GB1591415A - Soil materices with waterinsoluble polyelectrolyte polymers - Google Patents

Description

(54) MODIFYING SOIL MATRICES WITH WATER-INSOLUBLE POLYELECTROLYTE POLYMERS (71) We, UNION CARBIDE CORPORATION, a corporation organized and existing under the laws of the State of New York, United States of America, whose registered office is 270, Park Avenue, New York, State of New York 10017, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to the use of water-insoluble polyelectrolyte polymers as soil amendments for modifying soil matrices.

Various treatments for soil are known in the prior art. Organic, polymeric additives have been mixed with soil to improve the soil structure (tilth). For example, British Patent 762,995 and U.S. Patent 2,625,529 disclose the use of water soluble polyelectrolytes such as the salts of hydrolyzed polyacrylonitrile, as well as the colpolymers and salts of copolymers of maleic acid anhydride and'vinyl esters, to produce aggregation of fine soil particles to form crumblike granules. Aggregation improves the porosity and permeability of soils, especially clay soils which are inclined to form crusts upon cycles of wetting and drying. And U.S. Patent 2,889,320 discloses the use of non-polyelectrolytes such as N-methylol polyacrylamide to produce aggregation of fine soil particles. In general, these natural or synthetic organic polymers are all sugstantially soluble in water.

Insoluble and hydrophilic organic polymers have been admixed with soil to improve its water capacity. In general, these polymers swell when soil is irrigated and retain large amounts of water, thus moderating the stress on plants rooted in the soil. The use of various cross-linked and insoluble polymers such as cross-linked poly(ethylene oxide), polymeric alkylene ethers, cross-linked insoluble polymers such as chemically modified starches or partially hydrolyzed cross-linked polyacrylamides as means to increase water capacity of soils has been disclosed in U.S. Patents 3,336,129 and 3,900,378. Other known insoluble polym ers for increasing water capacity of soils include phosphorylated polyvinylacetate resin and acid soluble acrylonitrile polymers treated with metal ions such as Al, Fe and alkali earth metals to produce a metal ion-polymer complex.

It has now been discovered that water-insoluble polyelectrolyte polymers in particulate form may be employed to increase both the water capacity and air capacity of growth media compositions. Moreover, it has also been discovered that the water-insoluble, polyelectrolyte polymer particles are stable in such compositions.

According to one aspect of the present invention there is provided a method of improving the water and air capacity of a soil matrix, the germination of seeds and/or the growth of plants and seedlings situated in said soil matrix, said method comprising admixing with each liter of said soil matrix up to 32 grams of a soil amendment comprising polyelectrolyte polymers particles rendered insoluble by cross-linking and sized between 8 mesh and 200 mesh (U.S.Standard Sieve Series), said polymer particles having a cross-link density so as to provide a swollen hydrogel as defined herein having a gel strength greater than 0.3 p.s.i. in the presence of an aqueous solution, and a ratio of ionic to non-ionic groups so as to be capable of reversibly absorbing and desorbing more than 100 times their weight in distilled water, more than 75 times their weight in a standard fertilizer solution as defined herein and more than 15 times their weight in a solution containing 500 ppm of calcium ions, each gram of said soil amendment being capable, in the presence of soil solution in said matrix, of reversibly absorbing and desorbing more than 20 times its weight of said soil solution providing, when swollen with said soil solution, hydrogel particles which increase the drainable pore size of said composition by more than 15 cubic centimeters.

According to another aspect of the present invention there is provided a method of improving the germination of seeds, the early growth of seedlings and the growth of transplants comprising planting said seeds, seedlings and/or transplants into sites within a soil matrix suitable for their growth and depositing into said sites prior to or subsequent to said planting step a soil amendment comprising polyelectrolyte polymer particles rendered insoluble by cross-linking and sized between 8 mesh and 200 mesh (U.S.Standard Sieve Series), said polymer particles having a cross-link density so as to provide a swollen hydrogel as defined herein having a gel strength greater than 0.3 p.s.i. in the presence of an aqueous solution, and a ratio of ionic to non-ionic groups so as to be capable of reversibly absorbing and desorbing more than 100 times their weight in distilled water, more than 75 times their weight in a standard fertilizer solution as defined herein and more than 15 times their weight in a solution containing 500 ppm of calcium ions, said polymer soil amendment being deposited in its dewatered or water swollen hydrogel state, said hydrogel providing a reservoir of water in said sites for use by said seeds, seedlings and/or transplants, each gram of said soil amendment being capable of reversibly absorbing and desorbing more than 20 times its weight in soil solution.

According to a further aspect of the invention there is provided a method of rendering plants more resistant to moisutre stress comprising contacting the roots of said plants with an aqueous slurry of polyelectrolyte polymer particles rendered insoluble by cross-linking and sized between 8 mesh and 200 mesh (US Standard Sieve Series), said polymer particles having a cross-link density so as to provide a swollen hydrogen as defined herein having a gel strength greater than 0.3 p.s.i. in the presence of an aqueous solution, and a ratio of ionic to non-ionic groups so as to be capable of reversibly absorbing and desorbing more than 100 times their weight in distilled water, more than 75 times their weight in a standard fertilizer solution as defined herein and more than 15 times their weight in a solution containing 500 ppm of calcium ions.

The present invention also provides a plant growth media composition comprising a soil matrix in admixture with a soil amendment comprising polyelectrolyte polymer particles rendered insoluble by cross-linking and sized between 8 mesh and 200 mesh (US Standard Sieve Series), said polymer particles having a cross-link density so as to provide a swollen hydrogel as defined herein having a gel strength greater than 0.3 p.s.i. in the presence of an aqueous solution, and a ratio of ionic to non-ionic groups so as to be capable of reversibly absorbing and desorbing more than 100 times their weight in distilled water, more than 75 times their weight in a standard fertilizer solution as defined herein and more than 15 times their weight in a solution containing 500 ppm of calcium ions, up to 32 grams of said soil amendment being present in said composition per liter of said soil matrix, each gram of said soil amendment being capable, in the presence of soil solution in said matrix, of reversibly absorbing and desorbing more than 20 times its weight of said soil solution providing, when swollen with said soil solution, hydrogel particles which increase the'drainable pore size of said composition by more than 15 cubic centimeters.

The soil matrix amendments used in this invention comprise water-insoluble polyelectrolyte polymers in particulate form. The polyelectrolyte polymers can repeatedly and reversibly absorb and desorb aqueous media. When aqueous media is being retained by the polyelectrolyte polymers of this invention, the polymers are termed hydrogels. Hence, it can be said that the polyelectrolyte polymers of this invention can oscillate between water-loaded and dewatered states, the polymer defined as a hydrogel in its water-loaded state.

The polyelectrolyte polymer particles used in this invention are characterized by having a particular size distribution in their dewatered state. They are further characterized by having particular water capacities in a standard fertilizer solution (defined below) and in a solution containing 500 parts per million (ppm) of calcium ions, and in their hydrogel state, a particular gel strength. In another embodiment, the soil matrix amendment used in this invention comprises water-insoluble, polyelectrolyte polymer particles as described herein admixed with up to 5 percent by weight of a hydrophobic material in an extremely finely divided form.

The plant growth compositions of the present invention comprise up to about 2 pounds of particulate, insoluble, cross-linked, polyelectrolyte polymer in admixture with a cubic foot of soil (32 g/1). In another embodiment of this invention, the plant growth compositions comprise up to about 2 pounds of a particulate, insoluble, polyelectrolyte polymer coated with up to. 5 percent by weight of a particulate hydrophobic material admixed with a cubic foot of soil (32 grams per liter). In addition, the plant growth compositions of this invention may alternatively contain active agents, such as water, fertilizer, herbicides, fungicides, nematocides and/or insecticides, soil conditioning agents, such as sawdust and synthetic soil conditioning agents such as soil aggregating polyelectrolytes as well as cther materials subsequently discussed.

The soil amendment comprising insoluble, polyelectrolyte polymer particles or such polymer particles coated with up to 5 weight percent of a hydrophobic material, may have an active agent incorporated in the polymer. In addition, the soil amendment may alternately contain or be admixed with known diluents, wetting agents, and surfactants. Further, the soil amendments, without the addition thereto of soil, is amenable for use as growth media, especially in rooting of plant cuttings and germination of seeds.

A more detailed understanding of the invention will be had by reference to the drawings, the following description and the appended claims.

FIGURE 1 is a greatly enlarged schematic representation of a modified soil matrix of this invention containing polyelectrolyte polymer particles in a dewatered state.

FIGURE 2 is a greatly enlarged schematic representation of the modified soil matrix of FIGURE 1 illustrating the polyelectrolyte polymer particles in a water-swollen state.

As hereinbefore indicated, the soil matrix modifying agents and/or compositions of this invention comprise an insoluble polyelectrolyte polymer. By the term "polyelectrolyte", as employed in the specification, is meant a polymer with ionic groups in the chain or as pendant groups; the ionic groups can be either positive or negative and would be called polycations or polyanions, respectively. By the term "hydrogel" as employed in the specification is meant an insoluble organic compound which has absorbed aqueous fluids and is capable of retaining them under moderate pressures. As previously mentioned, the insoluble polyelectrolyte polymers are defined as hydrogels when they are in the state of having absorbed an aqueous media.

The term "insoluble" or "insolubilize" as employed throughout the specification are used herein to refer to the formation of a material, at least eighty percent (80%) of which is essentially insoluble in aqueous media. These polyelectrolyte polymers can swell and absorb many times their weight in water. The insolubilization can be effected by a wide variety of known methods and includes, but is not limited to, ionizing and non-ionizing radiation, and cross-linking through covalent, ionic and other types of bonds.

By "standard fertilizer solution" as used throughout the specification is meant a solution containing 200 ppm of nitrogen (N) and containing N, P205 and K20 in the relative proportion 20:20:20.

In practice, a large number of polyelectrolyte polymers can be employed to modify soil matrices and/or to prepare the novel compositions of this invention. The particular polyelectrolyte polymer chosen must be capable of absorbing relatively large quantities of aqueous liquids i.e. more than one hundred (100) times its weight in distilled water, more than seventy-five (75) times its weight in standard fertilizer solution, and more than fifteen (15) times its weight in a solution containing five hundred (500) parts per million (ppm) of calcium ions. This includes organic polymeric compounds such as those polymers which are crosslinked by covalent, ionic, Vander Waal forces, or hydrogen bonding.Polymer particles containing cationic groups preferably are capable of reversibly absorbing and desorbing more than 15 times their weight in a solution containing 500 ppm of polyvalent anions.

Illustrative polyelectrolyte polymers which can be employed to modify soil matrices and/ or to prepare the novel compositions of the present invention include, among others, the following polymers containing anionic groups: (1) salts of polyethylene sulfonate, polystyrene sulfonate, hydrolyzed polyacrylamides, hydrolyzed polyacrylonitriles, carboxylated polystyrene, (2) salts of copolymers and terpolymers of acrylic acid, substituted acrylic acids, maleic anhydride, ethylene sulfonate with ethylene, acrylate esters, acrylamide, vinyl and divinyl ethers, styrene, and acrylonitrile, (3) salts of grafted copolymers where the backbone may be a polyolefin, a polyether, or a polysaccharide, and the grafted units, acrylic acid, methacrylic acid, hydrolyzed acrylonitrile or acrylamide, ethylene sulfonate, styrene sulfonate, or carboxylated sytrene and (4) salts of polysaccharides modified by the addition of anionic groups, e.g. carboxylated. Potassium and/or ammonium is preferred as the cationic component of the associated anion.

The polyelectrolyte polymers may also include the following polymers containing cationic groups: (1) polyamine salts, quaternized polyamine salts, polyvinyl-N-alkylpyridinium salts, salts of ionene halides such as those from 3-dimethylamino-n-propyl chloride, (2) salts of grafted copolymers from materials such as polysaccharides, starch, cellulose polyolefins, and polyethers and 2-hydroxy-3-methacryloxypropyltrimethylammonium chloride, and (3) salts of copolymers or quaternized copolymers of compounds such as + HN(CH2-CH = CH2) 2,(CH3)2N(CH2CH = CH2)2Cl,

with acrylamide, acrylonitrile, ethylene and styrene. Nitrate is preferred as the anionic component of the associated cations described above.

The pH of the polyelectrolyte polymers of this invention is typically between about 6 and about 9.

It should be noted that the instant invention is not limited to the use of only one of the polyelectrolyte polymers listed previously but includes mixtures of two or more polyelectrolyte polymers. Additionally, it is also possible to employ salts of co-cross-linked copolymers of the previously listed polyelectrolyte polymers or compounds similar to these. For example, salts of copolymers of acrylic acid and acrylamide and minor or major amounts of salts of other copolymers can also be used.

As previously described, the polymer is in particulate form, thus by the term "polymer particle" as employed throughout the specification is meant a single particle or an aggregate of several sub-particles.

As mentioned previously, the insoluble polyelectrolyte polymers can be prepared by a number of methods including chemical cross-linking and cross-linking induced by ionizing radiation. Particular methods of rendering various polyelectrolyte polymers insoluble and possessive of the requisite characteristics of this invention is not in itself a criterion by which certain polyelectrolyte polymers are judged to be operable in the present invention; that is any insoluble, polyelectrolyte polymer possessing the requisite characteristics is amenable for use in the present invention regardless of the manner in which it is produced. Suitable methods are well-known and understood by those skilled in the art.

For example, U.S. Patent 3,661,815 is directed to a process for preparing an alkali metal carboxylate salt of a starch polyacrylonitrile graft copolymer. The copolymer is saponified with an aqueous methanolic or aqueous ethanolic solution of an alkali base consisting of sodium hydroxide, lithium hydroxide or potassium hydroxide. It is indicated that the saponified copolymers are characterized as water insoluble granular solids having the ability to absorb water in amounts in excess of 50 parts per part of polymer while retaining their granular character. This process can be modified to provide a copolymer suitable for this invention, the copolymer retaining a substantial fraction of its water capacity in a solution containing 500 ppm of calcium ions. Saponification and consequently the number of ionic groups produced must be controlled in the modified process.Control of saponification is by conventional methods (such as time, temperature, amount of base added, etc.) U.S. Patent 3,670,731 also discloses hydrocolloid absorbent materials such as a crosslinked sulfonated, polystyrene or a hydrolyzed linear polyacrylamide cross-linked with a nonconjugated divinyl compound such as methylene bis acrylamide. Additionally, it is indicated in the patent that an acrylamide can be copolymerized with a nonconjugated divinyl compound in the presence of peroxide catalysts or by photo polymerization, such as for example, with riboflavin activator. Other methods of effecting insolubilization and crosslinking of polymers are indicated in U.S. Patents 3,090,736; 3,229,769 and 3,669,103.

In addition to the aforementioned methods, another known method is to subject a water-soluble polyelectrolyte to sufficient ionizing radiation to cross-link and insolubilize it thereby forming a water-insoluble hydrophilic polyelectrolyte.

As used herein, the term "ionizing radiation" includes that radiation which has sufficient energy to cause electronic excitation and/or ionization in the polymer molecules and solvent molecules (where a solvent is employed) but which does not have sufficient energy to affect the nuclei of the constituent atoms. Convenient sources of suitable ionizing radiation are gamma ray producing radioactive isotopes such Co60 and Cs 137, spent nuclear fuel elements, X-rays, such as those produced by conventional X-ray machines, and electrons produced by such means as Van de Graff accelerators, linear electron accelerators, resonance transformers and the like. Suitable ionizing radiation for use in the present invention will generally have an energy level in the range from about 0.05 MEV to about 20 MEV.

The irradiation of the non-cross-linked polyelectrolytes can be carried out in the solid phase or in solution. Solid polyelectrolytes can be irradiated in the air, in a vacuum or under various gaseous atmospheres, while irradiation in solution can be carried out with the water-soluble polyelectrolyte dissolved in water, in organic solvents of high dielectric constant, or in mixtures of water and water miscible organic solvents. Any conventional method can be used to bring the polyelectrolyte solution into contact with the ionizing radiation.

The above described methods and other methods for preparing cross-linked, insoluble polyelectrolyte polymers known to those skilled in the art may be employed to prepare the polymers used in this invention. Minor modifications of reactant ratios, saponification conditions, reaction parameters, radiation dose, etc., may be necessary to produce compounds which have the proper physical and chemical properties. For example, control of cross-link density is used to prepare compounds with gel strengths greater than 0.3 p.s.i.; the ratio of ionic to nonionic groups is controlled so that a compound with the proper water absorbing ability and the indicated stability toward polyvalent cations such as calcium is produced.

As employed throughout the specification, the term "soil matrix" refers to any medium in which plants can be grown and which provides a means for support, oxygen, water and nutrients and may comprise the following or various mixtures therof: (1) natural growth media such as those comprised of disintegrated and decomposed rocks and minerals mixed with organic matter in all stages of decay plus other components which may have been added as fertilizers and (2) synthetic growth media such as glass beads, foamed organic materials such as foamed polystyrene or foamed polyurethane, foamed inorganic materials, calcined clay particles, and comminuted plastic. Examples of natural growth media included within the definition of soil matrix hereinabove are peat moss, bark, sawdust, vermiculite, perlite, sand finely divided plant matter, and any combinations or mixtures thereof.The term "soil" and soil matrix are interchangeably employed throughout the specification.

Physically, soil matrices comprise two or three distinct phases: (1) a solid phase, (2) a gas phase and usually (3) a liquid phase comprising a liquid solution of water, dissolved salts and dissolved gases. These phases are defined by a multiplicity of minute mineral and organic particles packed together to comprise a semi-rigid spongelike mass. The spaces or pores between the particles form a substantially interconnected network of channels or tunnels which permeate the soil mass. The amount of soil pore space or soil porosity determines how much soil volume is potentially available for roots, water and air.

Although soil porosity determines how much water can potentially be stored in the soil matrix, the size of the pores, pore size distribution and the number of pores determine the amount which is actually stored in a given soil matrix following irrigation and drainage. The same factors are also important in determining the rate of water movement through soil matrices, and/are also especially important to insure adequate aeration in container soils.

These factors may be effectively regulated through additions of the soil amendments of this invention as subsequently discussed.

Soil aeration is the exchange of oxygen and carbon dioxide between the soil and aboveground atmosphere. This exchange, which occurs primarily through non-water filled or open soil pores, is essential to maintain an oxygen supply for root growth and absorption. Poor soil aeration causes poor root growth, poor water and nutrient absorption, and greater susceptibility to soil pathogens.

In order to grow plants in a soil matrix, water is necessary. Yet, there must be good drainage of the water to ensure adequate soil aeration. In container soils typically used in horticultural situations, these diverse goals are met by mixtures of components. For example, peat moss, humus, and other similar organic materials often provide high water capacity but can cause poor drainage and aeration. Hence, aggregate materials, such as sand, vermiculite, perlite, bark, wood chips, and pumice are typically added to increase the drainage and aeration.

However, not all water in the soil matrix is available to the roots of plants. Components such as peat moss, which easily sorb water do not easily release it all to the plant. Hence, it is the available water or water potential of the soil solution in a soil matrix that is important.

Water potential corresponds to a thermodynamic free energy of water, i.e., energy per unit mass. Per unit volume, it has the same dimensions of pressure. Therefore, it is often termed pressure potential or water potential. Pure liquid water by definition has a zero potential.

Water situated at an elevation higher than a soil matrix has a positive potential. Any water available to a plant has a small negative potential.

Since all soil waters contain dissolved salts, there is an osmotic effect lowering water potential. Solid soil particles attract water. This sorbed water is also at a lower potential; thus, plants must compete with soil for it. The surface tension of water in capillaries is another effect which lowers water potential. Each of the physical phenomena of osmosis, adsorption and capillarity compete with the plant in a soil matrix for water.

Only water at small negative potential is available to plant roots. When a soil matrix is floooded or saturated with water, the water potential of the soil matrix approaches the zero value of pure water and plants thrive. When a soil matrix is almost dry, the remaining water has a high negative value, i.e., up to -100 atmospheres (bars). Most plants will reach the permanent wilting point in a soil matrix when the water potential of the soil solution reaches about -12 to -15 bars. The permament wilting point is that condition when plants do not recover overnight in the dark and at 100% relative humidity. When water is available to the plant, then the soil matrix has a negative potential less than about zero and more than about -12 bars.Roughly half the water sorbed by a high capacity water-sorbing component, such as peat moss, has too large a negative water potential to be available to plants prior to wilting.

On the other hand, it has been found that the water held by the soil amendments used in this invention is very available to plants, i.e., about ninety-five percent (95%) can be used prior to reaching the permanent wilting point. Thus, the addition of the soil amendments to a soil matrix increases the ability of the amended soil matrix to hold water. This, in turn, increases the amount of water available at a water potential that can be utilized by the plant and increases the time plants can survive without additional irrigation.

Any soil matrix contains a large proportion of pore spaces of varied size dependent on the components that comprise the soil matrix. Many of these pores are very small and, subsequent to watering, do not drain. The percentage of the non-draining pores, by volume, is called the water capacity (Cw) of the soil matrix. Some of the larger pores do drain, and therefore fill with air. The percentage of the air contained in the drained pores by volume, is called the air capacity (Ca). Ideally, a soil matrix should have a water capacity of at least sixty-five percent (65%) ie., 0.65 cc of water per cc of soil matrix, and an air capacity of at least twenty-five percent (25 O/o), i.e., 0.25 cc of air per cc of soil matrix.

However, it is well known that adding components to the soil matrix which increase its water capacity generally decrease its air capacity and vice versa. The basic physical relationship beteen the water capacity and air capacity of a soil matrix is depenaent on the pore size distribution. In general, increases in average pore size increase air capacity and decrease water capacity and vice versa. It has been discovered that additions of the polyelectrolyte polymer amendments used in this invention to a soil matrix decouples the relationship between air and water capacities. The additions of these amendments not only increases water capacity, but also increases air capacity of the growth media compositions of this invention.The increase in air capacity of the growth media compoisitions occurs because of an increase in total pore volume and pore size due to the change in the soil matrix structure caused by the water-swollen hydrogel particles. And yet, it has been found that water capacity of the composition does not decrease. Indeed, the water capacity increases due to the readily available water carried in the swollen hydrogel particles as subsequently discussed.

Referring to FIGURE 1, there is shown a soil matrix 10 comprising a multiplicity of soil particles 12 randomly aggregated to form a sponge-like mass having pores 14 between the particles 12 forming a generally interconnected network of channels which permeate the soil mass. Also randomly distributed throughout the matrix 10 are the polyelectrolye polymer particles 20 of this invention in a dewatered (unswollen) state in FIGURE 1 and in a water-swollen state in FIGURE 2. As previously discussed, each polymer particle of this invention is capable of absorbing large quantities of aqueous liquids.

The addition of the polyelectrolyte polymer amendments of this invention in particulate form to a soil matrix increases the water capacity of the soil matrix. This is due to each polymer particle absorbing large quantities of water and swelling accordingly as illustrated in FIGURE 2. The basic soil matrix is still capable of retaining a large fraction of the water it would normally hold in the absence of the polyelectrolyte hydrogel particles.

Moreover, it has been discovered that the swelling of the polymer particles to produce hydrogel particles actually increases the volume of the soil matrix presumably by making their own pore spaces. The swollen hydrogel particles are rigid enough to support the weight of the soil matrix thereby not only creating sites for themselves, but due to the irregularities in their shapes as well as the shapes of the soil particles, pushing the soil particles farther apart from each other and thereby increasing the overall open pore volume of the soil matrix.

The phenomenum described above is illustrated in FIGURES i and 2 by referring to soil particles 12a - 12f and polymer particle 20a. In FIGURE 1, the initial position of the respective particles is illustrated wherein particle 20a is surrounded by soil particles 12a - 12f and in contact with soil particles 12a and 12f. Pore volume 14a exists between particles 12a and 12f. In FIGURE 1, as mentioned previously, polymer particle 12a is shown in a dewatered (unswollen) state. In FIGURE 2, however, after absorbing an aqueous media, polymer particle 20a is shown in a waterswollen state (as a hydrogel particle). The swollen particle 20a has pushed the soil partcles 12a -12f to positions farther apart from each other than their initial positions (shown in FIGURE 1).While still surrounded by particles 12a -12f, swollen hydrogel particle 20a has increased the open pore volume 14a between particles 12a and 12f. Moreover, swollen hydrogel particle 20a now is in contact with particles 12b, 12c, 12d and 12f. Its swelling and gel strength has affected the relative positioning of the surrounding particles 12a- 12f.

Hence, it is believed that the increase in the air capacity (free pore volume) of the growth media composition occurs through the creation of voids in the soil matrix by the swelling of the polymer particles. In essence, the swollen hydrogel particles seem to act as an aggregate such as perlite except that they are substantially all water. The fact that the hydrogel particles are substantially all water accounts for the increase in water capacity of the growth media compositons.

The marked morphological changes in soil matrices that accompany the addition of the soil matrix amendments used in this invention are features which distinguish them from soil amendments which only increase water capacity but have little or no effect on air capacity or those that increase air capacity but decrease water capacity. Amendments commonly used to increase air capacity of soils, e.g., peat moss, perlite, vermiculite, generally increase the average pore size of soils and thus tend to recue the ability of soils to hold water by capillary forces. And amendments commonly used to increase the water capacity of soils generally do not have the rigidity when wetted to cause an increase in drainable pore space. Often, they simply fill existing pores in soil thereby decreasing air capacity of the soil.However, the soil amendments of this invention do not hold water by capillary forces and are rigid when water-swollen. As a result, they cause a simultaneous and marked increase in the water and air capacity of the growth media compositon.

In practice, it has been found that in order to maximize air capacities of the growth media composition by means of the soil amendments, it is necessary to control particle size and gel strength within specified limits. It has been observed that the polymer particle size distribu: tion prior to their admixture with the soil matrix should be such that essentially all particles in a dewatered state are smaller than 8 mesh, preferably smaller than 10 mesh, as measured on U.S. Standard Sieve Series. Also, essentially all of the polymer particles of this invention are sized larger than 200 mesh, preferably larger than 100 mesh and most preferably sized larger than 40 mesh (U.S. Standard Sieve Series). The size distribution of the polymer particles may be obtained by conventional methods such as grinding larger particles or aggregation of smaller particles.

The (water-swollen) hydrogel particles used in this invention should have a gel strength of greater than about 0.3 p.s.i. Gel strengths are measured in the following manner. A 20 mesh (U.S. Standard Sieve Series) stainless steel screen is attached to cover the mouth of a cylinder.

Approximately 100 grams of hydrogel particles swollen to equilibrium in excess tap water is added to the cylinder. The particle size of the swollen hydrogel must be larger than the pore size of the screen. For example, a polymer particle having a size greater than 80 mesh (U.S.

Standard Sieve Series), i.e., it is stopped by an 80 mesh screen, normally will swell to a size larger than 20 mesh. Therefore, the swollen hydrogel will not pass through the screen until pressure is applied.

The pressure needed to extrude the hydrogel through the screen is determined by applying a piston toward the screen and a series of weights to the piston. Pressure is increased until a pressure is reached at which the hydrogel will extrude continuously. From knowledge of the weight applied and the cross-sectional area of the piston, a pressure in pounds per square inch can be calculated at the point at which the hydrogel continuously extrudes through the 20 mesh (U.S. Standard Sieve Series) screen. This pressure is termed gel strength.

The advantages of the soil amendments used in this invention are measured by increases in water and air capacities of soils with which the amendment has been mixed compared to controlled soil samples. The water capacity of a soil matrix is the percent volume of water it contains compared to the volume of soil and water in the sample. The air capacity of soil is its total pore volume minus the water filled ores. The total pore volume is determined from the wet bulk density and particle density of the soil matrix. In evaluating a soil matrix amendment, the increase in water and air capacity per unit weight of amendment are important. The total pore volume percent can be expressed as follows: T = (1-Db) 100wherein Dp T = total pore volume percent Db = bulk density, i.e., dry soil weight divided by soil volume.

D = particle density, i.e., specific gravity of the soil mix.

Water and air capacities may be expressed as follows: Cw = percent water = volume of water (cc) x 100 capacity soil volume (cc) Ca = percent air capacity = T - Cw The increase in water and air content per unit weight of amendment may be expressed as follows: Xw = (g water held by treated soil)-(g water held by control soil g soil amendment.

and Xa = (Ce air in treated soil)-(cc air in control soil) gsoll amendment.

The polyelectrolyte hydrogels used in the present invention simultaneousiy increase both the percent air and percent water capacity of a soil matrix. Increases of Xw of greater than 20g water/g amendment are typically achieved, increases of greater than 30g water/g amendment are preferred, and increases of greater than 40g water/g amendment are most preferred. Increases of Xa of greater than 15 cc air/ g of amendment are typically achieved, increases greater than 25cc air/g of amendment are preferred and increases of greater than 35 cc air/g of amendment are most preferred.

Cross-linked polyelectrolytes have been found to have very large water capacities. The charged groups on the polymer interact when in solution and tend to extend the polymer chain to separate the charge as much as possible. The actual water capacity is controlled by a number of factors, many of which can interact. The more important ones are (1) chemical composition, (2) charge density (mole fraction ionic groups or distance between charges), and ionic strength and ionic composition of the aqueous solution which the polymer absorbs, and (3) molecular weight between cross-links, or cross-link density.

Polymer structures that are more hydrophillic absorb more water. Furthermore, the greater the charge density, the greater the water capacity will be in distilled water. However, the higher charge density compositions will be most affected by ions dissolved in the water.

These ions shield the polymer ions from each other. The polymer chain can then assume a less energetic, less extended configuration, and thus swell or absorb less water. For example, a cross-linked polyacrylic acid salt might be able to absorb 2 to 3,000 times its weight of ion-free.water, but the capacity would drop to 200 to 300 in a normal strength solution of soluble fertilizers.

Another related factor is cross-linking by multivalent ions, i.e., reactions of polyanions with multivalent cations and reactions of polycations with multivalent anions. As the crosslinking occurs, the polymer progressively loses its ability to swell and retain water. The extent of cross-linking is a function of the number and closeness of the charged groups and the multivalent ion concentration. Based upon tests and observations, the polyelectrolyte polymers used in this invention can be characterized as having a ratio of ionic to non-ionic groups and cross-link density sufficient to absorb more than 75 times their weight in a standard fertilizer solution and more than 15 times their weight in a solution containing 500 ppm of calcium ions.It is believed that the ratio of ionic to non-ionic monomer units in the polymer backbone or in the polymer chain for the polyelectrolyte polymers used in this invention should be up to 1:1, preferably up to 0.5:1 and most preferably between 0.3:1 and 0.4.1.

The problem of multivalent ion cross-linking is particularly acute when the polyelectrolyte polymer amendments are admixed in a soil matrix. Soil solutions routinely contain excessive amounts of cations such as calcium ions and other multivalent ions particularly as the soil dries out. And calcium cross-linking is substantially irreversible. Yet, the polyelectrolyte polymers used in this invention have been found to have water capacities great than 15 times their weight in soil solutions containing 500 ppm of Ca++. And it is believed that the polyelectrolyte polymers containing cationic groups have water capacities greater than 15 times their weight in soil solutions containing 500 ppm of polyvalent anions such as sulfate and carbonate.

Still another factor is the molecular weight between cross-links, or the cross-link density.

The distance between cross-links in the polyelectrolyte polymers is directly related to the water capacities of the polymers. Larger distances provide larger water capacities.

In another embodiment, the soil amendment used in this invention comprises an insoluble polyelectrolyte polymer whose outer surface has been modified by treatment with a hydrophobic material. The so-modified polymer is easier to admix with damp or wet soil. By "hydrophobic" material is meant a material which floats when placed on a water-air interface. It is preferred that the hydrophobic material be in an extremely finely divided state. The hydrophobic particles are sized extremely finer, are much less dense and have a much larger surface area than the polymer particles of this invention. This enables a small quantity of the hydrophobic particles to provide a thin coating on the outer surface of a much larger amount of polymer particles.

The surface treatment of the polyelectrolyte polymer particles may be conveniently accomplished by physically admixing the polymer particles with up to five (5% percent by weight of the hydrophobic fine particles to produce surface treated polymer particles wherein hydrophobic fine particles physically adhere to the outer surfaces of the polymer particles. It is therorized that the extremely fine hydrophobic particles coat or otherwise cling to the outer surface of the polymer particles by electrostatic attraction. Other methods of applying the hydrophobic fine particles to the polymer particles are well known and include blending, mechanical mixing, powder coating, spraying, brushing, shovelling and the like.

It has been found that the surface coating of hydrophobic particles is either physically removed or rendered ineffective in the soil. The in situ removal or ineffectiveness of the hydrophobic surface coating occurs after irrigation of the soil admixture. This is consistent with the theory of an electrostatic attraction between the polymer particles and hydrophobic fine particles since the presence of polyvalent cations or anions tends to interrupt or break down an electrostatic attraction. Hence, it is believed that once thoroughly admixed with the soil, the electrostatic attraction between polymer particles and hydrophobic particles tends to be broken down by the presence of multivalent ions in the soil. Once the surface coating is removed, the polymer particles can function normally and effectively as a hydrophillic material.

It is usually difficult to admix uncoated polyelectrolyte polymer particles with damp or wet soil. The polyelectrolyte particles tend to agglomerate making it difficult to homogeneously distribute them with the soil matrix. By damp or wet soils is meant a soil whose moisture content is substantially greater than about five (50/0) percent aqueous media by volume of the soil. It is increasingly difficult to admix uncoated polyelectrolyte polymers with soils approaching the equilibrium drain value (field capacity). These problems are substantially obviated by the use of the surface coated polymer particles.

Suitable hydrophobic fine particles include talc, wood flour, hydrophobic silica particles such as those described in U.S. patents 3,661,810 and 3,710,510, and strongly hydrophobic metallic oxides such as those described in U.S. patent 3,710,510. Particularly preferred is a hydrophobic fine powdered silica having an average equivalent spherical diameter of less than 100 millimicrons with a surface area greater than 50 m2/g with no external hydroxyl groups.

The active agents which can be incorporated in the soil amendments of the present invention are in general known in the art. As employed herein, the term "active agent" is defined to mean those materials, organic, inorganic, organo-metallic or metallo-organic, which when in contact or close association with plants will alter, modify, promote or retard their growth either directly or indirectly.

The active agents which can be incorporated in the growth media compositions of the present invention include water; fertilizers; including all elements and combinations of elements essential for the growth of plants in either organic or inorganic forms, solid, liquid or gaseous; algaecides, including quaternary ammonium salts, technical abiethylamine acetates, and copper sulfate; bactericides, including quaternary ammonium salts, antibiotics, and n-chlorosuccinimide; blossom thinners, including phenols; defoliants, including phosphorotrithioates, phthalates, phosphorotrithioites and chlorates; fumigants, including dithiocarbonates, cyanides, dichloroethyl ether, and halogenated ethanes; fungicides, including lime, sulfur, antibiotics, mono- and di-thiocarbamates, thiodiazines, sulfonamides, phthalimides, petroleum oils, naphthoquinones, benzoquinones, disulfides, thiocarbamates, meruric compounds, tetrahydrophthalimides, arsenates, cupric compounds, guanidine salts, triazines, glyoxalidine salts, quinolinium salts, and phenylcrotonates; germicides, including quaternary ammonium salts, phenolics, quaternary pyridinium salts, peracids, and formaldehyde; herbicides, including sulfamates, trazines, borates, alpha haloacetamides, carbamates, substituted phenoxy acids, substituted phenoxy alcohols, halogenated aliphatic acids and salts, substituted phenols, arsonates, substituted ureas, phthalates, dithiocarbamates, thiolcarbamates, disulfides, cyanates, chlorates, xanthates, substituted benzoic acids, n-1-naphthylphthalamic acid, allyl alcohol, amino triazole, hexachloroacetone, maleic hydrazide, and phenyl mercuric acetate; insecticides, including natural products (such as pyrethrins), arsenicals and arsenites, fluosilicates and alminates, benzoates, chlorinated hydrocarbons, phosphates, cresosote oil and cresylic acid, phosphorothionates, thiophosphates, phosphonates, phosphoro-monoand di-thioates, xanthones, thiocyano-diethyl ethers, fluorophosphines, pyrrolidines, phosphonous anhydride, thiazines, carbamates, chlorinates, terpenes, tartrates, thallous sulfate, and anabasis; miticides, including sulfonates, sulfites, azobenzines diimides, benzilate, sulfides, phosphoro-dithioates, substituted phenols and salts, chlorophenyl ethanols, phosphonates, oxalates, sulphones, chlorophenoxy methanes, selenates, and strychnine; nematocides, including halogenated propanes and propenes, dithiocarbamates, phosphorothioates, and methyl bromide; insect repellents, including polypropylene glycols, succinates, phthalates, furfurals, asafetida, ethylhexanediol, and butyl mesityl oxide; rodenticies, including 2-chloro-4-dimethylamino-6-methyl pyrimidine, fluorides, coumarins, phosphorus, red squill, arsenites, and indandion; and synergists, including carboximides, piperonyl derivatives. and sulfoxides.

The soil amendment in addition to the aforementioned active agents can, if desired, include one or more materials which may or may not affect, directly or indirectly, plant growth. The liquid materials include water, hydrocarbon oils, organic alcohols, ketones, and chlorinated hydrocarbons. The solid include bentonite, pumice, china clays, attapulgites, talc, pyrophyllite, quartz, diatomaceous earth, fuller's earth, chalk, rock phosphate, sulfur, acid washed bentonite, precipitated calcium carbonate, precipitated calcium phosphate, colloidal silica, sand, vermiculite, perlite, and finely ground plant matter, such as corn cobs.The soil amendments can, if desired, include wetting agents such as anionic wetting agents, non-ionic wetting agents, cationic wetting agents, including alkyl aryl sulfonates, polyethylene glycol derivatives, conventional soaps, amino soaps, sulfonated animal, vegetable and mineral oils, quaternary salts of high molecular weight acids, rosin soaps, sulfuric acid salts of high molecular weight organic compounds, ethylene oxide condensed with fatty acids, alkyl phenols and mercaptans.

The plant growth media composition of the invention comprises soil and the particulate, cross-linked polyelectrolyte polymers. A polyelectrolyte hydrogel or polymer can be applied to the surface of the soil or incorporated into the soil to form a mixture of soil and cross-linked polyelectrolyte hydrogel or polymer, respectively. Numerous variations of the basic composition are possible. For instance, the growth media compositon can comprise a mixture of soil and dry, particulate, cross-linked polyelectrolyte polymer per se. The polyelectrolyte polymer will sorb water during rainfall or irrigation. The sorption of water by the polyelectrolyte polymers prevents excessive loss of water. Naturally occurring nutrients in the soil are solublizied in the soil water and also sorbed by the polyelectrolyte polymers; here the polyelectrolyte hydrogel acts as a reservoir for natural nutrients.This minimizes leaching of natural nutrients from the soils. Other advantages achieved by adding the dry polyelectrolyte polymers per se to soils include a reduction of compaction of soil thereby increasing the penetration of moisture and oxygen into the subterranean growing areas. Moreover, as previously discussed a major advantage of adding the polyelectrolyte polymersperse to soils is the simultaneous increase in water and air capacity of the amended soil matrix.

The polyelectrolyte polymers of this invention are of particular benefit for amending the soils employed in containers. It is well known in the art that container soils pose a peculiar problem because of their relatively short soil column brought about by the shape of the container. After watering, the soils in containers tend to stay fully saturated with water and thus deficient in air. This phenomenon is often referred to as the perched water table. A common method to alleviate this problem is to use a large proportion of an aggregate such as perlite, vermiculite, pumice, comminuted plastic scrap, and bark in the soil mixture.

Although the aggregate, if used in sufficient quantity, can improve the air capacity, it generally does so at the expense of the water capacity, i.e., the water capacity decreases as the air capacity increases. Thus, the ability of the polyelectrolyte polymers to increase both the air and water capacity of a soil matrix is particularly advantageous in container soils.

Water can be incorporated within the polyelectrolyte polymer prior to admixture of the polymer with the soil. As previously indicated, each individual absorbent polyelectrolyte particle maintains its particulate character as it imbibes and absorbs many times its weight of water, and in doing so swells. The resulting water-swollen particle, defined herein as a hydrogel, substantially immobilizes the water therein. The absorbed water within the hydrogel is available for plant roots and is reversibly released to the plant or soil by the hydrogel.

Upon releasing the absorbed water therein, the hydrogel dehydrates and returns to substantially its original size and the state of being a polymer.

According to this invention, the germination of seeds, the early growth of seedlings and the growth of transplants can be effectively improved by placing them in proximity with water swollen hydrogels in the soil. The hydrogel can be placed in the soil prior to or subsequent to the placement of the seed, seedling or transplant. In these applications, the water is supplied from the polyelectrolyte hydrogel reservoir for efficient use by plant life as needed. The hydrogel is a reservoir of water. There is no excessive water loss due to percolation downward as experienced with some of the sandy soils. A fertilizer or other active agent can be incorporated into the polyelectrolyte hydrogel with water and/or organic solvents prior to addition of the hydrogel materials to the soil. The polyelectrolyte hydrogel acts as a reservoir and a carrier for the water, fertilizer or other active agents and prevents excessive loss of the water, fertilizer and other active agents by leaching.

A fertilizer or other active agents can be first solubilized in water and/or organic solutions and the insoluble polyelectrolyte polymers can then be exposed to these solutions. The solutions containing the active agent will thereby be incorporated into the polyelectrolyte polymer as it swells into a hydrogel state. The water or organic solvent can then be removed from the polyelectrolyte hydrogel, prior to application of the polymer to the soil, to form a substantially dry polyelectrolyte polymer containing only the active agent. This active-agentloaded polymer or growth modifer can then be added to soil to produce the growth media compositions of the present invention. As water is applied to the soil, the polymer will sorb the water. The active agents contained in and on the polymer will be solubilized therein.The liquid-swollen hydrogel will then act as a reservoir and carrier for watcr and active agents which are readily available to modify plant growth. The active agents will not be as rapidly leached from the soil by excessive rainfall or during other abrupt or extended applications of water. This aspect of the present invention has great utility as a means of adding herbicides simultaneously with seeding operations without undue loss of herbicide because of leaching.

The polymer can be admixed or mulched with the soil in dry or substantially dewatered condition along with substantially dry active agents such as fertilizers, herbicides, nematocides and insecticides, for example. Upon application of water to the soil the active agents will be solublized and the water and active agents will be sorbed by the polyelectrolyte polymer.

Again, the problem of excessive loss of water by evaporation or by loss to the natural water table and loss of the active agents by leaching is reduced. Also, because the activating carrier is able to sorb moisture from the so-called dry soils, activation of active agents may begin without additional rainfall.

A particular and distinct advantage of the present growth media composition is the manner in which the plant roots make use of the polyelectrolyte hydrogel. The plant roots grow into the polyelectrolyte hydrogel itself and thereby come into direct contact with water and the other active agents incorporated within the hydrogel. The ability.of the plant. roots to grow into the hydrogel permits more efficient utilization of water and other active agents because the water and active agents are directly contacted by the roots. Also, plants whose roots grow into the hydrogel, thereby causing the cross-linked hydrogel to cling to the plant roots particularly when removed from the soil for transplanting, are much more resistant to extended periods of moisture stress.The term "moisture stress" is defined herein to mean a situation wherein the internal moisture of the plant is transpired or evaporated at a rate greater than the rate which water enters the plant. The latter rate is due primarily to the lack of available moisture. There is much less destruction of seedlings during shipping and transplanting operations with such plants as tobacco, lettuce, celery, tomatoes, strawberries, annuals and perennials, hardy perennials, woody plants, ornamentals, seedlings and the like when they have been grown in the soil-compositions.of the present invention.

In another embodiment of this invention, plants can be rendered more resistant to moisture stress by the method which comprises contacting the roots with an aqueous slurry of one of the particulate cross-linked hydrogels useful in this invention prior to planting in the soil. The physical properties of the slurry may need to be adjusted so that a significant amount of hydrogel adheres to the plant roots when they are withdrawn. A particularly convenient way of increasing the effectiveness of the slurry is to add up to 10% by weight of a water soluble thickening agent such as high molecular weight polyethylene oxide, or hydroxy ethyl cellulose. The roots can be contacted with the slurry by spraying, dipping, or other convenient methods.

The following examples are given to illustrate the present invention but are not to be construed as limiting the invention thereto.

EXAMPLE 1 Three soil amendments were compared using a "soil column" procedure. Soil column refers to a sample of soil generally in a columnar glass vessel in which the soil and water can be observed. A 350 ml. glass Buchner funnel 18 cm high, cm in diameter, with 7 cm of height above the 0.5 cm fritted filter was employed. Several 0.5 cm holes were drilled into each filter to simulate normal drainage from a pot. The specific gravity of each soil mix was determined in a pycnometer by standard procedures, i.e, those of the U.S. Salinity Laboratory 1954.

Each soil mix was dried at 110 0C for 16 hours and weighed dry.

Each amendment was added and mixed on an individual basis to the soil in each column, respectively. The soil in a control column was mixed in a large plastic bag in the same manner.

Each sample was tamped in the same gentle manner after filling in order to settle but not cause unnatural compaction of the soil sample. After this gentle tamping, the height of each soil column was measured and the volume determined by a calibration of height vs. volume previously made.

The soil columns were watered with 200 ml of water and then allowed to drain overnight if possible or at least four to six hours. After this drainage time, each container was weighed and the weight of water absorbed by the dry soil calculated as follows: weight of water = (total weight) - (container tare) - (dry fill weight). The waterings were repeated six times until a constant value was observed. The volume was then measured again. Having thus determined soil volume and water weight, then percent water capacity was calculated thus, Cw = weight of water divided by the soil volume since the specific gravity of water is 1. Air capacity (Ca) was calculated by the relationships previously described: Ca =T-Cwand

For each variation in examples 1 - 4, three columns were run. The initial volume of soil was 280 cc.Depending on the type of soil, this weighed from 47 to 320 g. The soil amendments were added in amounts between 1 and 4 grams per column, which is equivalent to between 3.6 and 14.4 g/ 1. Watering was done with Peter's solution, a fertilizing solution of 200 ppm (nitrogen) strength. The Peter's solution was made from a commercially available fertilizer comprising 20%nitrogen, 20%P205 and 20%K2O, a so-called 20-20-20 fertilizer.

In example 1, a Cornell type potting soil, consisting of half peat moss and half vermiculite, was used. The four soil amendments compared were: (1) Viterra Hydrogel Soil Amendment (Viterra is a trademark for a 50% polyethylene oxide, 50% inert ingredients soil amendment made by Union Carbide Corporation); (2) General Mills product SPG-502S, a hydrolyzed polyacrylonitrile grafted copolymer of starch soil amendment and (3) an illustrative polyelectrolyte hydrogel soil amendment of this invention, a cross-linked polymer of potassium acrylate and acrylamide.

A solution containing 19% by weight potassium acrylate and 35% by weight acrylamide was made by mixing the appropriate amounts of acrylic acid, acrylamide, and water followed by a neutralization step using 50% by weight potassium hydroxide. The ratio of monomer units potassium acrylate/acrylamide employed = 0.348.

This solution was then case onto a paper backing material and conveyed beneath a 1.5 MeV Van de Graaf accelerator operating at 1,600 yamp beam current. The conveyor was placed such that the closest distance to the sample, directly beneath the exit window of the accelerator, was two feet. The total dose received by the sample at a conveyor speed of 8 feet/ minute is on the order of 1 megarad.

The resulting gel was then dried, ground, and classified according to the desired size of the particles by conventional techniques.

The experiment was conducted for three days with six waterings twice per day on three pots each. Xw and Xa values represent the increase in water and air content respectively per gram of additive, water in units of grams and air in units of cubic centimeters.

The results of the tests are summarized in Table I hereinbelow: TABLEI g Equil. g Amendment Dry Drained Water H2O Air cc Per Wt. Wt. Capacity Per Capacity Airl Xw Xa Pot g (g) Cw(%) Pot Ca(%) Pot (g)/g (cc)/g Control Soil - 47 257 71.2 210 18.5 55 - (Cornell Type) Soil Plus 3.4 50.4 298 73.9 248 16.4 55 11.2 0 12.1 g/l Viterra Hydrogel Soil Amendment Soil Plus 1.1 48.1 335 79 287 12.4 45 70 (-9) 3.9g/l cross General Mills Product (SPG-502S) Soil Plus 1.1 48.1 319 69.3 271 22.7 89 55.5 30.9 3.9/l Crosslinked Copolymer of Potassium Acrylate and Acrylamide.

These data show that while other polymeric materials may have increased the water capacity of soil, only the polyelectrolyte polymer of this invention, a cross-linked copolymer of potassium acrylate and acrylamide, markedly increased both air and water capacity. This is contrasted with the hydrolyzed polyacrylonitrile grafted copolymer of starch product which actually decreased the air capacity.

EXAMPLE 2 This example illustrates the effect on the standard soil physics characteristics of the same three soil amendments of Example 1 on a commercial potting soil, a field soil enriched with humus. The same experimental procedure was employed as described in Example 1. The results are summarized in Table II hereinbelow.

TABLE II g Equil. g Amendment Dry Drained Water H2O Air cc Per Wt. Wt. Capacity Per Capacity Air/ Xw Z Pot (g) (g) Cw(%) Pot Ca(%) Pot (g)/g (cc)/g Control Soil - 320 450 44.1 130 9.7 29 - Soil Plus. 3.4 323.4 504 49.8 180 12.3 45 14.7 4.7 12.1 g/l Viterra Hydrogel Soil Amendment Soil Plus 1.1 321.1 522 57.1 201 4.1 14 65 (-14) 3.9 g/l General Mills Product(SPG-502S) Soil Plus 1.1 321.1 503 48.6 182 14.9 56 47 25 3.9 g/l Crosslinked Copolymer of Potassium Acrylate and Acrylamide.

Again, only the soil amendment of this invention, exemplified by the cross-linked copolymer of potassium acrylate and acrylamide, increased both air and water capacity markedly.

EXAMPLE3 This example illustrates the effect on a soil/peat moss/perlite 1-1-1 by volume, type of potting soil of the addition of certain soil additives compared to the soil amendment of this invention. The same experimental procedures as in Example 1 were used. The results are summarized in Table III below: These data show that in this 1-1-1 type soil, only the insoluble polyelectrolyte polymer (cross-linked copolymer of potassium acrylate and acrylamide) of this invention has a truly marked effect on both air and water capacity of this soil.

TABLE III g Equil. g Amendment Dry Drained Water H2O Air cc per Wt. Wt. Capacity Per Capacity Air/ Xw Xa Pot (g) (g) Cw(%) Pot Ca(%) Pot (g)/g (cc)/g Control Soil - 150 279 50.6 129 22.1 56 - (1-1-1 Mix) Soil Plus 3.4 153.4 322 53 169 24.6 78 11.8 6.5 12.1 g/l Viterra Hydrogel Soil Amendment Soil Plus 1.1 151.1 347 60.7 196 17.5 57 61 0.9 3.9 g/1 General Mills Product(SP6-5025) Soil Plus 1.1 151.1 331 52.9 180 26.4 90 46.2 30.9 3.9 g/l Cross-linked Copolymer of Potassium Acrylate and Acrylamide EXAMPLE 4 In this example, the soil amendments were ground and screened to provide two size fractions, one - 10 to + 40 mesh (U.S. Standard) and the other more finely ground to pass a 40 mesh screen. In the latter case there was a considerable amount of material that was smaller than the 100 mesh screen size.The Viterra Hydrogel Soil Amendment and the copolymer of potassium acrylate and acrylamide were studied in the same manner as Example 1. The results are summarized in Table IV below: TABLE IV Equil. g g Dry Drained Water H2O Air cc Per Wt. Wt. Capacity Per Capacity Air/ Xw Xa Pot g (g) Cw(%) Pot Ca(%) Pot (g)/g (cc/g Control Soil - 150 279 50.6 129 22.1 56 - (1-1-1) 1-1-1 Soil + 3.4 153.4 340 58.7 187 18.9 60 17 1.2 12.1 g/l Viterra Hydrogel Soil Amendment Sized-40 Mesh 1-1-1 Soil + 3.4 153.4 320 51.6 167 26.3 85 11.2 8.5 12.1 g/l Viterra Hydrogel Soil Amendment Sized-10 to + 40 1-1-1 Soil + 1.1 151.1 356 62.3 205 16.4 54 69 (-1.8) 3.9 g/l Crosslinked Copolymer of Potassium Acylate and Acrylamide Sized-40 Mesh 1-1-1 Soil + 1.1 151.1 336 52.5 185 27.5 97 51 37 3.9 g/l Cross linked Copolymer of Potassium Acrylate and acrylamide Sized -10 to +40 Mesh The data summarized in Table IV indicate that in a 1-1-1 (soil-peat moss - perlite by volume) type soil, the more finely ground hydrogel particles increased water capacity but decreased air capacity. With the cross-linked copolymer of potassium acrylate and acrylamide, this phenomenon was accentuated. The finely ground particles gave a markedly higher water and a much lower air capacity than the larger sized particles. It is believed that the fine particles of hydrogel plug a substantial number of the soil capillaries and restrict drainage. Thus, capillaries that would normally contain air are maintained in a full state and the air capacity is reduced, often below that of a similar control soil without the finely ground additive.

EXAMPLES An "in pot" procedure was employed. "In pot" refers to soil in a commercial plant pot. The soil amendments were added to the soil mix of each container individually, with mixing. The controls were mixed in the same manner (shaken in a plastic bag) to ensure uniformity.

Gentle tamping, to settle the soil, precalibration of soil height vs. soil volume, watering, draining overnight, weighing and calculation of percent water capacity, Cw, as weight or volume of water (cc) per soil volume (cc), was done in the manner described previously with respect to the "soil column" procedure.

The total drainable pore space or percent air capacity was determined as follows. The pots were carefully flooded to the top of the soil surface with the drainage holes covered, the pots being tilted to one side while being watered on the down side to allow air to escape. Or the full pot was placed in a pan of water or fertilizer solution to such a depth as to keep the pot full to soil level. In either case, the pots were allowed to stand flooded overnight (16 hours) to ensure expulsion of all air. They were weighed when flooded. After drainage, they were reweighed. The difference in weight was drainable pore space at zero suction, since the specific gravity of water is one. Air capacity, Ca is then drainable pore space (cc).

soil volume (ccr A slight adjustment was made for the very high capacity hydrogels. Rather than using the drained weight after overnight flooding to subtract from the fully saturated weight, the equilibrium weight after normal watering was used. This was done because these high capacity gels would sometimes absorb more water during the overnight flooding procedure and this lead to spurious results. The Xa and Xw values were calculated as described previously, i.e, weight difference between the amended soil and control per unit weight of amendment for water and air volume difference per unit weight of amendment for air.

In this example, a cross-linked copolymer of potassium acrylate and acrylamide (having a ratio of potassium acrylate monomer units to acrylamide of 0.387, about 1 ionic group to 3 neutral groups) was tested at two particle sizes in the pot environment. The soil was a 2-2-1 mix of two parts top soil, two parts peat moss and one part perlite. The pots were 16.5 cm diameter containing 600 g (1200 cc) soil per pot. The cross-linked copolymer potassium acrylate and acrylamide was added at 3 g per pot (2.5 g/ 1). There were seven 500-ml waterings of each pot with tap water and equilibrium drainage in between. Each data point below represents the average of two pots.The results are summarized below in Table V: TABLE V Final Drained g cc Air/ Volume(cc) H2O/Pot Cw(%) Xw(g/g) Pot Ca(%) Xa(cc/g) Control 1075 562 52.3 - 125 11.6 2-2-1 Soil Mix 2-2-1 Soil Plus 1290 813 63.0 83 141 10.9 53 -40 Mesh, Cross-linked Copolymer of Potassium Acrylate and Acrylamide Powder 2-2-1 Soil Plus 1290 748 58.0 62 217 16.8 30.7 -10 to +40 Mesh Cross-linked Copolymer of Potassium Acrylate and Acrylamide Granules These data show that the cross-linked copolymer of this invention in granular form although slightly less effective in increasing the water capacity of this rich, organic soil, is markely more effective than the fine powder in raising air capacity.

EXAMPLE 6 This example employs the "in pot" procedure of Example 5 and illustrates the stability to successive waterings on a highly ionic polyelectrolyte polymer. This polyelectrolyte hydrogel contained about three ionic groups/nonionic group. The watering was done initially with tap water and then with fertilizer solution. This cross-linked copolymer of potassium acrylate and acrylamide had a ratio of monomer units of potassium acrylate to acrylamide of 2.82. A 2-2-1, mix soil, peat moss and perlite, was employed in 16.5 cm diameter pots. Five grams (4.2 g/ 1) of the polyelectrolye polymer were added to 600 g of soil, which had a volume of approximately 1200 cc. The first four waterings were made with tap water, after which soil measurements were taken.Then there were six waterings with 200 ppm (N) Peter's solution about 1.32 g/1, i.e., fertilizer with a 20-20-20 N, P2O5, K20 percentage. The results are summarized in Table VI below: TABLE VI Final Air Drained g Volume Volume H2O/ Xw (cc)/ Xa (cc) Pot Cw(%) (g)/g Pot Ca(%) (cc)/g Control 2-2-1 Soil 1150 675 58.7 - 138 12.0 After 4 Waterings, Tap Water Amended Soil After 1600 1111 69.4 87 338 21.1 40 4 Waterings,Tap Water Control 2-2-1 Soil 1100 686 62.4 - 133 12.1 After 10 Waterings, 4 Tap Water, 6 Peter's Solution Amended Soil After 1310 792 60.5 22 326 24.9 38.6 10 Waterings, 4 Tap Water, 6 Peter's Solution These data in Table VI show that certain polyelectrolytes lose substantial water capacity after reacting with a normal fertilizer solution.Note that the Xw value drops from 87 g H2O/g polymer to 22 g H20/g polymer.

EXAMPLE 7 The "in pot" procedure of Example 5 was employed. In this example, the soil was a commercial greenhouse mix consisting of 1-1-1, soil, peat moss and sand mixture. Pots 16.5 cm in diameter were filled with 735 g of soil, about 1200 cc, containing zero, 4.5 g (3.5 g/ 1) or 7.5 g (6.3 g/ 1) of a polyelectrolyte polymer. The appropriate amount of the polyelectrolyte soil amendment had been previously mixed with the soil. The polyelectrolyte polymer was a cross-linked copolymer of potassium acrylate and acrylamide having a ratio of potassium acrylate to acrylamide monomer units of 0.348. This ratio is equivalent to about 1 ionic group to 3 nonionic groups.The watering protocol was three 500-ml waterings with tap water followed by two 500-ml additions of Peter's solution - a 200 ppm (N) 20-20-20 N, Plus, K2O) solution. After each watering, free drainage for at least six hours took place. Each of the following data points represents the average of three pots. The measurements were made after the fertilizer solution was applied.The results are summarized in Table VII below: TABLEVII Final Air Drained g Volume Volume H2O/ Xw (cc)/ Xa (cc) Pot Cw(%) (g)/g Pot Ca(%) (cc)/g Control 1043 355 67 - 69 6.6 1-1-1 Control Plus 1302 547 71 43 152 11.7 21 3.8 g/1 Cross-linked Copolymer of Potassium Acrylate and Acrylamide Control Plus 1507 708 72 47 186 12.3 16 6.3 g/l Cross-linked Copolymer of Potassium Acrylate and Acrylamide The data in Table VII show that the addition of a polyelectrolyte polymer of this invention markedly increases both the water capacity and air capacity of this highly organic soil at both levels of amendment. Also a comparison with Example 6 shows that this polyelectrolyte (after watering with the fertilizer solution) has a much higher (more than double) water capacity (Xw) than the polyelectrolyte hydrogel with the high ratio of ionic/nonionic groups.

EXAMPLE8 The "in pot" procedure of Example 5 was employed. In this example, the soil consisted of two parts of peat moss. one part vermiculite. and one part perlite plus soluble fertilizers. The soil mix, 210 g, was well mixed with zero, 4.5 g (3.8 g/l) or 7.5 g (6.3 g/l) of the polyelectrolyte polymer and put into 16.5 cm diameter pots. The polyelectrolyte polymer was a cross-linked copolymer of potassium acrylate and acrylamide with a ratio of potassium acrylate/acrylamide monomer units of 0.348. This is a typical soil amendment of this invention. The watering protocol was six waterings of 500-ml each of tap water. Each of the following data points represents the average of five pots.The results are summarized in Table VIII below: TABLE VIII Final Air Drained g Volume Volume H2O/ Xw (cc)/ Xa (cc) Pot Cw(%) (g)/g Pot Ca(%) (cc)/g 2-2-1 Control 1150 357 62 - 218 19 Control Plus 1460 599 68 54 408 28 42 4 g/l of Cross-linked Copolymer of Potassium Acrylate and Acrylamide Control Plus > 1595* 766 74 55 > 478* > 30* 35* 6.4 g/l of Cross-linked Copolymer of Potassium Acrylate and Acrylamide *Soil overflowed the pot during Ca measurement.

The data of Table VIII show that for this soil, rich in aggregates, an insoluble polyelectrolyte polymer typical of this invention raised both the air capacity and water capacity to high levels. Moreover, the amount of the polymer added was not crucial, since both levels of amendment produced a soil with excellent properties. Note that the g of H20/pot increased as the level of amendment increased.

EXAMPLE 9 The "in pot" procedure of Example 5 was employed. This is a comparative example showing the limits of applicants' invention. It illustrates the inability of certain polymer soil amendments to increase both air capacity and water capacity in a pot environment. The soil amendments were Viterra Hydrogel Soil Amendment, a trade name for a 50% polyethylene oxide, 50% inert ingredients soil amendment made by Union Carbide Corporation; and Gelgard XD1300, a cross-linked partially hydrolized polyacrylamide (about 40% hydrolyzed sized finer than 100 mesh (U.S.A. Standard Sieve Series) made by The Dow Chemical Company.

The pots 16.5 cm in diameter were filled with 506 g, about 1200 cc of a 2-2-1 mix of two parts top soil, two parts peat moss and one part perlite, a rich organic soil. 15g per pot (12.5 g/l) of Viterra Hydrogel Soil Amendment were added to eight pots and 3.5 g per pot (2.9 g/l) of the modified polyelectrolyte were added to eight additional pots. Each data point below represents the average of eight pots. Each pot was watered seven times with 5()U ml portions of tap water with equilibrium drainage in between. The Ca values were calculated by the "column" rather than the "in pot" procedure.The results are summarized in Table IX below: TABLE IX Final Air Drained g Volume Volume H2O/per Xw (cc)/ Xa (cc) Pot Cw(%) (g/g) Pot Ca(%) (cc/g) Control 1100 639 58.1 - 177 16.1 2-2-1 Soil Mix 2-2-1 Soil Mix 1286 804 62.5 11 189 14.7 0.8 Plus Viterra Hydrogel Soil Amendment 2-2-1 Soil Mix 1380 986 71.4 99 109 7.9 (-19) Plus Gelgard XD 1300 (cross-linked partially hydrolyzed polyacrylamide) The data in Table IX illustrate that certain soil amendments may greatly increase the water capacity of soils without increasing the air capacity at all or even decreasing it.

EXAMPLE 10 The "in pot" procedure of Example 5 was employed. Five soil amendments were compared: a potassium bonded polyacrylate (potassium content 30-35% by weight of polymer) made by Toho Rayon Company of Japan; General Mills product SPG-5025, a hydrolyzed polyacylonitrile grafted copolymer of starch; Grain Processing 35-A100 product, a granular, water insoluble alkali metal carboxylate salt of starch-acrylonitrile graft copolymer produced by saponifying starch acrylonitrile graft copolymers with an aqueous alcoholic solution (described in U.S. patent 3,661,815); Gelgard XD-1300 Product, a cross-linked partially hydrolyzed polyacrylamide about 40% hydrolyzed and sized finer than 100 mesh, and a polyelectrolyte polymer of this invention.The polyelectrolyte polymer was a cross-linked copolymer of potassium acrylate and acrylamide having a ratio of potassium acrylate to acrylamide monomer units of 0.348.

A 2-1-1 mix (peat moss, vermiculite, perlite), fertilized with the standard Cornell recommended components including lime, (see Cornell Recommendations for Commercial Floriculture Crops, April, 1974, p.3, Cornell University Press) was employed. 130 g (1200 cc) of the soil mix was well mixed with 5 g (4.2 g/l) of the five polymers and put into 16.5 cm diameter pots. The following data points represent the average of three pots for each treatment. There were twenty waterings, six of tap water and fourteen of Peter's 20-20-20, 200 (N) ppm fertilizer solution at 500 ml. There was free drainage for at least eight hours after each watering. All pots were allowed to dry to a normal level four times prior to watering in simultation of normal growth conditions. Of course, the salt concentration of the soil solution increases as the soil dries.Just prior to taking the data, all pots were watered three times with tap water to leach any accumulated salts. The results are summarized in Table X below: TABLE X Final Drained g(H2) Xw Air Volume Volume (cc) per pot Cw(%) (g/g) (cc/pot) Ca(%) Xa(cc/g) Control Mix 1165 828 71.1 - 172 14.7 Control Mix Plus 1335 978 73.3 30 267 20.0 19.0 Cross-linked Copolymer of Potassium Acrylate and Acrylamide Control Mix 1272 870 68.4 8 228 17.9 11.0 Plus Toho Rayon Product Control Mix Plus 1272 896 70.4 13 110 8.6 (-12) General Mills Product SPG-5025 Control Mix Plus Grain 1241 886 71.4 12 162 13.1 (-2) Processing 35-A 100 Product Control Mix Plus 1365 1033 75.7 41 130 9.5 (-8) Gelgard XD-1300 Product The data in Table X above clearly shows that the only polymer which markedly improves the water and air capacity of the composition is the polymer of this invention.

EXAMPLE 11 This example compares the equilibrium solution capacities (X-values) of a number of known polymer soil amendments with an insoluble polyelectrolyte soil amendment of this invention. The polymers tested were: (1) the polyelectrolyte polymer of this invention described in Example 10; (2) a potassium bonded polyacrylate (potassium content 30-35% by weight of polymer) made by Toho Rayon Company of Japan; (3) General Mills SPG-5025 product, a hydrolyzed polyacrylonitrile grated copolymer of starch; (4) Grain Processing 35-A100 product, a granular, water insoluble alkali metal carboxylate salt of starchacrylonitrile graft copolymer produced by saponifying starch-acrylonitrile graft copolymers with an aqueous alcoholic solution of a base (described in U.S. patent 3,661,815), and (5) Gelgard (XD-1300; (Gelgard is a trademark for a cross-linked, partially hydrolyzed polyacrylamide (about 40% hydrolyzed and sized finer than 100 mesh) made by Dow Chemical Company).

The equilibrium capacities (X values) were calculated according to the following formula: X Value = Weight of Swollen Polvmer-Weight of Dry Polymer - Weight of Dry Polymer The test procedure was as follows: A weighed amount of each dried (dewatered) polymer was placed in solution and stirred gently overnight. The water swollen polymer particles were then filtered off and weighed. X values were calculated according to the formula previously given.

An effective soil amendment must be of suitable chemical formulation so as not to irreversibly cross-link in the presence of multivalent ions in the soil solution and thereby lose its water capacity. Table XI below lists the equilibrium capacities (X values) of several polymers in solutions of Cacti2 in deionized water. Concentrations of 36 ppm Ca++, an average concentration in tap water, and 500 ppm Ca++, a concentration commonly found in the soil solution, were employed. To illustrate the irreversibility of the calcium cross-linking, the polymers swollen in the Ca++ solutions were filtered out and soaked in excess deionized water overnight and the X values determined again.The results of these tests are summarized in Table XI below: TABLE XI Cross-linked Copolymer Toho of Potassium Acrylate Rayon General Mills Grain Processing Gelgard and Acrylamide Product Product Product Product 36 ppm Ca + + 220 120 180 101 388 500 ppm Ca + + 39 6 8 9 48 36/500 Ratio 17% 4.8% 4.4% 8.9% 12.4% After Deionized Water Wash: From 36 ppm Ca + + 446 187 365 124 692 From 500 ppm Ca + + 143 14 14 16 230 The data in Table XI show that a typical polyelectrolyte polymer of this invention retains its water capacity and does not irreversibly cross-link in the presence of multivalent ions in the soil solution. It is noted that the Gelgard product provides considerable water capacity in a solution of 500 ppm Ca++, Examples 9 and 10 illustrate that it decreases the air capacity of soils.

EXAMPLE12 The "in pot" procedure of Example 5 was employed. Marketer (Cv) cucumbers were grown in a soil consisting of two parts top soil, two parts peat moss and one part perlite. The treatments consisted of the control mix, the control mix plus Viterra Hydrogel Soil Amendment, a trademark for a 50% polyethylene oxide, 50% inert ingredients soil amendment made by Union Carbide Corporation, or 3 variants of a polyelectrolyte polymer of this invention, a cross-linked copolymer of potassium acrylate and acrylamide. The cross-linked polyelectrolyte polymers of this invention used were each of the same chemical composition, i.e, with a potassium acrylate to acrylamide monomer ratio of 0.387. However, each of the three samples differed in the degree of cross-linking, and hence in their respective water capacities.

The amounts of each of the three variants of this invention used were varied according to their equilibrium water capacity in tap water in an attempt to get approximately the same amount of hydrogel-bound water per pot. 600 grams (1200 cc) of soil were mixed with a soil amendment and put into 16.5 cm diameter pots. The amounts of each soil amendment used per pot was: control, 0 g; Viterra Hydrogel Soil Amendment, 15 g; and polyelectrolyte polymers of this invention, sample A, 4 g; sample B, 3 g; and sample C, 2.5 g. The watering regime was four 500-ml portions of tap water after which interim data was taken, followed by 15 additional waterings alternating between 200 ppm (N) of 20-20-20 Peter's solution (eight) and tap water (seven) over a total period of about 61 days. Each data point represents the average of five pots. Each pot contained one plant. The plant growth data was taken on the 43rd day. The results are summarized in Tables XII, XIII and XIV below: TABLE XII INTERIM SOIL PHYSICS (After 5 Days Watering with only Tap Water) Final Air Equilibrium Tap Drained g Volume Water Capacity Volume H2O/ Xw (cc)/ Xa (X V alue) (cc) Pot Cw(%) (g/g) Pot Ca(%) (cc/g) Control Soil 0 1017 615 60.5 - 163 16 Control Soil Plus 20 1166 719 61.7 7 210 18 3 12.5 g/l Viterra Hydrogel Soil Amendment Control Soil Plus 305 1224 908 74.2 73 355 29 48 3.3 g/1 Sample A Crosslinked Copolymer of Potassium acrylate and Acrylamide Control Soil Plus 470 1165 869 74.6 85 315 27 51 2.5 g/l Sample B Crosslinked Copolymer of Potassium acrylated and Acrylamide Control Soil Plus 533 1165 868 74.5 101 280 24 47 2.1 g/l Sample C Cross-linked Copolymer of Potassium Acrylate and Acrylamide TABLE XIII PLANTGROWTHAFTER 43 DAYS Number of Number of Leaves 21.3 cm (Stems) Breaks on Breaks Control Soil 2.2 1.6 Control Soil Plus 3.6 1.8 12.5 g/lViterra Hydrogel Soil Amendment Control Soil Plus 5.6 8.6 3.3 g/l Sample Am Cross-linked Copolymer of Potassium Acrylate and Acrylamide Control Soil Plus 5.2 6.2 2.5 g/l Sample B Cross-linked Copolymer of Potassium Acrylate and Acrylamide Control Soil Plus 5.0 7.2 2.1 gel Sample C Cross-linked Copolymer of Potassium Acrylate and Acrylamide TABLE XIV FIAL SOIL PHYSICS DATA (61 DAYS) Drained Air Volume H2O/ Xw Volume Xa (cc) Pot Cw(%) (g/g) (cc)/Pot Ca(%) (cc/g) Control Soil 1016 589 58.0 - 101 10 Control Soil Plus 1205 666 55.3 5 193 16 6 12.5 g/l Viterra Hydrogel Soil Amendment Control Soil Plus 1252 719 57.4 33 225 18 31 3.3 g/l Sample A Cross-linked Copolymer of Potassium Acrylate and Acrylamide Control Soil Plus 1205 694 57.6 35 205 17 34 2.5 g/l Sample B Cross-linked Copolymer of Potassium Acrylate and Acrylamide Control Soil Plus 1202 684 56.9 38 192 16 36 2.1 g/l Sample C Cross-linked Copolymer of Potassium Acrylate and Acrylamide The improvement in soil qualities is borne out by the plant growth data. The number of breaks is increased significantly up to 150% and the number of leaves greater than 1.3 cm in length on breaks is increased over 400 % compared to the control soil. One thus sees that the cross-linked copolymer of potassium acylate and acrylamide aids in the growth of plants in dramatic fashion.

EXAMPLE 13 The "in pot" procedure of Example 5 was employed. The effect of a cross-linked copolymer of potassium acrylate and acrylamide (having a ratio of potassium acrylate to acrylamide monomer units of 0.348) and Viterra Hydrogel Soil Amendment on the soil properties and the growth of red kidney beans (Phaseolus vulgaris) was measured. The soil used was a commercial indoor potting soil mix: 45% peat, 40% wood and bark chips, 10% pumice, and 5 % sand by volume plus fertlizier. There was one plant in each 16.5 cm diameter pot containing 320 g (1200 cc) soil. After four tap waterings data were taken, followed by nine more tap waterings and then two more with Peter's 20-20-20 fertilizer solution 200 (N) ppm; all were 500-ml each. Viterra Hydrogel Soil Amendment was added at 10 g per pot (8.3 g/l).The level of the cross-linked copolymer of potassium acrylate and acrylamide was 2 g per pot (1.7 g/l). Each data point represents the average of five pots. The total growth period was about 45 days.

When plants had shown maturity by flowering, all the pots were watered several times to assure saturation, the surface covered with plastic film to stop evaporation loss, and the plants allowed to wilt. At the first sign of wilting the water content was measured for each pot and compared to the control.The results are summarized in Tables XV and XVI below: TABLE XV (After 4 Waterings with Tap Water) Drained g Air/Pot Volume H2O/ Xw Volume Xa (cc) Pot Cw(%) (g)/g (cc) Ca(%) (cc)/g Soil, Control 1005 595 59.7 - 210 21 Soil Plus Viterra 1091 715 64.8 12 230 21 2 Hydrogel soil Amendment Soil Plus Cross- 1059 716 67.6 61 265 25 28 linked Copolymer of Potassium Acrylate and Acrylamide FINAL DATA AFTER MATURITY (45 DAYS) Soil Control 926 601 62.5 - 144 15 Soil Plus Viterra 1053 671 63.7 7 190 18 4.6 Hydrogel Soil Amendment Soil Plus Cross- 1076 684 63.6 42 237 22 47 linked Copolymer of Potassium Acrylate and Acrylamide TABLE XVI INCREASE IN WATER AVAILABLE FOR USE BY THE PLANT PRIOR TO WILTING %Available Available Water Water g H20 Used by Difference Capacity Plant/Pot (%) Control 36.6 352 Soil Plus Viterra 42.4 446 +27 Hydrogel Soil Amendment 10 g/pot Soil Plus Cross- 42.0 452 +28 linked Copolymer of Potassium Acrylate and Acrylamide 2g/pot These data show how well the cross-linked copolymer of potassium acrylate and acrylamide increases air capacity as well as water capacity during the growth of these beans over longer periods of time. The cross-linked copolymer of potassium acrylate and acrylamide showed a noticeable improvement in soil properties even when added at a much more modest level (one-fifth) than Viterra Hydrogel Soil Amendment. These data further demonstrate that the water held by the polymer of this invention is highly available for use by the plants. Note that 2 g of the polyelectrolyte polymer held an extra 100 grams of water that the plant could use prior to wilting.

EXAMPLE 14 A study was made of the growth of Big Boy (Cv) tomato plants with and without a cross-linked copolymer of potassium acrylate and acrylamide (having a ratio of monomer units potassium acrylate to acrylamide of 0.348) as a soil amendment. The soil was 1-1-1 by volume top soil, peat moss, sand mixture. The containers were #44 "Market Paks", a pressed fiber container approximately 14 x 19.7 x 7 cm in size. Each container was filled with 853 g (1200 cc) soil and there were 12 tomato transplants per container. Ten containers (120 plants) were grown, that is five controls, and five containers with the cross-linked copolymer at 7.3 g/container (6.1 g/l). The containers were watered as required during the 60-day growing period, and fertilized equally with 200 ppm (N) Peter's solution (20-20-20). After 60 days, all the plants were watered throughly and allowed to stand.The control tomato plants wilted in four days; the treated plants in seven days, a 75 % improvement. After wilting, the plants were cut down at soil level, oven dried at 1100C for 24 hours, and weighed for an indication of growth. The control plants (60) averaged 0.71 g per plant final dry weight. The tomato plants grown in the treated soil (also 60) averaged 0.92 g dry weight per plant, an improvement of 30%. It is thus seen that more mature plants are grown in soil treated with the cross-linked copolymer, and they can survive longer intervals between waterings without wilting.

EXAMPLE 15 Three cultivars of chrysanthemums were grown in control soil and soil amended with a cross-linked copolymer of potassium acrylate and acrylamide (having a ratio of potassium acrylate to acrylamide monomer units of 0.348). The soil was, by volume, three parts peat moss, two parts each perlite, vermiculite, sand. Into 20 cm diameter plastic pots containing 1,445 g mix per pot (2600 cc), were put three rooted cuttings of one of the following cultivars: Granchild, White Grandchild, or Illini Spinningwheel. There were 18 pots for each cultivar, hence 162 plants. Half of the pots were controls, half contained 10 g per pot (8.3 g/l) of the cross-linked copolymer.

These plants were grown outside watered by rain or sprinkling for nine weeks, then brought into a greenhouse for shelf life testing. After one final thorough watering, the plants were allowed to wilt. Time to wilt was taken at that point when all the leaves had wilted and the flowers were starting to wilt. Wilting time, of course, is an important parameter to the commercial florist. The results in days to wilt are summarized in Table XVII below: TABLE XVII Days to Wilting White Soil Illini Grandchild Grandchild Control 4 8 8 Treated with the Cross linked Copolymer 7 13 13 Improvement( +75 +63 +63 These data show the marked improvement in prolonging time to wilt for valuable flowers by treating the soil they are grown in with a typical polyelectrolyte polymer of this invention, a cross-linked copolymer of potassium acrylate and acrylamide.

EXAMPLE 16 In this example, two cultivars of poinsettia plants, Eckespoint C-1 Red and Dark Red Annette Hegg, were gtown in a Cornell type mix composed of peat moss, vermiculite, perlite plus one liter of top soil per bushel of mix. The treatment consisted of control soil and soil amended with Viterra H drogel Soil Amendment or a cross-linked copolymer of potassium acrylate and acrylamide (having a ratio of potassium acrylate to acrylamide monomer units of 0.348). The purpose of these tests were to grow stock plants, not to grow blooming plants for the consumer market. Hence, the criterion for success was the number of cuttings (longer than 5 cm) or total branches produced.

Twelve pots were used for the treatments of each of the two cultivars. They were grown in 16.5 cm diameter pots containing about 186 g (1100 cc) soil with one plant per pot. Viterra Hydrogel Soil Amendment treatments were at two levels, 8.8 g (8 g/l) and 13.2 g (12 g/l) per pot. The cross-linked copolymer was studied at one level of addition, 4.4 g per pot (4 kg/m3). The watering was as required, generally with a Peter's solution of 250 ppm (N) (25-10-10 (N)-P205)-K20) compoisition. On the seventh day after planting, the top 3-4 centimeters of new growth was taken off by hand to induce the formation of "breaks", that is branches (cuttings). After 25 days, a foliar spray of growth retardant, Cycocel (trimethyl 2-chloroethyl ammonium chloride from American Cyanamid Co.) at 3000 ppm was applied to regulate growth.After 45 days, all cuttings greater than 6 centimeters classified as usable cuttings were taken off. The smaller branches if larger than 2 cm, were also removed. They were called branches. The number of cuttings and branches were counted. Additionally, the total weight of cuttings and branches was measured to further quantify the beneficial effects of the soil amendments.The results are summarized in Tables XVIII and XIX below: TABLE XVIII Eckespoint C-1 Red Cultivar Total Weight Number of Number of Cutings and Cuttings from Small Branches Branches from Soil Treatment 12 pots %Increase from 12 Pots %Increase 6 Pots (g) %Increase Control Soil 42 - 60 - 82 Soil Plus 8 g/l 42 - 63 +5% 77 -6% Soil Amendment Soil Plus 12 g/l 54 +29% 68 +13% 122 +49% Viterra Hydrogel Soil Amendment Soil Plus 4 g/l 52 +24% 66 +10% 128 +56% Cross-linked Copolymer of Potassium Acrylate and Acrylamide TABLE XIX Dark Red Annette Hegg Cultivar Total Weight Number of Number of Cuttings and Cuttings from Small Branches Branches from Soil Treatment 12 pots %Increase from 12 pots %Increase 6 Pots(g) %Increase Control Soil 85 - 97 - 133 Soil Plus 8 g/l 95 +12% 108 +11% 137 +3% Viterra Hydrogel Soil Amendment Soil Plus 12 g/l 96 +13% 117 +21 177 +33% Viterra Hydrogel Soil Amendment Soil Plus 4 g/l 112 +32% 125 +29% 190 +43% Cross-linked Copolymer of Potassium Acrylate and Acrylamide The lower level of addition of Viterra Hydrogel Soil Amendment did not significantly improve the number of cuttings or their total weight. The higher level of addition of Viterra Hydrogel Soil Amendment did have a significant effect especially with the Eckespoint cultivar. The cross-linked copolymer caused a marked improvement in yield with both cultivars of poinsettia and at one third the rate at which Viterra Hydrogel Soil Amendment showed similar improvements.

EXAMPLE17 Four test plots of 40 inch raised beds with two rows per bed and 10 inch seed spacing were employed. The soil was a high clay content soil content found in the Salinas Valley, California. The seed sites were prepared with a dibble 3/4 inches wide by 1/2 inch deep. Each seed site was planted with one lettuce seed (CrHartnell) followed by one of the three subsequent treatments.

In one treatment, the control, approximately 1/2 teaspoon of vermiculite was placed on top of each seed in 50 sites and tamped firmly in to fill the sites in each plot. In the second treatment, the vermiculite was added admixed with about 0.025 grams of dry polymer also at 50 sites per plot. In the third treatment, approximately 1/2 teaspoon (about 2.5 g) of a hydrogel (about 0.01 g dry polymer) which had been fully preswollen in tap water was placed on top of each seed in 50 sites in each plot. The hydrogel was a fully swollen, cross-linked copolymer of potassium acrylate and acrylamide (having a ratio of monomer units potassium acrylate to acrylamide of 0.348).

The four plots were then uniformly watered with approximately 1/2 inch of water. Four rainless days after planting, germination/emergence counts were made with the following results: Control sites 0.5%Emergence Sites treated with dry polymer 3 0 % Emergence Sites treated with Hydrogel: 49%Emergence EXAMPLE 18 Cross-linked copolymer particles of potassium acrylate and acrylamide (having a ratio of monomer units potassium acrylate to acrylamide of 0.348) and a test coating in powder form, either dry or moistened and at concentrations of from 0.5 to 3 So by weight, were placed in a plastic bag and shaken vigorously to effect coating of the copolymer. The copolymer particles were sized between -10 mesh and 60 mesh.In each of seven tests, 3.2 gms of the coated copolymer particles were placed on and mixed with 200 cc of a moist field soil enriched with peat moss and humus.

The six coatings tested were the following: 1) super-hydrophobic fumed silica particles (sold under the trademark Tullonox 500 by Tulco, Inc. North Billerica, Massachusetts). The hydrophobic fumed silica particles had a nominal particle size diameter of 0.007 microns, a theoretical surface area of 325 m2/g, a surface area measured by nitrogen adsorption of 225 m2/g and a bulk density of 3 Ib/ft3; 2) a hydrophobic fumed silica (sold under the trademark CAB-O-SIL Type M-5 by Cabot Corporation).The fumed silica particles have an extremely small particle size and a large surface area ranging from 50 to 400 square meters per gram; 3) a hydrophobic fumed silica (sold under the trade name Silanox 101 by Cabot Corp., Boston, Massachusetts): 4) wood flour made from Douglas Fir (sold as grade T-100 by Menasha Corp., Oregon) and sized so that 99% passed through 100 mesh.The polymer particles were premoistened with 2% O/o by weight solution of polyvinyl alcohol to render their outer surfaces adhesive to the wood flour; 5) a diatomaceous earth filter powder which is hydrophilic (sold under the trademark Celite by Johns Manville Product Corp., Lampac, California) and sized so that 99%passed through 150 mesh; and 6) tale powder which is hydrophobic (sold as grade 127 by Whittaker Clark and Daniels, Inc., South Plainfield, New Jersey) and sized so that 99%passed through 120 mesh.

Observations were made on the effectiveness of each coating compared to an uncoated polyelectrolyte polymer of this invention in preventing the rapid adsorption of the soil mositure, forming clumps. Clumping would interfere with homogeneous mixing of the polymer particles with the soil. The results of these tests are summarized in Table XX below:: TABLE XX Effectiveness of Weight % Coating Compared Test Coating Coating Applied to Uncoated Polymer Hydrophobic fumed 1/2% very much better silica (Tullanox 500) Hydrophilic fumed 1/2% poorer silica (Cab-O-Sil) Hydrophobic fumed 1/2% very much better silica (Silanox 101) Wood Flour 3% better Diatomaceous Earth 1% equal to or (Celite) Filter slightly poorer powder Talc 1/2% slightly better While the various examples set forth in the specification were conducted using cross-linked copolymers of potassium acrylate and acrylamide as the polymeric component, the present invention is not limited thereto.The present invention contemplates the use of any of the previously mentioned cross-linked polyelectrolyte polymers as a soil amendment and as a component in the plant growth media composition of this invention.

The insoluble polyelectrolyte polymers used in this invention are not consumed to any significant extent by the plants themselves, but act as inert components in the plant growth media compositions until they absorb the soil solution and become a reservoir for plants. Due to their ability to incorporate or sorb organic and inorganic compounds and/or solutions of various solutes in aqueous or organic solvents within their matrix and release these sorbed agents to their surrounding environment and due to their ability to increase the air capacity of soils when swollen with such solutions, they have wide utility in the field of agriculture. The active agents mentioned previously are not chemically affected by nor do they react in any significant manner with the insoluble polyelectrolyte polymers.The polyelectrolyte polymers disclosed herein provide an efficacious and improved means for achieving the known functions of water and other known active agents or agricultural chemicals.

WHAT WE CLAIM IS: 1. A method of improving the water and air capacity of a soil matrix, the germination of seeds and/or the growth of plants and seedlings situated in said soil matrix, said method comprising admixing with each liter of said soil matrix up to 32 grams of a soil amendment comprising polyelectrolyte polymer particles rendered insoluble by cross-linking and sized between 8 mesh and 200 mesh (U.S.Standard Sieve Series), said polymer particles having a cross-link density so as to provide a swollen hydrogel as defined herein having a gel strength greater than 0.3 p.s.i. in the presence of an aqueous solution, and a ratio of ionic to non-ionic groups so as to be capable of reversibly absorbing and desorbing more than 100 times their weight in distilled water, more than 75 times their weight in a standard fertilizer solution as defined herein and more than 15 times their weight in a solution containing 500 ppm of calcium ions, each gram of said soil amendment being capable, in the presence of soil solution in said matrix, of reversibly absorbing and desorbing more than 20 times its weight of said soil solution providing, when swollen with said soil solution, hydrogel particles which increase the drainable pore size of said composition by more than 15 cubic centimeters.

2. A method of improving the germination of seeds, the early growth of seedlings and the growth of transplants comprising planting said seeds, seedlings and/or transplants into sites within a soil matrix suitable for their growth and depositing into said sites prior to or subsequent to said planting step a soil amendment comprising polyelectrolyte polymer particles rendered insoluble by cross-linking and sized between 8 mesh and 200 mesh (US Standard Sieve Series), said polymer particles having a cross-link density so as to provide a swollen hydrogel as defined herein having a gel strength greater than 0.3 p.s.i. in the presence of an aqueous solution, and a ratio of ionic to non-ionic groups so as to be capable of reversibly absorbing and desorbing more than 100 times their weight in distilled water, more than 75 times their weight in a standard fertilizer solution as defined herein and more than 15

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (33)

**WARNING** start of CLMS field may overlap end of DESC **. TABLE XX Effectiveness of Weight % Coating Compared Test Coating Coating Applied to Uncoated Polymer Hydrophobic fumed 1/2% very much better silica (Tullanox 500) Hydrophilic fumed 1/2% poorer silica (Cab-O-Sil) Hydrophobic fumed 1/2% very much better silica (Silanox 101) Wood Flour 3% better Diatomaceous Earth 1% equal to or (Celite) Filter slightly poorer powder Talc 1/2% slightly better While the various examples set forth in the specification were conducted using cross-linked copolymers of potassium acrylate and acrylamide as the polymeric component, the present invention is not limited thereto.The present invention contemplates the use of any of the previously mentioned cross-linked polyelectrolyte polymers as a soil amendment and as a component in the plant growth media composition of this invention. The insoluble polyelectrolyte polymers used in this invention are not consumed to any significant extent by the plants themselves, but act as inert components in the plant growth media compositions until they absorb the soil solution and become a reservoir for plants. Due to their ability to incorporate or sorb organic and inorganic compounds and/or solutions of various solutes in aqueous or organic solvents within their matrix and release these sorbed agents to their surrounding environment and due to their ability to increase the air capacity of soils when swollen with such solutions, they have wide utility in the field of agriculture. The active agents mentioned previously are not chemically affected by nor do they react in any significant manner with the insoluble polyelectrolyte polymers.The polyelectrolyte polymers disclosed herein provide an efficacious and improved means for achieving the known functions of water and other known active agents or agricultural chemicals. WHAT WE CLAIM IS:

1. A method of improving the water and air capacity of a soil matrix, the germination of seeds and/or the growth of plants and seedlings situated in said soil matrix, said method comprising admixing with each liter of said soil matrix up to 32 grams of a soil amendment comprising polyelectrolyte polymer particles rendered insoluble by cross-linking and sized between 8 mesh and 200 mesh (U.S.Standard Sieve Series), said polymer particles having a cross-link density so as to provide a swollen hydrogel as defined herein having a gel strength greater than 0.3 p.s.i. in the presence of an aqueous solution, and a ratio of ionic to non-ionic groups so as to be capable of reversibly absorbing and desorbing more than 100 times their weight in distilled water, more than 75 times their weight in a standard fertilizer solution as defined herein and more than 15 times their weight in a solution containing 500 ppm of calcium ions, each gram of said soil amendment being capable, in the presence of soil solution in said matrix, of reversibly absorbing and desorbing more than 20 times its weight of said soil solution providing, when swollen with said soil solution, hydrogel particles which increase the drainable pore size of said composition by more than 15 cubic centimeters.

2. A method of improving the germination of seeds, the early growth of seedlings and the growth of transplants comprising planting said seeds, seedlings and/or transplants into sites within a soil matrix suitable for their growth and depositing into said sites prior to or subsequent to said planting step a soil amendment comprising polyelectrolyte polymer particles rendered insoluble by cross-linking and sized between 8 mesh and 200 mesh (US Standard Sieve Series), said polymer particles having a cross-link density so as to provide a swollen hydrogel as defined herein having a gel strength greater than 0.3 p.s.i. in the presence of an aqueous solution, and a ratio of ionic to non-ionic groups so as to be capable of reversibly absorbing and desorbing more than 100 times their weight in distilled water, more than 75 times their weight in a standard fertilizer solution as defined herein and more than 15

times their weight in a solution containing 500 ppm of calcium ions said polymer soil amendment being deposited in its dewatered or water swollen hydrogel state, said hydrogel providing a reservoir of water in said sites for use by said seeds, seedlings and/or transplants, each gram of said soil amendment being capable of reversibly absorbing and desorbing more than about 20 times its weight in soil solution.

3. A method as claimed in Claim 1 or 2 wherein said polymer particles further include at leat one of the following materials: water, hydrocarbon oils, organic alcohols, ketones, chlorinated hydrocarbons, bentonite, pumice, china clays, attapulgites, talc, phyrophyllite, quartz, diatomaceous earth, fuller's earth, chalk, rock phosphate, sulfur, acid washed bentonite, precipitated calcium carbonate, precipitated calcium phosphate, colloidal silica, sand, vermiculite, perlite or finely divided plant matter.

4. A method of rendering plants more resistant to moisture stress comprising contacting the roots of said plants with an aqueous slurry of polyelectrolyte polymer particles rendered insoluble by cross-linking and sized beteen 8 mesh and 200 mesh (US Standard Sieve Series) said polymer particles having a cross-link density so as to provide a swollen hydrogel as defined herein having a gel strength greater than 0.3 p.s.i. in the presence of an aqueous solution, and a ratio, of ionic to non-ionic groups so as to be capable of reversibly absorbing and desorbing more than 100 times their weight in distilled water, more than 75 times their weight in a standard fertilizer solution as defined herein and more than 15 times their weight in a solution containing 500 ppm of calcium ions.

5. A method as claimed in Claim 4 wherein said aqueous slurry contains up to 10 percent by weight of a water soluble thickening agent.

6. A method as claimed in any one of Claims 1 to 5 wherein said polymer particles contain anionic groups.

7. A method as claimed in Claim 6 wherein said polymer containing anionic groups comprises one or more of the following polyelectrolyte polymers: (1) salts of polyethylene sulfonate, polystyrene sulfonate, hydrolyzed polyacrylamides, hydrolyzed polyacrylonitriles, carboxylated polystyrene, (2) salts of copolymers and terpolymers of acrylic acid, substituted acrylic acids, maleic anhydride, ethylene sulfonate with ethylene, acrylate esters, acrylamide, vinyl and divinyl ethers, styrene, acrylonitrile (3) salts of grafted copolymers where the backbone may be a polyolefin, polyethers or polysaccharide, and the grafted units, acrylic acid, methacrylic acid, hydrolyzed acrylonitrile or acrylamide, ethylene sulfonate, styrene sulfonate and carboxylated styrene, and (4) salts of polysaccharides modified by the addition of anionic groups.

8. A method as claimed in Claim 7 wherein potassium and/or ammonium is the cationic component of the associated anion in said polymer.

9. A method as claimed in any one of Claims 1 to 8 wherein said polymer comprises a copolymer of potassium acylate and acrylamide.

10. A method as claimed in any one of Claims 1 to 5 wherein said polymer particles contain cationic groups and are capable of reversibly absorbing and desorbing more than 15 times their weight in a solution containing 500 ppm of polyvalent anions.

11. A method as claimed in Claim 10 wherein said polymer containing cationic groups comprises one or more of the following polyelectrolyte polymers: (1) polyamines, quater nized polyamines, polyvinyl-N-alkyl-pyridinium salts, ionene halides, (2) grafted copolymers from polysaccharides, starch, cellulose, polyolefins, polyethers, and 2 hydroxy-3-methacryloxypropyltrimethylamm chloride, and (3) copolymers or quater nized copolymers of + HN(CH2-CH = Cm2)2, (CH3)2N(CH2CH = CH2) 2Cl, or

with acrylamide, acrylonitrile,ethylene or styrene.

12. A method as claimed in Claim 11, wherein nitrate is the anionic component of the associated cation in said polymer.

13. A method as claimed in any one of Claims 1 to 12 wherein said polymer particles further include an active agent as defined herein.

14. A method as claimed in any one of Claims 1 to 13 wherein said polymer particles further include a wetting agent.

15. A method as claimed in any one of Claims 1 to 14 wherein said polymer particles are sized between 10 mesh and 100 mesh.

16. A method as claimed in Claim 15 wherein said polymer particles are sized between 10 mesh and 40 mesh.

17. A method as claimed in any one of claims 1 to 16 wherein said polymer particles are coated with up to 5 percent by weight of a hydrophobic material as defined herein in finely-divided form.

18. A method as claimed in Claim 17 wherein said hydrophobic material comprises hydrophobic silica particles which have an average equivalent spherical diameter of less than 100 millimicrons and have a specific surface area of at least 50 square meters per gram.

19. A method as claimed in any one of Claims 1 to 18 wherein the polymer of the polymer particles has a ratio of ionic to non-ionic monomeric units of up to 0.5: 1.

20. A method as claimed in Claim 19 wherein the ratio of ionic to non-ionic monomeric units is from 0.3: 1 to 0.4:1.

21. A method as claimed in Claim 1 substantially as described in any one of Examples 1 tol0orl2tol6.

22. A method as claimed in Claim 2 substantially as described in any one of Examples 12 to 17.

23. A plant growth medium compositon comprising a soil matrix in admixture with a soil amendment comprising polyelectrolyte polymer particles rendered insoluble by cross-linking and sized between 8 mesh and 200 mesh (U.S. Standard Sieve Series), said polymer particles having a cross-link density so as to provide a swollen hydrogel as defined herein having a gel strength greater than 0.3 p.s.i. in the presence of an aqueous solution, and a ratio of ionic to non-ionic groups so as to be capable of reversibly absorbing and desorbing more than 100 times their weight in distilled water, more than 75 times their weight in a standard fertilizer solution as defined herein and more than 15 times their weight in a solution containing 500 ppm of calcium ions, up to 32 grams of said soil amendment being present in said composition per liter of said soil matrix, each gram of said soil amendment being capable, in the presence of soil solution in said matrix, of reversibly absorbing and desorbing more than 20 times its weight of said soil solution providing, when swollen with said soil solution, hydrogel particles which increase the drainable pore size of said composition by more than 15 cubic centimeters.

24. A composition as claimed in Claim 23 wherein said soil matrix comprises natural growth media.

25. A composition as claimed in Claim 24 wherein said natural growth media comprise peat moss, bark, sawdust, vermiculite, perlite, sand and any combinations or mixtures thereof.

26. A composition as claimed in any one of Claims 23 to 25 wherein said soil matrix comprises synthetic growth media.

27. A composition as claimed in Claim 26 wherein said synthetic growth media comprises glass beads, foamed organic materials, foamed inorganic materials, calcined clay particles or comminuted plastic.

28. A composition as claimed in any one of Claims 23 to 27 wherein said polymer particles contain anionic groups.

29. A composition as claimed in Claim 28 wherein said polymer containing anionic groups comprises one or more of the following polyelectrolyte polymers: (1) salts of polyethylene sulfonate, polystyrene sulfonate, hydrolyzed polyacrylamides, hydrolyzed polyacrylonitriles, carboxylated polystyrene, (2) salts of copolymers, and terpolymers of acrylic acid, substituted acrylic acids, maleic anhydride or ethylene sulfonate with ethylene, acrylate esters, acrylamide, vinyl and divinyl ethers, sytrene, or acrylonitrile, (3) salts of grafted copolymers where the backbone may be a polyolefin, polyethers and polysaccharide, and the grafted units, acrylic acid, methacrylic acid, hydrolyzed acrylonitrile or acrylamide, ethylene sulfonate, sytrene sulfonate or carboxylated styrene and (4) salts of polysaccharides modified by the addition of anionic groups.

30. A composition as claimed in Claim 29 wherein potassium and/or ammonium is the cationic component of the associated anion in said polymer.

31. A composition as claimed in any one of Claims 23 to 30 wherein said polymer comprises a copolymer of potassium acrylate and acrylamide.

32. A composition as claimed in any one of Claims 23 to 27 wherein said polymer particles contain cationic groups and are capable of reversibly absorbing and desorbing more than 15 times their weight in a solution contianing 500 ppm of polyvalent anions.

33. A composition as claimed in Claim 32 wherein said polymer containing cationic groups comprises one or more of the following polyelectrolyte polymers: (1) polyamines, quaternized polyamines, polyvinyl-N-alkyl-pyridinium salts, ionene halides, (2) grafted copolymers from polysaccharides, starch, cellulose, polyolefins, polyethers, and 2-hydroxy-3-methacryloxypropyltrimethylammonium chloride, and (3) copolymers or quaternized copolymers of