CA1134981A - Amendment for modifying soil matrices - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Amendment for modifying soil matrices comprising an insoluble polyelectrolyte polymer which, upon addition to a soil matrix, can markedly increase not only the water capacity but also the air capacity of the amended soil matrix.

Description

~ ~34~ o,805 BACKGROUND OF_THE INVENTION
1. FIELD OF THE INVENTION
This invention relates to water-insoluble poly-electrolyte polymer soil amendments and methods for modify-ing soil matrices. In another aspect, this invention relates to novel compositions for modifying plant growth. The novel compositlons include a soil matrix and/or active agents~or agricultural chemicals incorporated wLthin or admixed with polyelectrolyte pol~mer particles rendered in-solublc by cross-linking.

2. DESCRIPT_ON OF THE PRIOR ART
Various treatments ~or soil are known in the prior art, Organic, polymeric additives have been mixed with soil to improve the soil struc~ure (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 copolymers and salts of copolymers of maleic acid anhydride and ~inyl esters, to produce aggregation of ~ine soil 2n particles to form crub-like granules. Aggregation improves the porosity and permeability of soils, especially clay soils which are inclined to form crusts upon cycles of i wettLng and drying. And U.S. Patent 2,889,320 discloses ~he use of non-polyelectrolytes such as N-me~hylol poly-acrylamide to produce aggregation of fine soil particles, In general, these natural or synthetic organic polymers are all substantially soluble in water.
Insoluble and hydrophilic organic polymers have been admlxed with soil to improve its water capacity. In - 2 - ~ ~
, . .. ..

10,~05 ~ ~ 3 ~

general, these polymers ~well when soil is irrigated ~nd retain large amounts of water, thus moderating the stress on plan~s 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 ,~s chemically modified starches or partially hydrolyzed cross-linked polyacrylamides as means to increase water capacity of soils has been dls-closed in U.S. Patents 3,336,129 and 3,900,378. Other known insoluble polymers for increa~ing water capacity of soils include phosphorylated polyvinylacetate resin and acid soluble acrylonitrile polymers treated with metal ions such as Al, Fe and alkali e~rth metaLs to produce a metal ion-polymer complex.
It has now been discovered that water-insoluble, polyele~trolyte polymers in particulate form may be employed to increase both the wa~er capacity and air capacity of growth media compositions. Moreover, it has also been dis-covered that the water-insoluble, polyelectrolyte polymer particles of this inYention are stable in such compositions.
Accordingly, it is an ob~ect of this in~ention to provide an improved soil amendment for increasing the 2ir and water capacity o~ soil matrices comprising polyelectrolyte polymers w~ich are cross-linked to render ~hem water ~nsolu-ble. Another object is to provide an improved growth medium composition which aids germination of seeds, contributes to growth of young plants and seedlings which are through its use subjected to less moisture . ~ , . .. ... ..

10,805 ~ ~ 3~

stress, has an increased air and water capacity, thereby increasing aeration and soil solution capacity, aids growth of plant life under water-deficient conditions, effectively permits the utllization of. natural plant nutrients already present in the composition, effectively permits the use of fertilizers added to the composition, decreases loss of transplanted seedlings and permits the efficient utiliza-tion o~ plant grow~h modiying agents and plant protectants such as fungicides, insecticides, nematocides and the like.
It is another object of the present invention to provide improved growth media compositions containing active plant growth modifiers,w~ich compositions p~rmit more effi-cient use of active plant growth modifiers, in subsur~ace application techniques and soil and root applications. Still another object is to provide a method of promoting the ~ur-vival a~d growth of plants by contacting the plants with the soil amendment of this invention, the amendment optionally containing active plant growth modi~iers. Another object of this invention is to provide soil matrix amendments having the ~apacity to reversibly and repeatedly absorb water and/or controlled amounts of solutions and then releasing them to the soil gradually. It is a further object of this inven-tion to provide a novel coated soil amendment whose coating facilitates its admixture with soil matrices containing minor to major amounts of water.

:

10,805 ~ N
The soll matrix amendments of thls invention com-prise water-insoluble polyelectrolyte polymers in particulate form. The polyelectrolyte polymers can repeatedly and re-versibly 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 polyelectroly~e polymer particles of this ln-vention are characterized by having a particular size distri-bution in their dewatered state. They are fur~her character-ized by having par~icular water capacities in a standard fertilizer solution and in a solution containing about 500 parts per million tppm) of calcium ions and in their hydrogel state, a particular gel strength. In another embodlment, the 90il matriæ amendment of this in~en~ion compr~ses ~ater-in~olu~le, polyelectrolytQ polymer particles a~ described herein admixed with up to 5 perc~nt by weight of a hydro-phobic material in an extremely finely divided form.
The plant growth compositions of the presen~ in-vention comprise up to about 2 pounds of particulateg insoluble, cross-linked, polyelectrolyte polymer in admix-ture wi~h a cubic ~oot of soil (32 g/l). In another .
embodiment of this invention, the plant growth compositions ' 107~05 ~'~ 3~

comprise up to about 2 pounds of a particul~te, insoluble, polyelectrolyte polymer coated with up to about 5 percent by weight of a particulate hydrophobic material admixed with a cubic foot of soil (32 grams p~r liter). In addition, the plant growth compositions of this inventiorl may alter-natively contain ac~ive agents, such as water, fertilizer, herbicides, fungicides~ n~atocides and/or insecticid~s~
soil condltioning agents, such as sawd~st and synth-etic soil condi~ioning agents such as soil aggre~ating polyelectrolytes 0 ~8 well ~8 ~ther materials ~ubse~us~tlY di~cu~sed.
The soil amendment o this invention which com-prises insoluble, polyelectrolyte polymer p~rticles or such polymer particles coated with up to about S weight p~rcent of a hydrophobic material, may have an active agen~ incor-poratad in the polymer In addition, the soil amendment may alternately contain or be admixed with known diluents, wetting agents, and sur~actants. Further, the soil amend-ments, without the addition thereto of soil 9 iS amenable ~or use as growth media, especially in rooting of plant cuttings and germination o~ seeds.
DETAILED DESCRIPTION OF THE INVENTION
A more detailed understanding of the invention will be had by reference to the drawings, the followlng description and the appended claims.
FIGURE 1 is a greatly enlarged schematic represen-~ation of a modified soil matrix of this inventlon containing polyelectrolyte polymer particles in a ~ewater.ed state~
FIGURE 2 is a greatly.enlarged schematic represen~a-10, ~05 ~L~3~g81 tion of the modi~ied soil matrix o~ FIGURE 1 illustrating the polyelectrolyte polymer particles in a water-swollen state.
As hereinbefore indicated, the novel soil mat~ix modifying agents and/or compositions o~ this invention com-prise an insoluble polyelectrolyte polymer. By the term "polyelectrolyte", as employed in the speci~icat1On, iq 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 speci~ication -is meant an insoluble organic compound whi~h has absorbed aqueous fluids and is capable of retaining them under moderate pressures. As previously mentioned, the insoluble poly-electrolyte polymers are defined as hydrogels when they are in the state o~ having absorbed an aqueous media.
The term "insoluble" or "insolubilize" as employed throughout the specification are used herein to re~er to the formation of a material~ at least about 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 e~fected by a wide variety of known methods and includes, but is not limited to, îonLzing and non ionizing r~diation, and cross-linking through covalent, ionic and other types of bonds.
By "standard fertilizer solution" as used through-out the specification is meant a 200 ppm (N) 20-20-20 N, p2Os, K~0 solution.

~0,~05 In practice, a large number of polyelectrolyte polymers can be employed to modi~y soil matrices and/or to prepare the novel compositions of this invention. An important requirement of the particular polyelectrolyte polymer chosen is that it be~capable of absorbing relatively large quantities of aqueous liquids, preerably more than one hundred (100~ times its weight in distilled water, more than seventy-five (75) times its weight in standard ferti-lizer solution, and more than fifteen (15) times its weight in a solution containing ive hundred (500) parts per million (ppm) of calcium io~s. This includes organic polymeric compounds such as those polymers which are cross-linked by covalent, ionic, Vander Waal forces, or hydrogen bonding.
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 ter-polymers of acrylic, substituted acrylics, maleic anhydride, ethylene sulfonate with ethylene, acrylate esters, acryla-mide, vinyl and divinyl ethers, styrene, acrylonitrile and and the like, (3) salts of grafted copolym rs where the backbone may be a polyolefin, a polyether, a polysaccharide, and the like, and the gra~ted units, acrylic acid, methacry-: lic acid, hydrolyzed acrylonitrile or acrylamide, ethylene 10,805 sulfonate, styrene 6ulfonate~ carboxylated styrene ~nd the like, ~nd (4) salts of polysaccharides modified by the addition of anionic groups. Potassium and!or am~onium i8 preferred as the cationic component of the associated anion.
It is believed the novlel polyeleetrolyte polymers of this in~ention also include tlhe following polymers contain-ing ca~ion~c groups: (1) polyamine salts, qua~ernized polyamine salts, polyvinyl-N-alkyprldinium ~alts, salts of ionene halides such as those ~rom 3-dimethylamino-n-propyl chloride, (2) salts of grated copolymers from materials such as polysaecharides, starch, cellulose and the like, polyolefins, polyethers and the like, and 2-~ydroxy-3-methacryloxypropyl~rirnethylammoni~n chloride, and (3) salts of copolymers or quaternized copolymers of compounds such as HN(CH2-CH-CH2~2, (CH3)2 Ntc~2cH=cH2) C~12~C-COO CH2CH2N(C~3)3CH30S03, acrylamide, acryloni~rile, ethylene, styrene and the like.
Nitrate is preferred as the anionic component ~f ~he associated cations descr~bed above.
The pH of the polyelectrolyte polymers of this in ~ention is bet:ween about 6 and about 9.
Xt should be not2d 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 10,805 ~ ~ 3 ~
more polyelectrolyte polymers. Additionally, it is also possible to employ salts Oc co-cross-linked copolymers of the previously listed polyelectrolyte polymers or compounds similar to these. For example, salts of copolymer~ of acrylic acid ~nd acrylamide and minor or ma;or amounts of salts of o~her copomymers can also be used.
A9 previously described, ~he polymer is in par-ticulate ~orm) thus by ~he term "polymer partlcle" as employed throughout the speci~ication is meant a single particle or an aggregate of several sub-particles~
As mentioned previously, the insoluble polyelec-trolyte polymers can be prepared by a number o~ me~hods including chemical cross-linking and croqs-linking induced by ionizing radiation. Particular methods of rendering various polyelectrolyte polymers insoluble and possessive o~ the requisite characterisitcs of this invention is not in itself a cri~erion by which certain polyelectrolyte polymers are judged to be operable in the presen~ invention; that is any insoluble, polyelectrolyte polymer possessing the re-quisite characteristics ~s amenable for use in the present invention regardless of the manner in which it is.produced.
Suitable methods are well-known and understood by ~hose 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 c~polymer is saponified with an aqueous methanolic or aqueous ethanolic ~' 10,805 ` ~ 3~

solution o~ 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 watPr in amoun~s in excess o~ 50 parts per part of polymer while retaining their ~ranular character. This process can be modified to provide a c:opolymer suitable for this in-vention, the copolymer retaining a substantial fraction of its water capacity in ~ solution containing 500 ppm o cal-cium ions. Saponification and consequently the number of lonic groups produced must be controlled in the modi~ied process. Control of saponi~ication is by conventional methods (such as time, temperature, a~ount of base added, etc.) U.S. Patent 3,670,731 also discloses hydrocolloid absorbent materials such as a cross-linked sulfonated, polystyrene or a hydrolyzed linear polyacrylamide cross-linked with a nonconjugated div~nyl 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 pre-sence o~ peroxide catalysts or by photo polymerization, such as for example3 with ribofla~in activator. O~her methods of af~ect~ng insolubilization and cross-linking of polymers are indioated in U.S Pa~ents 3,090,736; 3,229,769 and 3,669,103.
In addition to the aforementioned methods, another known m2t:hod is to subject a water-soluble polyelectrolyte to sufficient ionizing radiation to cross-link and insolubi-lize it thereby forming a water-insoluble hydrophilic 10,805 ~ 3 polyele~trolyte, 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 301vent is employed) but which does not have su~ficient energy to a~fect the nuclei of the constituent atoms. Convenient sourceæ of suitable ionizing radiation are ga~ma ray producing radio-active isotopes such Co60 and Cs~37, spent nuclear ~uel elemen~s, X-rays, such as those produced by conventional X-ray machines, and electrons produced by such means as Van de Gra~f acceIerators, linear electron accelerators,-resonance trans~ormers and the like. Suitable ionizing radiation for use in the pre~ent in~ention 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 polyclec-trolytes can be carried out in the solid phase or in solution.-Solid polyelectrolytes can be irradiated in the air, in a vacuum, or under variou3 gaseous atmospheres, while irradia-tion in solution can be carried out with t~e water-soluble-polyelectrolyte dissolved in water, in organic so~vents of high dielPctric 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.

:

.. . , ~ . . .. . . . .. . . . .

10,805 ~ ~ 3~

The above described methods and other methods ~or preparing cross-linked, insoluble polyelectrolyte polymers known to those skilled in the art may be employed to prepare the polymers of this invention. Minor modification~ of reactant ratios, saponification conditions, reaction para-meters, radiation dose, etc., may be necessary to produce compounds which have the proper physical and chemical properties. For example, control of cross-link density ean be used to prepare compounds with gel strengths greater than 0.3 p.s.i.; the ratio o~ lonic to nonionic groups can be controlled so that a compound with the proper water absorbing abili~y and the ind~cated stability ~oward poly-valent cations such as calcium is produc~d.
As employed throughout the specification, th~ ~erm "soil matrix" refers to any medium in which plants can be grown and whic~ provides a means for support, oxygen, wa~er and nutrients and may comprise the following or various mixtures thereof: ~1) natural grow~h media romprised of dislntegrated and decomposed rocks and minerals mixed with organic matter i~ all stages of decay plus other components which may have been added as fertilizers and (2) unnatural growth media such as glass beads, foamed organic materials - such as f'oamed polystyrene or foamad polyurethane, foamed ; inorganic materials, calcined clay particles, comminuted plastic or the like. Examples of natural growth media included within ~he defini~ion of soil matrix hereinabove are peat moss, b?rk, sawdus~, vermiculite, perllte, sand and any combinations or mixtures thereof, The term "soil"

and soil matrix are interchangeably 2mployed throughout -13~

~ ~ 3 the speclfication.
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, dlssolved salts and dissolved gases. These ph~ses are defined by a multiplicity o~ minute mineral and organic particles packed together to comprise a semi-rigid sponge-like mass. The spaces or pores be~ween the particles form a substantially interconnected network of channels or tunnels which permeate the soil mass. The amount of soil pore space or 90il porosity determines how much 90il 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 draingage. The same factors are also important in determining the rate of water movement through soil matrices, and/are also especially impor~ant to insure adequate aeration in container soils.
These factors may be effectively regulated through additions o~ the soil amendments o~ this lnvention as subsequently discussed.
Soil aeration is the exchange of oxygen and carbon dioxide between the soil and above-ground atmosphere.
This exchange, which occurs primarily through non-water filled or open soil pores, is essential to maintain an oxygen supply ~or root growth and absorption. Poor soil aeration . . . . . .
, .. ~. , . ,, .. : .,.. : ; ; ... . .

10,805 -~ ~3 ~

causes poor root grow~h, poor water and nutrient absorption, and greater suceptibility to soil pathogens.

In order to grow plants in a soil matrix, water is necessary. Yet, there must be good drainage o~ the w~ter 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 pro-v~de high water capacity but can cause poor drainage and aeration, Hence, aggregate materials 9 such as sand, vermiculite, perlite, bark, wood chips, pumic and the like are typically added to increase the drainage and aeration~

However, not all water in the soil matrix is available to the roots of plantsO Components such as peat mo~s, which easily sorb water do not easily release it all to the plantO Hence, it is the available water or water potential of the soil solution in a soil matrix that ls important.
Water potential corresponds to a thermodynamic ; 20 free energy of water, i.e., energy per unit massO Per unit volume, it has the same dimen~ions of pressure. Therefore, it ifi 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 plan~ has a small negative potential.

10,805 ~ ~3 ~

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 lt. The surface tension of water in capillaries is another effect which lowers water potential~ Each o~ the physlcal 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 i9 ~looded or saturated with water, the water potential of the 90il matrix approaches the zero value of pure water and plants thrive. When a soil matrix is almost dry, the remaining wa~er has a hlgh negative ~alue, 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 permanent 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 leqs 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 avai.lable to plants prior to wilting .
- 16 ~

10,805 On the other hand, it has been found t~at the water held by the soil amendments of this invention is very avail-able to plants, i.e., about ~inPty-five percent (95%) can be used prior to reachin~ ~he permanent wilting point. Thus, the addition of the soil amendments of this invention to a soil matrix increases the ability of the amended 50il 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 wLthout addltional irrigation.
Any soil matrix contains a large proportion o~
pore ~paces of varied size dependent on the components tha~
comprise the soil matrix~ Many o~ these pores are very small and, subsequent to watering, do not drain. The per-centage of the non-draining pores, by volume, is called the water capacity (Cw) of the soil matrlx. Some of the larger pores do drai~, and therefore flll with air. The percentage of the air contained in the drained pores by volume, is called the air capacity (Ca)O Ideally, a soil matrix should have a water capacity of at least sixty-five percent (65%), i.e., 0.65 cc of water per cc o~ soil matrix, and an air capacity of at least twenty-~ive percent (25%), i.e., 0.25 cc of air per cc of soil matrix.
: ' :: :
' .

10,805 ~ ~ 3 ~

However, it is wel:L known that adding components to the soil matrix which ~ncrease its water capacity generally decrease its air capacity and vice versa. The basic physi-cal relationship between the water capacity and air capacity o~ a soil matrix is dependent on the pore size distribution In general, increases in average pore size increase air capa-city and decrease wa~er capacity and ViC2 versa. It has been discovered that additions of the polyelectrolyte polymer amendments of this invention to a soll 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 composi~ions of this invention. The increase in air capacity o~ the growth media compositions 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 particlesO And yet, it has been found that water capac~ty of the composition does not decrease. Indeed, the wa~er capac~ty increases due to the readily avaLlable water carried in the swollen hydrogel particles as subsequently discussed.

Referring to FIGURE 1, there is shown a soil matrix 10 comprlsing a multiplicity of soil particles 12 ~ randomly aggregated to form a sponge-like mass having pores :
~ .

lO,805 ~ ~ 3 ~

14 between ~he particles 12 forming a generally interconnec~ed network of channels which permeate the Roil ma~s. Also randomly distributed throughout ~he m~trix 10 are the poly-electrQlyte polymer part~cle~ 20 of this ~nvent$on in a dewa~ered (u~swollen) ~tate ~n FIG~RE 1 a~d in a water-swollen state in FIGURE 2. A~ previously di~cu~sed, ea~h polymer par~icle o~ this inven~ion is capable o~ absorbing large quant~ties o~ squeou~ liquids.
The ~d~ition of the poly~lectroly~e polymer amendments of this invention in particulate form to ~ soil matrix increases the water capacity of the 80il matrlx. This ~s due to each polymer partlcle absorblng large quantiti~s of water and swelling accordingly as illus~rated ln FIGURE 2, The basic soil matrix is still capable of reta~ning ~ large rac~ion of ~he water it would normally hold in the absence of the polyelec~rolyte hydrogel par~icles.
~oreover, it has been disco~ered that the swelling of ~he polymer particle~ to prvduce hydrogel particles actually increases the ~olume of the soil matrix p~esumably 29 by m~king their own pore space~. The swollen hydrogel particles ~re rigid enough to support the we~ght of the 60~1 matrix thereby not only creating site~ or themselves, but due to :~
the irregularltles in tbeir shapes as we11 as the æhapes of ~ ~' ' 10, ~O.S
~ ~ 3~

the soil particles, pushing the soil particles ~arther apart from each other and thereby Lncreasing the overall open pore volume of the soil matrix.
The phenomenum described above is illustrated in FIGURES 1 and 2 by referring to soil particles 12a - 12f and polymer particle 20a. In FIÇURE 1, the initial position of the respective particles i9 illustrated where~n particle 20a is surrounded by soil particles 12a - 12~ 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 ln a d~watered (unswollen) state. In FIGURE 2, howe~er, after absorbing an aqueous media, polymer particle 20a is shown in a water-swollen state (as a hydrogel particle)~ The swollen particle 20a has pushed the soil particles 12a -12~ to posi~ions 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. More-over, swollen hydrogel particle 20a now is in contact with particles 12b, 12c, 12d and 12~ s swelling and gel ~ :
strength has aff~ected the relative positioning of the sur-rounding particles 12a - 12fo :
Hence, it is believed that the increase in the air~ apacity (free pore volume) of the growth media composi-tion occurs through the creation of voids in the soil matrix .
by the swelling~of the polymer particles. In essence, the 10,80S
~3~

swoll~n hydrogel particles seem to ac~ as an aggregate such as perlite except that they are essentlally all.water, The fac~ that the hydrogel particles are essentially all water accounts for the increase in water capacity of the growth media composition.
The marked morphological changes in soil matrices that accompany the addition of the soil matrix amendments of this invention are features which distinguish them from soil amendments which only increase water capacity bu~ have l~ttle or no e~fect 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 reduce khe ability o~ 80il8 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 drain-able pore space. Oten, they simply fill existing pores in ~soil thereby decreasing air capacity of the soilO 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 composition.
In practice, it has been found that in order to maximize air capacities of the ~rowth media composition by means of the soil amendments of this inv~ntion, it is neces-sary to control particle size and gel strength within :

. .

~0,805 specified limits. It has been observed that the polymer particle size distribution prior to their admixture with the soil matrix should be such that essentially all particles in a dewatered state are smaller than about 8 mesh, pre~erably smaller than about 10 mesh, as measured on U.S. Standard Sieve Series. Also, essentially all o ~he polym~r particles of this invention are sized larger than about 200 mesh, preferably larger than abou~ 100 mesh and most preferably sized larger than about 40 mesh (U.S. Standard Sieve Series~.
The size distribution of the polymer particles may be ob-tained by conventional methods such as grlnding larger particles or aggregation of smaller particles.

The (water-swollen) hydrogel particles of this invention should have a gel strength of greater than about 0~3 p~ s oi~ Gel strengths are measured in the following manner, A 20 mesh (U.S. Standard Sie~e Series) s~ainless steel Ycreen is attached to cover the mouth of a cylinder, Approximately 100 grams o~ hydrogel particles swollen to equilibrium in excess tap water i9 added to the cylinder.
The part~cle size of the swollen hydrogel must be larger than the ~ore size of the screen. For example, a polymer particle having a size greater than 80 mesh (U.S. Standard Sieve Sesies), i.e., it is stopped by an 80 mesh screen, normally will swell to a size larger than 20 mesh. There-fore, the swollen~hydrogel will not pass through the screen until pressure is applied.

- ~2 -10,8~5 ~ ~3~ 8 ~

The pressure neecled to extrude the hydrogel through the screen is determined by applying a piston toward ~he screen and a series of wei~shts 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 poin~ at which the hydrogel continuously ex~rudes through the 20 mesh (U.S. Standard Sieve Series) screen. This pres-sure is termed gel strength.
The advantages of the soil amendmen~s of ~his in-vention are measured by increases in water and air capacitie~
o~ soils with which the amendment has been mixed co~pared 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 samplP. The air capacLty of soîl is its total pore volume minus the water filled pvres.
The total pore volume is determined from the wet bulk d~nsity and particle density of the soil matrix. In evaluat-ing 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 ~ollows:

T = (1 - ~_) 100 wherein P ,.~

T = total pore volume percent Db = bulk density, i.e., dry soil weight divided by soil volume , , . . , . . . . ~ .. ~ -

3 ~
10,805 Dp 8 particle density, i..e., specific gravity o the ~oil mix ~ater and air capac~ies may be expressed as ~ol- :
lows:

CW 8 percent water ~ olume of water (cc~ x 100 capacity 80il volume (cc) Ca ~ percent air capacity ~ T ~ Cw The increase in water and ~ir content per unit weight of amendment ~ay be e~pressed as ~ollows:

Xw'(R water ~ d 80i~-(g water held by control soil ~ ~oil ~mendment and Xa~
g ~oil amendment The polyelectrolyte hydrogels of the present in~ention ~imul~
taneously increase both the percen~ air and percent water capacity o~ a ~oil matrix. Increases of ~ of greater than bou~ 20g wa~er/g smendmen~ are typically achieved, inereases of greater ~han about 30g w~ter/g amendment are preferred, ~nd increases of greater than abou~ 40g wa~er/g amendment : are mos~ preferred. Increases of Xa of greater than abou~ `~
15 cc air/g of ~mendment are typically 2ehieved, increases greater than ~bout 25cc air/g of amendment are pre~errPd and increases of greater than about 35cc ~ir/g of amendment :
are most preferred.

: - 24 - :

.

10,805 ~ ~ 3~

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 æeparate the charge as much as possible, The actual water capacity is controlled by a number o~ ~ac-tors, many of which can interact. The more important ones are (1) chemical composition, (2) charge densi~y (mole ~rac-tion 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 configura-tion, 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 wa~er, but the capacity would drop to 200 to 300 in a normal strength solu-tLon of soluble ~ertilizers.

. - 25 -~ 10,~05 Another related factor is cross-linking by multi-valent ions, i.e., reactions of polyanions with multivalent cations and reactions of polycations with multivalent anions.
As the cross-linking occur~s, the polymer progressively loses its ability to swell and retain water. The extent of cross-linking is a function of the number and closeness o~ the charged groups and the multivalent ion concentration. Based upon tests and observations, the polyelectrolyte polymers o~
this invention can be characterized as having a ratio of ionic to non-ionic groups and cross-link density sufficient to absorb more than about 75 ~imes their weight in a standard fertilizer solution and more than about 15 times their weight in a solution containing 500 ppm o~ 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 o~ thi~ invention should be up to about l, preferably up to about 0.5, and most preferably between about 0.3 and about 0.4 The problem of multivalent ion cross-linking is particularly acute when the polyelectrolyte polymer amend-=ents are admixed in a soil matrix. Soil solutions routinely contain excessive amounts of cat;ons such as calcium ions and other multivalent ions particularly as the soil dries out. And calcium cross-linking is substantially irreversi-ble. Yet, the polyelectrolyte polyme~s of this invention have been found to have water capacities grea~er than abou~

15 times l:heir weight in so;l solutions containing 500 ppm of Ca++. And lt is believed that the polyelëctroly e polymers containing cationic groups have water capacities greater than about 15 times their weight in soil solutions containing 500 ppm of polvvalent anions such as sulfate, carbonate and the like.

10,805 Sti~l another factor is the molecular weight between cross-links, or the cross-link density. The distance between cro~s-links in the polyelectrolyte polymers of this invantion is directly related to their water capacities.
Larger distances provide larger water capacitles.
In another embodiment, the soil amendment of this invention comprises an insoluble polyelectrolytc 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 parti-cles of thls invention. This enables a small quantity of the hydrophobic particles to provide a thin coating o~ the outer sur~ace of a much lar~er amount of polymer particles.

The ~urface treatment of the polyelectrolyte polymer partic:Les may be conveniently accomplished by physically admixing the polymer particles with up ~o abou~
five (5~/O) percent by weight of the hydrophobic fine partlcles to produce surface treated polymer particles wherein hydro-phobic fîne particles physically adhere to the outer suraces of the polymer particles~ It is theorized that the extremely iine hydrophob:ic particles coat or otherwise cling to the 10,~05 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, shoveling and the like.
It has been found that the surface coating o~
hydrophobic particles is either physically removed or rendered ineffective in the soil. The in situ removal or inefectiveness of the hydrophobic surface coating occurs a~ter irrigation of the soil admixture. This is consistent with the theory of an elec~rostatic attraction between the polymer particles and hydrophobic fine par~icles since the presence of polyvalent cations or anions tends to interrupt or break down an electrostatic attraction. Hence, it is believe~ that once thoroughly admixed with the soil, the electros`tatic attraction between polymer particles and hydrophobic particles tends to be broken town by the presence of multivalent ions in the soil. Once the surace coating is removed, the polymer particles can function normally and effectively as a hydrophillic material.
It is usually diff~cult to admix uncoated poly electroy:Lyte polymer particles with damp or wet soil. The polyelect:rolyte par~icles 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 c~ntent is substantially greater than ~bout five (5%) percent aqueous media by volume o~ the soil. It is increa~ingly 10,805 ~ L3~f~

difficult to admix uncoated polyelectrolyte polymers with soils approaching the equilibrium drain value (field capacity). These problerns are substantially obviated by the use of the surface coated polymer particles of this invention.
Suitable hyd~ophobit fine particles include talc, wood flour, hydrophobic silica particles such as those described in U.S. patents 3,661,810 and 3,710510, 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 o~ less than about 100 millimicrons with a surface area greater than about 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 know in the art. As employed herein, the term "active agent" is de~ined to mean those material~, organlc, 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.

;' .

10,805 ~ ~ 3~

The active agent:s which can be incorporated in the grow~ media compositions o the present invention include water; fertilizers, including all elements and combinations of elemen~s 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 sul~ate; bacterlcides, 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, disul~ides, thiocarbamates, meruric compounds, tetrahydrophthalimides, arsenates, cupric compounds, guani-dine salts, triazines, glyoxalidine sal~s, quinolinium salts, ; and phenylcrotonates; germicides~ including quaternary : 20 ammonium salts, phenolics, quaternary pyridinium salts, peracids, and formaldehyde; herbicides, including sulfamates, trazines, borates, alpha haloacetamides, carbamates, sub-s~ituted phenoxy acids~ substituted phenoxy alcohols, halogenated aliphatic acids and salts, substituted phenols, , 10,805 arsonates, substituted ureas, phthala~es, dithiocarbamates, thiolcarbamates, disul~ides, cyanates, chlorates, xanthates, substituted benzoic acids, n-l-naphthylphthalamic acid, allyl alcohol, amino triazole, hexachloroacetone, maleic hydrazide, and phenyl mercuric acetate; insecticides, including natural products (such as pyrethrins), a~senicals and arsenites, fluosilicates and alminates, benzoates, chlorinated hydrocarbons, phosphates, cresosote oil and cresylic acid, phosphorothionates, thiophosphates, phos-phonates, phosphoro-mono- and dl-thioates, xanthones, thiocyano-diethyl ethers, fluorophosphines, pyrrolidines, phosphonous anhydride, thiazines, carbamates, chlorinates, terpenes, tartrates, ~hallous sula~e, and anabasis;
miticides, including sulfonates, sul~ites, azobenzines diimides, benzilate, sulfides, phosphoro-dithioates, sub-stituted phenols and sal~s, chlorophenyl ethanols, phos-phonates, oxalates, sulphones, chlorophenoxy methanes, selenates, and strychnine; nematocides, including halogenated propanes and propenes, dithiocarbamates, phosphorothioates, : 20 and methyl bromide; insect repellents, including poly-propylene glycols, succinates, phthalates, furfurals, asafetida, ethylhexanediol, and butyl mesi~yl oxide;
rodentici.es, including 2-chloro-4-dimethylamino-6-methyl : pyrimidiney fluorides, coumarins, phosphorus, red squill~
arsenites, and indandion; and synergists, including carboximides, piperonyl derivatives, and sulfoxides.

~3~3~ lo ~ ~os The novel soil amendmen~ In addi~ion to the aforementioned active agents can, if desired, include one or more materials whlch m~y or may ~ot affect, directly or indirectly, plant growth~ The l~quid materiRls include w~ter, hydroc~rbon oils, ~rganic alcohols, Icetones, ~nd chlorlnat~d hydrocarbons. The solid include bentonite, pumice, china clays, attapulgites, talc, pyrophyllite, quartz, diatomaceous earth, fuller's earth, chalk, rock phosphate~ sulfur, acid washed bentonite, pre-cipitated calcium carbonate, precipitated c~lcium phosphate, colloidal silica, sand, vermiculite, perlite, and f~nely ~round plant parts, such as corn cobs. The soil amendments can, if desired, i~clude wetting agents such as anionic wetting agents, non-ionic wetting Agents, cationic wetting flgents3 including alkyl aryl sulfonates, polye~hylene glycol derivatives, conve~tional soaps, amino soaps, sulonated animal~ vegetable and mineral oils, quaternary salts of high molecular weight acids, rosin soaps, suluric acid salts of high molecular weight organic compounds, ethylene oxide condensed with ~atty acids~ alkyl phenols and mercap-tans.
The plant growth media composit~on comprises 50il and ~he particula~e, cross-linked polyelectrolyte polymers of the present ~nvention. A polyelectrolyte hydrogel or polymer can be applied to the surface of the soil or incorporated int:o the soil to form a mixture of ~oil and cross-linked polyelectrolyte hydrogel or polymer, respec-- 3~ -10,805 ~'~3~ 8 ~

tively. Numerous variations of the basic composition are possible. For instance, the growth media composition can comprise a mixture of soil and dry, particulate, cross-linked polyelectrolyte po:Lymer per se. The polyelectrolyte polymer will sorb water during rainfall or irrigation.
The sorption of water by the polyelectrolyte pol~ners pre-vents excessive loss of water. Naturally occurring nutrients in the soil are solublizied in the 90il water and also sorbed by the polyelectrolyte polymers; here the polyelec-trolyte 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 o~ moisture and oxygen ~nto the subterranean growing areas. Moreo~er, as prevLously discussed a major advantage of adding the poly-electrolyte polymers ~ 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 be~efit for amending the soils employed in containers~ It is well known in the art that container soils pose a peculiar problem beeause of their relatively short soil column brought about by the shape of the con-tainer. 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 lOt~05 ~ ~ 3~

table. A common method to alleviate this problem is to use a large proportion of an aggregate such as perlite, ver-miculite, pumice, comminut:ed plastic scrap, bark and the like in the soil mixture. Although the aggregate, if used in sufficient quantity, can improve the air capacity, it gen-erally 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 in~
crease both the air and water capacîty of a soil matrix is particularly advantagaous in container soils.
Water can be i~corporated within the polyelectro-lyte polymer prior to admixture of the polymer with the soil As previously indicated, each individual absorbent poIyelectrolyte particle maintains its particulate charac-ter as it imbibes and absorbs many times its weight of water, and ln doing so swells The resulting water-swollen parti-cle3 defined herein as a hydrogel, substantially immobilizes the water therein. The absorbed water within the hydrogel is available or plant roots and is reversi~ly released to the plant or soil by the hydrogelO Upon releasing the absorbed water therein, the hydrogel dehydrates and returns to substantially i~s original size and the s~ate of being a polymer.
According to thi~ invention, the germination of seeds, the early growth o seedlings and the growth of transplants can be effectively improved by placing them in proximity with water swollen hydrogels of this invention in the soll. The hydrogel can be placed in the soil prior to or subsequent 10,805 to the placement of the seed, seedling or transplant. Ln these applications, the water is supplied from the poly-electrolyte 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 o~ the sandy soils. A ~ertilizer or other active agent can be inoorporated into the poly-electrolyte hydrogel with water and/or organic solvents prior to addition of the hydrogel materials to the 90il.
The polyelectrolyte hydrogel acts as a reservoir and a carrier for the water, fertilizer or other active agents and prevents excessive loss of ~he water, fertilizer and other active agents by leaching.
A fertiliæer or other active agents can be first solubilized in water and/or organic solutions and the in-soluble 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 contain ing only the active agent. This active-agent-loaded polymer or growth modifier 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 , , .. , . ,-, . /,, . - . ..... . . .. . . .......... . .
. ~ ,, . , . - , . . . .

, 10,805 will then act as a reservoir and carrier for water and active agents which are readily available to modi~y 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, herbi-cides, 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 leach-ing is reduced. Also, because the activating carrier is able to sorb moisture from the so-called dry soils, activa-tion of active agents may begin without additional rainfall.
;; ~ A partlcular and distinct advantage of the present growth media compos~tion 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 e~ficient utilization of water and other active agents :: ~

~ ~ - 36 -, - ~ . . . . . . .......... . .
- .. .

10,805 ~ '~3~
because ~he 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 rom the soil for transplanting, are much more resistant to ex-tended periods of moisture stress. The term "molsture stressl' is defined herein to mean a situation wherein the internal moisture of the pLant i9 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 ava~lable moisture. There is much less destruction of seedlings during shipping and transplanting operations with such plants as tobacco, lettuce, celery, tomatoes, stra-berries, annuals and perennials, hardy perennials, woody pl~nts, ornamentals, seedlings and the 1ike when they have been grown in the soil-compo$itions of ~he pres~nt in~ention.

In another embodiment of this invention, plants can be rendered more resis~ant to moisture stress by the method which comprises contacting the roots with an aqueous slurry of one of thP particulate cross-lin~ed hydrogels use-::
ful in this invention prior to planting in the soil. The physical properties of the slurry are adjusted so that a significant amount of hydro~el adheres to the plant roots when they are withdrawn. A particularly convenient way of incrèasing the effectiveness of the slurry is to add up to 1~% by weight of a water soluble thickening agent such as high molecular weight polyethylene oxide, hydroxy e~hyl cellulose or the like. The roots can be contacted with thP
slurry by spraying, dipping, or other convenient-methods.

10,80s The following examples are given to illustrate the present invention but are not t9 be construed as limiting the inven~ion ther~to.

E,XAMPLE 1 .. . ..
Three soil amendments were compared using a '1soil column" procedure. Soil column re~er5 to a sample of soil generally in a columnar glass vessel in which the 90il and water can be observed. A 350 ml. glass Buchner funnel 18 cm high, 9.5 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, l.e., those of the U.S. Salinity Laboratory 1954. Each soil mix was dried at 110C for 16 hours and weighed dry.
Each amendment was added and mixed on an individual basis to the soil in each column, respectively. The 50il 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 un-natural 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. volum~
. previously made.

', ' . . :, . ! ~ ' 3~
10,805 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 fo].lows: 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 - Cw and T ~ 100.

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/l. Watering was done with Peter's solution, a fertiliz-ing solution of 200 ppm (nitrogen) strength. The Peter's solution was made from a commercially available fertilizer , comprising 20% nitrogen, 20% P205 and 20% K20, a so-called 20-20-20 fertilizer.
In example 1, a potting soil, consist-ing of half peat moss and half vermiculite, was used. The four soil amendments compared were: (1) Viterra Hydrogel Soil Amendment ('Viterra is a trademark or a 50% polyethylene oxide, 50% inert ingredients soil amendment made by ' ~ 10,805 Union Carbide Corporation); (2) General MillS product SPG-502S, a hydrolyzed polyacrylonitrile grafted copolymer of starch soil amendment and (3) an illustrative polyelec-trolyte hydrogel soil amendment of this invention, a cross-linked polymer of potassium acrylate and acrylamide ~ 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 o monomer units potassium acrylate/acrylamide employed - O.348.
This solution was then cast onto a paper backing material and conveyed beneath a 1.5 MeV Van de Graaf accelerator operating at 1,600j~uamp beam current. The con~eyer 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 con~eyor speed of 8 feet/minute is on the order of 1 meg~rad.
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 s~x 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:

.

10, 805 ~3~

00 Ch K û I I c~ o ¦

~ ~31 1 I r~

u 5~ ~ L~

rl ~ U~
s~ u o~

. ~ ~1 c~
c~

o ~ ~ o o P~ 4 c~

w v ~~ C ~ ~ ~ cr~
æ
. i~
: :
C ~ r~

:: :

o ~ ! ,,~
C P~ I ~ ,i r~
: a~
~ ~ ~ ~ .
' o e~

'I ~ ~ X ~ ~ v~ ~1 ~~ bO
D u~ o ~ c7 ~ O ~ .-1 o t~

10,805 These data show that while other polymeric ma~eri-als 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 constrasted with the hydrolyzed polyacrylonitrile grafted copolymer o~
starch product which actually decreased the air capacity.

This example illustra~es the e~fect on the standard soil physics characteristics o~ the same three soil amendments o~ Example 1 on a commercial potting soil, a fie-ld soil enriched with humus. The same experimental procedure was employed as described in Example 1. The results are summarized in Table II hereinbelow.

- 42 ~

10, 805 .~3~

bl x~

U~rl O
~_ ~ ~ I~ er~
¢ ~ a~ ,/ ~ ~ , C~

O ~1 4 0 0 O 00 ~` ~

V
HaJ C~-- ~_1 00 r~
HJJ 5d ~ cr~ r~ 00 ~ ~ ~ ~ U~ ~ .
::
.~
e ~ ~ ~ o ~;1 Q .
~ ~1 ~1 h ~ ~-- O ~ .-i ~i C`l 3 - cr~ ~) ~0 ~ t:
~ ~ ~J I ~ ~1 00~ ~ O . ~ .
~ P~ ~ I
,., ~ . . ~
V~
: a~ o u, u~ h E3 ¢

o ~ o O F~ h o ~ O ~ C.~ ~ O ~ ~1 0 t~
~,~

.

10,805 Again, only the soil amendment of this invention, exemplified by the cross-linked copolymer of potassium acrylate and acrylmaide, increased both air and water capacity markedly.

This example illustrates the ef~ect on a soil/
peat moss/perlite 1-1-1 by volume, type of potting soil of the addition o~ certain soil addltives compared to the soil amendment of this invention. The same experimental pro-cedures as in Example 1 were used~ The resul~s 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) o~ this invention has a truly marked e~ect on both air and water capacity of this soil.

.

~ :
~: :

10, 805 C) h J
c~-rl O ~D 40 L O
JJ .
~ ~ ~ ~4 ~ U~ ~
~ ~ C~
¢ 1~ ~1 C`~
ta c.;) ,4 C'`J
V

O
~0 ~ O O C~l ~D
~q P.
H ~ ~D
~-I ~ C~-- , I~ U~
~O O
~3: G~ 1~1 0 C~
~ C,~_) ~O U') : ~
~1 C ~ C~
rl ~ _ r~ ~ r~
e~
_ ~ ~a h -- h ~J ~1 O C~ ~ o ~ ~ .

a~ I c~
e :~ C~

C~l I
. o ~ O
o ~
: ~ O ,~ V ~ ~

g ~ ~ ' ~ ~ ~ ~ O
~i ~ Vl 0 ~ O O ~ t~
X Pl V~ ~ U :Z ¢

.

3~ 0,~05 In this example, the soil amendments were ground and screened to provide two size frac~ions, 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 sc.een 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:

: ` . : : , , ` . ,, ., . : ' , `:, :: , .,. ", . : ~ '., ~ . : `

10, ~05 ~ ' ~1 U l co C~ ' ~ ~1 ~o ~1 ~- ' - ,1 t, ~ ~ I~o O ~ ~ r~
U~ ~ oo U~

~ ~ ~ a~ ~ ~ u, ~,. o ~ ~ .
c~l ~ .~ ~D 1`
¢ ~ C~

o ~ C~ ~ o CO

H ' ~
W , ~1 ~ ~ ~ 1 ~ ~ O
ii~ 3 C~ ~ U'~
' 9 O~ ~ O
C~

~ 3 1 u~
: ~ ~ ,t ,, ~ ~ ~ o ~
o W ~ ~
1 0 o o 0 N
h I JJ J ~rl O C C~ I N ~ ~ 1~ ~ co O P~
3 ~ + O u~+ O O ¢ E~o Cl;
~ ~i ~ ~ O~ -' ~ V ~.~7 o '~3 ~ o ~ o ~

II U ~rl N 1 ~ ~:1 0I ~ C `U ~ N ~ ~ O
~ e o ~ o ~ o ~

.

- ~7 - .

10,~05 ~ ~ 3~

,The da~a summarized i~ 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 ~he 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 o~ hydrogel plug a substantial number o~ 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, oten below that o~
a similar control soil without the finely ground additive.

An "in pot" procedure was employed. 'qn 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. ~entle tamping, to settle the soil, precalibration of soil height vs. soil volume, watering, draining overni~ht, wei~hin~ and calculation of percent wa~er' capacity, Gw, 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, :

:`

~ .

; :. , , . - ,.. . , ~ - .... . . .... .... .

1~,80S

The total dra~nable pore space or percent air cap~city was determined as follows. The pots were c refully flooded-to ~he top o~ the ~oil 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 ~ull pot was placed in a pan of water or fertilizer solution ta 6uch a depth as to keep the pot full to soil level. In In either c~se, the pots were allowed to stand flooed overnight (16 hours) to ensure expulsion of all air. They were weighed when flooded, Ater dralnage, ~he~
were reweighed. The diff~rence in weigh~ was drainable pore space at æero suction, since the ~pecific gravity of wat~r is one. Air capacity~ C~ ls then drainable ~_re space (cc).
80il ~olume (cc~
A slight adjus~men~ was made for the very hig~
capacity hydrogels. ~ather than using the drained weig~
after overnight flooding to substract from the ~ully saturated weight, the equilibrium waight after normal watering was used.
Thi~ was don~ because these high capacity gels would some-t~mes absor~ more water during the overnight flooding pro-cedure and this lead to spurious results. The Xa and Xw values were calculated as described previously, i.e., weigh~
difference between the amended soil and control par unit weight of amendment for water and air volume difference per unit weight of amendment for air.

l0,805 ~ ~ 3 ~

In this example, a cross-linked copolymer of potassi~ acrylate and acrylami~e (having a ratio o~ 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 o~ two par~s 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 potassi~ acrylate and acrylamide was added at 3 g per pot (2.5 g/l). 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 summerized below Ln Table V:

~ .;

: ~ .

.

~: - 50 ~

10, 805 -~u~
~ I U~ o o~ ~ o~ o~

~ . ~ ~ ~
~ U
¢ o U'l ~ ,~
U

~
bO~ , ool ~1 .,_ o~ ~ o o ~ ~ C`i ~ ~ , E~ :4 oo 1`

~:1 ~
~ U
n~ ~, ~ ~ U~ o o ~ o : 1:~4 ~

E al C
p, X ca h ~ ~ u C~
O ~; 1~ C.) ~C
~1 ~
O ~1 l ~ O ~ ~ C`l ~ V

~ 5 1 _ 10,805 3 ~

These da~,-a show that the eross-link.ed copolymer of this invention in granular orm although slightly less effective in increasing the water capacity of this rich, organic soil, is markedly more effective than the fine powder in raising air capacity.

This example employs the "in pot" procedure o~
Example 5 and illustrates the stability to successive water-ings 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 solutionO This cross-linked copolymer of potassium acrylate and acrylamide had a ratio of monomer units of 4Otassium acrylate to acrylamide of 2.82.-A 2-2-l, mix soil, peat mo9s and perlite, was employed in 16.5 cm diameter pots. Five grams (4.2 g/l) of the poly-electrolyte polyer were added to 600 g of soil, which had a volume of approximately 1200 cc. The first our waterings were made with tap water, a~ter which soil measurements were taken. Then there were six waterings with 2G0 ppm (N) Peter's solution about 1.32 g/l, i.e., fertilizer with a 20-20-20 N, P2O5, K2O percentage. The results are sum-mariæed in Table ~I below:

. .

.: .

10, 805 ~4~

b~ ~Dl ~, ~
-~1 ~ ,, ~

~ ~ ~, o ~ ~ ~ ~
¢ g U P~ ~ ~ ,1 ~

bO
~ ~ ~ ool ' C`.l _, H
P
~ ~ o ~00 0 U~ ,1 ~O
P; ~

O O O O

o ~ ~ ~ o~ ~ ~-3 ~ o ~ o ~

o ~ o 10,805 These data in Table VL show that certain polyelec-trolytes lose substantial water capacity after reacting with a normal fertilizer solution. Note that the Xw value drops from 87 g H20/g polyer to 22 g H2O/g pol~mer.

The "in pot" procedure of Example 5 was employed.
In this example, the soll was a cosnmercial greenhouse mix consistin~ of 1-1-1, soil, peat moss and sand mixture.
Pots 16.5 cm in diameter were filled with 735 g of soil, about 1200cc, containing zero, 4.5 g (3.5 g/l) or 7.5 g (6.3 g/l) of a polyelectrolyte polymer. The appropriate amount of the polyelectrolyte soil amendment had been pre-viously mixed with the soil. The polyelectrolyte polymer was a cross-linked copolymer o~ potassium acrylate and acrylamide ha~ing a ratio of potassium aerylate to acrylamide monomer units of 0.348. This ratio is equivaient to about 1 ionic group to 3 nonionic groups. The watering protocol : was three 500~ml waterings with tap water followed by two SOO-ml additions of Peter's solutivn - a 200 ppm (N~
20-20-2- N, P205, K20) 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 Tabl~ VII
below:

:

', , ', 7 -. , ,. ' `' :' ' ~ . ' ' 0, 805 ~0 I ,li ~ol ~ t~

~ ~ I~
`--~D' ,i ~)~ ~ ,1 h 8 ~ ~
o a~
O ~ ~D U~ oo , P~

~1 .

~ P~ ~

P ~ r~ I~
~, ~,~

b~ O O u~
~44 U~ ~ o U~

;~ ~ o o o ~ U~

:: :
a) ~ aJ aJ
~ ~ E
P~ O ~, o U o C,~

w o ~ O ~a .

, - _ 55 _ :, 10,805 ~'~3f~

The data in Table VII show that the addition of a polyelectrolyte polymer of this invention markedly in-creases 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 (~) ~han the polyelectrolyte hydrogel with the high ratio of ionic/non-ionic groups.

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 ~ertilizers. 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 water-;~ ing protocol was six waterings of 500-ml each o tap water.
Each o~ the ~ollowing data points represents the average of five pots. The results are summarized in Table VIII
below:

:
~ 5~ -. , .

.

L0, 805 ~'~3 oo ~, ~

~_ Cr~ CO o ~I

1 0 c~
~ ,1 U o _I C~ ,~
¢ , ~ e~
~\

~_ V~

~ o ~o o ,1 ~
g~J

,~
.
J ;~
~ ~ ~ O ~
C ~ ~ C 1 ~ O ~ ~ ~ O ~

- ~ ~ 3 ~ 10,805 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, s:ince both levels of amend-ment produced a soiL with excellent properties. Note that the g of H20tpot increased as the level of amendment increased.

The "in pot" procedure of Æxample 5 was employed.
This is a comparative example showing the limits of appli-cants' 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 amend-ment made by Union Carbide Corporation; and Gelgard XD1300, trade name for a cross-linked partially hydrolyzed polyacryl-amide ~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 wi~h `~
506 g, about 1~00 cc of a 2-2-1 mix of two parts top soil, two parts peat moss and one part perlite, a rich organic soil. 15 g per pot (12.5 gll) of Viterra Hydrogel Soil Amendment were added to eight pots and 3.5 g per pot (2.9 g/l) of the modified polyacrylamide were added to eight additional pots. Each data point below represents .
~,,~ . ..

, ~ .... . . . . . . . ..
, , , , . . !, . . .

10,805 ~ ~ 3~

the average of eight pots. Each pot was watered seven times with 500 ml portions o~ 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:

- S~ _ , . ; , ., 10, 805 ~3~

X t~ I ~
C~ ~_ I~
~_ ~)~

I~
,~ o ~o ~c ~ '~
:

-d .~ g ~ o a ~'' ~ O
O ~1 N
~1 X ~U

o ~ ~ ~
u~ o~ o ~
o ~~
~ o c`~ o O C~l I ~ U~ ~ ~ `~
w c`~

:

.. . , - . .... ...

10,805 ~ ~3 ~

The date in Table IX ~llustrate that certain 90il amendments may greatly increase the water capacity of soils without increasing the air capacity at all or even decreasing it.

The "in pot" procedure of Example 5 was employed.
Five soil amendments were compared: a potassium bonded polyacrylate (potassium content 30-35~/O by weight of polymer) made by Toho Rayon Company of Japan; General Mills product SPG-5025, a hydrolyzed polyacrylonitrile gra~ted copolymer of starch; Grain Processing 35-A100 product, a granular, water insoluble alkali metal car~oxylate salt o~ 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 Protuc~, a eross-linked partially hydrolyzed polyacrylamide about 40% ~ydrolyzed and si~ed finer than 100 mesh, and a polyelectrolyte polymer of this invention.
The polyelectrolyte polymer was a cross-linked copolymer of : 20 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 Floricull:ure Crops, April, 1974, p. 3 , Cornell University : Press) was employed. 130 g (1200cc) of the soil mix was well mixed with 5 g (4.2 g/i~ of the ~ve polymers and put .
~ . . , ~O j ~05 into 16. j cm diameter pots~ The followlng data points represent the average of three pot~ for each treatment. There were twenty waterin~s, SiK of tap water and fourteen of Peter~s 20-20-20, 200 (N) ppm fe:rtilizer solution at 500 ml ~Eh There was free drain~ge for at least eight hour~ ~fter each watering. All pots werP ~llowed to dry to ~ normal level four times prior ~o w~ering in simulation o~ normal growth conditions. Of course, the salt concentration of the qoil solution incr~ases as the soil dries. Just prior to ~aking the data, ~11 pots ~ere watered three times with ~ap water to leach any ~ccumulated salts. The results are summarized in Table X below:

~ 62 -10, 805 ,~ ~
o o ~1 ~ ,_ c~ ~ . . ~
C~ I ~ ~ I ~ I
I ~ ~1 ~d P~
~_ ~ ~ ,. U~
~ r~
_ . . r~
~ ~ o , C7 ,1 C~

o o c~ oo ~
C`~
~J

. . o ~ _~ ~ ~ ~0 0 ~1 u~
'S . ~ I~~` ~O ~ r~ i~
E~ c~

~ 00 CO O ~D
P: ~ ~ o ~ . ~1 00 0~

_ _ L~ U~ ~ C`~ ,1 U~
_~ ~ r~ I~
~p ~ v o c~
~ o ~ o o p~ oc~ o ~
h h,--1 o ~
~ ~ h ~ U~~t u~
X ~C. X P~

o o cn o ~: o ~O h u) O q~ O ta o o ~ ~ o ~ ~ ~ J' ~ ~
vo~a æ~

..~.................. . . . . . ...
; .... ~ .. .
;

~ ~ 3~ 10,805 The data in Tsble X above clearly shows that the only polymer which markedly improves the water and air capacity o~ the composition is the polymer of this in~ention.

This example compares the equilibrium solution capacities (X-values) o~ a number of known pol~ner 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 (postasgium content 30-35~/O 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 starch-acryloni-trile graft copolymer produced by saponifying starch-acrylonitrile graft copolymers with an a~ueous alcoholic solution of a base (described in U.S. patent 3,661,815), and ~5):Gelgard (XD~1300; (Gelgard is a trademark ~or a cross-linked9 partially hydrolyzed polyacrylamide (about : 40% hydrolyzed and sized finer than 100 mes~ made by Dow Chemical Company).
The equllibrium capacities (X values~ were cal-culated according to the following formula:

X Value Weight of Dry Polymer - --The test procedure was as follows: A weighed .

- 6~ ~

10,805 ~ ~ 3~

amount of each dried (dewat~red) 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 prevlously given.
An effective soil amendment must be o~ 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 solutlons of CaC12 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 c~lcium cross-linking, the polymers swollen in the Ca+~ solutions were filtered out and ~oaked in excess de-ionized watex overnight and the X values determined again.
The results o these tests are summariæed in Tab~e XI below:

- 65 _ .;

~ 10, ~05 ~o C~
~a ~
bO ~ 00 a~ o o C~
OJ h ~ ~ C~l C~ ~

~q ~o cr~
O ~1o~
O C`l ' ~1 ' ~_1 ~d _/
.~
X ~, E~`
r ~ :1 ~t t~ ~ . U~
~1 0 O 0 S~ oo ~ ~P~ ~/ , r C~
;~ . ,:
U
O
o ~ ~ o ~g ~ r--O ~ oO
4 r l ~1 ~1 ~
U
~:~
: O ~ ~
C ~ ~o : o cr~ o CO ~ C~ C~
U ~ ~ ~1 ~`SC
JJ
0~
o~
tn ~
W

~ $
~ O ~ -t ~ ~O to ~ &
` ~ o~ 1.~ ~ O
~:L O
W
O

~` :

10,80 ~ ~ 3~

The data in Table XI show that a typical poly-electrolyte polymer o~ 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.

The "in pot" procedure of Example 5 was employed.
Marketer (Cv) cucumbers were grown ln a soil consisting of two parts top soil, two psrts peat moss and one part perlite.
The treatments consisted of the control mix, the control mix plus Viterra Hydrogel Soil Amendment, a trademark ~or a 50/O polyethylene oxid~, 50% inert ingredients soil amend-ment 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 C.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 we~ varied according to their equilibrium -water capacity in ~ap water in an attempt to get approxi-mately the same amount of hydrogel-bound water per pot.

67 ~

10,805 600 grams (1200 cc) of soil were mixed with a 50il 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 reg~me was four 500-ml por-tions 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 ~ive 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:

, - ~, . - . . : .

lO,B05 , ' -oo ~ r~
C`l C~l sa O c~ O ~ o C`J ~ ~ C`J

3~
~ ~ l oo ol E~
~ ~ U~
,1 o g C~

~3 3 ~ 4,1 U~ C~ oo ~ oo ~o ~ ~ o ~o X~ ~ ~ ~ I` o~ oo oo .. ~ O ~ ~ Q~
_, ~ e ^
E~~ 3 ~ o , ~ ~q ~ O ~ ~ ~ ~ ~ ~1 Zi P` ~
, ~ ~
E~

:~ : ~ o o O Q
~1 5~
~ ~ X

: ~ o~ CO
o. ~a o E c~ ta C~
~ ~~ O ~s~ O ~ C~ o ,1 ~~i C~ E ~~ ~ E ~ ¢

O O ~o ,~ O ~ ~o ~ o ~

o o o o . aJ u~ ~ o ~ u~ ~ o tn ~ ¢
V ~ ~ I O
o ~ ~ ~, ~ ~ 0~ ~ O
.

~ 69 -. . .

.34'~ o, 805 TABLE XIII

Number of Number of Leaves ? 1. 3 cm ~S~ !L~E~ on Breaks Control Soil 2.2 1.6 Control Soil Plus 3.6 1.8 12.5 g/l Viterra Hydrogel Soil Amendment Control Soil Plus 5.6 8.6 3.3 .g/l Sample A, Cross~linked Copolymer o Po~assium Acrylate and Acrylamide Control SQil Plus 5.2 6.2 2.5 g/l Sample B
Cross-linked Copolymer o~
Potassium Acrylate a~d Acrylamide Control Soil Plus 5.0 7.Z
: 2.1 g/l Sample C
Cross-Iinked ~: Copolym~r of :: .Potassium Acrylate ~ a~d Acrylamide : ~ :
.

:::

. , :
~ - 70 -L3~gLf~ 0 ~ 805 oo u O ~D 00 ,~
C~

U~
~o ~; ôo x ~ ~

~ V~i-_ E~ . ~ ~ O ~

o ~ ' ~ ~.
~ ~c~ c~

~U
L o _ 0 ~1 e ~ O ?~ O
~ o c~~ o c~

o o ~ ~ ~ c ~

g o o o ~q o ~z o ~n o ~: o ~ o CG

'~ '~ ~ ~ c;) ~ '~ o ,~ w ,: c ~ o ~

`

IL~34~ o,~05 The improvement in soil ~ualities is borne out by the plant growth data, The number of breaks is increased significantly up to 150% and the number o~ leaves greater than 1.3 cm in length on breaks is increased over 4~0%
compared to the control soil. One thus sees that the cross-linked copolymer o~ potassium acrylate and acrylamide aids in the growth o~ plants in dramatic fashion, The "in pot" procedure o~ Example 5 was employed.
The effect of a cross-linked copolymer of potassium acry-late and acrylamlde (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 w lgaris) 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, ~ollowed by nine more tap waterings and then two more with Peter's 20-20-20 fertili-zer 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 lvel of ~he cross-linked copolymer of potassium acrylate and acrylamide was 2 g per pot ~1.7 glL). Each data point represen~s the avera~e of five pots. The total growth period was about 45 days.
Wh~n plants had shown maturity by flowering, all _ 72 -, , ~

10,80 ~ ~ 3 ~

the pots were watered several times to assure saturation, the surface covered with pl.astic ~ilm to stop evaporation loss, and the plants allowed to wilt. At the first sign o~ wilting the water content was measured for each pot and compared to the control. The results are summarized in Tables XV and XVI below:

L0, 805 ~3~

~u , oo I . r~
PC U ~ J ~ ~ ~

,_ s~

O O ~ ~ o r~

~3 ~ 1 ~1 ~ ~ ~ u~
r~
a~ ~ u~
~¢

~o o a~ ~ ~ o r~ oo u~ ~ ~
: ~ ~ ~:

u~ ~ ~ ~ ~ ~D
o a~
r~
~ o--~ ~ ~~
:: ~ p . ~ :

o p o~ ~ ~ o P

'~
o co ~ o ~I v~ ~? ~-~

.

: . .

10,805 3 ~

TABLE XVI
INCREASE IN WATER AVAILABLE FOR USE

% Available Available Water Water g H2O Used byDifference Capaci.ty Plant/Pot ___5~2____ 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 Pota~sium Acrylate and Acrylamide 2 ~ /pot These data show how well the cross-linked copoly-mer 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-fi~th) than Viterra Hydrogel Soil Amendment. These data further demonstrate that the : water held by the polymer of ~his invention is highly avail-able for use by the plants. Note that 2 g of the polyelec-trolyte polymer held an extra 100 grams of water that the ; plant could u~e prior to wilting.

, ~ 75 -~. ,. ... . ~ . , ~ , . . ... ..

~3~ 0, 80s EX~MPLE 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 potaissium acrylate to acrylamide of 0.348) as a soil amendment. The soil was l-l-l by volume top soil, peat moss, sand mixture. The containers were a pressed fiber container approxlma~ely l4 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 thoroughly and allowed to stand. The control tomato plants wilted in four days;
the treated plants in seven days, a 75% improvement. After wilting, the p1ants were cut down at soil level, oven dried 20 at 110C 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 50il (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. ~

:: , , .
':
,. ;, F~ ,, :.

~.39~3~ o ,805 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 acry:Lamide 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 cuttin~s of one o~ the following cultivars:
Granchild, White Grandchild, or Illini Spinningwheel.
There were 18 pots ~or 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 or nine weeks, then brought into a greenhouse for shelf life testing. A~ter 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 tv wilt are sl~mari~ed in Table XVII below:

:
, 10, 805 ~34L~

TABLE XV II

-Whi'ce SoiL Illlni Grandchild Grandchild Control 4 8 8 Treated With the Cross-lir~ced Copolymer7 13 13 I~provement (%)~75 t~3 t63 m ese da~a show the marked improYeme~t ln prolong-ing tlme to wilt for valuabl~ flowers by treating the ~oil ~hey are grown in w~th a typical polyelectroly~e polymer of this inventlon, a cross linked copolym~r of potassium acrylate and acrylamide.

. EXAMPLE 16 In this example, two cultivars of poinsettia plants, Eckespoint C-l Red and Dark Red Annette Hegg, were grown in a Cornell type mix composed of peat moss, vermiculite, perlite plus one liter of top soil per bushel of mix. The treatment consisted o control soil and soil ame~ded with Viterra Hydrogel 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 or success was the number of cuttings (longer ~han 5 cm) or total branches produced.

- 7~ -~.0,805 Twe~ve 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 Amlendment 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 gk/m3). The watering was as required, generally with a Peter's solution of 250 ppm (N) (25-10-10 (N)-P205)~K20) composition. 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, (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 w re 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:

'~
.. ~' ' - : , - , . . . . ~ , : . , . , :
., ~... . ... . .

~L.34~ o, 805 a~

~a ~ ~ ,;~0 - ~) E
C ~
oo ~a q~ ^
0 U~--oo ~ ~ I~ e~ oo CO
, 1 ~ O
o U~
a h I ~p.
C~ ~ U~ ~ o ~o a0~ 0 H ~ ~ ~
~i ~ S~
<-~ O ~
, ~ o ~ a: ~D
~ ~ e 3 ~n o~
~ a~
~ s~ ~ ~
c ~ ~
: p~

o ~ s~
o ~ ~q s~ 0 o c~
a) w ~ ~ c~
~ ~ u~

c~
a) o e ~ o :1~ ~ h e ~ h a~
rl ~ E~ C`l ~ E aJ O ~: E
a~ o E ~rl h ~1 O P~ S~ 4 ~ ~ U~ ~1 U~ ~;
'.,1 s-, ~u ~1 a,~ ~ : ~R O
O ~ ~ ~ ~r~ ~ ~ ~ ~1 0 ~ ~ ~
U~ ~ O rl-rl O ~ O O ~:
O O P tl~ O ~ u~ O

:: :

.

~34~ o, ~os ol . , o~ t~o , ~ ~ ~
o ~ + +

W U~ ~q In ~ I~ r~ o C ~ ~ ~ ~ ,~ o~
_, .,, ~, o v ~ ~a o ~

~a o~ ~o U , H

,~~.q ~o O C~ O
X 0~~
~ ~~ 5~ ~ 1~ oo 1~ U~
X :: ~ ~

~; a~ E ~1 E~ G v3 ~C
U~
~;
" o~ i~
C~l t~ I ~ ~1 ~ ~ + + +
o o~
O u~
G oo cr~
E rl C~l ~1 ~i C~
~J ~1 ~1 v ' ~ bO O ~ ~
JJ ~ ~ ~ u ~q ~ ra ~ ~ ~ i3 aJ o ct; E3 ~ O ~ ~
_I ~ ~ ~ ~ ~ S~ ~ ~ I ~ ~o U
,t o P~
O 5~ q O
U~ ~ ~ ~ ~ ~ ~ ~ ~ O P~ L? ~
~rl ~ O ~rl ~ O ~ 0 0 ~ -O O ~ U~ O ~ O ~

` ~ ~ 3~

The lower level of addition of Vlterra Hydrogel Soil Amendment did not signiicantly improve the number of cuttings or their total weight. The higher level of addi-tion of Viterra Hydrogel Soil Amendment did have a signifi-cant effect especially with the Ec~espoint cultivar. The cross~ ked copolymer caused a marked improvement in yield with both cultivars of poinsettia and at one third the rate a~ which Viterra Hydrogel Soil Amendment showed sim~lar improvements.
EXAMPL~ 17 Four test plots of 40 inch raisPd beds with ~wo rows per bed and lO inch seed spacing were employed. The soil was a high clay con~ent soil content found in the Salinas Valley, California. The seed sites were prepared with a dibble 3/4 inches wide by l/2 inch deep. Each seed site was planted with one lettuce seed (Cv-Hartnell) ~ollowed by one of the three subsequPn~ treatments.
In one treatment, the control, approximately l/2 teaspoon o~ vermiculite was placed on top of each seed in 50 sites and tamped firmly in to fill the sites in each plo~. In ~he second treatmen~, ~he vermiculi~e was added admixed with about 0.025 grams of dry poly~ller also at 50 sitPs per plot. In the third treatment, approximately l/2 teaspoon (about 2.5g) of a hydrogel (about 0.Olg dry polymer) which had been ully preswollen in tap water was placed on ~:
top of each seed in 50 sites in each plot. The hydrogel was a ully swollen, cross~linked copolymer of potassium acrylate and acrylamide ~aving a ratio of monomer units potassium acrylate to acrylamide of 0.348).

, 10,805 ~ ~ 3f~

The ~our plot~ were then unlformly watered with approximately 1/2 inch of water, Four rainless days after planting, germination/emergence counts were made with the following results:

Control sites O.S~/O Emergence Sites t~eated with dry polymer 30% Emergenee Sites treated with Hydrogel: 49% Emergence Cxoss-linked copolymer particles o 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 o from 0.5 to 3% by weight, were placed in a plastic bag and shaken vigorously to ef~ect coating o the copolymer.
The copolymer parti~les were sized between -10 mesh and 60 mesh. In each o seven tes~s, 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 coatlngs tested were the following:
1) super-hydrophobic fumed silica particles (sold under the trademark Tullonox 500 by Tulco~ Inc. North Billerica, Massachusetts). The hydrophobic fum2d silica particles had a nominal particle siæe diameter o 0.007 microns, a theore~ical surface area of 325 m2/g, a sur~ace area measured by nitrogen adsorption of 225 m2/g and a bulk density o~
3 lb/f~; 2) a hydrophobic fumed silica (sold under the trademar~ CAB-0-SIL Type M-5 by Cabot Corporation). The umed silica particle~ have an extremely small particle size and a læ ge sur~ace area ranging from S0 to 400 square meters . . .

10,805 per gram; 3) a hydrophobi.c 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 9~/0 passed through 100 mesh. The polymer particles were premoistened with 2% by weight solution of polyvinyl alcohol to re~dex their outer surfaces adhesive to the wood flour; S) a diatomQceous earth filter powder which is hydrophilic (sold under the trademark Celite by Johns Manville Product Corp., Lampao, Caliornia) and si.zed so that 99% passed through 150 me~h; and 6) talc powder which is hydrophobic (sold as grade 127 by Whittaker Clark and Daniels, Inc., South Plainfield, ~w Jersey) and sized so that 9~/0 passed through 120 mesh.
Observations were made on the ef~ectiveness o~
each coating compared to an uncoated polyelectrolyte poly-mer of this invent~on in preventing the rapid adsorption of the soil moisture, ~orming clumps. Clumping would interfere with homogeneous mixing of tha polymer particles ~0 with the soi~. The results of these tests are summarized in Table XX below:

, 10,805 TABLE XX

Efectiveness of Wei.ght % Caating Compared Test Coating Coating Applied to Uncoated P~

Hydrophobic fumed l./2% very much better silica (Tullanox 500) Hydrophilic fumed 1/2% poorer silica (Cab-0 S~l) Hydrophobic fumed 1/2% v~ry 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 conduct~d using cross-linked copolymers :~ 20 of~potassium acrylate and acrylamide as the polymeric com-:~ ~ ponent, the present invention is not limlt~d thereto. The present invention contemplates the use of any of th~ pre-viously mentioned cross-linked polyelectrolyte polymers as ; 8 soil amendment and as a component in the plant growth : media composition o~ this invention.

~: The insoluble polyelectrolyte polymers of 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.

: - 85 -~ 10,805 Due to their ability to incorporate or sorb organic and in-organic 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 increa6e the air capacity of soils when swollen with such solutions, they have wide utility in the field of agricuLture. The active agents ment-loned previously are not chemically a~ected by nor do they react in any signi~icant manner with the insoluble polyelectrolyte polymers of this invention, The polyelectrolyte polymers disclosed herein provide an efficacious and improved means for achieving the known functions o water and other known active agents or agricultural chemicals.

Claims (25)

10,805-C

WHAT IS CLAIMED IS:

1. A soil amendment suitable for admixing with a soil matrix having a moisture content less than about 5 percent by volume and/or as a growth medium per se comprising poly-electrolyte polymer particles rendered insoluble by cross-linking and sized between about 8 mesh and about 200 mesh, said polymer particles being further defined as providing a swollen hydrogel having a gel strength greater than about 0.3 p.s.i. in the presence of an aqueous solution, as capable of reversibly absorbing and desorbing more than about 100 times their weight in distilled water, more than about 75 times their weight in a standard fertilizer solu-tion and more than about 15 times their weight in a solution containing 500 ppm of calcium ions.

2. A soil amendment as defined in claim 1 characterized in that said polymer particles contain anionic groups.

3. A soil amendment as defined in claim 2 characterized in that said polymer containing anionic groups comprises one of the following polyelectrolyte polymers or mixtures thereof:
(1) salts of polyethylene sulfonate, polystryrene sulfonate, hydrolyzed polyacrylamides, hydrolyzed polyacrylonitriles, carboxylated polystyrene, (2) salts of copolymers and terpolymers of acrylic, substituted acrylics, maleic an-hydride, ethylene sulfonate with ethylene, acrylate esters, acrylamide, vinyl and divinyl ethers, styrene, acrylo-nitrile, (3) salts of grafted copolymers where the backbone may be a polyolefin, polyethers and polysaccharide, and the grafted units, acrylic acid, methacrylic acid, hydrolyzed 10,805-C

acrylonitrile or acrylamide, ethylene sulfonate, styrene sulfonate and carboxylated styrene, and (4) salts of poly-saccharides modified by the addition of carboxylated groups.

4. A soil amendment as defined in claim 3 characterized in that potassium and/or ammonium is the cationic component of the associated anion in said polymer.

5. A soil amendment as defined in claim 1 characterized in that said polymer comprises a copolymer of potassium acrylate and acrylamide.

6. A soil amendment as defined in claim 1 characterized in that said polymer particles contain cationic groups said polymer particles being further defined as capable of reversibly absorbing and desorbing more than about 15 times their weight in a solution containing 500 ppm of polyvalent anions.

7. A soil amendment as defined in claim 6 characterized in that said polymer containing cationic groups comprises one of the following polyelectrolyte polymers of mixtures thereof: (1) polyamines, quaternized polyamines, polyvinyl-N-alkyl-pridinium salts, ionene halides, (2) grafted co-polymers from polysaccharides, starch cellulose, polyo-lefins, polyethers, and 2-hydroxy-3-methacryloxypropyltri-methylammonium chloride, and (3) copolymers or quaternized copolymers of HN(CH2-CH=CH2)2, (CH3)2 ?(CH2CH=CH2)2C?, acrylamide, acrylonitrile, ethylene and styrene.

8. A soil amendment as defined in claim 6 characterized in that nitrate is the anionic component of the associated cation in said polymer.

9. A soil amendment as defined in claim 1 characterized by further including an active agent.

10. A soil amendment as defined in claim 1 characterized by further including at least one of the following materials:
water, hydrocarbon oils, organic alcohols, ketones, chlori-nated 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 phos-phate, colloidal silica, sand vermicultute, perlite or finely divided plant parts.

11. A soil amendment as defined in claim 1 characterized by further including a wetting agent.

12. A soil amendment as defined in claim 1 characterized in that said polymer particles are sized between about 10 mesh and about 100 mesh.

13. A soil amendment as defined in claim 1 characterized in that said polymer particles are sized betwen about 10 mesh and about 40 mesh.

14. A soil amendment as defined in claim 1 characterized in that said polyelectrol.yte polymer particles are coated with up to 5 percent by weight of a hydrophobic material in ex-tremely finely-divided form.

10,805-C

15. A soil amendment in claim 14 characterized in that said hydrophobic material comprises hydrophobic silica particles which have an average equivalent spherical dia-meter of less than about 100 millimicrons and have a specific surface area of at least 50 square meters per gram.

16. A plant growth media composition comprising a soil matrix in admixture. with a soil amendment as defined by claim 1, up to about 32 grams of said soil amendment being present in said composition per liter of said soil matrix, each gram of said soil amendment being further characterized as capable, in the presence of soil solution in said composi-tion, of reversibly absorbing and desorbing more than about 20 grams of said soil solution providing, when swollen with said soil solution, hydrogel particles which increase the drainable pore space of said composition by more than about 15 cubic centimeters.

17. A composition as defined in claim 16 characterized in that said soil matrix comprises natural growth media.

18. A composition as defined in claim 17 characterized in that said natural growth media comprise peat moss, bark, sawdust, vermiculite, perlite, sand and any combinations or mixtures thereof.

19. A composition as defined in claim 16 characterized in that said soil matrix comprises unnatural growth media.

10,805-C

20. A composition as defined in claim 19 characterized in that said unnatural media comprises glass beads, foamed organic materials, foamed inorganic materials, calcined clay particles or comminuted plastic.

21. A composition as defined in claim 16 further characterized in that said hydrophobic material is sized extremely finer than and has a much larger surface area than said polymer particles, said hydrophobic material adhering to the outer surfaces of said polymer particles.

22. A composition as defined in claim 16 characterized in that each gram of said polymer particles can reversibly absorb and desorb more than about 30 grams of said soil solu-tion in said composition providing, when swollen with said soil solution, hydrogel particles which increase the drain-able pore space of said composition by more than about 25 cubic centimeters.

23. A composition as defined in claim 22 characterized in that each gram of said polymer particles can reversibly absorb and desorb more than about 40 grams of said soil solution in said composition providing, when swollen with said soil solution, hydrogel particles which increase the drainable pore space of said composition by more than about 35 cubic centimeters.

24. A method of improving the water and air capacity if a soil matrix, the germination of seeds and/or the growth of plants and seedlings situated in said soil matrix, 10,805-C

said method comprising admixing with each liter of said soil matrix up to about 32 grams of a soil amendment as defined by claim 1, each gram of said soil amendment being further characterized as capable, in the presence of soil solution in said composition, of reversibly absorbing and desorbing more than about 20 times their weight of said soil solution providing, when swollen with said soil solution, hydrogel particles which increase the drainable pore size of said absorbing and desorbing more than about 20 times its weight in soil solution.

25, A method as defined in claim 24 wherein said polymer is a copolymer of potassium acrylate and acrylamide.