Evening star. [volume] (Washington, D.C.) 1854-1972, 1958-03-14


go to great lengths to feed their
plants.
There are three major plant
foods, nitrogen, phosphate and
potassium. Each of these may
be supplied in one or more
forms. Nitrogen. for example, is
available as organic material
which ranges from blood meal
to cottonSeed meal, or may be
bought as nitrate of soda or
sulphate of ammonia. Then
there are the new synthetic
urea compounds which are now
being modified with formalde-
hyde. All of them have their
particular uses and values. The
organic forms of nitrogen are
widely used in the organic fer
tilizers. particularly those which
are used to feed the broad
leaved evergreens and frequent
ly labeled "aZalea and camel
liza fertilizers" They are not
dangerous to use around tender
plants but they are rather slow
acting since the nitrogen must
be converted by bacterial ac-
ton into a form that can be
taken up by the plants.
The nitrate Of soda is fire.
Quently incorporated into COM
mercial fertilizers where it is
necessary to avoid an acid
forming material. Sulphate of
ammonia is the acid forming
type. Both are readily soluble
in the soil and consequently are
available almost Immediately to
the plants. This advantage is
partially offset by the danger
of teaching should there be
heavy showers after applica-
ton.
NOnburning Compounds
The urea compounds, and the
new forms, are nonburning and
now are so slow acting that
they feed the plants over a
period of many weeks.
There are a number of forms
of these new types of plant
feeding nitrogen which are
offered to the gardener. Many
of them are still being sold as
nitrogen and some are of rather
high analysis and that fact
should be taken into considera-
ton both at evaluating the
price and at the rate of appli-
cation. A fertilizer containing
5sper cent nitrogen is obviously
worth far less than one con-
tanning Is or 35 per cent nitro
gen since it is the more costly
item. The 5-10-5 mixtures
containing such nitrogen will
also cost more than one con-
tanning nitrate of soda or
sulphate of ammonia.
The phosphate in the mixture
is usually in the form of super
phosphate but it may also con-
tain some nitrogen combined
with phosphate and called
arnmo-phosphate or some SIM
liar name. The use of raw
rock phosphate has practically
ceased largely because the soil
has to be we'll supplied with
decaying humus which is neces-
sary to release the phosphate
in form that can be taken
up by the plants. This is also
true of bone meal, an organic
form Of phosphate.
Potash Content
The potash is usually in the
form Of muriate of potash or
of sulphate of potash. Some
times one form is preferred;
other users favor the other.
Generally speaking potash is
seldom the limiting plant food
in our soils, whereas the nitro
gen and the phosphates are
greatly needed.
In highly acid soils the phos-
phate tends to be converted
into a non-soluble form rather
quickly, hence frequent appli-
cations are needed if the plants
are to obtain the needed sup
plies. In soils that are only
slightly acid the phosphate
tends to be available until used
up. Also, it seldom teaches out
of a soil.
In addition to the three major
plant foods our soils may be
deficient in several Of the minor
or trace elements. Calcium, for
example, and iron are two that
need to be replenished If the
plants are to be thrifty and
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