's
various forms, that it may seem need
less to publish anything more; but,
il is noticeable from the many uues-
tions asked of the farm papers and at
Institutes, that there still seems to be |
a general lack of understanding of the
matter among farmers. Before GO
ing into the subject, it is perhaps well |
to remark that on this as on all other
matters of vital Importance to profit
able farming, the planter must do
some thinking for himself. Printed
or spoken words canot grow crops,
and at the best we can only give the
general principles, which the reader
must apply TO his local conditions.
Plant food is all expression used to
name that substance or substances
which promote the growth of plants,
and which is found in m2nures of all
kinds, commercial fertilizers, and
chemical manures. There is a dit-
ference in manures, say farmyard ma
nures for example Some are very
good, others seem to have little power
to make plants grow. Chemists, in
studying this subject, found that
plants need for their very life many
substances, though these substances
-,,,o11
the actual material of the plants. Tx
cept four of these needed substances,
all are found in ordinary soils to the
unlimited needs of crops. The four
liable to become so deficient as to
cause crop failure are nitrogen, pot
ash and phosphoric acid and lime.
Lime very rarely becomes actually de
fcient to the extent of hindering plant
growth, so that from a popular point
OF view, only the first three require
the serious attention of farmers.
1t is not, therefore, the mass OF de-
caying vegetable matter in farmyard
manures that makes plants grow. but
certain quantities of nitrogen, potash
and phosphoric acid contained in this
decaying vegetable matter. This point
was well established before chemical
fertilizers appeared on the market.
As few farms make enough farmyard
manures to cover the losses d1;e to
cropping, for farming VJuld not be
profitable unless there are sale crops,
scientific men began to Investigate
ether materials which also contained
the plant food elements. The result
was that it was discovered that all
crude materials containing nitrogen,
potash and phosphorus acid, or any one
OF any two of them. was available rs
plant food. Crops can use the potash,
for example, from the Cert an pot
ash salts quite as freely as the pot
ash in farmyard marures; n fact, the
German potash salts are found to be
more readily available &C the uses Of
plants than the manure. In like man
Ler, the crude phosphate rock has been
converted into available ph1sphoric
acid. and bones and raGkaSa cpntaing
tones. make source o. phosphO".c
acid if anything superior to that in
tarmvard manure. AlS0 the nitrogen
II nitrate of soda, dried blood, tank
age, cotton-seed meal, fish scrap, etc,
has been found fully equal to the nj
rogen in farmyard manures. These
facts, once made clear, Quickly lead TO
the establishment of what IS now
known as the fertilizer industry.
It is not enoush by any means to
rest here. We know that plant food
Is three certain elements, and we know
they are contained in various mate
rials. We must also learn that plants
REQUIRE all three of !hem. and in GER
tain pretty definite quantities. This
Is the one advantage Of farmyard ma
nures, they contain all three of the
plant food elements, and make what
IS called a complete manure. The
commercial or chemical fertilizer ma
terlals rarely contain more than two
OF the elements. and generally only
ore of them. Hence, by themselves
they are useless, for however hberaIly
any one or any two of the plant food
clements may be used, plants cannot
grow unles the third element is added.
II there is present in the soil, for eX-
ample, plant food nitrogen and phos-
phorlc acid for a full crop, but only
enough potash for a half crop, only