Note: Descriptions are shown in the official language in which they were submitted.
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S~RAW SOIL PRODUC~
ackground of the Invention
This invention relates to an improved soil product
and methods of making the same.
Various types of soil mixtures are used commercially
and for retail such as for potted plants, nursery beds,
etc. These mixtures include a minimum of actual soil
since good natural soil is difficult to obtain and has
other disadvantages such as for example it is heavy to
handle, it has poor moisture retention qualities, etc.
One mixture that is popularly used as a soil additive
or conditioner is barkdust since it has good moisture
retention qualities and it decomposes at a slow rate.
However, barkdust is now being used extensively in other
products, such as structural board, adhesive, etc., and
the demand thereof has made it too expensive for mass
usage as a soil conditioner. S-traw has been used as
a soil conditioner and has some attractive Eeatures,
namely, it is abundant and inexpensive and also makes
a good mulch when decomposed. Straw, however, has the
disadvantage that it decomposes at a fast rate and thus
is not feasiblé for commercial use. Artificial soil
mixtures have also been used but such mixtures are too
expensive at least for commercial use.
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Summary of the invention
According to the present invention and forming a
primary objective thereof, a soil product is provi,ded
which is inexpensive to manufacture, which uses a base
material that is abundant and economical, which is light
in weight and thus easy to handle, store and ship, which
has desired moisture retention qualities, which de-
composes at a relatively slow rate, and which releases
a nutrient as it decomposes.
In the formation of such a product, a base material
of straw is used. Such straw is coated with a water
insoluble material providing slow decomposition of
the s-traw and also providing slow nutrient release as
it decomposes. The water insoluble material comprises
urea formaldahyde resin. After applying the coating,
it is preferred that the coated product be formed into
blocks for handling and storage and subsequently ground
into particles to provide a soil-like texture for use as
a potting soil or nursery bed soil.
The invention will be better understood and addi-
tional objects and advantages will become apparent from
the following description taken in connection with the
drawing.
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srief Description of the Drawing
The drawing comprises a flow diagram of one
embodiment of the invention.
Detailed Description of Preferred Embodimen _
In brief, the product and a preferred manner of
forming the same comprises first reducing a straw to
shorter lengths than that which it is supplied from the
fields, for example, to lengths of about l/4 inch to
4 inches. The straw used can be almost any type, such
as for example, wheat straw, oat straw, grass straw,rice straw, or others, and its reduction to the shorter
lengths can be by any suitable machine or method. A
conventional hammer mill will provide the desired re-
duction, the output screen thereof being pre-selected
in size to provide the desired reduction of the straw.
A hammer mill is very effective since it not only re-
duces the length of the straw stems but it also breaks
up some of the tubular structure of the straw for maxi-
mum coverage by a water insoluble material as will now
be described.
Such water insoluble material comprises urea
formaldahyde resin. This resin is mixed with the straw
by any conventional means such as by an auger mixer.
The mixing step is accomplished in a short time such as
from l to 2 minutes, more or less, and thoroughly coats
the straw surfaces with the urea formaldahyde resin.
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Even the interior sur-face of the straw pieces that re-
main tubular after reduction thereof is coated.
The mixture is then formed into blocks. Preferably
the blocks are formed under pressure, such as from
200 to 3000 psi. The shape and size of the blocks is
not important, although it is desired that they be of a
shape and size which make them easy to handle, store,
and ship. A hay cuber known by the trade-mark John Deere
works efficiently in the formation of these blocks. If the
straw is not thoroughly coated with resin after the mixing
step, thorough coating is insured by the pressured formation
of the blocks. The blocks are allowed to cure into
solid form and when thusly cured have a density of
approximately 40 to 60 pounds per cubic foot. A suitable
catalyst is used with the urea formaldehyde resin, the
rate of curing depending upon the ratio of catalyst used.
Heat may be applied in this step to speed up ~he cure,
but such is not necessary.
After the blocks are cured into a solid ~orm, they
are reduced to a usable particle soil-like usable size,
such as from l/16th inch to 3/4 inch, or of course any
other size that may suit a particular use as a potting
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soil or a bedding soil. A conventional hammer mill
is readily adaptable to provide the desired re~uction.
The product can be stored in block form and ground into
the soil-like particle form as needed.
The soil product of the invention may be used alone
or in combination with other material such as natural
soil and has many advan~ages in its use as a potting soil
or bedding soil mixture. A first advantage of the straw
base material is that straw is very abundant in supply
and inexpensive to purchase. Also, by the combination
of straw and urea formaldahyde resin, there is an ad-
vantage that since the urea formaldahyde resin coats
the entire sur~ace of the straw particles and since the
-formaldehyde causes the mixture to be water insoluble,
the coating protects the straw from decompositionj at
least for a time. Although the mi.xture is substantially
water insoluble, moisture and microbial action ~rom the
soil or atmosphere will cawse decomposition to occur,
such being at a relatively slow rate. The procluct thus
will. have some water retention qualities from the be-
ginning and such retention qualities increase as de-
composition progresses.
~ s the urea formaldahyde molecules break down, the
urea releases nitrogen as a nutrient into the mixture.
Thus, the soil product has gradual decomposition by
moisture and microbial action and as it decomposes it
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provides one of the main fertilizersto the plants.
Other nutrients may be added as desired. The decomposi-
tion and nutrient feeding process will have a span as
least as long as a growing season for most plants. The
rate of decomposition and consequent release of nitrogen
will increase with a raise in temperature and thus more
nitrogen is released during the times that the plants are
the rnost active.
The soil product of the invention is thus inexpensive
to manufacture in view of the abundant supply and the
small cost of straw. The product is light in weight and
easy to handle either in its final particle form or in
its block form prior to final grinding. The block form
allows it to be easily handled for movement and storage
~5 and if kept dry it can be stored for long periods of
time. The product when used for plant growth retains
sufficient moisture for good root growth and for causing
decomposition to release nitrogen. It can be used
strictly as a soil itsel~ or can be mixed with natural
0 soil or other material to serve as a conditioner.
EXAMPLE I
A supply of oat straw was reduced in a hammer mill
and passed through a screen which reduced the straw
to lengths of from 1/4 inch to 3 inches in length. This
reduced straw was mixed with 5 lbs of urea formaldahyde
resin and catalyst per cubic foot of straw and then mixed
for about 2 rninutes. The mixture was then formed into
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blocks at about 200 psi and allowed to cure. After
hardening of the mixture, it was reduced in a hammer
mill to a particle size of from l/16th inch to 3/4 inch
in diameter.
EXAMPLE II
A supply of wheat straw was reduced in a hammer
mill and passed through a screen which reduced the
straw to lengths of from 1/2 inch to 4 inches in length,
This reduced straw was mixed with 15 lbs, of urea formalda-
hyde resin and catalyst per cubic foot of straw and then
mixed for one minute. The mixture was then formed into
blocks at about 3000 psi and allowed to cure. A~ter
hardening of the mixture, it was reduced in a hammer ',
mill to a particle size averaging l/8th inch in diameter,
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The exact initial size of reduction of the straw
in the above example,s is not too critical, Also, the
proportions of resin to straw as well as -the proportions of
urea to formaldahyde in the urea Eormaldahyde resin will
vary but the different proportions only serve to vary the
extent of insolubility and the rate of decomposition,
By using a strong catalyst to change the pH of the resin,
the blocks can be cured in a very short time. Although
mixing of the resin with the straw under atmospheric
pressure is preferred, it is to be understood that such
may be accomplished at elevated pressures,
Having thus described my invention, I claim:
