Note: Descriptions are shown in the official language in which they were submitted.
1~2881
PR-7541
FINE TE~CII~ED 50IL RECL~ION ME~HOD
Field of the Invention
This invention relates to a method for reclaiming fine textured
soils in arid and semi-arid climates which have been naturally, acciden-
tally or intentionally stripped of vegetation.
Background of the Invention
Efforts to revegetate naturally, accidentially or intentionally
S disturbed areas in arid and semi-arid regions have generally met with
failure because of harsh environmental factors and a lack of suitable
technology. Arid and semi-arid lands make up a significant per oe ntage of
the land mass of the United States and many other countries. These areas
commonly receive less than 12 inches of annual precipitation. Precipita-
tion patterns in arid and semi-arid areas are typically unpredictable,
with periodic drought the rule rather than the exception. In colder cli-
mates, much of the annual precipitation may occur as snow during the non-
growing season part of the year. Snow is vulnerable to sublimation by
high winds, characteristic of arid and semiarid parts of the world. Snows
may also melt while soils are frozen, thus resultlng in heavy run-off and
little percolation of water into the soil. Consequently, only a small
fraction of winter moisture is available for plant use. Summer rains in
arid and semi-arid areas commonly occur as high intensity, short duration
storms. This type of storm typically produces a great deal of runoff
while little moisture percolates into the soil to be available for plant
use. During severe storms, flash flooding and serious erosional problems
may o x ur.
Arid and semi-arid lands also experience high evapotranspiration
rates. Potential evaportanspiration rates may exceed 50 inches annually.
In many arid and semi-arid parts of the w~rld, a moisture deficit can
exist during most or all of the growing season. Moisture is clearly a
dominant limiting factor to vegetation establishment, growth and reproduc-
tion in arid and semi-arid lands.
381
Past geologic and climatic conditions have resulted in the for-
mation of soils in many arid and semi-arid areas of the w~rld that can be
characterized as fine textured, heavy soils. Table I defines the size
limits used in soil classification. m e percentages of the three major
texture components in the basic soil textural classes is graphically dis-
played in Figure 1.
TABLE I
Size Limits for Soil Comeonents
U.S. Department of Agriculture Scheme
Diameter (Range)
Nbme of ComponentMillimeters
very coarse sand 2.0 - 1.0
coarse sand 1.0 - 0.5
medium sand 0.5 - 0.25
fine sand 0.25 - 0.10
very fine sand 0.10 - 0.5
silt 0.05 - 0.002
clay below 0.001
Fine textured soils, particularly clay soils (defined as soils
containing at least 35 to 40 percent cla~ particles) have p~hysical and
chemical properties that accentuate the mositure deficit that can exist in
arid and semi-arid areas. Because of their very nature, fine textured
80ils reduce the amount of moi~ture than can percolate into the soil.
This is due to (1) fine textured 80ils not being particularly porous; (2)
the pores of fine t.extured soils are typically very small; (3) water move-
ment through the pores carry clay or silt particles which can clog the
lS pores; and (4) swelling of fine textured soils upon being wetted effec-
tively seals off surface pores as well as sub-surface pores, making the
soil virutally impervious to water. A great deal of the water that does
percolate into fine textured soils is also unavailable for vegetation use
due to the strong electrical attraction between the clay particles and the
water. The general relationship between soil moisture characteristics and
soil texture is shown in Figure 2. Note that the field capacity of fine
textured soils is much greater than the field capacity of coarse textured
soils, but the amount of unavailable water is also much greater in fine
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textured soils. m e wilting point in fine textured soils is also reached
when a great deal of moisture is still present in the soil.
Fine textured soils can also be highly saline and/or sodic.
~his is due in part to the redu oe d water intake into fine textured soils
not being able to leach salts out of the soil. The presen oe of salts in
soils negatively influences soil water uptake as well as the ability of
plant roots to utili~e soil moisture.
Fine textured soils are also known to inhibit germination and
growth of vegetation. m e tight, compacted nature of fine textured soils
makes it difficult for a seed to become buried by soil after it has been
broadcast upon the soil, either naturally or by man. When the seed germr
inates, its chances of survival are slim if it is laying on top of the
soil. If the seed does become buried k~ fine textured, heavy soils,
either by natural processes or by drill seeding, it is co~mon for the seed
not to be able to penetrate the hard compacted surface of fine textured,
heavy soils. It is clear that harsh climatic and soil conditions need to
be mitigated if reclamation in arid and semi-arid regions is to be
successful.
Currently, laws in the United States and other countries require
reclamation of open-pit mines, tailing impoundments and other anthropo-
genic disturbances. m e reclamation process usually consists of back-
filling pits such as occurs in open-pit mining or covering tailing ponds
with available soil and replanting native or adapted vegetation. Fine
textured soils coupled with sparce rainfall results in grasses, shrubs,
forbs and trees having great difficulty in germinating and establishing an
adequate root system during a wet period prior to subsequent dry periods.
Plants frequently fail to properly take root under these conditions,
resulting in high mortality. I have discovered a relatively simple method
to provide a hospitable environment for germination of the seed and growth
of t~he seedling and retention of available moisture for a longer period of
time, thus aiding the germination and establishment of a viable vegetation
population.
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Brief Description of the Invention
A method for revegetating fine textured soils in arid and semi-
arid regions, on which vegetation has been naturally, accidentally or
intentionally destroyed or disturbed has been discovered. m is method
consists of placing at least 1 and preferably 2 to 6 inches of sand over
the affected soils to provide a suitable germination and moisture trapping
layer in which seeds can germinate and become established on fine textured
soils. m is method is especially useful for revegetating fine textured
soils ~hich have been placed over open-pit mines, tailing ponds, or other
man-caulsed disturbances during reclamation work. This reclamation method
would also be useful for reclaiming land damaged by fire, overgrazing, or
other natural causes. This reclamation method would help prevent soil
erosion and promote the reestablishment of vegetation.
Description of the Drawings
Figure 1 graphically displays the percentages of the 3 major
texture components in the basic soil textural classes.
Figure 2 shows the general relationship between soil moisture
characteristics and soil texture.
Description of the Invention
A method for revegetating fine textured soils in arid soil semi-
arid regions, on which vegetation has been naturally, accidentally or
intentionally destroyed or disturbed has been discovered. Such soils can
be reclaimed by a process consisting of placing at least 1 inch, prefer-
ably at least 2 inches and most preferably 2 to 6 inches, of sand over the
fine textured soils, then reseeding or planting adapted vegetation at the
proper time of year. The sand texture may range in size fram fine (about
0.05 mm to about 0.5 mm) to coarse (about 0.5 mm to about 2.0 mm). The
sand creates a layer in which a seed can easily become buried either by
natural processes or by drilling. When the seed germinates upon the addi-
tion of irrigation w~ater or natural rainfall, it can easily penetrate
through the sand surface. Because of the sand's ability to allow ~uick
penetration of water, it also acts to soak up moisture that would ordin-
arily be lost due to runoff on the fine textured soils. The sand holdsthe water long enough for it to slowly seep into the fine textured soils
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for later use by vegetation. This greater than normal isture infiltra-
tion into the fine textured soils also causes high concentrations of
detrimental salts to be leached deeper down in the soil profile or to be
flushed from the system.
Fine textured soils on which this invention is effective are
those types of fine textured soils defined by the U.S. Department of
Agriculture as silt loam, silt, sandy clay loam, clay loam, silty clay
loam, sandy clay, silty clay, and clay. These soil types are defined as
follows:
Loam: Soil material that contains 7 to 27% clay, 28 to 50% silt
and less than 52% sand.
Silt Loa~: Soil material that contains 50% or more silt and 12
to 27% clay or 50 to 80% silt and less than 12% clay.
Silt: Soil material that contains 80% or more silt and less
than 12~ clay.
Sandy Clay Loam: Soil material that contains 20 to 35% clay,
less than 28% silt and 45% or more sand.
Clay Loam: Soil material that contains 27 to 40% clay and 20 to
45% sand.
Silty Clay LLam: Soil material that contains 27 to 40% clay and
less than 20% sand.
SandY Clay: Soil material that contains 35% or more clay and
45% or more sand.
Clay: Soil material that contains 40% or more clay, less than
45% sand and less than 40% silt.
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By "distubed soil" is meant any natural or man~made action or
result that destroys, reduces, changes or eliminates vegetation from the
soil surface.
Figure 1. Figure 1 graphically shows the relationship between
the class name of a soil and its particle size distribution. (Brady,
N.C., The Nature and Properties of Soils, Macmillan Publishing Co., Inc.,
New York, p. 639, (1974)). Figure 2 graphically shows the general
relationship between soil moisture characteristics and texture and amount
of water necessary to support a plant (Brady, supra). Sand which is
effective and may be utilized in the practice of this invention can range
from O.OS mm to 2.0 mm.
Although greater amounts than 6 inches of sand can be placed
over the fine textured soil, economy dictates that the least amount of
sand necessary to achieve the proper germination, mositure retention and
rooting results be utilized. I have found that between 1 and 6 inches of
sand produces effective results on fine textured soils. There is also no
need to mix the sand with the fine textured soil and, in fact, it is dele-
terious to do so since the fine textured particles in the 50il generally
overwhelm the sand, resulting in the soil setting up in a hard, concrete
like mixture during dry conditions.
This method is particularly effective in reclaiming lands which
have either been open-pit mined or utilized as tailing ponds for open-pit
or sub-surface mining operations. Normally in this circumstance, state
and/or federal law requires that the land be returned to as near to origi-
nal condition as possible, and in general, the tailing and/or overburdenare replaced into the open-pit or sub-surface mine and layers of indigen-
ous soil are placed over the tailings or overburden. If soils are of fine
texture and/or contain significant amounts of salts, it is most difficult
to achieve germination and rooting of plants in this top soil. The seed,
if it does germinate under these conditions, generally withers and dies
unless moisture is readily available for a considerable time period. If
vegetation does not become established, episodes of precipitation and run-
off can eventually erode away the top soil layer exposing pokentially
toxic overburden or tailings and possibly resulting in leaching of various
l~Z88:1
minerals from the tailings or overburden into streams or groundwater aqui-
fers.
~ Available water" i5 defined as the portion of water in a soil
tha~ can be readily absorbed by plant is its roots, considered by most
w~rkers to be that water held in the soil against a pressure of up to
approximately 15 bars.
"Field capacity" (field moisture capacity) is defined as the
percentage of water remaining in a soil two or three days after having
been saturated and after free drainage has practically ceased.
A "fine texture" soil is one consisting of or containing large
quantities of the fine fractions, particularly of silt and clay, and
includes all clay loams and clays (clay loam, sandy clay loam, silty clay
loam, sandy clay, silty clay and clay textural classes).
"Virgin soil" is defined as soil that has not been significantly
disturbed fram its natural environment.
"Moisture tension" (or pressure) is defined as the soil equiva-
lent negative pressure in the soil water. It is equal to the equivalent
pressure that must be applied to the 90il water to bring it to hydraulic
equilibrium, through a porous permeable wall or membrane, with a pool of
water of the same composition.
The method of this invention is demonstrated by the following
example which was designed to test the effectiveness of sand as a fine
textured soil amendment. In addition to testing the effectiveness of sand
as a fine textured soil amendment, the experimental design included other
tests. They included evaluation of (1) capillary barriers; ~2) five
rooting medium thicknesses; and ~3) three soil types. The goal of the
experiment was to determine methods of successfully reclaiming trona
tailings.
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Plot Construction
A 42 by 81 meter area adjacent to a trona tailing impoundment
was excavated to a depth of approxLmately 1 foot. A 1 foot deep layer of
dried trona tailing material was placed in the excavation. The plot was
then staked off into twenty-tw~ 5 x 27 mRter oells. The capillary bar-
riers were next to be laid. Barrier Type 1 consisted of a 23 centimeter(cm) deep layer of coarse screened gravel applied over the tailing surface
in 10 of the cells. A 10 cm layer of straw was then placed over the
gravel to prevent soil from piping into the capillary barrier created by
the gravel. Barrier Type 2 consisted of a 10 cm layer of straw placed
directly over the tailing in 9 cells. It is hoped that the straw would
act as a barrier to sodium migration. Barriers were not placed over the
tail;ng in 3 cells. These oells acted as control cells.
Soil depths of 1, 2, 3, 4 and 6 feet were used to evaluate the
minimum effective rooting depth required of planted vegetation. Soil
depth was varied in a stair-step like fashion within each cell. Three
different soil types were used in the experiment. Soil Type A was a high
p~ sodic clay soil obtained in the sanitary landfill area. Soil Type B
was a high pH, saline loamy sand soil taken from our designated topsoil
borrow area, and soil Type C was a high pH saline sodic sandy loam soil
obtained near the test site. A 15 cm layer of coarse sand was plaoed over
the clay and loamy sand soils in 4 of the cells to determine what effect
it wauld have on germination and survival in poor quality soils such as
the soils used in the experiment. An 0.3 meter buffer of coarse gravel
was used to separate each of the oells.
Vegetation Planting
During late October, each oell was seeded with 6 species of
perennial grasses. Indian ricegrass (Oryzopsis hymenoides), thickspike
wheatgrass (Agropyron dasystachum), galleta (Hilaria jamesii), squirrel-
tail grass (Sitanion hystrix), bluebunch wheatgrass (Agropyron spicatum)
and Great ~asin wildrye (Elymus cinereus) were the grasses planted. A
Plant Jr. Seeder was used to plant the grasses. The Plant Jr. Seeder is a
small scale drill seeder.
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During the following April, 440 individuals of 4 native shrubs
were planted within the test plot. ~he shrubs were all containerized
seedlings. Shrubs planted included Wyoming big sagebrush (Artemisia
tridentata wyamingensis), four-wing saltbush (Atriplex canescens), twist-
leaf rabbitbrush (Chrysothamnus vicidiflorus) and fringed sagebrush
(Artemisia frigida). m e shrubs were planted in rows spaced one meter
apart with each shrub in the row planted one meter from the adjacent
shrub. Each shrub was given approximately one liter of water at the time
it was planted. No additional supplemental water was applied to the plot.
So~l ~nalysis
A relatively complete physical and chemical analysis of the
three soil types used in the study was done. Soil parameters tested were
pH, electrical conductivity, saturation percentage, sodium adsorption
ratio (SAR), cation exchange capacity (CEC), soluble cations, exchangeable
sodium, organic matter, exchangeable sodium percentage (ESP), nitrogen,
total nitrogen, plant available phosphorus, potassium and texture.
Ve~etation Measurement
During the first September following planting , shrub survival
was determined. An index of shrub growth was also obtained by measuring
greatest shrub height and diameter. These 2 parameters were multiplied
together to obtain a growth index.
All 6 grass species were scheduled to be clipp d to determine
biomass produced at the end o~ the growing season; however, this could not
be accomplished. Antelope, rabbits and other rodents ate nearly every
blade of grass to ground level with the exception of the Great Basin wild-
rye, which was left virtually untouched. A randomly selected one-meter
section of Great Basin wildrye was clipped at 2 inches above ground level
at every soil depth within every sub-cell. The clipped grasses were then
allowed to air dry for 2 weeks, after which they were weighed and a
weight/linear meter determined for each treatment and soil depth.
Statistical Analysis of Data
The Newman-Reuls test using the statistic for multiple range
testing was used to determine a statistically reliable comparison between
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each treatment for four-wing saltbush growth. Statistical testing was not
done with the other shrubs due to the heavy grazing sustained by the other
shrubs. m is grazing affected both growth and survival of the shrubs.
Four-wQng saltbush was the only shrub species that was not grazed. me
S Newman-Kuels test was also employed to determine biomass production comr
parisons of Great Basin wildrye with the various treatments. Great Basin
wildrye was the only grass species not heavily grazed.
Results
Chemical An2lysis of Tailing
Tailing materials used were high in pH, electrical conductivity,
sodium, calcium, nitrate, fluoride, sodium absorption ratio and exchange-
able sodium percentage. All of these parameters would be toxic or highlyunfavorable to plant life. It is unlikely that any reasonably econamical
treatment could be found to neutralize and/or improve the toxic and
unfavorable co~ponents of the tailing material. me sodicity of the tail-
ing is the main problem.
Soluble elements of tailing materials that could migrate into a
tailing covered rooting medium due to water movement are chloride, boron,
fluoride and sodium at levels that would be unfavorable or toxic to plant
life. Sodium is again the ma~or problem.
Soil Physical and Chemical Analysis
Table II shows physical and chemical analysis of the three soil
types used in the test plot. Texture, SAR and p~ values for all three
soil types did not meet W~oming DEQ recommended safe limits for good plant
growth. In addition, soil Types A and C did not fall within acceptable
limits for exchangeable sodium percentage. Potassium and organic matter
measurements were also unfavorable to plank growth in all three soil
types.
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11
TABLE II
Physical and Chemical Soil Analysis
Soil Type
ParameterClay (A) Loamy Sand (B) Sandy Loam (C)
pH 10.5 10.2 10.3
Elect. Cont. (mmhos/cm)6.7 14.4 7.9
Saturation % 66.4 31.7 31.4
SAR 53.9 11.2 19.6
ESP 44.1 14.9 18.2
CEC (meg/L) 43.1 8.7 9.9
Soluble Cations (mg/L)
Sodium 61.78 64.67 61.00
Potassium 0.28 1.23 1.37
Calcium 2.23 41.12 8.69
Magnesium 0.40 26.04 10.76
Exchangeable Na. (meqtL)19.0 1.3 1.8
Organic Matter (%) 0.6 0.2 0.2
Nitrate Nitrogen (ppm) 41 16 10
Total Nitrogen (ppm) 180 43 16
Plant Available Phosphorus (ppm) 16 3 3
Potassium (ppm) 800 220 350
Texture (%)
Sand 20 82 76
Silt 19 14 18
Clay 61 4 6
Vegetation Da _
Shrub Survival
Table III shows survival data for each shrub species vs. soil
type. These figures are probably the most significant of all the shrub
cDmparisons made. As can be seen, survival of all four shrub species was
lcwest in the clay soil type yet highest in the clay soil treated with
sand. In contrast, the addition of sand to the loamy sand soil type did
not increase survival of the shrubs except for a non-statistically signi-
ficant increase in four-wing saltbush survival.
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12
TAELE III
Shrub Survival as Related to Soil Type
_
Per oe nt Survival*
4-Wing Twistleaf
Soil TypeBig Sage Saltbush Rabbitbrush Fringe Sage
clay 4 10a 1 6
sand treated clay48 70C 23 48
1oa~y sand 23 50b 8 32
sand treated loamy sand 10 58b 3 13
sandy loam 6 43b 4 17
* Values followed by the same letter are not significantly different at
the 5% level using the Newman-Keuls multiple range test.
Table IV shows overall shrub survival as related to soil depth.
This data reveals that for all shrubs, with the exception of fringe sage,
survival increases to the 4 foot soil depth then falls at the 6 foot soil
depth. Survival of fringe sage increases throughout the entire range of
soil depths.
TABLE IV
Overall Shrub Survival vs. Soil Depth
Per oe nt Survivial*
4-Wing Twistleaf
Soil Depth Big Sage Saltbush Rabbitbrush Fringe Sage
1' 8 40a 1 10
2' 9 44a 5 17
3' 13 43a 2 16
4' 25 50a 13 21
6' 17 38a 9 25
* Values followed by the same letter are not significantly different at
the 5% level using the Newman-Keuls multiple range test.
Shrub Growth Index
Table V shows shrub growth index vs. soil types. Since all
shrub species, with the exception of four-wing saltbush, were grazed ~uite
heavily, the growth index comparisons probably do not mean much m e
four-wing saltbush growth index is of course an exception to this state~
ment. Statistical analyses of the growth index data was therefore limited
to data collected on four-wing saltbush. Four-wing saltbush grew best in
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the san~ treated clay soils and grew poorest in the clay and sandy loam
soil.
TABLE V
Shrub Growth Index vs. Soil Type
Growth Index*
4-Wing Twistleaf
Soil Tyee Big Sage Saltbush Rabbitbrush Fringe Sage
clay 143 2,225bC 79 496
sand treated clay 323 8,774a 133 807
loamy sand 240 4,867b 311 729
sand treated loamy sand 585 5,122b 215 382
sandy loam 80 2,208C 129 282
* Values followed by the same letter are not significan~ly different at
the 54 level using the Newman-Reuls multiple range test.
Grass Biomass Production
Table VI shows that the growth response of Great Basin wildrye
parallels that of four-wing saltbush. Growth was poorest in the clay soil
type and greatest in the sand treated clay. The sand treated loamy sand
soil type was not statistically different from the loamy sand 90il type
just as was the case for shrub growth.
TABLE Vl
Growth Response on Great Basin Wildrye vs. Soil Type
Soil TypeGreat Basin Wildrye (grams/linear meter*)
clay 0.5a
sand treated clay 133.2b
loamy sand 45.7c
sand treated loamy sand 38.5c
sandy loam 27.4c
* Values followed by the same letter are not significantly different at
the 5~ level using the Newman~Reuls mNltiple range test.
Prior to the third growing season, the plot was fenced to prevent
grazing. All shrubs that died during the first 2 years were replaced with
live seedlings. Grasses were also reseeded. The plot has now gone
throuqh 5 growing seasons. The trends in survival and growkh seen during
14
the first growing season have not changed. Grcwth and survival of all
shrub and grass species has been lowest in the clay soil oells and highest
in the sand treated clay soils.
Iaboratory studies evaluating pla~t germination and growth in
various fine textured soils and fine textured soils treated with sand have
also been conducted. Results of these experLments have all been
consistent with the data presented above.
