Oxford Democrat. [volume] (Paris, Me.) 1833-1933, 1913-05-13
The Chemical Analysis Of Soils.

Since crops derive so large q proper
tion of their food from the soil, 1t Il
quite natural that VIC should come tt
think of the chemical composition Of th'
soil as the correct measure OF its fertil
Iity. The university is frequently asked
to make soil analyses, and for some rea
son requests of this nature have beer
unusually numerous during the present
spriug. In many instances samples ol
soil are forwarded, and specific informa
tion is asked for, the writer stating per.
haps that he grew potatoes last season,
and wishes to SOW oats this spring. The
analysis In such cases Is supposed to be
trustworthy guide In the selection of q
fertilizer. In other cases the writer
merely states that the soil in question
failed to give good returns last season,
and he looks for an analysis to suggest a
remedy.
A great many soil analyses have been
made, and the published results deserve
close study. One of the most interest
ing facts which such Investigations have
brought to light is that nearly every
soil, even those incapable Of producing
good crops, contain a store Of plant food
far in excess of the needs OF the very
crops they fail to produce. A plant is
able to take its food from the soil only
in soluble forms, while by far the great
or part of the elements needed by crops
exist in the soil in the form of insoluble
compounds, which are consequently not
available. A chemical analysis simply
shows that they are there. Up to the
present time the chemist has not devised
reliable method by which he can meas
ure the availability Of these materials to
the plant. Even If he succeeded in de-
termining the availability for a certain
crop, he would have made but little
progress, since he might find 1t neces-
sary to establish different standard for
every other crop. The roots of plants
take an active part in dissolving plant
food and no two kinds of plants possess
this power in the same degree.
The importance of the quality which
we call availability" may be illustrated
thus: Soils frequently carry over one
thousand pounds Of phosphoric acid in
the upper six or seven inches of an acre,
yet fail to produce good crops for want
of this very compound. Supposing
now, We duu W SuCu . Soi AotsHNoA
10 percent available phosphoric
acid, applying it at the rate of one thou
sand pounds to the acre, and working 1t
into the soil to the depth Of seven inches.
The half ton of fertilizer carries one hun
dred pounds of available phosphOric
acid, which has become mixed with two
million pounds Of earth. A little calcu-
lation will show that we have added
phosphoric acid to the extent OF one-half
of one-hundredth of one percent. II such
a soil were analysed before and after
such an application, an ordinary chemi'
cal analysis would not detect the differ
ence. Yet in spite of the fact that the
soil may have already contained ten or
twenty times this amount, the crop
knows the difference.
There is but one way to learn the fer
tilizer requirements of the soil, and that
ia by close observation and careful ex-
on the part of the man
who tills the soil. II the application OF
potash salts alone produces satisfactory
results, nitrogen and phosphoric acid
sho uld not be used. The indiscriminate
use of complete fertilizer" is fairly
certain to increase the crop, but the
practice is in many cases wasteful one.
The University holds itself ready to aid
the farmer in every way within its pow
or, but for the reason stated 1t cannot
undertake soil analysis.-L. d. Merrill,
Professor of Agricultural Chemistry,
University of Maine.