Note: Descriptions are shown in the official language in which they were submitted.
64t7Z2
This invention relates to agricultural soil compositions
formulated to control the delivery of the optimum amount of water
to the root systems of growing plants. These compositions can
be used in any agricultural application, whether in small con-
tainers as for house plants or in open fields.
As is well ~nown to all gardeners and farmers, the
essential condition for growth of any agricultural product is
accessability to water in beneficial amounts. Too little water
will result in stunted growth and even failure to grow at all
and too much water will cause rotting and eventual destruction
of the plant.
It is, therefore, the object of this invention to pro-
vide soil compositions adaptable to any environment whereby the
water supply is regulated and controlled in accordance with the
requirements of whatever is growing therein.
In my ~oint (with Robert J. Lippé) U.S. Patent ~o.
3,710,510, assigned to Cabot Corporation, there are described
plant growth media for germinating seeds and nurturing seedlings
through the initial stages o~ their growth. My new invention is
designed principally to provide for the next stages of plant
growth which the compositions of said patent are incapable of
doing, although, of course, seeds can also be germinated in the
compositions of this invention.
The compositions of the present invention comprise the
usual soil materials present in any garden to which has been
added a hydrophobic solid particulate material in the pro-
portion of one part by volume to about fifteen to forty parts by
volume of the soil material. The criticality of these proportions
will be explained and demonstrated hereinafter.
The hydrophobic particulate solids utilized in the com-
positions of this invention can be any of those which axe des-
~,
~6~7zz
,
cribed in detail in my said U.S. patent No. 3,710,510.
According to the invention there is provided an
agricultural soil composition comprising a ~ixture of (a)
one part by volume of hydrophobic finely-divided particulate
metallic oxide having a BET-N2 surface area of at least about
50 m /g and (b) between 15 and about 40 parts by volume of
conventional soil material.
Accordiny to an embodiment of the invention there is
provided a potted plant soil system comprising a containerized
bed of soil comprising the soil composition of the invention
and means to deliver water to the bottom of the bed.
According to another aspect of the invention there
is provided a method for growing plants which comprises immersing
the roots thereof in a soil composition of the invention, and
delivering a growth-supporting quantity of water to the
composition.
According to yet another aspect of the invention there
is provided a method for growing plants from seed which com-
prises placing seeds into contact with a soil composition of
the invention, and delivering a seed germinating and growth-
supporting quantity of water to the bed composition.
Suffice it to say that the particulate material should
be finely divided and hydrophobic to the extent that it will
float on the surface of water. The preferred particulate is
~ilica having a BET surface area of at least about 50 square
meters per gram and having hydroxyl groups initially on the sur-
face which have been substantially completely reacted with hyd~o-
phobizing agents such as organosilicon compounds. The surface
treatment i5 suitably sufficient to attach organo groups totalling
at least 0.5% and preferably at least 1% by dry weight of the
particulate to the surface thereof.
A ~ -2 _
1(1647~2
The unexpected result achieved by incorporating the
critical proportion of hydrophobic particulates in the soil for
any given condition is the delivery of water throughout the body
of soil and the maintenance of the water level therein at a pre-
selected height regardless of the water level in the surrounding
terrain. Once water is present in the body of the composition
equilibrium will be maintained so long as water continues to be
supplied from below. The reason for this is that the degree of
capillary rise is controlled by the proportion of the hydro-
phobic paxticulate material in the composition which is selected
so that inflow of fresh water will be no greater than the rate
of evaporation from the surface of the total mass. Thus the
improved soil composition never can become water saturated be-
cause the hydrophobic constituent of the soil, not being wettable,
p~rmits inflow of air along with water and maintains sufficient
porosity in the body of the soil to prevent drowning of plants
therein.
It is in the constant and regulated delivery of water
to the composition of my invention wherein lies the principal
- 2a -
~ . j!
r~;,
, ~, ~, ~
~(~6~7ZZ
distinctibn of this composition from that of my said patent No.
3,710,510. As noted in column 6 of the patent the strongly
hydrophobic nature of the added particulate material which is
present in amounts at least as great as one part by volume to
eight, and preferably substantially fewer, i.e. three, parts by
volume of soil materials prevents aqueous liquid from being
drawn up into the soil bed. While some water vapor may diffuse
into the interstices of the bed I have found in practice that the
amount of diffusion is so slight that total evaporatior- of the
initial water content plus whatever vapor may become added ul-
timately occurs and rather soon. Since water depletion becomes
complete while the seedling is still young it must be trans-
planted in a more salubrious environment such as that of this
- invention. Furthermore, the water content of the composition
of the patent cannot be reconstituted since that composition will
not accept fresh water because of its extreme hydrophobicity r
and must, therefore, be discarded after use.
When my new composition is expected to remain in a
container for long periods of times, even years, it may be ad-
vantageous to secure the hydrophobic particulate material by
. . .
means of an adhesive to some heavier component of the soil.Otherwise, the particulates, which are much lighter and less
dense than the remainder of the soil, tend, with passage of time
to entrain in the upward migration of water. To counteract this
trend and maintain more even distribution throughout the growth
medium the particulate material can easily be attached to a heavier
component such as sand by a suitable-adhesive which is
indestructible in the growing environment. A preferred class of
such adhesives is that consisting of completely polymeric fluids
having low viscosity and capability of being catalyzed or heat
converted to a solid. Typical of these are the epoxy and poly-
-- 3 --
ester resins and reactive silicone fluids.
The joining of the light to heavier material is easilyachieved. The heavy material is first tumbled in a rotating drum
while adhesive is added. When in the tacky state the light
material is added so that it sticks to the surface of the sub-
strate. Thexeafter, the adhesive is set by conventional means.
It is merely necessary that the light hydrophobic component lie
on the surface of the substrate so that its surfaces are exposed
to the atmosphere. Useful procedures for making this material
are described in my joint (with Lippé & Fletcher) U.S. patent
No. 3,562,153.
A major utility of the composition of this invention
is as a potting soil, that is, as bedd1ng for the starting,
feeding and development of plants in pots. Such pots must have
openings in the bottom and be set in a container of water. When
the correct amount of hydrophobic particulate material is incor-
porated in the bedding for the selected plant growing therein
precisely the right amount of water for good growth conditions
will migrate upwardly at a consistent rate so long as the reser-
; 20 voir below is supplied with water. The inflow rate will be most
advantageously regulated so that the top one inch or so of soil
is dry from evaporation. Such practice reduces the chance of
sustained fungus growth on the soil surface. And it is hecause
of the hydrophobic ingredient in the mix that evaporation will
occur at the surface at a rate greater than the water replenish-
ment from below. Thus by proper compounding a balance can be
struck whereby the dry level can be established at the most de-
sirable distance from the top, or, to put it otherwise, to pro-
vide water where it is most needed, at the root network.
It will be evident that so long as the reservoir in
which the plant pot is seated contains water the water supply to
-- 4 --
6~72~
the pot in continuously regulated amount is assured. Thus con-
stant attention need not be applied to watering except to keep
the reservoir supplied which can be done automatically and easily.
Surface watering of conventional soils can, of course, be done
automatically but this requires a much more complicated system
! in a reserved area which is not usually available for ornamental
plants in homes, offices, show rooms and the like.
It is evident -that the composition of my invention has
tremendous potential for general agricultural use. ~ater control
is of paramount importance in raising food crops for the world.
By selective compounding of the hydrophobic element into the
farmland water can most efficiently be used. Rainfall will pass
through the soil more readily because of the myriad of nonadsorp-
tive passa~es provided. The water will collect on the layers
below and reverse flow upward will occur although at a slower
rate,,when the supply from above is terminated. So long as water
remains at lower levels it will be metered upward at the desired
rate to meet the requirements of the growing thing~. And
where the soil contains too much water as in swampy terrain the
higher concentrations of hydrophobic particulates will be used
to resist hydraulic pressures.
- The following examples are illustrative of the compo-
sitions of my invention and of the results achieved by the use
thereof.
Example 1
A potting soil consisting of equal volumes of vermic-
ulite, perlite, and peat moss was blended with different pro-
portions of hydrophobic pyrogenic silica having a BET surface of
about 250 sq. meters per gram and 0.5% by weight of - Si(OEI3)3
surface groups obtained from treatment with hexamethyldisilazane.
The silica was each time blended into the dry potting soil by
-- 5 --
6~7Z2
tumbling in a one gallon container for fîve minutes. The various
blends were evaluated for their water uptake by placing six ounce
paper cups with perforated ~ottoms containing same in a tray of
water one inch in depth. To initiate capillary rise four ounces
(113.4 gm.) of water were poured into the top of each cup to
saturate the mixture. The following gains in weight from water
p}ck- ~ over =he pe~iods of days indicat~d weFe recorded.
-
.
'
.
: ~ :
: ~ :
72~2
r~ u~
r r r~
IQ ~ r--l r~ (s) r--l r~l r~ ~) ~ c~l ~? r~ 0
rl r-~ ~> ~D . ~) n d~ 0 a) ~ 0
u ~ $ ~) ~) O O r; r; r; r; r; r; r;
,
~ ~_
r~
~$ u~
~ 4~ ~ u~ ~ O ~ ~ O l 0
1--1 3 ~I ~ ~ ~ N ~ Lr~ ~ ~) ~D
:. .
rd u~
rl r l r~
a)r-l ~I 0 ~ ~ ~) ~9 1~ t~-1 ~) ~ ~1)
~ O ~ , ~ ~ 0 ~ ~
~ ~ ~ o o ,~ ~1 ,~ ,~ ~ ~ ,;
. , : . .
r~~-
$ u~ . .
r~ ~ ~ ~ ~ ~D ~ ~ 0 ~ ~ ~ ~
~ ~_ ~ N ~ d' u~ d' ~9 n In n .
: '
' ' ~) . . .
_.
O r-l ~ ~ N ~ ~J ~ d~ ~)
r~ ~ Yl ~ ~) ~ ) 1~ ~) ~)
_~ .
rl Id O
a ~ r l
r~ r--l _~
~Ua ~ I r ¦ ~.~ r r r-¦ r r
r--l ~) rl O O U l 11~ O Lt) ll 1 O O
rl r-l r-l r-l r l N N N d~ d~
~u~ c~tq . .
~ ,
-- 7 --
~L~6~7Z~,
It will be evident from the foregoing data that too
high a concentration of the hydrophobic constituent greatly in-
hibits the access of water to the soil (10/1 mix) whereas the
soil with no hydrophobic content (control) absorbs much yreater
- quantities of water. As between the'15/1 and 40/1 mixes the
difference in quantity of water pick-up is not particularly great
but shows the trend.
Example 2
To demonstrate the effect of the hydrophobic silica
content of the potting soil on controlling the moisture level
in the pot, clear plastic cylinders 4 inches in diameter and
1~ inches long were filled with the soil to within 2 inches of
the top. The bottom~closures were pierced with 10 quarter inch
holes and'the cylinders placed upright in a tray containing
water maintained at a constant level of one-half inch. Water
was initially poured into the top of each cylinder to accelerate
commencement of capillary uptake. I'he following data were ob-
tained.
' Depth of drv soil from Top (inches)
After 10 days A~ter 20 daYs After 60 days
Control (no silica) 0' 0 0
20/1 Soil/silica 0.5 1.0 1.0
40/1 Soil/silica 0.75 0.5 0.5
Similar results were achie~ed using other soil blendswith the same proportions of hydrophobic silica.
This example demonstrates the utility of hydrophobic
silica as a control means for maintaining a constant and regulated
supply of water to the growing bed. In each case the base
potting soil was'the same as that in Example l although it will
be obvious that any soil suitable for plant growth can be used
in the practice of this invention.
-- 8 --
1~64~7Z~:
~ Example 3
To demonstrate the effectiveness of the composition of
this in~ention both for seed germination and growth of the re-
sulting plant green beans and tomato seeds were planted in blends
containing the indicated ratios of hydrophobic si~ica to com-
mercial topsoil sold under the trademark "Ferlite". The results
were as follows:
Green Beans Tomatoes
~ermina- Av.Ht.Ins. /OGermina- Av.~It.Ins.
Volume Ratiotion- @ 30@ 30 days tion- @ 30~ 30 days
Soil/Silica days
_
10/1 0 o o o
lO15/l 80 12 0 o
20/l 90 16 20 7
30/1 80 14 40 lO
40/l 0 0 70 14
50/l 0 0 85 13
Control (no 0 0 90 8
silica)
It is, of course, well-known to those skilled in the
art o~ farming that water requirements are not the same for all
crops. But in the light of my invention selection of the opti-
mum proportion of silica to soil can readily be determined.
However, as shown by this example, ratios of soil to silica
less than about 15/l are not satisfactory and anything above
~0/l is at best marginal.
So far as the control is concerned it is clear that
the soil is saturated with water which is good for germination
of tomato seeds but not for continued growth of the plant. And
it is also well-known that if usual soils are watered only from
the bottom and hence are kept saturated any plant therein will
ultimately die. This is why watering must always be done from
the top for such plantings and not too frequently so that the
soil, after saturation from watering, has time to dry out. In
contrast to the constant cycling between wet and dry in conven-
_ g _
7ZZ
tional practice the composition of my invention makes possible a
closely controlled and consistent supply of just the right amount
of water for the particular planting.
: ~ '
.
~ ,
-- 10 --
