Pullman herald. [volume] (Pullman, W.T. [Wash.]) 1888-1989, 1909-09-03
PERCENTAGES


Palouse Average
soil u. S. soil
Potash ..........0.464 0.290
Lime ............. .... O.SS3 2.lb0
Phosphoric acid ...0.1S9 0.234
Nitrogen 49,. .......... ,O.I64 O.29O
Humus 1900 1850
These figures show that with the
single exception of the element pot
ash, the amounts of total plant food
present in the Palouse soil are rath-
er below than above the average for
fertile agricultural lands. 1t should
be. understood, however, that these
percentages represent the total sup
ply in the soil, and not the amounts
which are present in available forms
for plant use. lhe wonderful fertil-
ity of the Palouse lands is due to the
fact that an abundant supply of
available fertility. is still present in
the soil, not having yet been serious
ly reduced by the wasteful systems
of cropping. But the fact that great
numbers of soils in other parts of
the country containing even larger
percentages of total plant food than
does the Palouse soil, have been
worn out by these same practices
of cropping points out the danger
The real significance of the figures
shown in the table above is this; the
amounts of total plant food Of all
kinds, both in the Palouse soil and in
the average soil and in the average
soil of the United States, are large
enough to last practically indefinate-
| ~, if properly handled. The total
amount of potash, for example, would
be sufficient to furnish enough for
5000 crops of wheat grown year after
year. 1he problem of soil fertility
| is, therefore, one of keeping a sufi-
cient supply of these several elements
in available form for plants to use
The chief agent in making plant food
available is decaying vegetation or
'humus,' Hence, the practical me-
thod of maintaining a sufficient sup
ply of available fertility in any soil,
is to see that its supply of humus is
ample. The danger to the fertility
of the Palouse soil lies in the fact that
our soil is not naturally rich in hu-
|
age and cropping are those which are
most destructive to the decaying
vegetation in the soil. 1t will be
noted from the table of analyses that
the Palouse soil contains only a little
over one-half as mucn humus as the
average fertile soil of the United
States. Furthermore, the growing of
grain crops, particularly if all straw
and stubble are burned up, and the
land is alternately summer fallowed,
adds no vegetable matter to the sol
to replace that which is removed by
the crop or destroyed by the action
of the air and heat when the soil is
summer fallowed.
The maintenance or increase of the
supply of available fertility being a
matter of keeping sufficient supply
of humus in the soil, the means of
guarding against the soils becoming
worn OUT or of restoring fertility
to a depleted soil is evident. Most
of the soils in the older sections of
the United States have been able to
stand system of grain farming with
out the addition of transforming
materials in the form or manure or
green crops plowed under for periods
Of from forty to one hundred years,
and have then become worn out. "
The same soils are now being restor-
ed to fertility by the addition of hui
mus-forming materials, which must
be supplemented with commercial fer
! tiliZers until such time as the sup
! ply of available plant food can again
be brought up to a profitable point.
In some sections where the original
amount of some mineral element of
plant food was low, the use of com
mercial fertilizers to supply this de-
! fciency will have to be continued,
! but in soils such as those of the Pa
louise where the supply of mineral
elements is ample and well-balanced,
transforming materials should be
the only form of fertilizer which will
ever be necessary to use. The re
suits of our experiments in determin-
ing which of the possible humus-
forming materials can be most pro-
ftably used in connection with our
systems of farming will be presented
in later article.