Evening star., 1942-06-21
Hunus in Garder
Major Factor
OF Growth
An Understanding
OF Its Functions
Is Necessary
By the Master Gardener.


Humus, which is decayed organic
matter, Is undoubtedly one Of the
major factors In the growing Of
plants Humus is especially neces-
sary in the South where the soil
micro organisms are so plentiful
and active as to make applications
Of organic matters necessary.
However, 1 believe that most of
US do not have the proper idea Of
what humus does to the soil, and
its own particular function in
plant feeding practices. To make
this clear I would like to quote
from an article in the Gardeners
Chronicle, February, 1910:
Many horticulturists and ag-
riculturists believe in the theory
that manure was applied to the
soil for its nutritive value. This
idea should no longer exist; for
il 1t were the nutritive value Of
the manure, 1t would be a very
expensive method of incorpo-
rating the nutrients into the
soil. A plant food is less ex-
pensive; it is applied with
greater ease, and it supplies a
greater quantity of plant nutri-
ent to the soil do not say that
manure does not contain nutri-
ents, as it does. Nevertheless,
the nutritive value is secondary
to the colloidal and bacterial ac-
ton Of the manure"
This all brings us to a listing Of
what we should expect from humus
provided by organic materials such
as manure and compost.
Soil reaction, or pH, is Influenced
by the amount of humus in the
soil. This is particularly true be-
cause PHI is due to the relation OF
the bicarbonates to the carbonates
This means that in q very alkaline
soil humus provided by decomposed
peat, muck or manure will improve
the PHI value Of the soil by making
1t little more acid.
One of the chief values of humus
is its ability to improve the physi-
cal properties Of the soil. Humus
binds the particles of a sandy sol
closer together, thus reducing the
rapid drainage and aeration; II
spreads apart the fine particles oi
clay soil, which enlarges the pore
spaces and improves drainage and
aeration. A gardeners problem!
are much less difficult when .ths
conditions Of drainage and aera.
ton are optimurn.
Soil chemistry affects plant growth
immensely, and the use of humu
for the part it plays In soil chemistr.
Is essential. Humus acts as a sol
buffer or protector for plants. I
keeps excess minerals and toxic
materials from harming the plan
roots; In this case humus helps t,
make gardening more foolproof
Humus aids In making soil nutrient
more readily available to the plan
because Of its production Of organi,
acids and carbon dioxide. Remem'
Der, however, that the nutrient!
must be In the soil before humus car
do this work.
Because Of the loose granular
structure produced in a soil with
adequate amounts Of humus, ans
the texture of the particles of humu
themselves, q soil has better absorp
ton properties, and yet drains well
There Is a closer relationship be.
tween soil air and soil water wher
the humus content is right. To<
much, of course, tends to hold watel
and the soil takes on the propertie!
Of pure peat or muck.
Organic materials, such as ma.
nures Of all types, have very little
plant food value. In fact, a gooe
grade of COW manure contains only
three -fourths Of a unit of nitrogen
one-half unit available phosphorit
acid, one-half unit of potash ane
practically no minor elements. Ger.
tainly the value of organic matter
and humus does not lie in tht
amount OF plant food it contains; il
is valuable for It's physical properties
Agronomists have proved many
times that grass. as well as many
other plants, makes its own humu.
when it is properly and regularly fed
Every year about IS per cent b.
weight Of these fine roots die anc
remain in the soil, to decompose anc
form humus. Humus added to the
soil in this manner is automatically
placed right where it is most needed
One needs only to think back to the
early days In conquering the West.
ern plains to visualize the kind of q
soil found with dense, vigorous
growing sod; soils loaded with
humus because Of the root activity
This same condition can be seer
even today when the sod along q
fence row Is plowed for the first
time.