Pullman herald. [volume] (Pullman, W.T. [Wash.]) 1888-1989, 1914-04-03
FERTILIZERS FOR ALFALFA.


cultural Experiment Station of Wash
ington upon the fertilizer reouir0
ments of alfalfa offer increasing av,
dence that nitrogen and sulphur ara
inseparably associated with each
other in the growth of this crop: thu,
in the absence of either, an off-color
and stunted growth results. Saws
Professor George A. Olson:
Reference has been made here.
tofore to the dark green color oh
served in alfalfa plants where gym.
sum and superphosphates had been
added. Similar results were obtain.
Ell from the use of sulphuric acid
In all three instances, it is noted that
this addition of chemical substances
containing sulphur has in some wav
not only produced healthier looking
plants, but also remarkably large
yields, in comparison to untreated
plots, were obtained.
The occasional yellow color of
alfalfa has always been attributed
by authorities to the lack of nitrogen
food, or nitrogen-gathering bacteria
OF both. While such staten ents as
those are accepted as true, they ap-
pear to be contrary to observations
made in our Washington investiga-
tions.
The Importance of nitrogen
gathering bacteria in keeping the
nitrogen balance of the soil can not
be disputed. Nevertheless, we found
Instances wherein the nitrogen
gathering bacteria were well distri-
buted in our soil and numerous
nodules were on the roots of the
alfalfa plants; yet, the yellow color
continued to predominant. The yell
low color remains unchanged, even
where nitrate of soda has been ap-
piled. These results indicate that
nitrogen food itself does not con-
tribute to the formation of the dark
green color in alfalfa; at least as
has been generally supposed. 1t
should not be overlooked, however,
that some interfering substance may
1F he 40 ly
green color. Perhaps the presence
of black alkali (sodium carbonates),
or, possibly, lack of sufficient
available sulphur in the soil, or both,
interfere with the proper coloring
Of the plant.
However, experiments wherein
the black alkal is neutralized with
hydrochloric acid have not altered
the yellow color; while sulphuriC
acid has restored the color So have
calcium sulphate and dicalcium acid
phosphates which contain calcium
sulphate. We are, therefore, in
clined to believe that sulphur in
some form contributes largely to the
formation of the dark green color in
alfalfa.
Finally, when the added sulphur
has been exhausted, the yellow color
appears in subsequent crops. We are
also looking for diminished yields on
these plots, due to the reduction OF
sulphur content to the quantity nor
mally found in the soil.
There is another possible expla-
nation that is certainly worth con-
sidering, which is that both nitrogen
and sulphur contribute to the for
nation of dark green color, and
when in proper combinations, stimn-
late a more vigorous and healthy
growth. Soils, therefore, which are
abundantly supplied with available
sulphur, but are poor in nitrogen
food, respond to the application OF
nitrates, or to the introduction oil
the desirable nitrogen bacteria to
produce the darker green color, only
because the sulphur was present In
those soils in ample quantity. This
thought also explains why it has been
believed that a lack of nitrogen pro-
duces the undesirable color and
much smaller yields.
Whatever the functioning process
may be, the Importance Of sulphur
as plant food constituent is self
evident. Applications of sulphur
compounds in the forms of sulphates
or sulphuric acid have produced won
derful results. The yields are too
high to be ignored, and they are be-
yond the possibilities of experiment
tai errors. Whether or not the con-
tinued use of sulphur applications
will prove detrimental to the grow
ing of alfalfa or other crops can DO
determined only by many years OF
careful study The question of what
form of sulphur is best suited 10
maintain the sulphur balance In our
ka