Iron supply method

Abstract

To provide a method for supplying iron to the soil containing iron or aluminum in abundance.SOLUTION: A soil improving method includes the steps of: putting tannin into contact with iron in a neutral or alkaline liquid, to prepare a solution containing a colloid of Fe(III)-gallic acid complexes; and spraying the solution containing the colloid of Fe(III)-gallic acid complexes over the soil containing iron and / or aluminum in abundance.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for supplying iron to plants, and particularly to a method for using an iron tannin colloid dispersion for promoting plant growth.

Background Art

[0002] In volcanic ash soils and the like, minerals such as aluminum and iron precipitate together with phosphoric acid, making it difficult for plants to utilize them, which has been a problem. When the iron content is insufficient, there has been a problem that the synthesis amounts of chlorophyll in chloroplasts and the electron transport system decrease, photosynthesis and ATP production become insufficient, and plant growth deteriorates. Also in the ocean, there has been a problem that the supply of iron to photosynthetic bacteria is rate-limiting and the photosynthesis amount is restricted.

[0003] As a solution to this, it is possible to spray a chelating agent. However, in the case of EDTA and the like, there has been a problem that since chemical substances are used, it cannot be called an organic farming method. There is also a method of using divalent iron (Patent Document 1), but when soluble iron ions are sprayed on a field, there has been a problem that they combine with phosphoric acid to form insoluble precipitates, which adversely affects phosphorus absorption by plants. The same was true for aluminum, which causes the phosphorus absorption problem in volcanic ash soils.

[0004] On the other hand, to improve soil in which iron or aluminum has combined with phosphoric acid to become insoluble, it is conceivable to spray tannin, but there has been a problem that tannin causes inhibition of plant growth (Non-Patent Document 1). Therefore, there has been a demand for a method that does not cause inhibition of plant growth and changes iron and phosphorus into forms that are easily utilized by plants. There has also been a demand for a method of preventing the aging of fields and maintaining the sustainability of agriculture.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Non-Patent Documents

[0006] [Non - Patent Document 1] Ministry of Agriculture, Forestry and Fisheries, Production Environment Promotion Sub - committee, Technology for Removing Growth - Inhibiting Factors by Iron Treatment of Cryptomeria and Hinoki Bark Pulverized Fibers (https: / / www.naro.affrc.go.jp / org / warc / research_results / h18 / 02_kankyo / p83 / index.html) [Summary of the Invention] [Problems to be Solved by the Invention]

[0007] To provide a method for supplying iron to soil rich in iron or aluminum. [Means for Solving the Problems]

[0008] (1) A step of producing a solution containing a colloid of Fe(III) - gallic acid complex by bringing tannin into contact with iron in a neutral or alkaline liquid; A soil improvement method comprising a step of spraying the solution containing the colloid of the Fe(III) - gallic acid complex onto soil rich in iron and / or aluminum content (soil in which mineral components such as aluminum and iron precipitate with phosphoric acid and are in a state difficult for plants to utilize). Here, Fe(III) means trivalent iron ions. (2) The soil improvement method according to (1), characterized in that copper and / or magnesium co - exist in the step of producing the solution containing the colloid of the Fe(III) - gallic acid complex. (3) The soil improvement method according to (1) or (2), wherein the soil improvement is by the release of phosphoric acid from sparingly soluble phosphate compounds. (4) A method for promoting plant growth by spraying the solution containing the colloid of the Fe(III) - gallic acid complex according to (1) or (2) onto plants and / or soil. (5) The method for promoting plant growth according to (4), further characterized by improving the taste and / or texture of plants. By spraying a solution containing the colloid of the Fe(III)-gallic acid complex according to (1) or (2) above on plants and / or soil, a method for promoting plant growth according to (4) or (5), characterized by enhancing the insect resistance of plants. (7) A method for promoting the growth of filamentous fungi and / or actinomycetes in soil by spraying a solution containing the colloid of the Fe(III)-gallic acid complex according to (1) or (2) above on the soil. (8) A method for promoting the growth of plants and / or microorganisms by spraying a solution containing the colloid of the Fe(III)-gallic acid complex according to (1) or (2) above on the sea, rivers or lakes. (9) A method for recovering chlorosis caused by over-fertilization with phosphorus fertilizer by spraying tannin.

Effects of the Invention

[0009] According to the present invention, there is provided a method for soil improvement by spraying a solution containing the colloid of the Fe(III)-gallic acid complex on soil having a high iron and / or aluminum content.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0011] The present invention uses a mixture of tannin solution and iron to improve soil and / or promote the growth of crops. More specifically, trivalent iron forms a complex (a strong chelate structure) with gallic acid (3,4,5-trihydroxybenzoic acid) (Fe(III)-gallic acid complex), and a solution that becomes a colloidal solution (this solution may be referred to as tannin iron solution) is sprayed on crops and / or soil to achieve soil improvement, promotion of crop growth, improvement of crop taste and texture, improvement of crop insect resistance, and / or promotion of the growth of soil microorganisms. The present invention has found that tannin iron solution can be obtained simply by bringing metallic iron and tannin into direct contact. Furthermore, it is novel in that iron can be supplied to plants in a liquid state containing a colloidal-dispersed iron compound without dissolving iron ions as much as possible. The property of being insoluble in water is a necessary property to avoid chemical reactions with phosphorus compounds that are naturally present in agricultural land and the natural world. It has been confirmed that the tannin iron of the present invention can maintain a state of being dispersed as a colloid without precipitation for more than one year. This is an unexpected property, quite different from the precipitation of ordinary colloids over time.

[0012] The Fe(III)-gallic acid complex of the present invention is produced by bringing iron and tannin into contact in a liquid. That is, when iron or an iron compound and tannin are added to a liquid with a neutral to alkaline pH (for example, distilled water, tap water, well water, agricultural water, lake water, seawater, etc.), the iron or iron compound and tannin dissolve and come into contact in the liquid, and a chelate reaction (or complex formation reaction) occurs between the two materials to produce tannin iron (Chemical Formula 1, Fe(III)-gallic acid complex). Tannin iron can be obtained simply by adding metallic iron to an aqueous tannin solution. For example, by leaving 2 to 5 commercially available iron nails (about 5 cm long) in commercially available green tea in a PET bottle and waiting for about a week, a colloidal solution of tannin iron can be easily obtained. A solution containing the colloid of tannin iron is referred to as tannin iron solution, and the tannin iron solution may contain a polyphenol iron complex. Tannin iron may also be produced by spraying powdered tea on groundwater rich in iron or soil rich in iron.

[0013] [Chemistry]

[0014] After leaving it as it is, tannin iron is colloidal-dispersed. As a result, a colloidal solution of tannin iron is produced and can be used as an iron supply agent. In the manufacturing process of such an iron supply agent, it is preferable to stir the inside of the container or introduce air bubbles to increase the oxygen concentration in order to prevent fermentation. Also, fermentation can be prevented by putting a copper plate into the container. It has also been confirmed that fermentation can be prevented by adding carbon materials such as charcoal and white charcoal. Magnesium not only has a bacteriostatic effect but also has an effect of supplying magnesium which is a component of plant chlorophyll.

[0015] The pH of the water used for the production of a solution containing a colloid of Fe(III)-gallic acid complex is preferably neutral to alkaline. Neutral to alkaline means pH 7 or higher, and the upper limit of pH is 11 or lower, more preferably 10 or lower, still more preferably 9 or lower, and even more preferably 8 or lower.

[0016] As the iron used for the production of a solution containing a colloid of Fe(III)-gallic acid complex, iron / cast iron (for example, iron plate, iron nail, iron pot, casting, etc.) (castings can naturally form a combination of iron / carbon, and iron is likely to elute due to the effect of local batteries. Ordinary cast iron contains ferrite (iron), graphite (carbon), pearlite (iron / carbon)) or steelmaking slag containing iron oxide, etc., but is not limited to these. As other iron supply materials, organic substances such as fallen leaves with a high iron content, wall clay containing iron, soil with a high iron content, and groundwater containing a large amount of iron may be used. Furthermore, if the container for containing the liquid is made of iron, iron can also be supplied from the container. You may use a bathtub for a traditional Japanese bath. Since the surface area of iron is large, there is an advantage that it dissolves extremely fast. In short, any iron that can form a complex with tannin in the liquid to become a colloidal solution of Fe(III)-gallic acid complex is acceptable.

[0017] Examples of tannins used in the production of a solution containing a colloid of an Fe(III)-gallic acid complex include, but are not limited to, tea husks, coffee husks, fermentation residues of beer and whiskey, onion skins or fallen leaves containing polyphenols, plant residues, food residues, rainwater, and groundwater, and are not particularly limited as long as they are materials capable of producing an Fe(III)-gallic acid complex.

[0018] The present invention is characterized in that a solution containing a colloid of the Fe(III)-gallic acid complex of Chemical Formula 1 is used. This solution containing a colloid of the Fe(III)-gallic acid complex contains tannins not bound to iron ions. The solution containing a colloid of the Fe(III)-gallic acid complex may be referred to as tannin iron solution in this specification. The upper limit of the concentration of tannin iron in the solution containing a colloid of the Fe(III)-gallic acid complex is preferably 10% by weight or less, more preferably 9% by weight or less, still more preferably 8% by weight or less, even more preferably 7% by weight or less, particularly preferably 6% by weight or less, and most preferably 5% by weight or less, and the lower limit is preferably 1% by weight or more, more preferably 2% by weight or more, even more preferably 3% by weight or more, particularly preferably 4% by weight or more, and most preferably 5% by weight or more.

[0019] In the present invention, an insoluble iron chelate in which trivalent iron ions and gallic acid are strongly bound is used instead of water-soluble divalent iron ions. This is because when water-soluble divalent iron is sprayed, it binds to phosphoric acid in the soil to form iron phosphate, which becomes unavailable to plants and causes problems with phosphorus absorption. Phosphorus in the fertilizer component also becomes unavailable. In contrast, in the case of insoluble Fe(III)-gallic acid, since it is insoluble in water, no problem with phosphorus absorption occurs.

[0020] In the present invention, by spraying tannin iron solution on the surface of crops and / or soil, the growth of crops such as lettuce and komatsuna can be promoted, the production volume can be increased, and furthermore, the taste can be improved. In the case of lettuce, it becomes more than twice as large in appearance and three times as heavy. Also, in the case of lettuce, the leaves become thicker and the taste is improved. The increase in the production volume of these vegetables means that the fixation of carbon dioxide by photosynthesis has increased, and it also has the effect of suppressing global warming caused by carbon dioxide. In addition, there is a possibility that the problem of crop rotation in fields with phosphorus absorption problems can be solved, and it also has the effect of contributing to the sustainable development of agriculture and SDGs.

[0021] In the present invention, when spraying tannin iron solution, basically, soil spraying is preferred. The reasons for this are: (1) there is no obstacle to soil spraying (ordinary iron materials may cause obstacles), (2) overspray is less likely to occur, (3) when spraying on the leaf surface, the taste remains in leafy vegetables, etc. However, when soil spraying is not suitable for root vegetables, etc., leaf surface spraying is used. Spraying may be carried out using a watering can, or a power sprayer, etc. A filter may be used to prevent clogging.

[0022] Soils suitable for applying the present invention include, for example, soils with a high iron and / or aluminum content. "Soils with a high iron and / or aluminum content" refer to soils in which mineral components such as aluminum and iron precipitate together with phosphoric acid, making it difficult for plants to utilize them. Examples include volcanic ash soils. In volcanic ash soils, the phosphate absorption coefficient is 1500 or more. The phosphate absorption coefficient is an index representing the ability of the soil to adsorb and fix phosphoric acid. Specifically, it is the value obtained by adding a 2.5% ammonium phosphate solution in an amount twice that of the soil, stirring it from time to time to cause a reaction, and expressing the amount of phosphoric acid absorbed by the soil after 24 hours in mg per 100 g of soil (http: / / lib.ruralnet.or.jp / nrpd / #koumoku=15544). The tannin iron spraying of the present invention is likely to be effective when the phosphorus absorption coefficient is 1200 or more, more preferably 1300 or more, still more preferably 1400 or more, and particularly preferably 1500 or more. In the volcanic ash soil of Kamikama Plateau where phosphorus absorption problems are likely to occur, the weight of lettuce increased by about three times by spraying the tannin iron solution of the present invention. However, even when sprayed on other soils (soils without phosphorus absorption problems, soils in a state suitable for crop growth, etc.), some effects considered to be growth regulation by the plants themselves were obtained. Growth regulation refers to actions such as promoting (or suppressing) plant growth, promoting fruit setting, and promoting root growth. In a specific example of Kamikama Plateau, the sugar content of watermelon improved from 11 / 12 to 15 / 17.

[0023] The general taste of tannin-iron-cultivated vegetables has less bitterness, astringency, acridity, and eggy flavor, a strong original vegetable aroma, and a gentle sweetness. The umami is strong, and instead of a grassy aftertaste, sweetness and umami remain. This is thought to be because the supply of iron by the tannin-iron solution causes the nitrogen atoms of nitrate nitrogen to be incorporated into amino acids, reducing the bitterness and eggy taste of nitrate ions and increasing umami. Due to the high water content, it is fresh, has a crispy texture, is easy to chew but not tough. The knife cuts through well, the heat penetrates well, it is not easily overcooked, and the texture remains. It is firm, heavy, and has good keeping quality. (The vegetables cultivated with tannin-iron have strong and firm cell membranes, but each cell contains a lot of water, so they are mostly water with cell membranes here and there, making it easy for the knife to cut through and not feeling hard when chewed with teeth. For its part, it becomes like a state where a tire tube is filled with air, so it is firm and heavy. Since the cell membrane becomes strong, the water does not escape easily, so it has good keeping quality. The reason for the strengthening of the cell membrane and the increase in water content is unknown. The reduction in bitterness, astringency, acridity, and eggy flavor is due to the enzyme with iron as the active center synthesizing nitrate and ammonia nitrogen compounds absorbed from the roots into amino acids. The iron absorbed from the roots reacts with tannins in the plant to become tannin-iron, so the bitterness and astringency caused by tannins disappear. The iron effect increases the chlorophyll synthesis ability and the ability to produce nutrients, so the sugar content easily increases. Furthermore, due to the increase in iron, the production efficiency of ATP in the mitochondrial electron transport system increases, so a large amount of energy can be produced with less nutrients, and the plant can live more easily. Excess nutrients can be utilized. Since the chlorophyll synthesis efficiency increases, it is possible to reduce the nitrogen fertilizer of the materials. Similarly, since the metabolic efficiency of ATP increases, it is possible to reduce the phosphorus fertilizer of the materials. As a result, low-fertilizer cultivation of nitrogen and phosphorus, which is usually impossible to achieve, becomes possible, and the acridity and eggy flavor derived from residues are extremely reduced. When sensory tests were conducted on more than 100 people, all but one person answered that the vegetables sprayed with tannin-iron were more delicious. These improvements in taste and texture were also supported by the results of amino acid analysis (see Example 9, Table 6).

[0024] The tannin iron solution of the present invention can also be used as a soil conditioner. In soils rich in iron and aluminum, phosphoric acid binds to these elements to form insoluble iron phosphate and aluminum phosphate, which are in a form that plants cannot utilize, resulting in a problem of phosphoric acid deficiency. However, by spraying the tannin iron solution of the present invention on the soil, tannin dissociates iron and aluminum from iron phosphate and aluminum phosphate, releasing phosphoric acid, thereby supplying phosphorus that can be utilized by plants. The tannin iron colloid dispersion is in a state of a mixture of tannin iron / tannin. The dissociated iron is utilized as tannin iron.

[0025] As for the spraying time of the tannin iron solution of the present invention, an effect was observed at any time during the cultivation period, from before planting to one week before harvesting. Basically, it is soil spraying.

[0026] For fruit vegetables, legumes, etc., when sprayed at intervals of about one week during the cultivation period, the astringency and bitterness decreased and the sweetness increased. For other varieties such as leafy vegetables and root vegetables, sufficient effects were obtained by spraying once during the cultivation period. The spraying amount is sufficient as long as the area near the planting location of the ridge turns color and gets wet.

[0027] When sprayed before planting or at the early growth stage, an effect of preventing plant elongation and promoting root growth was observed. However, it is preferable to avoid spraying about 5 days before sowing / planting and 5 days after planting, as there is a possibility of growth disorders due to tannin. In the cultivation of baby leaves, etc., it is preferable to use a 100-fold diluted solution of the normal concentration (the concentration of the combination of commercially available green tea in a PET bottle and iron nails is the standard). The concentration can be managed by visual inspection of the color, and strict concentration management is not necessary in practical use. However, caution is required when it does not turn completely black.

[0028] When spraying on the cultivation soil during seedling raising, depending on the plant species, growth disorders may occur due to tannins. Therefore, as described above, it is preferable to use a 100-fold diluted solution of the normal concentration. However, since germination and seedling raising may be improved depending on the plant, it is preferable to spray by diluting the concentration step by step and determine the optimal dilution rate for each plant. Examples of the dilution rate when diluting include 5-fold, 10-fold, 20-fold, 30-fold, 40-fold, 50-fold, 60-fold, 70-fold, 80-fold, 90-fold, 100-fold, 150-fold, 200-fold, etc., but it is not limited to these. As long as it is the optimal dilution ratio for growth promotion, other dilution ratios may also be used.

[0029] By spraying the tannin iron solution of the present invention on the foliage and / or soil of crops, the insect resistance of the crops has been improved. This may be because the insect resistance has been improved due to the improvement of the physiological state of the crops, or it is also possible that tannins, iron compounds, copper, etc. are involved. Due to the above effects, it is considered possible to reduce the nitrogen fertilizer content remaining inside the plant body. It has been pointed out that excessive application of nitrogen fertilizer may attract insects due to the nitrogen fertilizer content remaining in the plant body. For example, last year in Kansai, the damage caused by planthoppers in rice cultivation was severe, but in the tannin iron rice cultivation without pesticides and fertilizers, there was almost no insect damage for a cultivation area of 4 hectares. The adjacent paddy fields were damaged.

[0030] By spraying the tannin iron solution of the present invention, the proportion of filamentous fungi and actinomycetes among the microorganisms in the soil increased (Example 5, Table 3). Actinomycetes are known to secrete chitinase, etc., and suppress pests and diseases by decomposing the cell walls of filamentous fungi and the chitin and proteins that make up the eggs of nematodes. Filamentous fungi secrete amylase, cellulase, protease, etc., and promote the growth of other bacteria by decomposing starch, cellulose, and proteins.

[0031] When spraying the tannin iron solution of the present invention before planting, since there is an effect of activating soil microorganisms, when the soil temperature rises sufficiently (to 55 - 60 °C) due to solar heat disinfection and fermentation heat, weed seeds and fungi are decomposed by microorganisms, and neither weeds nor fungi grow. When the temperature rise is low, the weeds will be inactivated and the fungi will remain, resulting in a state where there are no weeds and only fungi grow (the fungal temperature zone). When the temperature rise is even lower, the weeds grow like mountains.

[0032] When tea is used as a tannin source in the production of tannin iron solution, the tea may ferment. To suppress this, it has been found that it is effective to add a copper plate (Example 6). The repellent effect against powdery mildew was also confirmed. Since copper ions have a weak insect - proof and disease - prevention effect as known in Bordeaux mixture, it is considered that the addition of copper ions to the tannin iron solution of the present invention further enhances the insect - proof and disease - prevention effects.

[0033] In this specification, tannin refers to a general term for water - soluble compounds derived from plants that react with proteins, alkaloids, metal ions, etc., strongly bind to form poorly soluble salts. Tannin contains polyphenol compounds and is a complex aromatic compound with a large number of phenolic hydroxy groups. Some tannins strongly bind to proteins and other macromolecules to form complexes. In this specification, in a narrow sense, tannin may refer to gallic acid.

[0034] When investigating whether green tea polyphenols can release iron, aluminum, and phosphate from iron phosphate and aluminum phosphate, a high release effect was observed (Examples 4, Tables 1 and 2). That is, when iron phosphate and tea were mixed, the elution amount of iron showed an elution effect about 60 times that of pure water (0.3 mg / L) and tea (17.9 mg / L). The phosphorus elution amount in the same experiment was 53 mg / L for pure water and 96 mg / L for tea.

[0035] In the aluminum phosphate elution test, the aluminum elution amount was 0.53 mg / L for pure water and 4.4 mg / L for tea, and tea had an elution effect about 8 times that of pure water. The phosphorus elution amount was 8.9 mg / L for pure water and 20 mg / L for tea.

[0036] From these experimental results, it was found that tea leaf polyphenols can release iron and aluminum from iron phosphate and aluminum phosphate, and also release phosphorus. Due to this effect, it is considered that the iron tannin solution of the present invention can also release phosphorus from iron phosphate and aluminum phosphate, and can improve the soil.

[0037] The plants to which the iron tannin of the present invention is applied are not particularly limited, and include monocotyledonous plants, dicotyledonous plants, gymnosperms, angiosperms, etc.

[0038] The iron tannin solution of the present invention is expected to be particularly effective for soils rich in iron and aluminum. For example, volcanic ash soils, Kanto loam layers, etc. can be mentioned, but it is not limited to these, and any soil rich in iron and aluminum and forming a precipitate with phosphoric acid and having insufficient phosphorus absorption can be preferably used.

[0039] The iron tannin solution of the present invention is not limited to fields, and may also be sprayed on forests. It is also possible to spray on lakes, rivers and / or the sea to promote growth by breeding algae, aquatic plants and photosynthetic bacteria that serve as fish feed.

[0040] The iron tannin technology of the present invention has the following three functions, and thus has the ability to balance the supply of iron, aluminum, phosphorus, etc. 1. Supply of iron in a form that is easy for plants to absorb 2. Recovery of phosphorus from iron phosphate and aluminum phosphate, and reuse of iron 3. Mitigation of growth disorders when tannin is used alone In addition, iron tannin is a chemical substance that is naturally formed by the chemical reaction between the fallen leaves of broad-leaved trees and iron in the soil, so it is safe and has no environmental load. The present invention will be described below using examples, but these are only a part of the embodiments of the present invention, and the present invention is not limited by these examples.

Examples

[0041] (Example 1) Method for producing iron tannin solution As a simple method for making tannin iron solution, put two nails (about 5 cm long) into 2 L of bottled tea, let it stand for more than one week, and then use it. When making a larger quantity, put tannin materials and iron materials into bags respectively and put them into a container such as a bathtub and leave them for more than 24 hours. In the case of a 300 kg container, about 300 g of tannin and one commercially available skillet (a type of iron frying pan) can be put in for the iron. As the iron, cast iron, pure iron of used agricultural implements, carbon steel, etc. can also be used. The shape may be that of a cast iron round bar cut into pieces. When making a large quantity, the bags containing tannin materials and iron materials should be placed on a rack or the like to keep a distance from the bottom rather than attaching them to the bottom. When bubbling with air, iron tannate of the desired purpose can be formed without fermentation or putrefaction. Instead of a bathtub, if an iron bathtub is used as the container, there is no need to put in cast iron. Just put in tannin and water and bubble. As the tannin, industrial tannic acid (Fuji Chemical Industry) etc. can be used.

[0042] (Example 2) In the volcanic ash soil of Kammuro Plateau, Hyogo Prefecture, head lettuce was cultivated, and the tannin iron solution of the present invention was sprayed on the leaves once during the growth process. Cultivation period: from April 20, 2018 to June 30, 2018. A photo of the lettuce after harvest is shown in Fig. 1. As shown in Fig. 1, the lettuce sprayed with the tannin iron solution of the present invention was about twice or more larger (three times in weight) than the lettuce not sprayed. The leaves were also thick, soft and had a better taste. From this, it was considered that the tannin iron solution of the present invention has a growth promoting effect and a taste improving effect in volcanic ash soil.

[0043] (Example 3) In a field of the Kanto Loam layer in Saitama Prefecture, the effect of the tannin iron solution of the present invention on the cultivation of Komatsuna was investigated. The experiment was conducted in three plots: a plot where neither tannin (tea) nor iron was sprayed (the upper part of Figure 2), a plot where tea was sprayed (the middle part of Figure 2), and a plot where the tannin iron solution of the present invention was sprayed (the lower part of Figure 2). As a result, as shown in Figure 2, in the plot where the tannin iron solution of the present invention was sprayed, the growth was the best. Next, growth disorders were observed in the plot where nothing was sprayed and the plot where only tea was sprayed. Also, in the plot where the tannin iron solution of the present invention was sprayed, it was also stronger against insects, and it was considered that the tannin iron solution of the present invention enhanced the insect resistance of Komatsuna. Cultivation period: April 23, 2020 to July 10, 2020. The tannin iron colloid solution was sprayed on the soil of a 5 m long and 60 cm wide ridge twice, 5 days before sowing and 10 days after germination, at 10 L per ridge.

[0044] (Example 4) When tannin was added to iron phosphate or aluminum phosphate, the degree of elution of iron or aluminum was investigated. For the quantification of iron and aluminum, atomic absorption spectrometry was used, and for the measurement of the elution amount of phosphorus, molybdenum blue colorimetry was used. The results are shown in Table 1 and Table 2.

[0045]

Table 1

[0046]

Table 2

[0047] As shown in Table 1, when pure water was added to iron phosphate, the iron elution amount was 0.3 mg / L, while when tea was added, 17.9 mg / L of iron was eluted. This is about 60 times that when pure water was used, and it is considered that the tannin contained in tea eluted iron from iron phosphate.

[0048] As shown in Table 2, when 125 mL of pure water was added to aluminum phosphate (aluminum orthophosphate), the elution amount of aluminum was 0.53 mg / L. However, when tea was added, 4.4 mg / L of aluminum was eluted. From this, it was considered that tea tannin has the ability to liberate aluminum from aluminum phosphate. Regarding the elution amount of phosphorus as well, tea showed a higher elution amount compared to pure water.

[0049] (Example 5) The effect of the tannin iron solution of the present invention on the number of soil microorganisms was investigated. The soil of the control plot and the plot sprayed with the tannin iron solution of the present invention was collected, and the number of filamentous fungi, actinomycetes, and bacteria was counted by the dilution plate method. The results are shown in Table 3.

[0050]

Table 3

[0051] As shown in Table 3, compared with the control plot, in the iron tea plot (the plot sprayed with the tannin iron solution of the present invention), both filamentous fungi and actinomycetes increased significantly. There was almost no difference in the number of general bacteria. Therefore, the ratio of bacteria / filamentous fungi was 2100 in the control plot and 1200 in the iron tea plot, and in the iron tea plot, the number of filamentous fungi and actinomycetes tended to be larger than the number of bacteria. This is considered to have a favorable effect on the growth of crops.

[0052] (Example 6) When producing tannin iron, a problem may occur that the tea leaves, which are organic substances, ferment. To solve this, the effect of adding a copper plate was investigated. When one 30 cm square copper plate was added to a 500 L tank for making tannin iron, fermentation could be prevented. At the same time, the generation of foaming could also be suppressed.

[0053] (Example 7) The effect of tea on copper elution was investigated. 2.5 grams of copper powder (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade 99% reagent powder) was made up to a fixed volume with 25 mL of tea (O-cha (registered trademark), Itoen) or 25 mL of pure water, shaken at 120 rpm for 1 minute, then allowed to stand for 24 hours. For the supernatant, the amount of copper was measured by atomic absorption spectrometry. The results are shown in Table 4. For the water extraction with an elution amount of 1.3 mg / L, the tea extraction had an elution amount of 53 mg / L, which was about 40 times that of the water extraction.

[0054]

Table 4

[0055] (Example 8) The effect of tea on magnesium elution was investigated. 2.5 grams of magnesium powder (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade 99% reagent powder) was made up to a fixed volume with 25 mL of tea (O-cha (registered trademark), Itoen) or 25 mL of pure water, shaken at 120 rpm for 1 minute, then allowed to stand for 24 hours. For the supernatant, the amount of magnesium was measured by atomic absorption spectrometry. The results are shown in Table 5.

[0056]

Table 5

[0057] As shown in Table 5, 15 times more magnesium eluted in the tea extraction than in the water extraction. The tea in the lower row is the measurement of the magnesium content of the original tea solution. From the above experiments, it was shown that the tannin in tea is effective not only for iron elution but also for magnesium elution. Magnesium is a component of chlorophyll for photosynthesis, and when magnesium is deficient, it causes chlorosis where the leaves turn yellow, hindering photosynthesis. According to the data in Table 5, tannin has the advantage of significantly increasing the elution amount of magnesium and being able to supply it to plants efficiently.

[0058] (Example 9) The effect of tea (tannin) on iron elution was investigated. After dissolving 2.5 g of iron powder in 25 mL of water or 25 mL of tea, the mixture was shaken at 120 rpm for 1 minute and then allowed to stand for 24 hours. Itoen's thick Oh-ii tea (500 mL) was used for the tea. 85% reagent grade (Fuji Film Wako Pure Chemical Industries) was used for the iron powder. The results are shown in Table 6. Compared with water extraction, the elution in tea extraction was 545 times higher.

[0059]

Table 6

[0060] (Example 10) Measurement of Amino Acid Content Spinach was cultivated in the plot (plot A, sprayed in the same manner as in Example 3) where the tannin iron solution of the present invention was sprayed and in the non-sprayed plot (plot B), and the amino acid content was measured (Table 6). ※1 indicates that the measurement was taken excluding the stock and damaged leaves. ※2 indicates that after peracetic acid oxidation treatment, hydrochloric acid hydrolysis was performed for measurement. The measurement was performed by the automatic amino acid analysis method using an automatic amino acid analyzer (manufactured by JEOL Ltd.) except for tryptophan. For tryptophan, measurement was performed by high performance liquid chromatography.

[0061]

Table 7

[0062] As shown in Table 7, the spinach in the plot (plot A) cultivated by spraying the tannin iron solution of the present invention had a higher content of all amino acids than the non-sprayed plot (plot B). From this, it is considered that spraying the tannin iron solution of the present invention has the effect of increasing the amino acid content of plants.

[0063] (Example 11) When two round nails were put into a commercially available 2 L green tea PET bottle and left for one week, the color changed from light yellow-green to black (the bottle on the right side of Figure 3, the left is untreated). Even when this PET bottle was left for one year, the colloidal state was maintained and no precipitation occurred. Furthermore, it was dissolved until sodium hydrogen carbonate was saturated, and no precipitation occurred even when the pH was adjusted to 7.9. When this solution was naturally dried, it became a powder and could be redispersed by adding water.

Industrial Applicability

[0064] The present invention can be used in agriculture, fishery, fertilizer industry, environmental restoration business, etc.

Claims

**Claim 1** A step of producing a solution containing a colloid of Fe(III)-gallic acid complex by bringing tannin into contact with iron in a neutral or alkaline liquid; A step of spraying the solution containing the colloid of the Fe(III)-gallic acid complex onto soil in which mineral components such as aluminum and iron are precipitated together with phosphoric acid and are in a state difficult for plants to utilize; A step of dissociating iron and aluminum from iron phosphate and aluminum phosphate contained in the soil to release phosphoric acid; A method for supplying phosphoric acid available to plants, comprising the above steps. **Claim 2** The method for supplying phosphoric acid available to plants according to Claim 1, wherein copper and / or magnesium coexist in the step of producing the solution containing the colloid of the Fe(III)-gallic acid complex. **Claim 3** A method for promoting the growth of plants, using the method for supplying phosphoric acid available to plants according to Claim 1 or 2. **Claim 4** The method for promoting plant growth according to Claim 3, further characterized by improving the taste and / or texture of the plants. **Claim 5** In the method for supplying phosphoric acid available to plants according to Claim 1 or 2, when producing the solution containing the colloid of the Fe(III)-gallic acid complex, by introducing a copper plate, A method for preventing fermentation and / or the generation of bowfly. **Claim 6** A method for promoting the growth of filamentous fungi and / or actinomycetes in soil, using the method for supplying phosphoric acid available to plants according to Claim 1 or 2.

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