Chemistry: fertilizers – Processes and products – Inorganic material
Reexamination Certificate
1999-04-06
2001-07-03
Griffin, Steven P. (Department: 1754)
Chemistry: fertilizers
Processes and products
Inorganic material
C071S001000, C071S031000
Reexamination Certificate
active
06254656
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The invention relates to a fertilizer especially suitable for gramineous plants such as rice and wheat, and a method for improving the growth of the same.
BACKGROUND OF THE INVENTION
Heretofore, fertilizers for growing rice, for example, lime fertilizers, magnesia fertilizers, silicate fertilizers, nitrolime, phosphate fertilizers, potassium salts, calcium perphosphate, compound fertilizers (N, P
2
O
5
), ammonium sulfate, ammonium phosphate, urea, ammonium urate and the like were used.
It is also known that rice and wheat absorb high amounts of silicate. The ash of rice straw contains ca.80% SiO
2
and the ash of wheat straw contains ca.70% SiO
2
. When these gramineous plants lack silicates, silificication of epidermal cells does not occur. As a result, stalks become weak and easily fall down. Moreover, the plants become vulnerable to disease such as blast.
It was 1955 when silicate became known as a fertilizer component. Since then, by-product slag from iron industries or non-iron metal industries came to be used with the name of SICA fertilizer (Keikaru fertilizer). This slag also contains CaO and MgO.
Since many SICA fertilizers consist of alkaline calcium silicate and magnesium silicate, they play a role in neutralizing acidic soils. When such SICA fertilizers are used, the effect of the fertilizer appears slowly, since the decomposition of the alkaline silicate salt is needed for silicic acid (SiO
2
.nH
2
O) to be generated. Also, the influence of calcium residues and the change in the pH values are not negligible after the decomposition.
As aforementioned, nowadays, when silicic acid is to be fed to rice or wheat, the SICA fertilizer is used. But in that case, CaO, MgO and other impurities are strewn at the same time. As a result, problems such as changes in pH values of soil or unforeseeable troubles due to impurities can occur.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a fertilizer which has an increased ability to furnish silicic acid and provide a high absorption/availability efficiency of the silicic acid to the plants.
Another object of the invention is to provide a method for using the fertilizer.
These and other objects are attained by the invention by providing a fertilizer, especially fitted to gramineous plants, characteristically composed of silica gel or silica sol as a main component. In the invention, “fertilizer” means a material to be added to soils as food nutrients necessary for plant growth.
In the invention, a fertilizer was discovered which is far more effective than conventional silica fertilizers (for example, SICA fertilizer), when silica gels, which were hitherto used mainly as adsorbents, were studied as potential silica fertilizers. Specifically, the supplying efficiency of silicic acid to plants or the absorption/availability efficiency of silicic acid by plants (the ratio of fertilizer actually absorbed by gramineous plants to that spread to the soil) proved to be extremely high. As a result, plant stalks become strong by being silicificated and in the case of rice, for example, the stalks are prevented from being borne down and broken, even when the ears of rice become heavy with full grains. Also, they are prevented from being borne down by the wind or rain.
Moreover, the harvest yield of the grain increases. The reason may be that the photosynthetic efficiency of plants which have absorbed a lot of silicic acid is improved, and their resistance to diseases is strengthened. In addition, in the treated district where the fertilizer of the invention is used, damage to plants by pathogenic fungi or injurious insects is suppressed. Especially, the emergence of blast is effectively suppressed. The blast preventive effect is thought to be the result that it becomes difficult for the hyphae which induce blast to invade the plant bodies because of the silicification of stalks, though its mechanism is not clear.
So-called silica gel is a gel of silicic acid, expressed as SiO
2
.nH
2
O. In general, silica gel by a wet process is composed of a three-dimensional network structure where colloidal particles of non-porous amorphous silica are bound together with siloxane bonds. The total surface areas of all colloidal silica particles consisting of one unit weight is the specific surface, and the total spaces surrounded by the three-dimensional networks of the colloidal silica particle is the pore volume.
When silica gel is prepared, for example, from an aqueous solution of sodium silicate and sulfuric acid, monosilicic acid Si(OH)
4
is produced by the hydrolysis of sodium silicate. Further, polysilicate particles with colloidal size, which become a liquidous material or so-called silica sol, are produced by dehydration condensation of monosilicic acid. Thereby, the size of the colloidal particle is influenced by concentrations of both SiO
2
and salt, pH and the like. Each colloidal particle of silica sol then coagulates to form a three dimensional network structure, losing fluidity of silica sol and producing a gelatinous solid. The gelatinious solid is called silica hydrogel. The contained sodium silicate and sodium sulfate are washed out with water or the like from the hydrogel. Then, silica hydrogel is obtained which consists of the water of a quantity dependent on the initial stage of silica hydrosol, silicic dioxide and the trace of other impurities. Silica xerogel is obtained by dehydration and drying of the silica hydrogel.
The silica gel which can be used as the main component of the fertilizer of the invention contains all stages of silica gel from silica hydrogel to silica xerogel. As an example of typical silica gel, the silica gel which has a specific surface from 100 to 800 m
2
/g, a particle size equal to or less than 5 mm and pH of its 5% slurry from 4 to 8 can be shown. In that case, the form of silica gel may be either of powder, crashed particles, sphere particles or the like. Also, silica sol (silica hydrosol) can be used as the main component of the invention.
When a fertilizer of the invention is used, for example, in rice fields, the faster the dissolving speed of silicic acid from the silica sol or silica gel into water, the better the fertilizer. Generally, the speed with which rice plants absorb silicic acid is relatively high. Especially, when ears of rice come out, a substantial amount of silicic acid is absorbed by the plants. Therefore, the higher is the concentration of dissolving silicic acid, that is, the higher is the supplying ability of silicic acid, the better the efficiency of silicic acid absorption by rice, conspicuously accelerating the growth of rice. Specifically, it is preferable for the silica gel or silica sol to have such a property that the silicic acid concentration becomes equal to or higher than 5 ppm, more preferably, equal to or higher than 15 ppm, within 24 hours after the silica gel or silica sol is thrown into water (water which does not contain silicic acid, like ion-exchanged water or distilled water). As the silica gel having the former property, there are silica hydrogel, silica xerogel and silica gel in the state between silica hydrogel and silica xerogel, for example, Fuji Silica Gel Type A and Type B (produced by Fuji Silysia Chemical Ltd.). As the silica gel having the latter property, there is hydrous silica gel (silica gel in a state at which the decrease in the pore volume has already stopped in the process of dehydration of silica hydrogel, that is, silica gel in a state at which a strong three dimensional network structure of colloidal particle has been formed and, in addition, silica gel between a state at which it contains water and a state before it changes to xerogel).
The dissolving rate of silicic acid into water is thought to be highly related with the particle size of silica gel. In order to get a higher dissolving rate, the particle size is preferably equal to or less than 100 &mgr;m.
The preferable quantity of application of the fertilizer of the invention is 1-100 kg/10 a as the weight of silica gel. Whe
Honda Hirofumi
Noda Takanobu
Davis & Bujold P.L.L.C.
Fuji Silysia Chemical Ltd.
Griffin Steven P.
Nave Eileen E.
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