2002-07-08_GENERAL DOCUMENTS - M2002004 ‎(3)‎

• Permit No: M2002004
• IBM Index Class Name: GENERAL DOCUMENTS
• Doc Date: 7/8/2002
• Doc Name: ATTACHMENT, PART 2
• From: HABITAT MGMT
• To: DRMS
• Media Type: D
• Archive: No

affects of organic matter are the
because nutrients, especially N,
mineralization (43). Campbell
iortional to the N released from
important but N is required in
be deficient" (15).
ctly or indirectly influences the
of organic matter decreases in a
n associated reduction in poros-
density and reduced aeration
absorption, and inhibits micro-
12). Organic matter is one of the
:lopment. Soils with good struc-
ng water and nutrients to plants
:cur in soils with granular struc-
. Such soil structure is formed
ial grasses and legumes. The
structure include (1) consolida-
n highly branched root systems
humic acid, (3) penetration into
ions of humin and humic acids,
:sive soil aggregate by means of
if humus substances into a soil
;ses (42). After plowing or disk -
nd soil crumbs is slow and re-
2). Similarly, increased stability
se in organic matter (15). Thus,
an absence of continued plow -
substances on a regular basis.
fences microorganism activity.
ransformation, has little effect
aganic materials as a source of
;regation. Fungi and actinomy-
ocesses that synthesize complex
remain in the soil. The sum of
soil aggregates. This stability,
binding action of the cells and
fects of the products of micro-
SOIL ORGANIC MATTER 197
bial synthesis; and the stabilizing action of the decomposition products.
Organic matter usually improves infiltration, reduces evaporation, im-
proves drainage in fine - textured soils, and encourages more extensive and
deeper root systems. Collectively, these actions should improve water avail-
ability and the water use efficiency of plants (4). These effects vary with
plant species, soil type, and climate. If fertilizers are added to the soil, the
effects of organic matter may increase (15). Except for clayey soils, organic
matter in general increases plant - available water - holding capacity.
Organic matter increases infiltration by helping to hold water on the soil's
surface long enough for it to enter the soil and by improving the physical
condition of the soil. Organic matter also reduces crust formation, which
increases the rate of infiltration. Similarly, if organic matter is mixed into a
soil, eventually improving soil aggregation and soil structure, percolation
increases. Contrary to this generally favorable principle of organic matter
increasing infiltration, some forms of organic matter reduce infiltration
because of the presence of hydrophobic (nonwettable) organic substances.
One of the most important chemical properties of soil is its ability to re-
tain and exchange positively charged ions on colloidal surfaces. The
primary controlling factors of cation exchange are the amount and type of
clay and the quantity of organic matter in the soil (34). The organic matter
in most mineral soils accounts for about 30 to 65 percent of the total cation
exchange capacity (15). In sandy and organic soils, more than 50 percent of
the cation exchange capacity is due to the organic component of the soil.
A buffer solution is one that resists changes in pH upon the addition of
acid or base. Soils behave like buffers. Most of this ability is a result of their
colloidal properties associated with the humus and clay minerals, which
hold H, Al, and other cations (15). Resistance to pH change thus is low in
soils with lower organic matter levels but higher in soils with higher organic
matter levels.
There is a wide range of chemically stable organic anions capable of bind-
ing metal cations into weakly ionized forms (34). These substances— chelat-
ing agents —occur naturally in soils. They are associated with the solid
organic fraction as well as soluble organic materials in the soil solution.
Organic matter can hold metallic ions both by cation exchange and by
chelation (15). In soils having metallic ion concentrations that are toxic to
plants, chelation may hinder adverse effects through the immobilization of
the metallic ion.
Soil organic matter and revegetation planning
Because virgin organic matter levels vary from region to region and
within a particular mine site, there should be no single set of suitability
levels for organic matter to rate topsoil as good, fair, poor, or unsuitable.
The same is true of surface soil horizons used for agricultural purposes (15).
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