Humic acid extract and method for promoting growth of plant roots

Abstract

Provided are a humic acid extract having an excellent effect of promoting the growth of plant roots and a method for promoting the growth of plant roots using the same. 【Solution means】A humic acid extract containing humic acid having a mass average molecular weight of 400 to 1,000, a total organic carbon concentration of 10,000 to 45,000 mg / L, and a free nitric acid content of 1 mass% or less. A method for promoting the growth of plant roots, wherein the humic acid extract is diluted with water and applied to plants.

Description

Technical Field

[0001] The present invention relates to a method for promoting the growth of humic acid extract and plant roots.

Background Art

[0002] Humic acid is a high-molecular organic substance that naturally exists in soil and surface water, and is classified into humin, which is an insoluble fraction, fulvic acid, which is soluble in alkali but insoluble in acid, and fulvic acid, which is soluble in acid. Humic acid includes those derived from nature and those obtained industrially. Humic acid is said to have effects such as growth promotion on plants, and it has been proposed to use humic acid for fertilizer purposes. In addition, in order to use humic acid as a liquid fertilizer, a technique for extracting and liquefying humic acid has also been proposed (Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Documents 1 and 2, the effects of the humic acid extract on the above-ground parts of plants have been evaluated, but the effects on the roots have not been examined.

[0005] An object of the present invention is to provide a humic acid extract having an excellent effect of promoting the growth of plant roots and a method for promoting the growth of plant roots using the same.

Means for Solving the Problems

[0006] The present invention has the following aspects. [1] A humic acid extract containing humic acid with a mass average molecular weight of 400 to 1,000, having a total organic carbon concentration of 10,000 to 45,000 mg / L, and having a free nitric acid content of 1 mass% or less. [2] The humic acid extract according to [1] above, wherein the content of the free nitric acid is 0.1 mass% or more. [3] The humic acid extract according to [1] or [2] above, having a pH of 4.5 to 7.5. [4] The humic acid extract according to any one of [1] to [3] above, containing an alkali metal salt of nitric acid, wherein the content of the alkali metal salt is 6 to 9 mass% in terms of potassium. [5] A humic acid extract containing humic acid with a mass average molecular weight of 400 to 1,000, having a total organic carbon concentration of 10,000 to 45,000 mg / L, and having a free nitric acid content of 3 mass% or less. [6] A method for promoting the growth of plant roots, comprising diluting the humic acid extract according to any one of [1] to [5] above with water and applying it to plants.

Advantages of the Invention

[0007] According to the present invention, it is possible to provide a humic acid extract excellent in the effect of promoting the growth of plant roots and a method for promoting the growth of plant roots using the same.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0009] In this specification, the numerical range represented by "~" means a numerical range having the numerical values before and after "~" as the lower limit value and the upper limit value, respectively. In this specification, "humic acid" is a general term for humic acid and fulvic acid. Humic acid is insoluble in acid and soluble in alkali, and fulvic acid is soluble in acid. The "humic acid extract" is obtained by extracting humic acid from a humic acid-containing raw material such as young coal with an extraction solvent. Hereinafter, embodiments of the present invention will be described.

[0010] [Humic acid extract] The humic acid extract of this embodiment contains humic acid. The mass average molecular weight (Mw) of the humic acid is 400 to 1,000, preferably 500 to 900, and more preferably 600 to 800. When Mw is within the above range, even if the humic acid extract is added to a concentrated liquid fertilizer containing components such as the three major elements, it is difficult to form a precipitate, which is useful for fertilizer applications. Mw is measured by size exclusion chromatography (SEC method) using sodium polystyrene sulfonate as a standard. Specifically, it is as described in the examples.

[0011] The total organic carbon concentration (TOC) of the humic acid extract is 10,000 to 45,000 mg / L, preferably 11,000 to 40,000 mg / L, and more preferably 12,000 to 35,000 mg / L. There is a strong correlation between the concentration of humic acid and TOC, and TOC serves as an indicator of the concentration of humic acid. Although it varies depending on the type of raw material, etc., the concentration of humic acid is estimated to be about 1.4 to 1.8 times that of TOC. When transporting or manufacturing secondary products, a higher concentration of humic acid in the humic acid extract is useful. On the other hand, when the concentration of humic acid increases, it is more likely to gel due to a decrease in temperature or pH. If TOC is below the above upper limit value, gelation can be sufficiently suppressed. TOC is measured by the combustion catalyst oxidation method using a total organic carbon meter.

[0012] The humic acid extract of this embodiment typically contains an extraction solvent. As the extraction solvent, water is preferred.

[0013] The humic acid extract of this embodiment can contain nitric acid. When the humic acid extract is produced by the production method described later, the obtained humic acid extract usually contains nitric acid. The nitric acid in the humic acid extract may be in the form of free nitric acid or in the form of a salt. At least a part of the nitric acid in the humic acid extract is preferably in the form of a salt. Examples of the nitrate salt include alkali metal salts such as sodium salt and potassium salt, and ammonium salts. From the viewpoint of storage stability, alkali metal salts are preferred.

[0014] In the humic acid extract, the content of free nitric acid is 1% by mass or less, preferably 0.5% by mass or less, and may be 0% by mass, based on the total mass of the humic acid extract. When the content of free nitric acid is below the above upper limit, the effect of promoting the growth of plant roots is excellent. The content of free nitric acid is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, based on the total mass of the humic acid extract. When the content of free nitric acid is above the above lower limit, the miscibility with liquid fertilizers and the like tends to be excellent. The content of free nitric acid is measured by potentiometric titration. Specifically, it is as described in the examples.

[0015] When the humic acid extract contains an alkali metal salt of nitric acid, its content is preferably 6 to 9% by mass, more preferably 6.5 to 8.5% by mass, and still more preferably 7 to 8% by mass in terms of potassium, based on the total mass of the humic acid extract. When the content of the alkali metal salt is above the above lower limit, the content of free nitric acid tends to be below the above upper limit, and when it is below the above upper limit, the solubility of humic acid tends to be excellent.

[0016] The pH of the humic acid extract is preferably 4.5 to 7.5, more preferably 5 to 7. When the pH is above the above lower limit, the content of free nitric acid tends to be below the above upper limit. When the pH is below the above upper limit, the content of free nitric acid tends to be above the above lower limit.

[0017] [Method for producing humic acid extract] The humic acid extract of the present embodiment can be produced, for example, by a production method including the following steps (1) to (6). (1) A step of adding an aqueous nitric acid solution in an amount of 24 to 28 parts by mass in terms of nitric acid (HNO3) to 20 parts by mass of young coal. (2) Step of reacting the mixture obtained in the step (1) at 70 - 80 °C for 1 - 3 hours to prepare a crude humic acid product. (3) Step of adding water and an alkali to the crude humic acid product to prepare a mixture with a pH of 2.0 - 4.0 and a solid - liquid ratio of 1:4 - 1:6. (4) Step of subjecting the mixture obtained in the step (3) to extraction treatment under the conditions of a liquid temperature of 40 - 80 °C for 0.5 hours or more. (5) Step of separating the solid and liquid of the extracted mixture and recovering the separated liquid part. (6) Adding an alkali to the liquid part to make the content of free nitric acid 1 mass% or less.

[0018] Young coal is coal with a lower carbon content compared to bituminous coal etc., and is defined as having a carbon content rate of 83 mass% or less. Young coal is, for example, peat, lignite, brown coal, sub - bituminous coal, etc., and one or a mixture of two or more of these can be used. The nitric acid concentration of the aqueous nitric acid solution added to young coal is, for example, 40 - 60 mass%.

[0019] (3) In the step, for example, water is added to the crude humic acid product so that the solid - liquid ratio is below the target value, then an alkali is added so that the pH reaches the target value, and if necessary, more water is added to obtain a mixture with the target pH and solid - liquid ratio. Here, the solid - liquid ratio is the ratio of the amount of young coal as the raw material used to prepare the crude humic acid product to the amount of the extraction solvent. For example, when 100 parts by mass of an extraction solvent (water) is added to a crude humic acid product prepared from 20 parts by mass of young coal, the solid - liquid ratio is 1:5.

[0020] Examples of the alkali include alkali metal hydroxides such as potassium hydroxide and sodium hydroxide, and ammonia. Among these, from the viewpoint of storage stability, alkali metal hydroxides are preferred. The alkali can be used alone or in combination of two or more. The alkali can be selected according to its use, such as using potassium hydroxide that can be utilized as a fertilizer component. The alkali is added while measuring the pH. Alternatively, it is also possible to conduct a test in advance with different amounts of alkali added to the crude humic acid product to determine the amount of alkali addition for the target pH, and then add the determined amount of alkali.

[0021] The pH of the mixture obtained in the step (3) is 2.0 to 4.0, preferably 2.0 to 3.0. When the pH is within the above range, precipitation is less likely to occur during the component adjustment after solid-liquid separation. The solid-liquid ratio of the mixture obtained in the step (3) is 1:4 to 1:6, preferably 1:5 to 1:6. When the solid-liquid ratio is within the above range, it tends to be excellent in handleability and extraction efficiency.

[0022] In the step (4), the liquid temperature of the mixture is set to 40 to 80 °C using a water bath or the like, held for 0.5 hours or more, then cooled to 40 °C or lower, and fed to the step (5). The extraction time is 0.5 hours or more, and there is little difference in the extraction efficiency of humic acid. Considering the working efficiency, the range of 0.5 to 1 hour is preferable. In the step (5), the solid-liquid separation can be carried out by known methods such as centrifugation and filter press.

[0023] In the step (6), by adding alkali to the liquid part, at least a part of the free nitric acid is neutralized, and the content of the free nitric acid decreases. The content of the free nitric acid can be adjusted by the amount of alkali added. Examples of the alkali include the same ones as described above. The liquid part with the content of free nitric acid being 1 mass% or less can be used as the humic acid extract of this embodiment. If necessary, dilution or concentration may be performed for the adjustment of TOC.

[0024] [Method for promoting the growth of plant roots] In the method for promoting the growth of plant roots of this embodiment, the above-mentioned humic acid extract is diluted with water and applied to plants. Thereby, the growth (such as rooting) of plant roots can be promoted. By promoting the growth of plants, the rhizosphere expands, the ability of plants to absorb water and nutrients from the soil and the like improves, leading to the healthy growth of plants and the improvement of crop yield and quality.

[0025] The amount of water used for diluting the humic acid extract is, for example, 40,000 to 400,000 parts by mass, preferably 50,000 to 300,000 parts by mass, based on 100 parts by mass of the humic acid extract. The pH of the aqueous dilution of the humic acid extract is, for example, 6.0 to 8.0.

[0026] There is no particular limitation on the type of plant, and examples include leafy vegetables such as Komatsuna, Spinach, Chinese Cabbage, and Lettuce, and fruit vegetables such as Tomato, Eggplant, and Pepper. From the viewpoint of promoting the growth cycle, leafy vegetables such as Komatsuna, Spinach, and Lettuce are preferred. There is also no particular limitation on the cultivation form of plants, and examples include soil cultivation and hydroponics. Soil cultivation is preferred in terms of higher usefulness in promoting root growth.

[0027] As the timing for applying the aqueous dilution of the humic acid extract, for example, the time of planting can be mentioned. The number of times of applying the aqueous dilution of the humic acid extract may be once or two or more times. When applying two or more times, the application interval is, for example, 1 to 4 weeks.

[0028] Fertilizer may be applied together with the aqueous dilution of the humic acid extract, or before and / or after applying the aqueous dilution of the humic acid extract. As the fertilizer, known fertilizers can be used according to the plant. For example, liquid fertilizers containing all fertilizer components of primary elements (nitrogen, phosphorus, potassium), secondary elements (calcium, magnesium, sulfur), and trace elements (manganese, boron, iron, copper, zinc, molybdenum, chlorine) can be mentioned. When applying fertilizer together with the aqueous dilution of the humic acid extract, they may be applied separately, or they may be mixed in advance and applied.

[0029] The present invention has been described with reference to the embodiments, but the present invention is not limited to the above embodiments. Each configuration and their combinations in the above embodiments are examples, and additions, omissions, substitutions, and other changes of the configuration are possible without departing from the spirit of the present invention. For example, the content of free nitric acid in the humic acid extract may be 3% by mass or less based on the total mass of the humic acid extract.

Example

[0030] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited by these examples.

[0031] <Measurement method> [Measurement of pH] The pH measurement was carried out by the glass electrode method. The measurement was carried out while stirring the suspension solution containing the residue of the crude humic acid product with a magnetic stirrer.

[0032] [Mass average molecular weight] The mass average molecular weight (Mw) of humic acid is a value measured by the HPSEC method (GPC method) using an ACQUITY APC SYSTEM manufactured by Waters. The column was manufactured by Waters, the standard sample was sodium polystyrene sulfonate, and the detection wavelength was 260 nm. The mobile phase was a 100 mmol / L sodium phosphate buffer solution containing 20% by mass of acetonitrile, the flow rate was 0.3 mL / min, and the temperature of the column was 40 °C (the set value of the column oven).

[0033] [Total organic carbon concentration] The total organic carbon concentration (TOC) was measured by the combustion catalyst oxidation method using a total organic carbon meter (TOC-L manufactured by Shimadzu Corporation).

[0034] [Content of free nitric acid] For the humic acid extract, potentiometric titration was performed using a potentiometric titration apparatus (manufactured by HIRANUMA, product name "COM-A19S", glass electrode: GE-1010B, reference electrode: RE201, thermistor electrode: TE403) according to the following procedure to determine the content of free nitric acid. Weighed 5 g of the sample into a 100 mL beaker, added ultrapure water up to 50 mL to make a measurement sample. For the measurement sample, potentiometric titration was performed using a 0.1 M NaOH aqueous solution.

[0035] <Preparation of humic acid extract> [Example 1] In a draft, 20 g of lignite with a carbon content of 77% by mass was placed in a 500 mL beaker, 50.0 g of a nitric acid aqueous solution with a nitric acid concentration of 48% by mass was added, and an oxidation reaction was carried out in a water bath at 80 °C for 3 hours to obtain a crude humic acid. 80 mL of water was added to the obtained crude humic acid, 10.0 g of potassium hydroxide was added, and the mixture was stirred. While stirring, a 1.0 mol / L potassium hydroxide aqueous solution was appropriately added while monitoring with a pH meter to adjust the pH to 3.5. The volume was made up to 100 mL with water (resulting in a solid-liquid ratio of 1:5), and extraction was carried out at 80 °C for 1 hour. Then, the mixture was cooled to 40 °C or lower, the volatile moisture was replenished to make the total volume 100 mL, and centrifuged at 3,500 × g for 20 minutes, and the supernatant liquid part was recovered. This liquid part was used as the humic acid extract of Example 1. The humic acid extract of Example 1 had an Mw of humic acid of 640, a TOC of 12,000 mg / L, a free nitric acid content of 1.7% by mass, and a pH of 2.3.

[0036] [Example 2] Potassium hydroxide was added to the liquid part obtained in the same manner as in Example 1 so that the pH became 5, and the humic acid extract of Example 2 was obtained. The humic acid extract of Example 2 had a free nitric acid content of 0.41% by mass. The Mw and TOC of the humic acid were the same as those in Example 1.

[0037] [Example 3] Potassium hydroxide was added to the liquid part obtained in the same manner as in Example 1 so that the pH became 9, and the humic acid extract of Example 3 was obtained. No free nitric acid was detected in the humic acid extract of Example 3. The Mw and TOC of the humic acid were the same as those in Example 1.

[0038] <Evaluation of plant root growth> Using the humic acid extract of each example as a sample, the growth of plant roots was evaluated according to the following procedure. For each sample, seven media (Takii seedling soil) were prepared, and Komatsuna seeds were sown in each (n = 7). Two weeks and three weeks after sowing, a water dilution solution obtained by diluting 4.4 g of the sample with 1,996 g of water was sprayed on the media. Four weeks after sowing, Komatsuna was collected from the seven media, and the dry weights of the above-ground part and the underground part (roots) were measured, and the average value and standard deviation were obtained. The dry weight was the value after drying under the conditions of 105 °C for 24 hours.

[0039] The results are shown in FIGS. 1 and 2. FIG. 1 is a graph showing the dry weight of the above-ground part, and FIG. 2 is a graph showing the dry weight of the underground part. For the underground part (roots), in Examples 2-3, the dry weight increased compared to Example 1. In particular, the result of Example 2 was excellent. For the above-ground part, at the four-week time point, Examples 1-3 had the same dry weight, but since the growth of the underground part was promoted in Examples 2-3, it is expected that the dry weight of the above-ground part will increase in Examples 2-3 in the future.

Claims

1. A humic acid extract containing humic acid with a mass average molecular weight of 400 to 1,000, having a total organic carbon concentration of 10,000 to 45,000 mg / L, having a free nitric acid content of 1% by mass or less, and having a pH of 4.5 to 7.

5.

2. The humic acid extract according to Claim 1, wherein the free nitric acid content is 0.1% by mass or more.

3. The humic acid extract according to Claim 1, containing an alkali metal salt of nitric acid, wherein the content of the alkali metal salt is 6 to 9% by mass in terms of potassium.

4. A method for promoting the growth of plant roots, comprising diluting the humic acid extract according to any one of Claims 1 to 3 with water and applying it to plants.

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