JP2014009152A - Liquid silicic acid fertilizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid silicic acid fertilizer excellent in long-term preservability and immediate effect that has essential elements necessary for plant growth dissolved in a silica sol and is diluted with water and used in foliar spray, soil drenching, water culture and the like.SOLUTION: There is provided a liquid silicic acid fertilizer excellent in long-term preservability that is nearly free from gelation or suspension and promotes robust and sound growth of a plant by blending a reducing organic acid with a silica sol, or containing a divalent iron ion reduced from a trivalent iron ion, or further by containing calcium, magnesium, boron, manganese, zinc, copper and molybudenum in an ionic state.

Description

  The present invention relates to a liquid silicate fertilizer that is diluted with water for use in a foliar spray solution, a soil irrigation solution, and a culture solution in hydroponics. That is, by adding citric acid, which is a reducing organic acid, to silica sol, silicic acid can be contained as a molecularly dispersed silicic acid having no charge that is easily absorbed by plants, and when trivalent iron ions are added to this, When citric acid can be reduced to contain divalent iron ions that are easy for plants to absorb, calcium, magnesium, which is a major element of essential elements, and boron, manganese, zinc, copper, and molybdenum, which are trace elements, are added. The present invention relates to a liquid silicic acid fertilizer that can be contained in an ionic state that can be easily absorbed by plants, and that has long-term storage that hardly causes gelation or suspension.

Silicic acid (SiO ₂ ) is not recognized as an essential element for plants, but in the case of gramineous plants (rice, turf, etc.), strengthening of plant tissue, that is, promotion of photosynthesis by proliferation of silicified cells, lodging resistance The effects of fertilizers, such as improving virginity, increasing root vitality and improving disease resistance, are well known. For plants other than Gramineae plants, pest resistance is improved, that is, invasion of pathogenic bacteria by accumulation of silicic acid in epidermal cells, reduction of insect damage caused by insects, promotion of the production of antibacterial substances in plants, and under adverse conditions It is said that it is effective in improving stress tolerance. (See Non-Patent Document 1)

On the other hand, the form when silicic acid is absorbed by the plant is a molecularly dispersed silicic acid having no charge, and anionic silicic acid is considered to be inferior in absorbability. When silicic acid is dissolved in water, it is a molecularly dispersed silicic acid (H ₄ SiO ₄ ) having no charge at pH 8 or lower, but anionic silicic acid (H ₃ SiO ₄ ) when pH 8 is exceeded. ⁻ , H ₂ SiO ₄ ²⁻ , HSiO ₄ ³⁻ , SiO ₄ ⁴⁻ ), and the number of negative charges increases as the pH increases. (See Non-Patent Document 2)

  The present invention is a liquid silicate fertilizer that can combine the fertilizer effect of the above-described silicic acid with the fertilizer effect of essential elements, and can quickly exhibit a synergistic fertilizer effect.

  Currently, the official standards for siliceous fertilizers are defined as five types of mineral siliceous fertilizer (Keical), lightweight cellular concrete fertilizer, silica gel fertilizer, silica hydrogel fertilizer, and wollastonite fertilizer. There is no immediate effect due to the low dissolution rate in water.

  Therefore, in order to provide an immediate effect, a liquid silicate fertilizer using potassium silicate or silica sol as a silicic acid component has been proposed.

Potassium silicate-based liquid silicate fertilizer Potassium silicate has a high pH of the aqueous solution itself of 10 or more and cannot be applied as it is. Moreover, when an acid is added and the pH is reduced to about 8 or less, the silicate ions are dehydrated and condensed, resulting in gelation and suspension, and silicic acid is precipitated, so that it cannot be used as a liquid fertilizer. However, liquid silicate fertilizers in which various substances are added to potassium silicate have been proposed. For example, citric acid (see Patent Document 1), ethylenediaminetetraacetate magnesium (see Patent Document 2), and gluconic acid (see Patent Document 3) are added to an aqueous potassium silicate solution. However, these liquid silicic acid fertilizers have a pH of 8 or more, but the silicic acid is deposited within a relatively short time and does not endure long-term storage. Therefore, it was necessary to use it as soon as possible after production. Moreover, although the method (refer patent document 4) of adding the condensed potassium phosphate salt which does not have a hydrogen atom in a molecule | numerator in potassium silicate aqueous solution is proposed, pH is 10 or more and a basic thing is strong. As described above, the potassium silicate-based liquid silicate fertilizer needs to maintain a strong basic pH to suppress silicic acid precipitation,
In application, it is necessary to pay attention to the increase in soil pH, and as mentioned above, silicic acid is present as an anion in such a basic liquid, so that it has a molecularly dispersed state that does not have a charge that is easily absorbed by plants. It is not in the form of silicic acid.

Silica sol-based liquid silicic acid fertilizer Silica sol is also referred to as silicic acid sol, and is a state in which silicic acid is dispersed in water in a colloidal form, and liquid silicic acid fertilizer using silica sol as a component has also been proposed. For example, colloidal form using acidic silicate sol consisting of stable sol particles obtained by dealkalizing alkali silicate aqueous solution with cation exchange resin, aging with acid or alkali and strengthening siloxane bond and building up There is a liquid fertilizer containing silicic acid (see Patent Document 5) and a liquid fertilizer containing water-soluble normal silicic acid obtained by hydrolyzing tetraalkoxysilane with an acid (see Patent Document 6). Since these liquid silicic acid fertilizers have a pH of 1 to 4, they contain silicic acid as a molecularly dispersed silicic acid that is not easily absorbed by plants, but the liquid silicic acid fertilizers in both examples The silicic acid content is as low as 2.5% by weight or less in terms of SiO ₂ . When the concentration of silicic acid is higher than this, in the former case, the fertilizer component mixed with silicic acid reacts and gelation is likely to occur, and in the latter case, gelation is likely to occur during the acid hydrolysis reaction of tetraalkoxysilane. Therefore, it was difficult to contain silicic acid at a high concentration.

Silicic acid and crop production Japan Society of Soil Fertilizer Hakutosha (2002) Silicic and Lime Plants Eiichi Takahashi Nobunbun (1987) p. 62

JP 62-56389 A JP 5-78189 A JP 7-101792 A JP 2011-184207 A JP-A-9-268092 JP-A-2005-67996

  In view of the problems of the prior art as described above, the purpose of the present invention is to contain a higher concentration of silicic acid, and contains a wide variety of essential elements in a stable ionic state that is easily absorbed by plants, An object of the present invention is to provide a liquid silicate fertilizer having an immediate effect which is less likely to cause silicic acid precipitation or insoluble matter precipitation such as gelation or suspension during long-term storage.

  As a result of intensive studies in order to solve the above problems, the present inventors have completed the present invention. The details will be described below.

  Silica sol is a transparent or milky white colloidal solution usually having a pH of 2 to 11, but when a water-soluble compound containing an essential element is added directly to this silica sol, gelation or suspension may occur instantaneously. . The present inventors have found that, as a method of dissolving a water-soluble compound containing a wide variety of essential elements in silica sol without causing this gelation or suspension, the citric acid of a reducing organic acid is blended, The present invention has been completed.

  Claim 1 is a liquid silicate fertilizer having a pH of 4.0 or less, which is obtained by blending a reducing organic acid into silica sol. By controlling the pH to 4.0 or less, preferably 3.5 or less, gelation is suppressed and long-term storage is possible, and silicic acid is absorbed into a form of molecularly dispersed silicic acid that is not easily absorbed by plants. Can be maintained.

Claim 2 is a liquid silicate fertilizer according to claim 1, wherein the content of silica is 1 to 30 wt% in terms of SiO _2. The content of silicic acid, 1 to 30 wt% in terms of SiO _2, preferably from 2 to 25 wt%. The liquid silicate fertilizer of the present invention is diluted about 100 to 2000 times with water and used for foliar spray solution, soil irrigation solution, and culture solution in hydroponics, but the content of silicic acid is set in the above range By doing so, it can be supplied at an optimum concentration according to the growth state of the plant, the soil, or the silicic acid-containing state of the hydroponics culture solution.

  Claim 3 is the liquid silicate fertilizer according to claim 1 or 2, wherein the reducing organic acid is citric acid. Examples of reducing organic acids include citric acid, malic acid, succinic acid, gluconic acid, tartaric acid, lactic acid, gallic acid, ascorbic acid, glucuronic acid, glycolic acid, glyceric acid, erythorbic acid, 2-hydroxybutyric acid, glyoxylic acid, etc. However, in the present invention, citric acid is preferred from the viewpoints of solubility in water, availability, and economy.

  The liquid silicate fertilizer according to any one of claims 1 to 3, wherein a water-soluble trivalent iron compound is dissolved and iron is contained as divalent iron ions by reduction with a reducing organic acid. It is.

  Claim 5 is the liquid silicate fertilizer according to claim 4, wherein iron is contained in an amount of 0.01 to 5% by weight in terms of Fe. The iron content is 0.01 to 5% by weight, preferably 0.05 to 4% by weight in terms of Fe. The liquid silicate fertilizer of the present invention is diluted about 100 to 2000 times with water and used for foliar spray solution, soil irrigation solution, and culture solution in hydroponics, but the iron content is set in the above range. Thus, it can be adjusted to the optimum concentration according to the growth state of the plant, the soil, or the iron-containing state of the hydroponics culture solution, and can effectively exert the fertilizer effect in a well-balanced manner with silicic acid.

  Claim 6 is the liquid silicate fertilizer according to any one of claims 1 to 5, wherein at least one of calcium, magnesium, boron, manganese, zinc, copper, and molybdenum is contained in an ionic state. is there.

In claim 7, calcium is 0.05 to 5% by weight in terms of CaO, magnesium is 0.05 to 5% by weight in terms of MgO, boron is 0.01 to 3% by weight in terms of B ₂ O ₃ , and manganese is MnO. 0.05 to 5% by weight in terms of zinc, 0.01 to 2% by weight in terms of zinc, 0.01 to 2% by weight in terms of Cu, 0.01 to 2% by weight in terms of Mo It is the transparent liquid silicate fertilizer of Claim 1 thru | or 6.

  The liquid silicate fertilizer of the present invention is diluted about 100 to 2000 times with water and used for foliar spray solution, soil irrigation solution, and culture solution in hydroponics, but in the above range, calcium, magnesium, boron, By setting the content of manganese, zinc, copper, and molybdenum, it can be adjusted to the optimum concentration according to the growth status of the plant and the essential element content of the soil or hydroponics culture solution, effectively balanced with silicic acid The fertilizer effect can be demonstrated.

The liquid silicate fertilizer of the present invention is
(1) It contains a high concentration of silicic acid stably.
(2) It contains silicic acid as molecularly dispersed silicic acid that does not have a charge that is easily absorbed by plants.
(3) Trivalent iron ions are contained as divalent iron ions that are reduced by citric acid and easily absorbed by plants.
(4) It contains large amounts of calcium, magnesium, and trace elements of iron, boron, manganese, zinc, copper, and molybdenum in the form of ions that are easily absorbed by plants.
(5) Gelation and suspension hardly occur for a long time.
At the same time has the characteristics. Therefore, it is superior in storage stability and, more than conventional liquid silicic acid fertilizer, promotes the strengthening of plants and promotes healthy growth of plants, so it is resistant to environmental stresses such as salt damage, high temperature, and drying, and pest control The frequency of drug spraying can be greatly reduced.

  The components of the liquid silicic acid fertilizer of the present invention are (a) silica sol, (b) reducible organic acid, (c) raw material compounds of essential elements, and other components that can be added within a range that does not impair their properties (d). . Hereinafter, the manufacturing method and fertilization method of these components and the liquid silicate fertilizer of this invention are demonstrated.

  The components of the liquid silicate fertilizer will be described.

(A) Silica sol Silica sol is a liquid medium of the liquid silicate fertilizer of the present invention, and is also a source of silicic acid. There are the following known production methods for producing silica sol.

(1) A method for producing silica sol, so-called active silicic acid, by bringing an alkali metal silicate aqueous solution, for example, an aqueous solution of sodium silicate into contact with an H-type strongly acidic cation exchange resin, and dealkalizing by ion exchange. Furthermore, a silica sol production method in which the active silicate is built-up, the sol particle internal structure is made dense, the sol particle diameter is increased and the dispersion state is stabilized.

(2) A method for producing silica sol (active silicic acid) by subjecting an alkali silicate aqueous solution, for example, an aqueous solution of sodium silicate, to ion exchange by electrodialysis using an ion exchange membrane for dealkalization. Furthermore, a silica sol production method in which the active silicate is built-up, the sol particle internal structure is made dense, the sol particle diameter is increased and the dispersion state is stabilized.

(3) A method for producing a silica sol by acid hydrolysis of an alkyl silicate such as tetraethylsilane.

(4) A method for producing a silica sol, in which siliceous mineral fine powders such as silicic acid hydrogel, silicic acid xerogel and quartz are hydrothermally treated with alkali to peptize. For example, a method for producing a silica sol in which sodium sulfate is washed and removed from a silicic acid hydrogel obtained by a reaction between an aqueous solution of sodium silicate and an acid, and then hydrothermally treated in an autoclave or the like.

  The silica sol used in the liquid silicate fertilizer of the present invention may be obtained by any of the above production methods, and when the silicate content is high, it can be diluted with water as necessary. The water may be tap water.

The physical properties of the silica sol used for the liquid silicate fertilizer of the present invention are shown below.
(1) silicate content may be from 5 to 40% by weight in terms of SiO _2. That is, silicic acid content of the liquid silicate fertilizer produced may if achieve 1 to 30 wt% in terms of SiO _2.
(2) The pH is 2 to 12, preferably 3 to 11.
(3) When the contained alkali component is present, the molar ratio is, for example, 10 or more, preferably 40 or more in terms of SiO ₂ / Na ₂ O.
(4) The liquid phase is preferably colorless and transparent to a colloidal translucent light transmission, but more preferably colorless and transparent. The reason is that the smaller the colloidal particle diameter of silicic acid, the more transparent the liquid phase is like water, but the smaller the colloidal particle diameter, the more the specific surface area increases and the silicic acid from the colloidal particle surface increases. When the liquid silicate fertilizer of the present invention is diluted with water, the concentration of molecularly dispersed silicic acid (H ₄ SiO ₄ ) having no charge that is easily absorbed by the plants contained therein is rapidly increased. This is because it increases. In addition, if the liquid phase of silica sol is opaque, it becomes impossible to detect insoluble matter precipitation such as suspension or precipitation during the production or storage of liquid silicate fertilizer, which causes a problem in quality control. .

(B) Reducing organic acid As a reducing organic acid having the action of reducing trivalent iron ions to divalent iron ions, citric acid, malic acid, gluconic acid, succinic acid, tartaric acid, lactic acid, gallic acid, ascorbine Examples include acid, glucuronic acid, glycolic acid, glyceric acid, erythorbic acid, 2-hydroxybutyric acid, glyoxylic acid, etc. In the present invention, citric acid is used in terms of solubility in water, availability, and economy. It is preferable to use it.

Citric acid works as a pH adjuster and an iron reducing agent in the liquid silicate fertilizer of the present invention, and specific actions are as follows.
(1) Generation of molecularly dispersed silicic acid having no charge by making the silica sol acidic (2) By making the silica sol acidic, the essential element metal ions become hydroxides and become insoluble Prevention (3) Reduction of trivalent iron ion to divalent iron ion (4) Prevention of divalent iron ion from being naturally oxidized to divalent iron ion by dissolved oxygen or oxygen in the air to become trivalent iron ion

  Citric acid may be mixed with other reducing organic acids described in paragraph (0032). Further, a citrate having the same reducing action as citric acid, for example, trisodium citrate, tripotassium citrate and the like may be mixed with citric acid.

  Furthermore, citric acid may be used in combination with other reducing organic acid salts described in paragraph (0032). For example, disodium malate, disodium succinate, sodium gluconate and the like.

(C) Raw material compound of essential element The physiological action and raw material compound of the essential element according to claim 4 and claim 6 added to the liquid silicate fertilizer of the present invention will be described. Must be a water-soluble compound.

(1) Iron is involved in the energy transfer system centering on redox reactions, and when deficient, chlorophyll is reduced and new leaves turn yellow. As water-soluble compounds of iron-containing raw materials, ferric nitrate, ferric sulfate, ferric chloride, ferric phosphate, ferric acetate, ferric citrate as trivalent iron compounds , Ferric gluconate, ferric ascorbate and the like can be mentioned, but these may be used alone or in combination of two or more. In addition, as divalent iron compounds, ferrous sulfate, ferrous nitrate, ferrous chloride, ferrous phosphate, ferrous acetate, ferrous citrate, ferrous gluconate, ferrous ascorbic acid Although iron etc. can be mentioned, you may mix these with said trivalent iron compound. That is, trivalent iron ions generated by dissolution are automatically reduced by citric acid to become divalent iron ions. Therefore, when selecting a water-soluble iron compound, particularly distinguish between iron divalent and trivalent. There is no need, and the range of choices is wide and economical.

(2) Calcium binds to pectic acid and is involved in the formation and strengthening of plant cell membranes. When deficient, the growth of apical buds and root hairs of the roots deteriorates. Examples of the water-soluble compound of the raw material compound containing calcium include calcium nitrate, calcium chloride, calcium acetate, calcium lactate, calcium gluconate, calcium lignin sulfonate, and the like. These may be mixed.

(3) Magnesium is a constituent element of chlorophyll and is involved in carbohydrate metabolism and phosphate metabolism. Examples of the water-soluble compound of the raw material compound containing magnesium include magnesium nitrate, magnesium chloride, and magnesium acetate. These may be used alone or in combination of two or more.

(4) Boron is involved in calcium absorption and translocation, and is involved in maintaining the structure of the cell wall by binding to pectic polysaccharides. When deficient, the growth of new leaves stops and the root elongation of cells grows worse. Examples of the water-soluble compound of the raw material compound containing boron may include boric acid and sodium borate. These may be used alone or in combination of two or more.

(5) Manganese is involved in the production of chlorophyll, photosynthesis, and vitamin C synthesis. Examples of the water-soluble compound of the raw material compound containing manganese include manganese sulfate, manganese nitrate, manganese chloride, and manganese acetate. These may be used alone or in combination of two or more.

(6) Zinc is a constituent element of the enzyme in the body and is involved in the glycolytic system and the citric acid cycle, and when deficient, new leaf malformations and interleaf veins are yellowed. Examples of the water-soluble compound of the raw material compound containing zinc include zinc sulfate, zinc nitrate, zinc chloride, and zinc acetate. These may be used alone or in combination of two or more.

(7) Copper is a constituent element of in-vivo enzymes, is involved in redox in the plant body, and when deficient, the growth of new leaves deteriorates and the leaves turn yellow. Examples of the water-soluble compound of the raw material compound containing copper include copper sulfate, copper nitrate, copper chloride, and copper acetate. These may be used alone or in combination of two or more.

(8) Molybdenum is a constituent element of in-vivo enzymes, and is involved in rhizobial nitrogen fixation and nitrate reduction. When deficient, leaf malformation and atrophy occur. Examples of the water-soluble compound of the raw material compound containing molybdenum include sodium molybdate and ammonium molybdate, and these may be used alone or in combination of two or more.

  In addition, selection of the essential element of said (1)-(8) contained in the liquid silicate fertilizer of this invention, and its density | concentration are the essential element of the kind of plant, the growth condition of a plant, soil, or a hydroponics culture solution. What is necessary is just to perform according to a content condition.

(D) Other components The liquid silicate fertilizer of this invention can mix | blend the following component as needed in the range which does not impair the characteristic. Amino acids (eg, methionine, glutamic acid, proline, etc.), saccharides (eg, glucose, chitosan, trehalose, etc.), vitamins (eg, vitamins B1, B2, B6, choline, etc.), animal or plant protein hydrolysates, Chelating agents (for example, ethylenediaminetetraacetic acid and its salts), surfactants, preservatives.

  Below, the manufacturing method (procedure) of the liquid silicate fertilizer of this invention is demonstrated in detail.

  First, citric acid is mixed in the form of a solid powder or an aqueous solution with stirring to a silica sol adjusted to a desired silicic acid concentration, and the pH is 4.0 or less, preferably 3.5 or less, more preferably 2.0 to Prepare a 3.5 silica sol citric acid solution.

  When adding an iron component, a water-soluble compound of a raw material compound containing desired iron is added to the silica sol / citric acid solution in the form of a solid powder or an aqueous solution while stirring, and the iron ion-containing silica sol / citric acid solution is added. To prepare.

  Further, when adding an essential element component other than the iron component, a water-soluble compound of a raw material compound containing a desired essential element is added to the silica sol / citric acid solution or the iron ion-containing silica sol / citric acid solution as a solid powder or an aqueous solution. And may be added with stirring.

  In addition, as a procedure of the production method, a water-soluble compound of a raw material compound containing a desired essential element may be dissolved in an aqueous citric acid solution, and silica sol may be added thereto while stirring.

  The final pH of the liquid silicate fertilizer containing the essential elements produced by the above procedure is 4.0 or less, preferably 3.5 or less, more preferably 0.2 to 3.5. During the production, if the pH is out of the above range, an alkali metal hydroxide such as sodium hydroxide, potassium hydroxide, or an aqueous ammonia solution or citric acid is added with stirring as required. What is necessary is just to adjust to pH. At this time, citric acid can be mixed with inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, and phosphoric acid.

  In addition, the essential element calcium, magnesium, iron, manganese, zinc, copper metal ions may become a hydroxide and insolubilize and precipitate when the pH is high, the liquid silicate fertilizer of the present invention, By adjusting the pH to the above range, it can be prevented that these metal ions become hydroxides and insolubilized, and become hydroxides and insolubilized even when the pH rises when diluted with water for application. Can be prevented.

  In the above manufacturing process, the stirring operation is indispensable, but heating is not particularly required. In addition, when a water-soluble compound of trivalent iron is added, the reduction reaction of trivalent iron ions to divalent iron ions proceeds gradually even when left at room temperature, It is desirable to continue stirring.

  Next, the application method will be described.

  The liquid silicate fertilizer of the present invention is a fertilizer that is diluted with water and applied in foliar application, soil irrigation, hydroponics and the like, and the water may be tap water. The dilution factor is selected according to the concentration of silicic acid and essential elements contained in the liquid silicic acid fertilizer of the present invention, the growth stage and growth status of plants, the content of essential elements in the soil or hydroponics culture solution, etc. For example, it is about 100 to 2000 times. The application method can be manual or electric spraying for foliar spraying, and for soil irrigation and hydroponic cultivation, dilute in existing nutrient solution tanks and use existing irrigation pipelines and infusion lines. Can be used.

  Hereinafter, although the liquid silicate fertilizer of this invention is demonstrated in detail by an Example, this invention is not limited to these Examples.

  Citric acid was blended with a silica sol prepared by an ion exchange method and a peptization method and a silica sol produced by a commercial built-up process, and the gelation time when the pH was changed stepwise was measured. From the relationship between the pH and the gelation time, a range of pH that can be stably stored for a long time without gelation of the silica sol was confirmed.

(Preparation of silica sol 1 ion exchange method)
Sodium silicate No. 3 aqueous solution (Kishida Chemical Co., Ltd. SiO ₂ content 29.1% by weight, Na ₂ O content 9.3% by weight, molar ratio 3.23) was diluted with ion-exchanged water, and H-type strongly acidic Sodium hydroxide was removed by contacting with a cation exchange resin (Mitsubishi Chemical Corporation Diaion SK1B-H), and active silicic acid having a silicic acid content of about 5.5% by weight as SiO ₂ and a pH of 4.3 was prepared. Since this active silicic acid gels after several hours, a 5N sodium hydroxide aqueous solution is added with stirring, and ion-exchanged water is further added. The pH is 10.3, and the silicic acid content is 5.0% by weight as SiO _2. Silica sol was prepared. Table 1 shows the physical properties.

(Preparation of silica sol 2 Peptization method)
Sodium silicate No. 3 aqueous solution (Kishida Chemical Co., Ltd. SiO ₂ content 29.1 wt%, Na ₂ O content 9.3 wt%, molar ratio 3.23) was diluted with ion-exchanged water to obtain SiO ₂ content The amount was 5.0% by weight. 2N hydrochloric acid was added to this aqueous solution with stirring to adjust the pH to 7.4, and then allowed to stand to gel. The obtained silica hydrogel was crushed and washed with tap water for 2 hours to remove sodium chloride. The washed silica hydrogel was put in an autoclave and hydrothermally treated at 120 ° C. for 2 hours to obtain a silica sol having a silicic acid content of SiO ₂ of 4.5% by weight. This silica sol was concentrated with a rotary evaporator to prepare a silica sol having a SiO ₂ content of 14.5 wt% and a pH of 10.1. Table 1 shows the physical properties.

(Geling time measurement test)
The silica sol used was a silica sol prepared by the ion exchange method shown in Table 1 (SiO ₂ content 5.0 wt%) and a silica sol prepared by the peptization method (SiO ₂ content 14.5 wt%). in diluted, SiO2 content 10.0% by weight silica sol, and commercially available SNOWTEX 30 is a silica sol (SiO ₂ content of 30.5 wt%, Na ₂ O content of 0.33 wt%, pH 10.0 Nissan Chemical Industries, Ltd.) is diluted with tap water, and there are three types of silica sols with a SiO ₂ content of 20.0% by weight. A silica sol / citric acid solution in which the pH was changed stepwise by mixing solid powder of citric acid / monohydrate (Yoneyama Pharmaceutical first grade reagent) with 100 g of these three types of silica sol, stored at 20 ° C. and gel The stabilization time was measured and the stability was evaluated. Gelation was performed when the silica sol liquid level could not be kept horizontal when the container was tilted. The results are shown in Table 2.

  From the test results shown in Table 2, it was found that when citric acid was added to a pH of 4.0 or less, gelation did not occur even after 30 days and the product was stable and could be stored for a long time.

  The names of the drugs used in the following examples and comparative examples are abbreviated as follows. Citric acid monohydrate (Yoneyama Pharmaceutical first grade reagent) is citric acid, ferric nitrate nonahydrate (Yoneyama Pharmaceutical first grade reagent) ferric nitrate, ferric chloride anhydride (Yoneyama Pharmaceutical) The primary reagent) is ferric chloride, calcium nitrate tetrahydrate (Yoneyama Chemical) The primary reagent is calcium nitrate, magnesium acetate tetrahydrate (Kishida Chemical primary reagent) is magnesium acetate, boric acid (Yoneyama) Chemical first grade reagent) is boric acid, zinc sulfate heptahydrate (Yoneyama Pharmaceutical first grade reagent) is zinc sulfate, manganese sulfate pentahydrate (Yoneyama Chemical first grade reagent) is manganese sulfate, copper sulfate, five water Japanese products (Yoneyama Pharmaceutical first grade reagent) are represented by copper sulfate, sodium molybdate dihydrate (Kishida Chemical special grade reagent) and sodium molybdate.

A silica sol / citric acid solution having a pH of 2.8 was prepared by mixing 3.3 g of a solid powder of citric acid with stirring in 100 g of silica sol having a silicic acid content of SiO ₂ of 5.0% by weight prepared by the ion exchange method in Example 1. Then, while stirring, 4.0 g of ferric nitrate was added and dissolved as a solid to obtain a liquid silicate fertilizer containing iron ions. Table 3 shows the physical properties.

A silica sol having a silicic acid content of 14.5 wt% as SiO ₂ prepared by the peptization method in Example 1 was diluted with tap water, and 100 g of silica sol having a SiO ₂ content of 10.0 wt% was added to a solid powder of citric acid. After mixing 3.3 g with stirring to obtain a silica sol / citric acid solution having a pH of 2.5, 8.0 g of ferric nitrate is added and dissolved as a solid while stirring to obtain a liquid silicic acid containing iron ions. Got fertilizer. Table 3 shows the physical properties.

Commercially available Snowtex 30 (SiO ₂ content 30.5% by weight) was diluted with tap water, and 100 g of silica sol with SiO ₂ content 20.0% by weight was stirred with 3.3 g of citric acid solid powder. After mixing to make a silica sol / citric acid solution having a pH of 2.8, 20.0 g of ferric nitrate was added and dissolved as a solid with stirring to obtain a liquid silicate fertilizer containing iron ions. Table 3 shows the physical properties.

  From the results of Table 3, the liquid silicate fertilizers of Examples 2 to 4 have stable storage properties without gelation or suspension even after 30 days of storage at 20 ° C. I understood. In addition, ferric nitrate is used as a water-soluble compound of trivalent iron. When a 0.1 mol / L aqueous solution of potassium ferricyanide is added to these liquid silicate fertilizers, the iron contained is the original trivalent. If it was an iron ion, it only turned reddish brown, but a dark blue precipitate, which was a color of divalent iron ion, was produced. From this, it was found that the trivalent iron ions in the liquid silicate fertilizer containing citric acid were reduced to divalent iron ions.

A silica sol / citric acid solution having a pH of 2.8 was prepared by mixing 3.3 g of a solid powder of citric acid with stirring in 100 g of silica sol having a silicic acid content of SiO ₂ of 5.0% by weight prepared by the ion exchange method in Example 1. Then, while stirring, 3.0 g of calcium chloride and 6.0 g of magnesium chloride were added and dissolved as solids in this order to obtain a liquid silicate fertilizer containing calcium ions and magnesium ions. Table 4 shows the physical properties.

A silica sol having a silicic acid content of 14.5 wt% as SiO ₂ prepared by the peptization method in Example 1 was diluted with tap water, and 100 g of silica sol having a SiO ₂ content of 10.0 wt% was added to a solid powder of citric acid. After mixing 3.3 g with stirring to obtain a silica sol / citric acid solution with a pH of 2.5, with stirring, 3.0 g of calcium chloride and then 6.0 g of magnesium chloride were added and dissolved as solids in this order. A liquid silicate fertilizer containing calcium ions and magnesium ions was obtained. Table 4 shows the physical properties.

Commercially available Snowtex 30 (SiO ₂ content 30.5% by weight) was diluted with tap water, and 100 g of silica sol with SiO ₂ content 20.0% by weight was stirred with 3.3 g of citric acid solid powder. After mixing to form a silica sol / citric acid solution with a pH of 2.8, 3.0 g of calcium chloride and then 6.0 g of magnesium chloride are added and dissolved in this order in the order of calcium chloride and magnesium ion. The contained liquid silicate fertilizer was obtained. Table 4 shows the physical properties.

  From the results of Table 4, the liquid silicate fertilizers of Examples 5 to 7 have stable storage properties without gelation or suspension even after 30 days of storage at 20 ° C. I understood.

A silica sol / citric acid solution having a pH of 2.8 was prepared by mixing 3.3 g of a solid powder of citric acid with stirring in 100 g of silica sol having a silicic acid content of SiO ₂ of 5.0% by weight prepared by the ion exchange method in Example 1. Then, with stirring, ferric nitrate 4.0 g, zinc sulfate 1.0 g, manganese sulfate 2.0 g, copper sulfate 0.50 g, sodium molybdate 0.25 g, boric acid 1.0 g in this order. As it was added and dissolved, a liquid silicate fertilizer was obtained. Table 5 shows the physical properties.

A silica sol / citric acid solution having a pH of 2.6 is prepared by mixing 3.3 g of a solid powder of citric acid with stirring in 100 g of silica sol having a silicic acid content of SiO ₂ of 14.5% by weight prepared by the peptization method in Example 1. Then, while stirring, 7.5 g of ferric chloride, 2.1 g of calcium nitrate, and 2.5 g of magnesium acetate were added and dissolved in the order of solids to obtain a liquid silicate fertilizer. Table 5 shows the physical properties.

A commercial product Snowtex 30 (SiO ₂ content 30.5 wt%) 100 g of solid powder of citric acid was mixed with stirring to obtain a silica sol / citric acid solution of pH 3.2, and then stirred. Ferric nitrate 40.0 g, magnesium acetate 5.0 g, manganese sulfate 4.0 g, and boric acid 2.5 g were added and dissolved in the order of solid to obtain a liquid silicate fertilizer. Table 5 shows the physical properties.

In 100 g of silica sol having a silicic acid content of 5.0% by weight as SiO ₂ prepared by the ion exchange method in Example 1, ferric nitrate 4.0 g and zinc sulfate 1. 0 g, manganese sulfate 2.0 g, copper sulfate 0.50 g, sodium molybdate 0.25 g, and boric acid 1.0 g were added and dissolved in the order of solids to obtain a liquid silicate fertilizer. Table 5 shows the physical properties.

In Example 1, silica sol having a silicic acid content of 14.5% by weight as SiO ₂ prepared by the peptization method was mixed with 100 g of silica sol and 7.5 g of ferric chloride and calcium nitrate with stirring without adding citric acid. 1 g and 2.5 g of magnesium acetate were added and dissolved in the order of a solid to obtain a liquid silicate fertilizer. Table 5 shows the physical properties.

Without adding citric acid to 100 g of commercially available Snowtex 30 (SiO ₂ content 30.5 wt%), ferric nitrate 40.0 g, magnesium acetate 5.0 g, manganese sulfate 4.0 g with stirring. In this order, 2.5 g of boric acid was added and dissolved as a solid to obtain a liquid silicate fertilizer. Table 5 shows the physical properties.

From the results of Table 5, the liquid silicate fertilizers of Examples 8 to 10 containing citric acid were stored at 20 ° C., and gelation and suspension did not occur even after 30 days. I found it. On the other hand, the liquid silicate fertilizers of Comparative Examples 1 and 2, which did not contain citric acid, did not gel during storage at 20 ° C., but suspended in a short period of time, resulting in precipitation. In the liquid silicate fertilizer of Comparative Example 3, gelation or suspension did not occur after 30 days.

  In addition, from the results of Table 5, ferric nitrate or ferric chloride is used as a water-soluble compound of trivalent iron, but a 0.1 mol / L aqueous solution of potassium ferricyanide is added to the liquid silicate fertilizer. In Examples 8 to 10 containing citric acid, dark blue precipitation, which is the coloration of divalent iron ions, was produced, so the trivalent iron ions in the liquid silicate fertilizer were reduced to divalent iron ions. I found out that On the other hand, Comparative Examples 1 to 3 that did not contain citric acid did not cause dark blue precipitation, and the liquid color changed to reddish brown, indicating that the iron ions remained in their original trivalent state. .

Application Example The liquid silicate fertilizer obtained in the above example was applied to an actual plant and its effect was investigated. Below, the application example is demonstrated.

Application example 1
In the house cultivation of prince melon, one week after planting the seedlings, the liquid silicate fertilizer of Example 8 with 500-fold diluted tap water (pH 5.5) was irrigated around the strain at about 100 ml per strain. Thereafter, the leaves were sprayed with a 500-fold dilution of the same liquid silicate fertilizer every 2 weeks until harvest. As a result, compared with the strain which did not perform soil irrigation and foliar application, the occurrence frequency of powdery mildew decreased to about 1/3, and the frequency of spraying agents such as fungicides decreased. This is thought to be due to the enhanced resistance to pathogens of plants due to the synergistic fertilizer effect of the essential elements iron, boron, manganese, zinc, copper and molybdenum contained in silicic acid.

Application example 2
Four seedlings of rice (variety Koshihikari) were used as one strain, and 6 plants were prepared by planting 3 plants per Wagner pot (1 / 2000a). The soil was paddy (collected from rice farm the previous year), and the entire fertilizer was applied with 1.3 g of nitrogen, 1.8 g of phosphorus and 0.5 g of potassium per pot. The 6 Wagner pots were divided into 2 groups of 3 pots, and the growth of the group B not applied to the group A applied with the liquid silicate fertilizer of the present invention was compared.

  The application method is that the 1000-fold diluted liquid silicate fertilizer (pH 5.8) of Example 9 is charged every 100 weeks per pot from the setting period 1 week after planting to the heading period through the tilling period. did. The results are shown in Table 6.

From the results in Table 6, group A to which the liquid silicate fertilizer of the present invention was applied clearly had more tillers and fir yields. In addition, Group A had darker green leaves and higher plant height than Group B without application. This is thought to be due to the synergistic fertilizer effect of the essential elements iron, calcium and magnesium, as well as the fertilizer effect of silicic acid on rice.

Application example 3
The golf green grass (bentgrass), tap water 500 times dilution (pH 5.5) of the liquid silicate fertilizer of Example 2, every 10 days over the 3-6 month, subjected to foliar application of 1 m ² per 500ml It was. As a result, compared with the place where foliar application was not performed, there was an increase in rooting, stiffening of the leaves, an increase in the thickness of stems and leaves, a decrease in drought damage, and a strong increase in turf. It was. This is thought to be due to the synergistic fertilizer effect of the contained iron as well as the silicic acid fertilizer effect on the turf.

The present invention relates to a liquid silicate fertilizer that is diluted with water for use in a foliar spray solution, a soil irrigation solution, and a culture solution in hydroponics. That is, by incorporating citric acid, a reducing organic acid, into alkaline silica sol, silicic acid can be contained as a molecularly dispersed silicic acid that has no charge and is easily absorbed by plants, and when trivalent iron ions are added to this. , It can be reduced and contained in divalent iron ions that are easily absorbed by plants with citric acid, and in addition to calcium, magnesium and trace elements boron, manganese, zinc, copper and molybdenum, which are essential elements. The present invention relates to a liquid silicic acid fertilizer that can be contained in an ionic state that can be easily absorbed by plants, and that has long-term storage that hardly causes gelation or suspension.

Silicic acid (SiO ₂ ) is not recognized as an essential element for plants, but in the case of gramineous plants (rice, turf, etc.), strengthening of plant tissue, that is, promotion of photosynthesis by proliferation of silicified cells, lodging resistance The effects of fertilizers, such as improving virginity, increasing root vitality and improving disease resistance, are well known. For plants other than Gramineae plants, pest resistance is improved, that is, invasion of pathogenic bacteria by accumulation of silicic acid in epidermal cells, reduction of insect damage caused by insects, promotion of the production of antibacterial substances in plants, and under adverse conditions It is said that it is effective in improving stress tolerance. (See Non-Patent Document 1)

On the other hand, the form when silicic acid is absorbed by the plant is a molecularly dispersed silicic acid having no charge, and anionic silicic acid is considered to be inferior in absorbability. When silicic acid is dissolved in water, it is a molecularly dispersed silicic acid (H ₄ SiO ₄ ) having no charge at pH 8 or lower, but anionic silicic acid (H ₃ SiO ₄ ) when pH 8 is exceeded. ⁻ , H ₂ SiO ₄ ²⁻ , HSiO ₄ ³⁻ , SiO ₄ ⁴⁻ ), and the number of negative charges increases as the pH increases. (See Non-Patent Document 2)

  The present invention is a liquid silicate fertilizer that can combine the fertilizer effect of the above-described silicic acid with the fertilizer effect of essential elements, and can quickly exhibit a synergistic fertilizer effect.

  Currently, the official standards for siliceous fertilizers are defined as five types of mineral siliceous fertilizer (Keical), lightweight cellular concrete fertilizer, silica gel fertilizer, silica hydrogel fertilizer, and wollastonite fertilizer. There is no immediate effect due to the low dissolution rate in water.

  Therefore, in order to provide an immediate effect, a liquid silicate fertilizer using potassium silicate or silica sol as a silicic acid component has been proposed.

Potassium silicate-based liquid silicate fertilizer Potassium silicate has a high pH of the aqueous solution itself of 10 or more and cannot be applied as it is. Moreover, when an acid is added and the pH is reduced to about 8 or less, the silicate ions are dehydrated and condensed, resulting in gelation and suspension, and silicic acid is precipitated, so that it cannot be used as a liquid fertilizer. However, liquid silicate fertilizers in which various substances are added to potassium silicate have been proposed. For example, citric acid (see Patent Document 1), ethylenediaminetetraacetate magnesium (see Patent Document 2), and gluconic acid (see Patent Document 3) are added to an aqueous potassium silicate solution. However, these liquid silicic acid fertilizers have a pH of 8 or more, but the silicic acid is deposited within a relatively short time and does not endure long-term storage. Therefore, it was necessary to use it as soon as possible after production. Moreover, although the method (refer patent document 4) of adding the condensed potassium phosphate salt which does not have a hydrogen atom in a molecule | numerator in potassium silicate aqueous solution is proposed, pH is 10 or more and a basic thing is strong. As described above, the potassium silicate-based liquid silicate fertilizer needs to maintain a strong basic pH in order to suppress silicic acid precipitation, but it is necessary to pay attention to an increase in soil pH during application, and as described above. Since silicic acid exists as an anion in such a basic liquid, it is not in the form of a molecularly dispersed silicic acid that does not have a charge that is easily absorbed by plants.

Silica sol-based liquid silicic acid fertilizer Silica sol is also referred to as silicic acid sol, and is a state in which silicic acid is dispersed in water in a colloidal form, and liquid silicic acid fertilizer using silica sol as a component has also been proposed. For example, colloidal form using acidic silicate sol consisting of stable sol particles obtained by dealkalizing alkali silicate aqueous solution with cation exchange resin, aging with acid or alkali and strengthening siloxane bond and building up There is a liquid fertilizer containing silicic acid (see Patent Document 5) and a liquid fertilizer containing water-soluble normal silicic acid obtained by hydrolyzing tetraalkoxysilane with an acid (see Patent Document 6). Since these liquid silicic acid fertilizers have a pH of 1 to 4, they contain silicic acid as a molecularly dispersed silicic acid that is not easily absorbed by plants, but the liquid silicic acid fertilizers in both examples The silicic acid content is as low as 2.5% by weight or less in terms of SiO ₂ . When the concentration of silicic acid is higher than this, in the former case, the fertilizer component mixed with silicic acid reacts and gelation is likely to occur, and in the latter case, gelation is likely to occur during the acid hydrolysis reaction of tetraalkoxysilane. Therefore, it was difficult to contain silicic acid at a high concentration.

Silicic acid and crop production Japan Society of Soil Fertilizer Hakutosha (2002) Silicic and Lime Plants Takahashi Eiichi Nongbunkyo (1987) p.62

JP 62-56389 A JP 5-78189 A JP 7-101792 A JP 2011-184207 A JP-A-9-268092 JP-A-2005-67996

  In view of the problems of the prior art as described above, the purpose of the present invention is to contain a higher concentration of silicic acid, and contains a wide variety of essential elements in a stable ionic state that is easily absorbed by plants, An object of the present invention is to provide a liquid silicate fertilizer having an immediate effect which is less likely to cause silicic acid precipitation or insoluble matter precipitation such as gelation or suspension during long-term storage.

  As a result of intensive studies in order to solve the above problems, the present inventors have completed the present invention. The details will be described below.

Alkaline silica sol is a transparent or milky white colloidal solution usually having a pH of 8 to 11. However, when a water-soluble compound containing an essential element is added directly to this alkaline silica sol, gelation or suspension is instantaneously generated. There is a case. The present inventor has found that citric acid, a reducing organic acid, is blended as a method for dissolving a water-soluble compound containing a wide variety of essential elements in an alkaline silica sol without causing gelation or suspension. The present invention has been completed.

In the first aspect, the alkaline silica sol is mixed with citric acid, the pH is 4.0 or less, and the silicic acid content is SiO. ₂ In a silica sol / citric acid solution of 1 to 30% by weight in terms of iron, 0.01 to 5% by weight of iron in terms of Fe and at least one or two of calcium, magnesium, boron, manganese, zinc, copper, and molybdenum It is a liquid silicate fertilizer characterized by containing more than seeds in an ionic state.

By adding citric acid to alkaline silica sol and adding essential elements such as iron to silica sol / citric acid solution whose pH is 4.0 or less, gelation is suppressed and long-term storage becomes possible. Further, silicic acid can be maintained in the form of molecularly dispersed silicic acid which has no electric charge which is easily absorbed by plants.

The content of silicic acid, 1 to 30 wt% in terms of SiO _2, preferably from 2 to 25 wt%. The liquid silicate fertilizer of the present invention is diluted 100 to 2000 times with water and used for foliar spray solution, soil irrigation solution, and culture solution in hydroponics, but the content of silicate is set in the above range. Thus, it can be supplied at an optimum concentration according to the growth state of the plant, the soil, or the silicic acid-containing state of the hydroponics culture solution.

Examples of reducing organic acids include citric acid, malic acid, succinic acid, gluconic acid, tartaric acid, lactic acid, gallic acid, ascorbic acid, glucuronic acid, glycolic acid, glyceric acid, erythorbic acid, 2-hydroxybutyric acid, glyoxylic acid, etc. However, in the present invention, citric acid is preferred from the viewpoints of solubility in water, availability, and economy.

The iron content is 0.01 to 5% by weight, preferably 0.05 to 4% by weight in terms of Fe. The liquid silicate fertilizer of the present invention is diluted 100 to 2000 times with water and used for foliar spray solution, soil irrigation solution, and culture solution in hydroponics, but the iron content should be set in the above range Thus, it can be adjusted to an optimum concentration according to the growth state of the plant, the soil, or the iron content of the hydroponics culture solution, and can effectively exert the fertilizer effect in a well-balanced manner with silicic acid.

By containing at least one or more of calcium, magnesium, boron, manganese, zinc, copper, and molybdenum in an ionic state, a fertilizer effect can be effectively exhibited.

In claim 2 , calcium is 0.05 to 5% by weight in terms of CaO, magnesium is 0.05 to 5% by weight in terms of MgO, boron is 0.01 to 3% by weight in terms of B ₂ O ₃ , and manganese is MnO. 0.05 to 5% by weight in terms of zinc, 0.01 to 2% by weight in terms of zinc, 0.01 to 2% by weight in terms of Cu, 0.01 to 2% by weight in terms of Mo It is the liquid silicate fertilizer of Claim 1 .

  The liquid silicate fertilizer of the present invention is diluted 100 to 2000 times with water and used for foliar spray solution, soil irrigation solution, and culture solution in hydroponics, but in the above ranges, calcium, magnesium, boron, manganese By setting the content of zinc, copper and molybdenum, it can be adjusted to the optimum concentration according to the growth status of the plant and the content of essential elements in the soil or hydroponic culture broth, effectively fertilizing with good balance with silicic acid The effect can be demonstrated.

The liquid silicate fertilizer of the present invention is
(1) It contains a high concentration of silicic acid stably.
(2) It contains silicic acid as molecularly dispersed silicic acid that does not have a charge that is easily absorbed by plants.
(3) Trivalent iron ions are contained as divalent iron ions that are reduced by citric acid and easily absorbed by plants.
(4) It contains large amounts of calcium, magnesium, and trace elements of iron, boron, manganese, zinc, copper, and molybdenum in the form of ions that are easily absorbed by plants.
(5) Gelation and suspension hardly occur for a long time.
At the same time has the characteristics. Therefore, it is superior in storage stability and, more than conventional liquid silicic acid fertilizer, promotes the strengthening of plants and promotes healthy growth of plants, so it is resistant to environmental stresses such as salt damage, high temperature, and drying, and pest control The frequency of drug spraying can be greatly reduced.

The components of the liquid silicate fertilizer of the present invention are (a) an alkaline silica sol, (b) a reducing organic acid, (c) a raw material compound of essential elements, and other components that can be added within a range that does not impair the characteristics thereof. is there. Hereinafter, the manufacturing method and fertilization method of these components and the liquid silicate fertilizer of this invention are demonstrated.

  The components of the liquid silicate fertilizer will be described.

(A) Alkaline silica sol
Alkaline silica sol is a liquid medium of the liquid silicate fertilizer of the present invention, and also a source of silicic acid. For the production of the alkaline silica sol, there are the following known production methods.

(1) A method for producing silica sol, so-called active silicic acid, by bringing an alkali metal silicate aqueous solution, for example, an aqueous solution of sodium silicate into contact with an H-type strongly acidic cation exchange resin, and dealkalizing by ion exchange. Furthermore, the manufacturing method of the alkaline silica sol which stabilized the dispersion state by making the sol particle diameter grow large, and making the internal structure of the sol particle dense by the built-up process of the active silicic acid.

(2) A method for producing silica sol (active silicic acid) by subjecting an alkali silicate aqueous solution, for example, an aqueous solution of sodium silicate, to ion exchange by electrodialysis using an ion exchange membrane for dealkalization. Furthermore, the manufacturing method of the alkaline silica sol which stabilized the dispersion state by making the sol particle diameter grow large, and making the internal structure of the sol particle dense by the built-up process of the active silicic acid.

( 3 ) A method for producing an alkaline silica sol, in which siliceous mineral fine powders such as silicic acid hydrogel, silicic acid xerogel and quartz are hydrothermally treated with alkali to peptize. For example, a method for producing an alkaline silica sol in which sodium sulfate is washed and removed from a silicic acid hydrogel obtained by a reaction between an aqueous solution of sodium silicate and an acid, followed by hydrothermal treatment with an autoclave or the like.

The alkaline silica sol used in the liquid silicic acid fertilizer of the present invention may be obtained by any of the above production methods. When the silicic acid content is high, it can be diluted with water as necessary. The water may be tap water.

The physical conditions to be provided for the alkaline silica sol used in the liquid silicate fertilizer of the present invention are shown below.
(1) silicate content may be from 5 to 40% by weight in terms of SiO _2. That is, silicic acid content of the liquid silicate fertilizer produced may if achieve 1 to 30 wt% in terms of SiO _2.
(2) The pH is 8 to 12, preferably 9 to 11.
(3) When the contained alkali component is present, the molar ratio is, for example, 10 or more, preferably 40 or more in terms of SiO ₂ / Na ₂ O.
(4) The liquid phase is preferably colorless and transparent to a colloidal translucent light transmission, but more preferably colorless and transparent. The reason is that the smaller the colloidal particle diameter of silicic acid, the more transparent the liquid phase is like water, but the smaller the colloidal particle diameter, the more the specific surface area increases and the silicic acid from the colloidal particle surface increases. When the liquid silicate fertilizer of the present invention is diluted with water, the concentration of molecularly dispersed silicic acid (H ₄ SiO ₄ ) having no charge that is easily absorbed by the plants contained therein is rapidly increased. This is because it increases. In addition, if the liquid phase of the alkaline silica sol is cloudy and opaque, when insoluble precipitates such as suspension and precipitation occur during the production and storage of the liquid silicate fertilizer, it cannot be detected, which causes quality control problems. is there.

(B) Reducing organic acid As a reducing organic acid having the action of reducing trivalent iron ions to divalent iron ions, citric acid, malic acid, gluconic acid, succinic acid, tartaric acid, lactic acid, gallic acid, ascorbine Examples include acid, glucuronic acid, glycolic acid, glyceric acid, erythorbic acid, 2-hydroxybutyric acid, glyoxylic acid, etc. In the present invention, citric acid is used in terms of solubility in water, availability, and economy. It is preferable to use it.

Citric acid works as a pH adjuster and an iron reducing agent in the liquid silicate fertilizer of the present invention, and specific actions are as follows.
(1) due to the acidic range to the alkaline silica sol, due to the acidic range of molecular dispersed, generation silicate (2) an alkaline silica sol having no charge, the metal ion of the essential elements is insolubilized becomes hydroxide preventing become prevention (3) trivalent iron ions of divalent iron reduction to ions (4) ferrous ions are natural oxide Ri by the dissolved oxygen or air oxygen trivalent iron ions that

Citric acid may be mixed with other reducing organic acids described in the paragraph number ( 0031 ). Further, a citrate having the same reducing action as citric acid, for example, trisodium citrate, tripotassium citrate and the like may be mixed with citric acid.

In addition, citric acid may be used in combination with other reducing organic acid salts described in paragraph ( 0031 ). For example, disodium malate, disodium succinate, sodium gluconate and the like.

(C) will be described physiological effects and the starting compound for the plant essential element of claim 1 is added to the liquid silicic acid fertilizer raw material compound present invention essential elements, the material compounds containing the essential elements, the water-soluble compound Must.

(1) Iron is involved in the energy transfer system centering on redox reactions, and when deficient, chlorophyll is reduced and new leaves turn yellow. As water-soluble compounds of iron-containing raw materials, ferric nitrate, ferric sulfate, ferric chloride, ferric phosphate, ferric acetate, ferric citrate as trivalent iron compounds , Ferric gluconate, ferric ascorbate and the like can be mentioned, but these may be used alone or in combination of two or more. In addition, as divalent iron compounds, ferrous sulfate, ferrous nitrate, ferrous chloride, ferrous phosphate, ferrous acetate, ferrous citrate, ferrous gluconate, ferrous ascorbic acid Although iron etc. can be mentioned, you may mix these with said trivalent iron compound. That is, trivalent iron ions generated by dissolution are automatically reduced by citric acid to become divalent iron ions. Therefore, when selecting a water-soluble iron compound, particularly distinguish between iron divalent and trivalent. There is no need, and the range of choices is wide and economical.

(2) Calcium binds to pectic acid and is involved in the formation and strengthening of plant cell membranes. When deficient, the growth of apical buds and root hairs of the roots deteriorates. Examples of the water-soluble compound of the raw material compound containing calcium include calcium nitrate, calcium chloride, calcium acetate, calcium lactate, calcium gluconate, calcium lignin sulfonate, and the like. These may be mixed.

(3) Magnesium is a constituent element of chlorophyll and is involved in carbohydrate metabolism and phosphate metabolism. Examples of the water-soluble compound of the raw material compound containing magnesium include magnesium nitrate, magnesium chloride, and magnesium acetate. These may be used alone or in combination of two or more.

(4) Boron is involved in calcium absorption and translocation, and is involved in maintaining the structure of the cell wall by binding to pectic polysaccharides. When deficient, the growth of new leaves stops and the root elongation of cells grows worse. Examples of the water-soluble compound of the raw material compound containing boron may include boric acid and sodium borate. These may be used alone or in combination of two or more.

(5) Manganese is involved in the production of chlorophyll, photosynthesis, and vitamin C synthesis. Examples of the water-soluble compound of the raw material compound containing manganese include manganese sulfate, manganese nitrate, manganese chloride, and manganese acetate. These may be used alone or in combination of two or more.

(6) Zinc is a constituent element of the enzyme in the body and is involved in the glycolytic system and the citric acid cycle, and when deficient, new leaf malformations and interleaf veins are yellowed. Examples of the water-soluble compound of the raw material compound containing zinc include zinc sulfate, zinc nitrate, zinc chloride, and zinc acetate. These may be used alone or in combination of two or more.

(7) Copper is a constituent element of in-vivo enzymes, is involved in redox in the plant body, and when deficient, the growth of new leaves deteriorates and the leaves turn yellow. Examples of the water-soluble compound of the raw material compound containing copper include copper sulfate, copper nitrate, copper chloride, and copper acetate. These may be used alone or in combination of two or more.

(8) Molybdenum is a constituent element of in-vivo enzymes, and is involved in rhizobial nitrogen fixation and nitrate reduction. When deficient, leaf malformation and atrophy occur. Examples of the water-soluble compound of the raw material compound containing molybdenum include sodium molybdate and ammonium molybdate, and these may be used alone or in combination of two or more.

  In addition, selection of the essential element of said (1)-(8) contained in the liquid silicate fertilizer of this invention, and its density | concentration are the essential element of the kind of plant, the growth condition of a plant, soil, or a hydroponics culture solution. What is necessary is just to perform according to a content condition.

(D) Other components The liquid silicate fertilizer of this invention can mix | blend the following component as needed in the range which does not impair the characteristic. Amino acids (eg, methionine, glutamic acid, proline, etc.), saccharides (eg, glucose, chitosan, trehalose, etc.), vitamins (eg, vitamins B1, B2, B6, choline, etc.), animal or plant protein hydrolysates, Chelating agents (for example, ethylenediaminetetraacetic acid and its salts), surfactants, preservatives.

  Below, the manufacturing method (procedure) of the liquid silicate fertilizer of this invention is demonstrated in detail.

First, citric acid is blended in the form of a solid powder or an aqueous solution with stirring to an alkaline silica sol adjusted to a desired silicic acid concentration, and the pH is 4.0 or less, preferably 3.5 or less, more preferably 2.0. Prepare ~ 3.5 silica sol / citric acid solution.

  When adding an iron component, a water-soluble compound of a raw material compound containing desired iron is added to the silica sol / citric acid solution in the form of a solid powder or an aqueous solution while stirring, and the iron ion-containing silica sol / citric acid solution is added. To prepare.

  Further, when adding an essential element component other than the iron component, a water-soluble compound of a raw material compound containing a desired essential element is added to the silica sol / citric acid solution or the iron ion-containing silica sol / citric acid solution as a solid powder or an aqueous solution. And may be added with stirring.

As a procedure of the production method, a water-soluble compound of a raw material compound containing a desired essential element may be dissolved in a citric acid aqueous solution in advance, and an alkaline silica sol may be added thereto while stirring.

  The final pH of the liquid silicate fertilizer containing the essential elements produced by the above procedure is 4.0 or less, preferably 3.5 or less, more preferably 0.2 to 3.5. During the production, if the pH is out of the above range, an alkali metal hydroxide such as sodium hydroxide, potassium hydroxide, or an aqueous ammonia solution or citric acid is added with stirring as required. What is necessary is just to adjust to pH. At this time, citric acid can be mixed with inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, and phosphoric acid.

  In addition, the essential element calcium, magnesium, iron, manganese, zinc, copper metal ions may become a hydroxide and insolubilize and precipitate when the pH is high, the liquid silicate fertilizer of the present invention, By adjusting the pH to the above range, it can be prevented that these metal ions become hydroxides and insolubilized, and become hydroxides and insolubilized even when the pH rises when diluted with water for application. Can be prevented.

  In the above manufacturing process, the stirring operation is indispensable, but heating is not particularly required. In addition, when a water-soluble compound of trivalent iron is added, the reduction reaction of trivalent iron ions to divalent iron ions proceeds gradually even when left at room temperature, It is desirable to continue stirring.

  Next, the application method will be described.

  The liquid silicate fertilizer of the present invention is a fertilizer that is diluted with water and applied in foliar application, soil irrigation, hydroponics and the like, and the water may be tap water. The dilution factor is selected according to the concentration of silicic acid and essential elements contained in the liquid silicic acid fertilizer of the present invention, the growth stage and growth status of plants, the content of essential elements in the soil or hydroponics culture solution, etc. For example, it is about 100 to 2000 times. The application method can be manual or electric spraying for foliar spraying, and for soil irrigation and hydroponic cultivation, dilute in existing nutrient solution tanks and use existing irrigation pipelines and infusion lines. Can be used.

  Hereinafter, although the liquid silicate fertilizer of this invention is demonstrated in detail by an Example, this invention is not limited to these Examples.

By incorporating a citric acid made alkaline silica sol produced by a commercially available built-up process with an alkaline silica sol prepared by an ion exchange method and peptization method was measured gelation time when changing the pH stepwise. From the relationship between the pH and the gelation time, a range of pH that can be stably stored for a long time without gelation of the silica sol was confirmed.

(Preparation of alkaline silica sol 1 ion exchange method)
Sodium silicate No. 3 aqueous solution (Kishida Chemical Co., Ltd. SiO ₂ content 29.1% by weight, Na ₂ O content 9.3% by weight, molar ratio 3.23) was diluted with ion-exchanged water, and H-type strongly acidic Sodium hydroxide was removed by contacting with a cation exchange resin (Mitsubishi Chemical Corporation Diaion SK1B-H), and active silicic acid having a silicic acid content of about 5.5% by weight as SiO ₂ and a pH of 4.3 was prepared. Since this active silicic acid gels after several hours, a 5N sodium hydroxide aqueous solution is added with stirring, and ion-exchanged water is further added. The pH is 10.3, and the silicic acid content is 5.0% by weight as SiO _2. An alkaline silica sol was prepared. Table 1 shows the physical properties.

(Preparation of alkaline silica sol 2 Peptization method)
Silicate isocyanatomethyl Li um No. 3 aqueous solution (Kishida Chemical Co., Ltd. SiO ₂ content of 29.1 wt%, Na ₂ O content of 9.3 wt%, molar ratio 3.23) was diluted with deionized water, SiO ₂ The content was 5.0% by weight. 2N hydrochloric acid was added to this aqueous solution with stirring to adjust the pH to 7.4, and then allowed to stand to gel. The obtained silica hydrogel was crushed and washed with tap water for 2 hours to remove sodium chloride. The washed silica hydrogel was put in an autoclave and hydrothermally treated at 120 ° C. for 2 hours to obtain an alkaline silica sol having a silicic acid content of SiO ₂ of 4.5% by weight. This alkaline silica sol was concentrated with a rotary evaporator to prepare a silica sol having a SiO ₂ content of 14.5 wt% and a pH of 10.1. Table 1 shows the physical properties.

(Geling time measurement test)
Alkaline silica sol used was an alkaline silica sol prepared by the ion exchange method described in Table 1 (SiO ₂ content of 5.0 wt%), an alkaline silica sol prepared by peptizing method (SiO2 content 14.5% by weight) diluted with tap water, SiO2 content 10.0% by weight and the alkaline silica sol, and commercially available SNOWTEX 30 is alkaline silica sol (SiO ₂ content of 30.5 wt%, Na ₂ O content of 0.33 wt% PH 10.0, NISSAN CHEMICAL INDUSTRIES CO., LTD.) Is diluted with tap water, and is an alkaline silica sol having a SiO ₂ content of 20.0% by weight. Prepare a silica sol / citric acid solution in which the pH is changed stepwise by mixing solid powder of citric acid / monohydrate (Yoneyama Pharmaceutical first grade reagent) with 100 g of these three types of alkaline silica sol, and store at 20 ° C. Gelation time was measured and stability was evaluated. Gelation was performed when the silica sol liquid level could not be kept horizontal when the container was tilted. The results are shown in Table 2.

  From the test results shown in Table 2, it was found that when citric acid was added to a pH of 4.0 or less, gelation did not occur even after 30 days and the product was stable and could be stored for a long time.

The names of the drugs used in the following examples and comparative examples are abbreviated as follows.
Citric acid monohydrate (Yoneyama Pharmaceutical first grade reagent) is citric acid, ferric nitrate nonahydrate (Yoneyama Pharmaceutical first grade reagent) ferric nitrate, ferric chloride anhydride (Yoneyama Pharmaceutical) The primary reagent) is ferric chloride, calcium nitrate tetrahydrate (Yoneyama Chemical) The primary reagent is calcium nitrate, magnesium acetate tetrahydrate (Kishida Chemical primary reagent) is magnesium acetate, boric acid (Yoneyama) Chemical first grade reagent) is boric acid, zinc sulfate heptahydrate (Yoneyama Chemical first grade reagent) is zinc sulfate, manganese sulfate pentahydrate (Yoneyama chemical first grade reagent) is manganese sulfate, copper sulfate, five water Japanese products (Yoneyama Pharmaceutical first grade reagent) are copper sulfate, sodium molybdate dihydrate (Kishida Chemical special grade reagent), and sodium molybdate.

A silica sol / citric acid having a pH of 2.8 was prepared by mixing 3.3 g of a solid powder of citric acid with stirring in 100 g of an alkaline silica sol having a silicic acid content of SiO ₂ of 5.0% by weight prepared by the ion exchange method in Example 1. After making into a solution, 4.0 g of ferric nitrate was added and dissolved as a solid while stirring to obtain a liquid silicate fertilizer containing iron ions. Table 3 shows the physical properties.

In Example 1, an alkaline silica sol having a silicic acid content of 14.5% by weight as SiO ₂ prepared by the peptization method was diluted with tap water, and 100 g of alkaline silica sol having an SiO ₂ content of 10.0% by weight was mixed with citric acid. After mixing 3.3 g of solid powder with stirring to obtain a silica sol / citric acid solution having a pH of 2.5, 8.0 g of ferric nitrate was added and dissolved while stirring to contain iron ions. A liquid silicate fertilizer was obtained. Table 3 shows the physical properties.

Commercially available Snowtex 30 (SiO ₂ content 30.5 wt%) was diluted with tap water, and 100 g of alkaline silica sol with SiO ₂ content 20.0 wt% was stirred with 3.3 g of solid powder of citric acid. The mixture was mixed to obtain a silica sol / citric acid solution having a pH of 2.8, and then 20.0 g of ferric nitrate was added and dissolved while stirring to obtain a liquid silicate fertilizer containing iron ions. Table 3 shows the physical properties.

  From the results of Table 3, the liquid silicate fertilizers of Examples 2 to 4 have stable storage properties without gelation or suspension even after 30 days of storage at 20 ° C. I understood. In addition, ferric nitrate is used as a water-soluble compound of trivalent iron. When a 0.1 mol / L aqueous solution of potassium ferricyanide is added to these liquid silicate fertilizers, the iron contained is the original trivalent. If it was an iron ion, it only turned reddish brown, but a dark blue precipitate, which was a color of divalent iron ion, was produced. From this, it was found that the trivalent iron ions in the liquid silicate fertilizer containing citric acid were reduced to divalent iron ions.

Reference Example 5

A silica sol / citric acid having a pH of 2.8 was prepared by mixing 3.3 g of a solid powder of citric acid with stirring in 100 g of an alkaline silica sol having a silicic acid content of SiO ₂ of 5.0% by weight prepared by the ion exchange method in Example 1. After preparing the solution, it was added and dissolved in the order of 3.0 g of calcium chloride and 6.0 g of magnesium chloride while stirring to obtain a liquid silicate fertilizer containing calcium ions and magnesium ions. Table 4 shows the physical properties.

Reference Example 6

In Example 1, an alkaline silica sol having a silicic acid content of 14.5% by weight as SiO ₂ prepared by peptization was diluted with tap water, and 100 g of silica sol having a SiO ₂ content of 10.0% by weight was mixed with citric acid solids. After mixing 3.3 g of the powder with stirring to obtain a silica sol / citric acid solution having a pH of 2.5, 3.0 g of calcium chloride and then 6.0 g of magnesium chloride are added and dissolved in this order while stirring. Thus, a liquid silicate fertilizer containing calcium ions and magnesium ions was obtained. Table 4 shows the physical properties.

Reference Example 7

Commercially available Snowtex 30 (SiO ₂ content 30.5 wt%) was diluted with tap water, and 100 g of alkaline silica sol with SiO ₂ content 20.0 wt% was stirred with 3.3 g of solid powder of citric acid. After mixing to form a silica sol / citric acid solution with a pH of 2.8, the mixture is added and dissolved in the order of 3.0 g of calcium chloride and then 6.0 g of magnesium chloride with stirring to obtain calcium ions and magnesium ions. A liquid silicate fertilizer containing was obtained. Table 4 shows the physical properties.

From the results in Table 4, the liquid silicic acid fertilizers of Reference Examples 5 to 7 have stable storage without gelation or suspension even after 30 days of storage at 20 ° C. I understood.

A silica sol / citric acid having a pH of 2.8 was prepared by mixing 3.3 g of a solid powder of citric acid with stirring in 100 g of an alkaline silica sol having a silicic acid content of SiO ₂ of 5.0% by weight prepared by the ion exchange method in Example 1. After preparing the solution, with stirring, ferric nitrate 4.0 g, zinc sulfate 1.0 g, manganese sulfate 2.0 g, copper sulfate 0.50 g, sodium molybdate 0.25 g, boric acid 1.0 g in order. As it was added and dissolved, a liquid silicate fertilizer was obtained. Table 5 shows the physical properties.

A silica sol / citric acid having a pH of 2.6 was prepared by mixing 3.3 g of a solid powder of citric acid with stirring in 100 g of an alkaline silica sol having a silicic acid content of SiO ₂ of 14.5% by weight prepared by the peptization method in Example 1. After preparing the solution, 7.5 g of ferric chloride, 2.1 g of calcium nitrate, and 2.5 g of magnesium acetate were added and dissolved as they were in the order of solid to obtain a liquid silicate fertilizer. Table 5 shows the physical properties.

A commercial product Snowtex 30 (SiO ₂ content 30.5 wt%) 100 g of solid powder of citric acid was mixed with stirring to obtain a silica sol / citric acid solution of pH 3.2, and then stirred. Ferric nitrate 40.0 g, magnesium acetate 5.0 g, manganese sulfate 4.0 g, and boric acid 2.5 g were added and dissolved in the order of solid to obtain a liquid silicate fertilizer. Table 5 shows the physical properties.

Comparative Example 1

In Example 1, 100 g of alkaline silica sol having a silicic acid content of 5.0% by weight as SiO ₂ prepared by the ion exchange method was mixed with 4.0 g of ferric nitrate and 1 g of zinc sulfate while stirring without adding citric acid. 0.0 g, 2.0 g of manganese sulfate, 0.50 g of copper sulfate, 0.25 g of sodium molybdate, and 1.0 g of boric acid were added and dissolved in the order of solids to obtain a liquid silicate fertilizer. Table 5 shows the physical properties.

Comparative Example 2

In Example 1, 100 g of alkaline silica sol having a silicic acid content of 14.5% by weight as SiO ₂ prepared by the peptization method, 7.5 g of ferric chloride and 2 mg of calcium nitrate were stirred without mixing citric acid. 0.1 g and 2.5 g of magnesium acetate were added and dissolved in the order of solids to obtain a liquid silicate fertilizer. Table 5 shows the physical properties.

Comparative Example 3

Without adding citric acid to 100 g of commercially available Snowtex 30 (SiO ₂ content 30.5 wt%), ferric nitrate 40.0 g, magnesium acetate 5.0 g, manganese sulfate 4.0 g with stirring. In this order, 2.5 g of boric acid was added and dissolved as a solid to obtain a liquid silicate fertilizer. Table 5 shows the physical properties.

  From the results of Table 5, the liquid silicate fertilizers of Examples 8 to 10 containing citric acid were stored at 20 ° C., and gelation and suspension did not occur even after 30 days. I found it. On the other hand, the liquid silicate fertilizers of Comparative Examples 1 and 2, which did not contain citric acid, did not gel during storage at 20 ° C., but suspended in a short period of time, resulting in precipitation. In the liquid silicate fertilizer of Comparative Example 3, gelation or suspension did not occur after 30 days.

  In addition, from the results of Table 5, ferric nitrate or ferric chloride is used as a water-soluble compound of trivalent iron, but a 0.1 mol / L aqueous solution of potassium ferricyanide is added to the liquid silicate fertilizer. In Examples 8 to 10 containing citric acid, dark blue precipitation, which is the coloration of divalent iron ions, was produced, so the trivalent iron ions in the liquid silicate fertilizer were reduced to divalent iron ions. I found out that On the other hand, Comparative Examples 1 to 3 that did not contain citric acid did not cause dark blue precipitation, and the liquid color changed to reddish brown, indicating that the iron ions remained in their original trivalent state. .

Application Example The liquid silicate fertilizer obtained in the above example was applied to an actual plant to investigate its effect. Below, the application example is demonstrated.

Application example 1
In the house cultivation of prince melon, one week after planting the seedlings, about 10 ml of the liquid silicate fertilizer tap water (pH 5.5) of Example 8 was irrigated around the strain. Thereafter, the leaves were sprayed with a 500-fold dilution of the same liquid silicate fertilizer every 2 weeks until harvest. As a result, compared with the strain which did not perform soil irrigation and foliar application, the occurrence frequency of powdery mildew decreased to about 1/3, and the frequency of spraying agents such as fungicides decreased. This is thought to be due to the enhanced resistance to pathogens of plants due to the synergistic fertilizer effect of the essential elements iron, boron, manganese, zinc, copper and molybdenum contained in silicic acid.

Application example 2
Four seedlings of rice (variety Koshihikari) were used as one strain, and 6 plants were prepared by planting 3 plants per Wagner pot (1 / 2000a). The soil was paddy (collected from rice farm the previous year), and the entire fertilizer was applied with 1.3 g of nitrogen, 1.8 g of phosphorus and 0.5 g of potassium per pot. The 6 Wagner pots were divided into 2 groups of 3 pots, and the growth of the group B not applied to the group A applied with the liquid silicate fertilizer of the present invention was compared.

  The application method is that the 1000-fold diluted liquid silicate fertilizer (pH 5.8) of Example 9 is charged every 100 weeks per pot from the setting period 1 week after planting to the heading period through the tilling period. did. The results are shown in Table 6.

  From the results in Table 6, group A to which the liquid silicate fertilizer of the present invention was applied clearly had more tillers and fir yields. In addition, Group A had darker green leaves and higher plant height than Group B without application. This is thought to be due to the synergistic fertilizer effect of the essential elements iron, calcium and magnesium, as well as the fertilizer effect of silicic acid on rice.

Application example 3
The golf green grass (bentgrass), tap water 500 times dilution (pH 5.5) of the liquid silicate fertilizer of Example 2, every 10 days over the 3-6 month, subjected to foliar application of 1 m ² per 500ml It was. As a result, compared with the place where foliar application was not performed, there was an increase in rooting, stiffening of the leaves, an increase in the thickness of stems and leaves, a decrease in drought damage, and a strong increase in turf. It was. This is thought to be due to the synergistic fertilizer effect of the contained iron as well as the silicic acid fertilizer effect on the turf.

Claims (7)

A liquid silicate fertilizer having a pH of 4.0 or less, which is obtained by blending a reducing organic acid with silica sol. Liquid silicate fertilizer according to claim 1, wherein the content of silica is 1 to 30 wt% in terms of SiO _2. The liquid silicic acid fertilizer according to claim 1 or 2, wherein the reducing organic acid is citric acid. The liquid silicate fertilizer according to any one of claims 1 to 3, wherein a water-soluble trivalent iron compound is dissolved and iron is contained as divalent iron ions by reduction with a reducing organic acid. The liquid silicate fertilizer according to claim 4, wherein iron is contained in an amount of 0.01 to 5% by weight in terms of Fe. The liquid silicate fertilizer according to any one of claims 1 to 5, wherein at least one or more of calcium, magnesium, boron, manganese, zinc, copper, and molybdenum are contained in an ionic state. Calcium is 0.05 to 5% by weight in terms of CaO, magnesium is 0.05 to 5% by weight in terms of MgO, boron is 0.01 to 3% by weight in terms of B ₂ O ₃ , and manganese is 0.05 in terms of MnO. 1 to 5% by weight, zinc is 0.01 to 2% by weight in terms of Zn, copper is 0.01 to 2% by weight in terms of Cu, and molybdenum is 0.01 to 2% by weight in terms of Mo. The transparent liquid silicate fertilizer according to claim 6.