Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TITLE OF THE INVENTION
METHOD AND COMPOSITION TO FORM A FLEXIBLE CRUST
FOR SOIL PROTECTION AND ENHANCEMENT
FIELD OF THE INVENTION
This invention relates to a soil protection and enhancement compound formed
from a
binary system that can be applied to a substrate to stabilize the substrate,
to prevent
desiccation of the substrate, and to selectively provide soil and crop
enhancement.
BACKGROUND OF THE INVENTION
Treatment to protect soils is important, particularly to avoid moisture loss
from the soil,
which can prevent crops or other plants from germinating or growing. It is
also
important to enhance the soil substrate by providing specific soil enhancers,
such as
nutrients and herbicides, preferentially within the soil in order to achieve
maximum
benefit of those soil enhancers.
Known anti-desiccant treatments often focus on slowing or preventing
transpiration from
the plant itself. Products such as MoisturinT"", Wilt-PrufTM, Anti-StressTM,
and Cloud
CoverTm coat the plant leaves or needles with a prophylactic shield of resin
or polymer,
preventing the leaves or needles from releasing moisture into the air. U.S.
Patent No.
7,470,319 to Hunter discloses a foliar prophylactic including a phyllosilicate
mineral, a
chelating agent and multivalent ions. Another anti-transpirant method, known
as a root
soak, involves applying product such as abscisic acid to the soil, where the
plant roots
soak it up. Once the acid passes through the plant system, It chemically
triggers the
leaf stomata to close, preventing transpiration. In each case, these products
are
generally described as bio-degradable, but direct application to each
individual plant is
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often impractical, in cases where expansive fields of crops are being grown.
Further,
application of chemicals directly to the plant is usually undesirable for
crops, particularly
food crops.
A known soil enhancing treatment is perlite, an amorphous volcanic glass. When
heated to temperatures over 850 C, water trapped in the glass vaporizes,
causing
tremendous expansion in the structure of the glass. The expanded perlite is a
very
lightweight product that is useful to promote drainage and aeration in soil;
by replacing
some of the soil with perlite, the density and compaction of the soil is
reduced. The
cavities covering the surface of the perlite can hold oxygen, providing
improved soil
aeration and growing conditions. The cavities also trap and hold moisture in
the soil,
providing water to the plant roots and preventing the soil from drying out too
quickly.
Mulches have also been used to protect soil from environmental effects, such
as sunny
conditions which would increase water evaporation from the soil. Known mulches
include shredded rubber tires or plastic sheets with slits or holes to allow
water
penetration. An issue with these non-organic mulches is that the mulch is not
inherently
biodegradable and can be difficult to remove from the soil. Harvesting crops
around
foreign materials such as rubber pieces or plastic sheets can be difficult, as
the foreign
material can interfere with the harvesting machinery. Further, plastic sheets
must be
physically held down over an area, which requires an extra step of burying or
otherwise
containing each side of the sheet. The cost of using a plastic mulch sheet can
be
increased because of the burying step and, because there must physically be
enough
spare sheet to bury, by requiring a sheet that is somewhat larger in area than
the field
being covered.
Organic mulches have also been used directly on the soil around plants. U.S.
Patent
No. 5,163,247 to Weber discloses a type of mulch comprising a fibrous
cellulose web
with a latex-coated surface. The web is polymeric, based on a self-cross-
linking acrylic,
styrene-butadiene or ABS. The web is biodegradable and so can naturally
compost and
disappear before the crop is harvested, or is suitable for composting once the
crop is
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harvested. Other organic mulches have been found to be susceptible to matting
down,
which may prevent moisture loss from the soil, but may also prevent water and
other
nutrients from ever reaching the soil. The organic mulch may tend to trap
water before
it reaches the soil, as well as actually wicking moisture out of the soil,
allowing the water
to evaporate even more readily than in unprotected soil.
U.S. Patent No. 6,270,291 to Gamliel discloses a liquid polymer applied to
soil to form a
plastic mulch membrane film directly on the soil. Gamliel attempts to deal
with some of
the above issues with mulch by specifying that different levels of protection
may be
provided by applying different volumes of the plastic mulch; evidently
applying a lower
volume will create a thinner, more uneven and more porous membrane, which
should
allow more water penetration. However, as the mulch membrane gets thinner, the
level
of protection provided by the plastic mulch would likely decrease as well.
Gamliel also
appears to require several soil preparation steps, such as rotating and
compacting the
soil to provide a relatively flat, smooth surface to receive the plastic mulch
as evenly as
possible. Further, gaining optimal protection from the plastic mulch requires
the
application of two layers of mulch compound, each preferably a different
composition
from 8% to 40% polymer. Such additional steps take time and energy and will
increase
the costs associated with growing the crops.
U.S. Patent No. 4,320,040 to Fujita discloses a hydrophilic gel including
acrylic acid or
methacrylic acid in the presence of polyvinyl alcohol that may be used as a
water
retaining agent for plants, although no detail as to that specific application
Is provided.
U.S. Patent No. 6,558,705 to O'Brien discloses application of a composition
containing
higher fatty alcohols (alkanols) to suppress water evaporation in soil.
Specifically, the
higher fatty alcohol Is mixed with slaked agricultural lime or acidified
gypsum.
U.S. Patent No. 6,322,724 to Sanderson discloses a coating comprising a cross-
linked
absorbent polymer combined with a low molecular weight compound. The
combination
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reduces the rate at which water evaporates from the polymer, providing a
source of
water for the soil.
In prior art patents such as Fujita, O'Brien and Sanderson, a potential
drawback is that
the coating or covering applied to the soil sits on top of the soil, providing
protection only
to the very top layer of the soil. In cases where the coating itself is
actually providing or
holding moisture for the crops, such superficial protection may not provide
enough
water to plant roots buried deep under the soil. Further, the coating provides
protection
only vertically, above or below the top level of soil, which does not prevent
water loss to
drainage in horizontal directions. Finally, if the coating is damaged, it
tends to be
unable to repair itself, leaving a hole through which water evaporates
relatively quickly.
It is also known to apply mulch or similar soil covering not only to protect
the soil, but to
deliver soil enhancers into the soil. For example, U.S. Patent No. 4,705,816
to Pole
discloses liquid rubber mulch composed of natural or synthetic rubber,
chloroprene,
polyisoprene, nitrile runner or similar compounds, along with binders,
fillers, surfactants,
viscosity control chemicals and soil enhancers such as nutrients, fertilizers
or
herbicides. The liquid mulch creates a friable crust over the soil that is
intended to
reduce evaporation while still allowing post-applied chemicals to enter the
soil. The soil
enhancers are released into the soil over time. An issue with this type of
mulch is
similar to that of shredded rubber mulches, namely that the mulch is not
inherently
biodegradable and can be difficult to remove from the soil. With respect' to
the
effectiveness of the delivery of the soil enhancers, the depth of penetration
of the
enhancers is likely relatively shallow, slow and uneven.
PCT Publication No. WO 00/47037 to MacAlister discloses a soil-enhancing mulch
sheet impregnated with a soil enhancer, such as fertilizers or herbicides,
which is
released into the soil when water saturates the sheet. While the rate and
duration of
release of the soil enhancer may be controlled by changing the water
solubility and
mechanical durability of the film, the depth of penetration of the enhancers
into the soil
is likely only shallow and is difficult to control.
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It is therefore an object of the invention to provide a compound to form a
flexible crust
for a soil substrate that overcomes the foregoing deficiencies.
It is a further object of the invention to provide a compound to form a
flexible crust that
can be applied under most practical working conditions.
It is a further object of the invention to provide a compound to form a
flexible crust in
which the viscosity of the compound over time can be controlled, in order to
customize
the properties of the flexible crust.
It is a further object of the invention to provide a compound to form a
flexible crust that
can be broken up and worked into the soil, without contaminating the soil.
It is yet a further object of the invention to provide a compound to form a
flexible crust
that is non-toxic, biodegradable and environmentally safe.
It is a further object of the invention to provide a compound to form a
flexible crust for a
soil substrate that is controllably porous, to allow soil enhancers to
penetrate the crust
and reach the seeds or plants in the soil substrate.
It is yet a further object of the invention to provide a soil-enhancing
compound that can
deliver soil enhancers to a selected part of the soil substrate, to provide
maximum
benefits to the crop.
It is yet a further object of the invention to provide a soil-enhancing
compound that that
can deliver soil enhancers to the soil substrate over an extended period of
time, as
appropriate to provide maximum benefit to the soil substrate.
It is yet a further object of the invention to provide a compound to form a
flexible crust
that can reform or repair small defects in the crust.
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These and other objects of the invention will be appreciated by reference to
the
summary of the invention and to the detailed description of the preferred
embodiment
that follow. It will be noted that not all objects of the invention are
necessarily realized in
all possible embodiments of the invention as defined by each claim.
SUMMARY OF THE INVENTION
The invention relates to a soil protecting and enhancing compound comprising a
binary
system which forms a matrix that binds with the top layers of a soil
substrate, effectively
producing a flexible crust. Upon mixing, the components of the binary compound
begin
to complex, or weakly cross-link, such that the viscosity of the compound
increases at a
controlled rate.
The formation of the crust takes place in the top layers of the soil
substrate, at a depth
that can be selected to match the specific application, such as the likely
depth at which
the seeds are planted, or to which the roots of the crop to be planted will
reach in a
given time frame, depending on when the crust is being applied. The depth
chosen is
controlled by controlling the rate at which the viscosity of the binary
compound
increases.
The porosity of the final crust is also influenced by the amount of binary
compound and
the depth to which it penetrates. This allows the user to apply soil enhancing
agents as
needed, and be assured that those agents will reach the crop through the
crust.
Controlling the rate of viscosity increase also allows the viscosity increase
to occur
predominantly within the soil substrate, rather than within the holding,
mixing or
application apparatus, thereby simplifying the application process. The binary
nature of
the compound allows the different components to be used as a soil pre-
treatment, to be
applied directly to the soil substrate at any stage of the crop-growing
process, such as
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at seeding or post-germination, and to be used as a slow-release carrier to
provide soil
enhancers to the soil.
Once formed, the crust significantly reduces the amount of water that can
escape from
the soil, by retaining water within the bound layers of the soil within the
crust matrix.
However, because the crust Is only weakly cross-linked, it can be physically
broken up if
it is manipulated mechanically, so the soil substrate can be accessed easily
if required for
further processing. Nor does the crust contain any strong or toxic chemicals,
so it may
be incorporated directly into the soil substrate material without adversely
affecting the
properties or value of the soil substrate.
The weak-cross-linking of the crust is also reversible, which provides a self-
healing
property to the crust. This characteristic may be useful if the crust is
damaged by an
impact, such as a stone, branch or other foreign object falling onto the
crust.
Various additives may also be used to tailor the properties of the crust to
specific
application conditions and/or to an application process. The compound may also
be
manipulated to allow the compound to perform a specific application, such as
preventing desiccation, providing moisture, allowing post-application of soil
enhancers
and/or providing soil enhancers at a controllable rate.
In one aspect, the invention comprises a method of forming an anti-desiccant
crust on a
soil substrate comprising the steps of combining a first component with a
second
aqueous component, the first component comprising a polysaccharide and the
second
component comprising a borate provider, to form a compound; applying the
compound
to the soil substrate; allowing the compound to penetrate the soil substrate
to a pre-
determined depth, thereby forming the anti-desiccant crust; wherein the
compound
further comprises an alkaline component in an amount effective to facilitate
release of
borate into the compound from the borate provider. The crust may form
substantially
independently of any evaporation of ingredients of the first and second
components.
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In yet another aspect, the invention comprises a soil substrate anti-desiccant
compound
comprising a first component, comprising a polysaccharide, which may be a
starch, and
may further be a modified starch; a second aqueous component, comprising a
borate
provider; an alkaline component in either the first component or the second
component,
in an amount effective to facilitate release of borate from the borate
provider; wherein
mixing the first and second components forms cross-links within the compound
at a
controlled rate; and wherein the compound is immediately applicable to a soil
substrate.
The alkaline component, which may be a hydroxide, selected from the group
comprising
sodium hydroxide, ammonium hydroxide and potassium hydroxide, may be selected
to
provide a pH of at least 12 to the compound. The controlled rate is preferably
selected
to allow a majority of the cross-links to form within the soil substrate.
Additives, such as a retardant, which may be selected from the group
comprising water,
alcohols and glycols, may be added to manipulate the controlled rate of cross-
linking.
Other additives may include surfactants, thickeners and plasticizers, each of
which will
affect the crust properties and penetration of the crust into the soil
substrate and can be
manipulated in order to precisely control the delivery of the binary compound.
In another aspect, the invention comprises use of a compound comprising a
first
component, comprising a polysaccharide; a second component, comprising a
borate
provider; an alkaline component in either the first component or the second
component,
in an amount effective to facilitate release of borate from the borate
provider; wherein
mixing the first and second components in the presence of water forms cross-
links
within the compound at a controlled rate, as an anti-desiccant for a soil
substrate.
In another aspect, the invention comprises use of a compound comprising a
first
component, comprising a polysaccharide; a second component, comprising a
borate
provider, an alkaline component in either the first component or the second
component,
in an amount effective to facilitate release of borate from the borate
provider; wherein
mixing the first and second components in the presence of water forms cross-
links
within the compound at a controlled rate, as a soil enhancer for the soil
substrate.
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In another aspect, the Invention comprises a soil enhancing compound to
provide
controlled release of a soil enhancer within a soil substrate, comprising a
first
component, comprising a polysaccharide; a second component, comprising a
borate
provider; an alkaline component in either the first component or the second
component,
in an amount effective to facilitate release of borate from the borate
provider; and a
carrier holding the soil enhancer; wherein mixing the first and second
components in the
presence of water forms cross-links within the compound at a controlled rate
within the
soil substrate.
In yet another aspect, the invention comprises use of a compound comprising a
first
component, comprising a polysaccharide; a second component, comprising a
borate
provider; an alkaline component in either the first component or the second
component,
in an amount effective to facilitate release of borate from the borate
provider; and a
carrier holding the soil enhancer; wherein mixing the first and second
components in the
presence of water forms cross-links within the compound at a controlled rate
within the
soil substrate, as a soil enhancer for the soil substrate.
The foregoing was intended as a broad summary only and of only some of the
aspects
of the invention. It was not intended to define the limits or requirements of
the invention.
Other aspects of the invention will be appreciated by reference to the
detailed
description of the preferred embodiment and to the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The preferred embodiment of the invention will be described by reference to
the
drawings in which:
Fig. 1 is a flowchart showing the preferred steps in the method to create a
binary soil
protection and enhancement compound;
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Fig. 2 is a graph showing the viscosity (centipoise) versus time (minutes) of
various
compounds made according to the invention as well as some reference compounds;
Fig. 3 is a table showing the viscosity of various polysaccharides dissolved
in water; and
Fig. 4 is a table showing the viscosity change over time of various
polysaccharide
compounds prepared according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
The soil protection and enhancement compound of the Invention is a binary
system
comprising two main components, which, when mixed in the presence of water,
create a
compound whose viscosity begins to increase at a controlled rate, as a result
of the
complexation, or weak bonding, that begins within the compound upon mixing.
The first main component of the binary compound is a mixture containing 0.1 to
15% by
weight of a polysaccharide such as starch, a modified starch or other
polysaccharide.
Suitable polysaccharides include starches having amylase or amylopectin, alpha-
or
beta-glucan, cellulose, dextrans, pectin, chitosan, modified glucan including
glucan with
gluten protein, acid- or alkaline-treated starch, enzyme-treated starch,
bleached starch,
oxidized starch, monostarch phosphate, distarch glycerol, distarch phosphate
esterified
with sodium trimetaphosphate, phosphated or acetylated distarch phosphate,
starch
acetate esterified with acetic anhydride or vinyl acetate, acetylated distarch
adipate or
glycerol, hydroxypropyl starch, hydroxypropyl distarch phosphate,
hydroxypropyl
distarch glycerol, starch sodium octenyl succinate, carrageenan and gums
including
xanthan gum, guar gum, guaran, carob gum and locust bean gum. The first
component
is preferably an aqueous mixture, encompassing aqueous polysaccharide
solutions,
dispersions or any other combination of polysaccharide in a flowable medium;
however,
the first component may be a dry powder mixture of a polysaccharide, such as
starch
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alone or starch mixed with guar gum, in a 20:1 ratio. A dry powder mixture
could be
mixed with water at a staging area associated with the soil to be protected. A
suitable
mixture of starch/guar gum powder would be 0.5% to 5% powder in water.
The second component of the binary compound is a mixture containing
approximately
0.1 - 20% of a borate provider, such as borax or boric acid.
Once the two components are combined in the presence of water to form the
binary
compound, the polysaccharide, molecules, particularly the glucose molecules,
begin to
link with the borate supplied by the borate provider at a controlled rate.
This process,
referred to as complexation, forms weak covalent bonds, comparable to weak
cross-
links in a polymer, within the polysaccharide matrix, as shown in the
following diagram:
H2O
OH }{O p I OH 2 OH I
O OK HO 0
ftrioj /sO O Ha 0
O
O B\O 0
OH n HO i O i n
I Glucose polymer 2 Metaborate ion I Glucose polymer 3 Glucose complexed with
Borate
The complexation reaction results in an increase of viscosity throughout the
mixture as
starch molecules bond with borates. The bonds formed by the complexation
reaction
are preferably weaker than those formed when a conventional cross-linker is
added to a
starch solution. The immediate result is a liquid gel; over time, the liquid
gel continues
to cross-link until a final matrix is formed. The final matrix has some
strength and
flexibility, but does not become extremely hard or substantially
indestructible. Nor does
the matrix necessarily form a completely cohesive, closed film. This may be
preferred,
in order to allow soil enhancers, such as water, nutrients and biocides, to
penetrate
through the crust to reach the intended target in or on the soil substrate.
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Further, matrix formation is controlled by the rate and amount of
polysaccharide-borate
cross-linking within the mixture. This provides a substantial advantage in wet
conditions, as the matrix will soften if it is dampened or soaked with water.
This
softening is caused by the breaking of some of the weak links in the matrix,
essentially
reversing the earlier cross-linking reaction. However, the matrix will still
maintain its
inherent cross-linked structure, and some of the links broken when the matrix
is wetted
will reform in new ways as the water evaporates or is absorbed by the
underlying soil or
plant seeds or roots. This means that the crust will re-harden, and can in
fact re-form to
cover small areas that had previously been damaged, providing a new level of
protection.
Either solution may be modified by addition of a caustic, such as sodium
hydroxide,
ammonium hydroxide or potassium hydroxide, in order to increase the amount and
rate
of cross-linking. The caustic improves the release of borate from the borax or
boric acid
in solution, as borax and boric acid tend to polymerize in alkaline solutions,
creating
more borate ions to cross-link with the starch molecules. Depending on the
particular
starch used, a suitable amount of caustic is preferably in the range of up to
20%, for a
borax solution, preferably a 2% caustic to 2% borax ratio. The effect of the
caustic is to
increase the pH of the borax solution, which leads to an increased level of
borate being
released, which in turn improves the complexation rate with the starch. If
boric acid is
used, a slightly higher level of caustic is generally required, in the range
of 2% caustic to
0.96% boric acid. Typically, a more alkaline mixture will create a more
effective cross-
linking reaction.
The complexation reaction can be further manipulated by changing the
ingredients in
the two main components of the binary compound. Adding a retardant to delay or
slow
the rate at which the binary compound increases viscosity can be beneficial;
it may be
preferable in some situations to transport or store the mixture rather than
applying it
immediately after combining the solutions. Further, having the compound
viscosity
increase within the layers of the soil substrate allows the depth of
penetration to be
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controlled and allows the compound to be manipulated and applied under
practically
any circumstances without the need for heating or mixing.
Either component may therefore be modified by adding a retardant to slow the
complexation reaction. This allows the rate of complexation and the
corresponding
increase in viscosity of the resulting mixture to be controlled according to
the needs of
the specific application. For example, the soak time, during which the mixture
is
flowable enough to penetrate the soil substrate to which it is applied, can be
adjusted by
controlling the rate of increasing viscosity. By adjusting the soak time, the
amount of
interaction of the mixture with the soil substrate (including the depth of
penetration of
the mixture into the soil substrate) can be controlled, allowing the amount of
soil
substrate material captured by the mixture and encapsulated in the final crust
matrix to
be controlled. The flexibility and toughness of the resultant crust is also
impacted by the
amount of soil substrate material within the crust matrix and can therefore be
controlled
by controlling the soak time. The soak time is therefore dependent on the
application.
For example, in a soil anti-desiccant application, the desired depth of
penetration is
likely to a depth at least equivalent to the approximate depth at which the
seeds are
planted, such that moisture is readily available to the seeds. For anti-
desiccant
protection post-germination, the desired depth of penetration may be deeper,
to provide
ready moisture to the root system of the plant, as it embeds itself more
firmly in the soil.
The properties of the compound can be controlled to provide penetration of
mere
centimetres or even completely through the depth of the soil substrate, as
required by
the application and soil properties.
Different retardants can be added in different amounts, allowing the mixture
properties
to be further tailored for the application. Preferred materials for the
retardant include
water, alcohols, such as methanol, and glycols, such as propylene glycol.
Water has
the advantage of being inexpensive, environmentally friendly, and generally
available at
most application sites. However, although water can be used at most
application
temperatures, it is less suitable for sub-zero applications. An alcohol with a
lower
freezing point can be used in that case, to lower the freezing point of the
main solutions
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and to ensure that the mixture remains flowabie for as long as necessary. Good
retardant and freezing point suppression results have been observed with
ranges of 1 -
30% of methanol and glycol. The resulting compounds can then be applied at
most
practical working temperatures, including the preferred range of -5 C to +40
C.
in some cases, less penetration of the binary compound into the soil substrate
is
preferred, such as in highly porous or sandy soil substrates. In these cases,
thickeners
may be added to either solution in order to further tailor the properties by
slowing the
penetration of the mixed compound as the complexation reaction occurs.
Thickeners
may be either inorganic, organic, natural, synthetic or combinations thereof.
Examples
of inorganic thickeners include kaolinite clays, montmorillonite clays, and
bentonite,
while some examples of natural organic thickeners include casein, guar gum,
pectin,
gum taraganth, gum karaya, xanthan gum, and starch. The organic or inorganic
thickeners may be modified with natural or synthetic products to enhance their
properties. Examples of synthetic organic thickeners may include modified or
unmodified cellulose ethers such as methyl cellulose, hydroxyethyl cellulose
hydroxypropyl cellulose, as well as polymers or copolymers of acrylic acid and
its
esters, methacrylic acid and its esters, vinyl acetate and its hydrolyzates,
and
polyurethane and derivatives.
Another possible additive is a surfactant, which will generally improve the
wetting ability
of the binary compound, affecting the depth of permeation of the compound into
the soil
substrate, as well as the porosity of the final crust. Some preferred
surfactants include
alkyl ethoxylates, alkyl propoxylates, block EO/PO, alkyl sulfonates and/or
benzyl
sulfonates. Generally, a surfactant is preferably added in approximate
concentrations of
up to 25% of the compound. Depending on the application, a surfactant type and
concentration may be chosen to provide the desired soil substrate penetration,
the
desired porosity, and to be compatible with the soil substrate.
If a more flexible crust is preferred, glycerine or a similar plasticizer can
also be added
to the crust to increase the flexibility. Glycerine may be added to either
component and
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CA 02719571 2010-11-05
can be present in the mixture at a concentration of up to 50%. Glycerine may
also have
a freezing-point suppressing effect.
The method of making the binary compound is shown in the flowchart in Fig. 1.
A first
component 2 comprising a polysaccharide and a second component 4 comprising an
aqueous mixture containing a borate provider are provided, along with an
alkaline agent
as an ingredient in either the first or second component. The separate
components are
delivered 6 to a staging area associated with the soil to be protected. The
staging area
may also be a site from which an airborne applicator, such as a helicopter,
can be
loaded and launched. If a significant delay 8 is required between the time of
mixing and
the time of application, retardant 10 may be added to either of components 2
and 4 at
the staging area or before delivery thereto. At the staging area, the first
and second
components are mixed 12 to create a liquid compound. The liquid compound is
applied
14 to the surface of the soil before the compound undergoes a substantial
increase in
viscosity and while the compound can still easily be distributed over the
soil, and will be
able to penetrate the soil; the liquid compound can therefore reach the
desired
penetration depth within the soil before the compound reaches a high
viscosity, at which
it is essentially no longer flowable. At this point, crust 18 has been formed.
Alternatively, mixing 12 can take place any time subsequent to application 14.
This
might occur, for example, if component 2 is applied to the soil first,
followed by
component 4, or if a dual nozzle applicator is used. In the further
alternative, the mixing
and application processes can be combined into a single process 16.
The method may be modified by predetermining a desired delay period for the
liquid
compound to reach its maximum viscosity and adding a retardant to the liquid
compound, in an amount effective to correlate the time before the compound
undergoes
a substantial increase viscosity to that desired delay period, in order to
facilitate storage,
handing or transport of the mixture if necessary before it is applied to a
soil substrate.
Controlling the rate of viscosity change in the binary compound is important
in producing
a final crust having the desired properties. As shown in Fig. 2, the viscosity
over time of
CA 02719571 2010-11-05
binary compounds having similar components, in varying ratios, can produce
compounds
having different maximum and minimum viscosities, which are reached at
different
times. Binary compounds can therefore be tailored for various applications and
application conditions. In Fig. 2, the viscosity of the liquid get formed from
the
compound is plotted against time. The lines represent different borax to
caustic ratios,
each tested in a solution having a starch concentration of 4%. xB indicates
the amount
of borax in the second component. For example, 2B indicates 2% borax in the
second
component. As the liquid gel is made up of 90% of the starch component and 10%
of
the second component, 2B denotes a compound having 0.2 % borax. Similarly, xN
stands for percent caustic (in this set of compounds, sodium hydroxide (NaOH)
is the
caustic) in the second component. 4N - 2B therefore denotes for a compound
having
0.4% caustic and 0.2% borax.
The binary compound may be applied at any stage of the crop growing process.
If
applied during seeding, the depth at which the seeds are planted would
influence the
depth to which the crust is applied. Further, maximum protection from the
elements and
predators, such as birds, might be preferred, and a firmer, less porous crust
might be
applied. At a later stage of crop growth, such as immediately post-
germination, a
thicker crust might be preferred, in order to encourage the crop roots to
penetrate more
deeply by providing a deeper source of moisture. A more porous crust may be
also be
preferred at this stage, to allow for the application of nutrients to help the
crops grow, or
of herbicides to combat weeds.
Because the compound properties can be controlled very closely, the compound
itself
can be applied under most practical working conditions, without the need to
wait once
the solutions are combined. This saves man-hours, as it allows more soil
substrate to
be protected in a given time. Conversely, the solutions can be modified to
allow for a
longer time prior to forming the final matrix, if it is necessary to pre-mix
the solutions
some time before the mixture is applied to the soil substrate. This might be
necessary if
a mixture has to be stored for some period of time, or transported to a
different location
before being applied to a soil substrate. For example, if the mixture is being
applied
16
CA 02719571 2010-11-05
from an airborne vehicle, such as a helicopter, it would be preferable to
simply spray the
final mixture, instead of being concerned with carrying the various solutions
and having
to combine them in the proper proportions immediately before application.
The binary compound can also be modified so that it is applicable even at
temperatures
below the freezing point of water, without the need for special equipment to
heat the
mixture before applying. Conversely, the binary compound can be modified to be
unaffected by higher atmospheric temperatures.
Because the rate of viscosity increase is controlled, it is possible to apply
the binary
compound using any known application means, including various spray
applicators.
Spray applicators configured in various ways may be used, including an
external dual
spray gun where the two components are mixed as they leave the gun nozzles.
Alternatively, the two components may be mixed as they exit the nozzles of a
dual-
nozzle spray applicator. If further ingredients are employed to control the
increase in
viscosity, it is also possible to pre-mix the ingredients and apply them with
a single
nozzle applicator. The solutions might also be mixed in a mixing chamber just
as they
enter the spray applicator, or even within the spray applicator nozzle. The
viscosity
increase may also be controlled to allow some delay, during which the mixture
may be
transported to the soil where it is to be applied. Any spray application
system may be
used, as no special equipment or supplies are required to control the
properties of the
compound.
In addition to spray-application of a liquid form of the binary compound,
other
application methods may successfully be used. For example, either of the main
components of the compound (i.e. the polysaccharide or the borate provider)
may be
applied directly to the soil substrate in dry solid or powder form. As soon as
it is desired
to form a crust, the second component of the crust can be applied in an
aqueous form,
providing the water and the rest of the components required to begin the
complexation
reaction, thus beginning the formation of the soil enhancing and protecting
crust.
Similarly, both components may be applied in a powder form, and allowed to
simply sit
17
CA 02719571 2010-11-05
in an inactive form on the soil substrate. Water, either in the form of rain,
or applied by
spraying, will begin the complexation reaction and lead to crust formation.
It will be understood that the two components may be applied at different
times, whether
the components are applied in dry or aqueous forms. This time delay, which may
supplement the time delay provided by the controlled viscosity increase within
the
binary compound, can allow time to treat or otherwise deal with the soil
substrate or the
plants or seeds in the soil substrate, before providing the full protection
afforded by the
complete binary compound.
The binary compound may also be used as a pre-treatment for bagged soil or
soil
mixtures. In this application, one of the main components may be pre-mixed
with the
soil, while the second component may be provided separately. Only upon mixing
of the
pre-treated soil and the second component in the presence of water would the
complexation reaction begin, forming the binary compound. Of course, if the
second
component is provided in an aqueous form, the reaction would begin upon
mixing,
without the need for additional water. As a further application, both
components could
be pre-mixed into the bagged soil in dry form, as long as care is taken to
keep the soil
relatively dry.
In another application, the binary compound may be used to enhance the soil
substrate,
by carrying specific soil-enhancing additives, such as water, pigments,
nutrients,
fertilizers, fungicides, herbicides, pesticides, other biocides or
combinations of these, to
a controllable depth within the soil substrate. Because the specific depth to
which an
additive should be delivered will vary with the plant and/or the additive,
being able to
control the depth to which the additive is carried by the binary compound
allows the
user to obtain the maximum benefits from the additive by delivering it to the
depth that is
most advantageous for the plant. For example, water should be placed close to
the
roots of a plant, rather than staying at the surface of the soil substrate.
Pesticides, on
the other hand, might be preferentially deposited closer to the surface, for
pests that
attack the leaves of a plant or for pests that crawl over the soil substrate
to reach the
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CA 02719571 2010-11-05
plant. Such selectivity and flexibility in application of various soil
enhancing additives
allows the user to obtain the maximum effect of the additives applied, as well
as
possibly decreasing the amount of additive needed to reach that level of
effectiveness.
Applying the additive using the binary compound of the present invention can
also
prevent run-off and loss of the additive before it can be absorbed by the
plant or before
it performs its intended function, by holding the additive within the crust.
In a further refinement of the soil enhancing application, the binary compound
may be
used to provide a long term or slow-release soil enhancement. In this
application, the
soil-enhancing additive, such as water, pigments, nutrients, fertilizers,
fungicides,
herbicides, pesticides, other biocides or combinations of these, may be
encapsulated
within or otherwise held by a carrier, which is then mixed with one or both
components
of the binary compound, and incorporated into the soil substrate. When the
compound
penetrates the soil substrate, the carrier is moved to the same depth as the
compound,
allowing the user to target the area of the soil substrate at which the
additive would be
most effective.
The carrier is preferably composed of porous or semi-porous particles that are
impregnated with or otherwise hold the additive. Expanded perlite is an
example of a
suitably porous carrier. When exposed to the desired additive, the pores and
cavities
over the surface of the perlite will absorb and hold the additive. When the
perlite is
added to the soil enhancing compound, the particles are carried to the desired
depth,
where the additive may be released from the pores of the perlite over a period
of time.
The duration of the release of the compound from the porous particle may be
controlled
by adjusting the particle's physical properties such as overall size, internal
cellular
structure, and shell porosity, and can also be enhanced by utilizing chemical
or natural
treatments to alter the hydrophilicity or hydrophobicity of the particle. Thus
it will be
understood that the desired release rate can be achieved through judicious
selection of
various carriers having different physical properties, and exposing those
carriers to
different impregnation methods. Again, because the location and containment of
the
additive are controlled, this application can decrease the amount of additive
needed to
19
CA 02719571 2010-11-05
effectively perform its intended function, and can prevent unnecessary loss or
run-off of
the additive before it has performed that function.
Experiment 1: Germination Trial for Binary Compound as Anti-desiccant
Treatment 1. Control: Seeds + water. Under this treatment, trays were checked
daily
and hand watered as needed for optimum germination for the duration of the
trial.
Treatment 2. Seeds + no water + binary compound. For this treatment, trays
were
watered at seeding but not watered again for the duration of the trial. The
binary
compound was created by adding 1.0 litre of polysaccharide component to 2.5
litres of
water, agitating, then adding 0.1 litre of borate provider component, and
gently shaking.
The solution was sprayed evenly over the trays using a backpack sprayer.
Treatment 3. Seeds + no water. In this treatment, the soil was watered at
seeding but
the trays were not watered again for the duration of the trial.
Plastic trays with 32 individual cells for soil and seeds were planted with
either marigold
or pea seeds. Twenty trays (ten of each species) were planted for each
treatment. To
begin, all sixty trays were placed side by side on a bench in a greenhouse,
and blocked
into the three treatments, leaving approximately 30cm buffer zones between
treatments.
The marigold and pea trays for each treatment were kept separate from each
other but
blocked together. At seeding, all trays were thoroughly watered. The anti
desiccant
compound was sprayed on Treatment 2 trays. Three fans were set up to blow air
across all treatments. After two weeks, the number of cells with germinated
seed was
counted in each tray.
There was a significant difference among the three treatments in the number of
cells in
trays with germinated seeds for pea (Table 1) and marigold (Table 2). For both
crops,
germination was significantly lower in Treatment 3, which had no binary
compound or
CA 02719571 2010-11-05
water than in the Control (Treatment 1, regular watering). Germination in
Treatment 2,
in which plants were treated with the binary compound but without further
water, fell
between the other two treatments. While there was no significant difference
between
individual pairs of treatments in the trial, the trend was for improved
germination in un-
watered seeds with the binary compound, although not as much improvement as in
the
regularly watered Control treatment.
Germination (out of 32) Peas
33 A
32 A,B
31 B
30 -
29- T
28
27
28 - --- -
No ant(-desiccant or water Anti-desiccant, no water Control
Treatment
Table 1. Effect of anti-desiccant treatment on mean ( s.e.m.) pea seedling
germination
(n =10/treatment).
Germination (out of 32) Marigolds
35 A
A, B
30 B
20
10
5
0
No anti-desiccant or water Antii-desiccant, no water Control
Treatment
Table 2. Effect of anti-desiccant treatment on mean ( s.e.m.) marigold
seedling
germination (n = 10/treatment).
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CA 02719571 2010-11-05
Based on these test results, the binary compound was shown to provide
protection
against desiccation both for the pea seeds, which have relatively larger water
reserves,
and for the marigold seeds, which have less metabolic water stored in
relatively small
seeds.
Experiment 2: Seedling Survival Trial for Binary Compound as Anti-desiccant
Treatment 1. Control: Seeds + water. Under this treatment, trays were checked
daily
and hand watered as needed for optimum growth before and after germination.
Treatment 2. Seeds + water + anti-desiccant. Under this treatment, seedlings
were
hand watered as needed for optimal growth before and after germination. At the
cotyledon stage (first leaves) the binary compound was mixed by adding 1.0
litre of
polysaccharide component to 2.5 litres of water, agitating, then adding 0.1
litre of borate
provider component, and gently shaking. The solution was sprayed evenly over
the
trays with a backpack sprayer.
Treatment 3. Seeds + no water. In this treatment, the seedlings were watered
before
germination, but not after.
Treatment 4. Seeds + no water + anti-desiccant. In this treatment, seedlings
were
watered before but not after germination. At the cotyledon stage (first
leaves) the binary
compound was mixed and applied as in Treatment 2.
Plastic trays with 32 individual cells for soil and seeds were planted with
either marigold
or pea seeds. Twenty trays (ten of each species) were planted for each
treatment. To
begin, all sixty trays were placed side by side on a bench in a greenhouse,
and blocked
into the four treatments, leaving approximately 30cm buffer zones between
treatments.
The marigold and pea trays for each treatment were kept separate from each
other but
22
CA 02719571 2010-11-05
blocked together. At seeding all flats were thoroughly watered. After
germination
(approximately 1 week later) the anti desiccant compound was applied to the
trays in
Treatments 2 and 4, as noted. Four fans were set up to blow air across all
treatments.
Two weeks after application, seedling survival results were compiled.
There was a significant difference among the four treatments in the number of
seedlings
surviving for both pea (Table 3) and marigold (Table 4) seeds. For both crops,
seedling
survival was highest in the Control and anti-desiccant + water treatments and
significantly lower in the treatments without anti-desiccant or water.
Seedling survival (out of 32) Peas
32.5 A A
32
B A,B
31.5
31-
30.5
29.5
29 T ,
No anti-desiccant Anti-desiccant, Control Anti-desiccant
or water no water Treatment and water
Table 3. Effect of anti-desiccant treatment on mean ( s.e.m.) number of
surviving pea
seedlings (n = 10/treatment).
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CA 02719571 2010-11-05
Seedling survival (out of 32) Marigold
35 A A A
25 B
15
5
0 - --,
No anti-desiccant Anti-desiccant, Control Anti-desiccant
or water no water and water
Treatment
Table 4. Effect of anti-desiccant treatment on mean ( s.e.m.) number of
surviving
marigold seedlings (n = 10/treatment).
As for germination, the trend was for the binary compound to protect the pea
seedlings
from desiccation. The improvement in survival in marigold was significantly
higher with
the anti-desiccant treatment than for the untreated un-watered seedlings.
It will be appreciated by those skilled in the art that other variations to
the preferred
embodiment described herein may be practised without departing from the scope
of the
invention, such scope being properly defined by the following claims.
24
