Note: Descriptions are shown in the official language in which they were submitted.
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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
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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
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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.
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~ 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
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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-
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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.
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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
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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)
IH3
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
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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
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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
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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.
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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
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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
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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.
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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
.
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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.
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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
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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
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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
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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
- 23
,
, . . , . . . . ~ .. ~ -
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.
- 26 -
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
- 27 -
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
- 28 -
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.
;'
.
- 29 -
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,
- 30 -
,
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.
- 31 -
~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
- 33 -
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
- 34 -
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
- 35 -
, , .. , . ,-, . /,, . - . ..... . . .. . . .......... . .
. ~ ,, . , . - , . . . .
, 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.
- 37 -
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.
- 38 -
', ' . . :, . ! ~ '
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
- 39 -
'
~ 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:
- 40 -
.
10, 805
~3~
00 Ch
K û I I c~ o ¦
~ ~31 1 I r~
u 5~ ~ L~
rl ~ U~
s~ u o~
00
. ~ ~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~
- 41 -
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.
EXAMPLE 2
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~
~,~
.
- 43 -
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.
EXAMPLE 3
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.
.
~ :
~: :
- 44 - -
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 ¢
.
-- 45 --
3~ 0,~05
EXAMPLE 4
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:
- 46 -
: ` . : : , , ` . ,, ., . : ' , `:, :: , .,. ", . : ~ '., ~ . : `
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.
EXAMPLE 5
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,
:
:`
~ .
- 48
; :. , , . - ,.. . , ~ - .... . . .... .... .
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.
- 49 -
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.
EXAMPLE 6
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:
. .
- 52 -
.: .
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
- 53 -
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.
EXAMPLE 7
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:
:
- 54 -
', , ', 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.
EXAMPLE 8
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 ~
- 57 -
- ~ ~ 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.
EXAMPLE 9
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
- 58 -
.
~,,~ . ..
, ~ .... . . . . . . . ..
, , , , . . !, . . .
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`~
:
- 60 -
.. . , - . .... ...
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.
EXAMPLE 10
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
- 61 -
.
~ . . ,
~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.
EXAMP 11
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
0
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
- 66 -
~` :
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.
EXAMPLE 12
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:
,
- 68 -
- ~, . - . . : .
lO,B05
34
, '
-
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
PLANT GROWTH AFTER 43 DAYS
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 ~
- 71 -
`
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,
EXAMPLE 13
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:
- 73 -
L0, 805
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- 74 -
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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. ~
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~.39~3~ o ,805
EXAMPLE 15
Three cultivars of chrysanthemums were grown in
control soil and soil amended with a cross-linked copolymer
of potassium acrylate and acrylamide (having a ratio of
potassium acrylate to 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:
:
,
- 77 -
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:
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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).
,
- 82 -
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~ ~ 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
EXAMPLE 18
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
- 83 -
. . .
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:
- 84 -
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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.
- 86 -
