CA1292881C - Fine textured soil reclamation method - Google Patents
Fine textured soil reclamation methodInfo
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- CA1292881C CA1292881C CA000555224A CA555224A CA1292881C CA 1292881 C CA1292881 C CA 1292881C CA 000555224 A CA000555224 A CA 000555224A CA 555224 A CA555224 A CA 555224A CA 1292881 C CA1292881 C CA 1292881C
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Abstract
FINE TEXTURED SOIL RECLAMATION METHOD
Abstract of the Disclosure A method for reclaiming fine textured heavy soils and disturbed fine textured soils under arid and semi-arid conditions. The reclamation method consists of applying at least about 1 inch of sand having a part-icle size of 0.05 mm to 2.0 mm in size over fine textured soils and seed-ing or planting adapted vegetation.
Abstract of the Disclosure A method for reclaiming fine textured heavy soils and disturbed fine textured soils under arid and semi-arid conditions. The reclamation method consists of applying at least about 1 inch of sand having a part-icle size of 0.05 mm to 2.0 mm in size over fine textured soils and seed-ing or planting adapted vegetation.
Description
1~2881 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.
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 lZ~
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 12~2~
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.
1~t2~81 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 12~Z881 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.
Zt~l 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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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 lZ~Z~
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 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.
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.
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 lZ~
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.
l~Z~8~
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 12~2~
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.
1~t2~81 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.
lZ~?Z~38~
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.
1~9Z~
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 12~Z881 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.
Zt~l 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.
129Z~38~
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 lZ~Z~
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 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.
Claims (6)
1. A process for reclaiming fine textured soils and distrubed fine textured soils in arid and semi-arid areas on which vegetation establishment is desired or required consisting of covering the fine tex-tured soils or disturbed fine textural soils with at least 1 inch of sand having a texture ranging between about 0.05 mm and about 2.0 mm and plant-ing or seeding locally adapted vegetation in the sand.
2. The process of Claim 1 wherein the depth of sand is at least about 2 inches.
3. The process of Claim 1 wherein the depth of sand is from about 2 to about 6 inches and the sand texture ranges from between about 0.5 mm to about 2 mm.
4. A process for revegetating mined lands, mine tailing disposal sites, and other natural and other man-caused disturbances consisting of (a) covering the disturbed land with fine textured soils selected from the group consisting of silt loam, silt, sandy clay loam, clay loam, silty clay loam, sandy clay, silty clay, clay and mixtures thereof;
(b) covering the fine textured soil with at least 1 inch of sand having a texture ranging between about 0.05 mm and about 2.00 mm; and (c) planting or seeding of adapted vegetation in the sand.
(b) covering the fine textured soil with at least 1 inch of sand having a texture ranging between about 0.05 mm and about 2.00 mm; and (c) planting or seeding of adapted vegetation in the sand.
5. The process of Claim 4 wherein the depth of sand is at least about 2 inches.
6. The process of Claim 4 wherein the depth of sand is from about 2 to about 6 inches and the sand texture ranges from between about 0.5 mm to about 2 mm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000555224A CA1292881C (en) | 1987-12-23 | 1987-12-23 | Fine textured soil reclamation method |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000555224A CA1292881C (en) | 1987-12-23 | 1987-12-23 | Fine textured soil reclamation method |
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| CA1292881C true CA1292881C (en) | 1991-12-10 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115868377A (en) * | 2022-11-09 | 2023-03-31 | 华能澜沧江水电股份有限公司 | Method for recovering vegetation in hydropower development area of dry and warm valley of plateau |
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1987
- 1987-12-23 CA CA000555224A patent/CA1292881C/en not_active Expired - Lifetime
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115868377A (en) * | 2022-11-09 | 2023-03-31 | 华能澜沧江水电股份有限公司 | Method for recovering vegetation in hydropower development area of dry and warm valley of plateau |
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