The log cabin Democrat., 1911-06-26


states have for number of years had
fertilizer laws. These laws require
the manufacturers and dealers in fer.
tilizers to guarantee their products
and label them with the guaranteed
analysis. To one not accustomed to
the use of chemical terms these guar.
antees are more or less meaningless.
1t is generally understood that a
fertilizer contains some form of plant
food. The three forms of plant food
that are likely to be deficient in a
soil are nitrogen (N), phosphoric acid
,P2O5) and potash, (K2O), hence most
fertilizers are mixtures which contain
relatively high percentages of some
cne, two, Or even all three Of these
different substances
The plant has the power of utiliz-
ing these food elements only when
they are dissolved in the soil water.
CA simple determination of the water
soluble substance will not give the
amount of available plant food, bow
ever, since plants exert some specific
solvent effects. and the different acids
in the soil also increase the total
amount of soluble matter). The soiu-
bility or availability of the plant food
in a fertilizer, then, is the question
that most concerns the purchaser.
The chemical analysis is supposed to
show this. AS an illustration take
the analysis of the following fertil-
izer:
Armour No. 1856, nitrogen (N) fig.
ured as ammonia, 80 per cent; pot
ash, K2O, 60 per cent; available phos-
phoric acid, pos, 80 per cent; solu-
BILE phosphoric acid, pos, 60 pei
cent; reverted phosphoric acid,
P2O5, 20 per cent; insoluble phos
phoric acid, pos, 20 per cent.
Practically all of the nitrogen can
be considered available, as that which
is not in the soluble form when it is
added will, under normal conditions
become available as fast as it is need
ed by the plant. However, if the nj
trogen in the fertilizer is obtained by
mixing ground hair, hoofs, horns or
leather scraps in with the other ingre.
dents the nitrogen value is less.
ened considerably, as these sub.
stances, although rich in nitrogen, de.
cay so slowly that they are not con.
sidered a good source of nitrogenous
plant food In this state their use
n commercial fertilizers is restricted
by law.
The form in which the potash exists
does not matter much for ordinary
field crops, the value depending on
the percentage Of potash present
Such is not the case with phosphoric
acid. Its value depends more upon
|hether it is in the soluble or in
soluble" form. The term Soluble"
phosphoric acid as used in the analv
lis means that part of the total phos
)horic acid which is soluble in water
tnasmuch as the water soluble sub
stance is Immediately available to
the plant, it Is considered the most
valuable. Superphosphates contain q
nigh per cent of soluble" phosphoric
lcid.
The reverted" phosphoric acid is
hat part of the total phosphoric acid
which is not soluble IN water, but
which will be dissolved by the solvent
action of plant roots, etc. 1t is not
quite as valuable as the water 'solu-
5le,' as it cannot be as readily absorb
ed. The "insoluble" phosphoric acid
is that part of the total phosphoriC
acid which is neither soluble in waite
lor rendered soluble readily by the
olVent action of plants or soil acids
1t is least valuable from the CONNER.
:ial standpoint. The term available"
Dhosphoric acid means the tota'
amount of the phosp horic acid which
readily available for the plant. H.
other words, it is the sum of the sol
nile" and the reverted" phos phorio
acid.
lnasmuch as one usually fertilizes
or immediate returns, the amount OF
itrogen, potash and available" phes
phoric acid are the substances most
lesired. The value of the "insoluble
phosphoric acid must not be under
estimated, however. because it AIDA
- lht tOtdl StOl VI piilt lOOu III III
oil and it will be rendered available
by slow natural processes Yet it /.
neaper to buy ''inso.utle" phospho-.,
tcid in the form of ground phosphate
eek that to pay a higher price for Il.
II a mixed fertilizer. in fact, if phos
,aates alone are to be used and
trong, quick action is not especially
desired, instead OF buying the super
!hosphate, which contains large
part of it's phosphoric acid in tbs
available" form. it would pay to
pend the same amount of money o.
smelly ground phosphate rock. In the
after case phosphoric acid could
e applied for the same expenditure
aud the ultimate value of the invest
meat would he greater. as the phos
phoric acid of the phosphate roch
would lie slowly rendered available
riG its fertilizing eject extended over
number of wears