Growth promotion method and growth promoter

Abstract

To provide a technique for promoting seed growth, and saving labor of seed preparation work.SOLUTION: A growth promotion method for promoting seed growth comprises: a step of immersing seeds in a suspension where a growth promoter including calcium and silica is suspended.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for promoting seed growth and a seed growth promoter. [Background technology]

[0002] In rice cultivation, a series of preparatory steps (seed preparation) are carried out before sowing to ensure good germination and subsequent growth. Specifically, seeds must be selected, disinfected, soaked, and forced to germinate, resulting in seeds in a slightly germinated state known as pigeon breast. Direct seed sowing methods are broadly divided into surface sowing, where seeds are sown on the soil surface, and subsurface sowing, where seeds are sown underground. Surface sowing is known to have problems with lodging and floating rice due to poor rooting, while subsurface sowing is known to have problems with poor seedling establishment due to oxygen deficiency.

[0003] In order to solve the problems that may arise when directly sowing such seeds, the techniques of Patent Documents 1 to 3 describe methods of coating the surface of seeds with iron, calcium, or the like. Patent Documents 1 and 2 describe techniques for coating the surface of seeds with a material containing slag or incineration ash. Patent Document 3 describes direct sowing of seeds coated with a coating material containing iron powder. Also known is a technique for coating seeds with a calcium peroxide agent to solve the problem of oxygen deficiency when sowing seeds in soil. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-136861 [Patent Document 2] Japanese Patent Application Publication No. 2017-046674 [Patent Document 3] Japanese Patent Publication No. 2023-110185 Summary of the Invention [Problem to be solved by the invention]

[0005] Among the seed preparation steps, the soaking process, in which the seeds are soaked in temperature-controlled water to fully absorb the water, takes about a week and accounts for the majority of the work period. During the soaking process, the water must be changed every few days to prevent the seeds from becoming oxygen-deprived or rotting, which increases the time spent by agricultural workers and places a burden on them.

[0006] Furthermore, the techniques of Patent Documents 1 to 3 and calcium peroxide coating require skilled techniques to properly coat the surface of the seeds. Furthermore, there is a method of preventing poor rooting and oxygen deficiency by rooting the seeds and sowing them in a shallow layer of soil, but the rooting process takes about two days, requiring more time for agricultural workers than the seed soaking process.

[0007] One aspect of the present invention has been made to solve the above-mentioned problems, and its purpose is to realize a technology that promotes seed growth and, for example, to reduce the labor required for seed preparation work. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention includes, for example, the following aspects. (1) A method for promoting seed growth, comprising a soaking step of soaking the seeds in a suspension containing a growth promoter containing calcium oxide (CaO) and silica (SiO2). (2) A growth promoter for rice seeds containing steel slag. [Effects of the Invention]

[0009] According to one aspect of the present invention, a technique for promoting seed growth is realized, which can reduce the labor required for seed preparation, for example. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram comparing the germination of seeds soaked in a slag suspension in an example. [Figure 2] FIG. 1 is a diagram comparing the germination of seeds soaked in a slag suspension in an example. [Figure 3] FIG. 1 is a diagram comparing root growth of seeds immersed in a slag suspension in an example. [Figure 4] FIG. 1 is a graph comparing the number of seeds that emerged after immersion in a slag suspension by sowing method in an example. [Figure 5] 1 is a graph comparing the number of seeds that germinate after immersion in a slag suspension by sowing method in an example. [Figure 6] FIG. 2 is a diagram showing the particle size of slag used in the examples. [Figure 7] 1 is a graph showing the results of investigating the relationship between the particle size of slugs and the number of germinated seeds and the average coleoptile length in an example. [Figure 8] FIG. 1 is a diagram showing the slag suspensions used in the examples by concentration. [Figure 9] 1 is a graph showing the results of an investigation into the relationship between the concentration of a slag suspension and the number of germinated seeds and the average coleoptile length in an example. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Embodiment] Hereinafter, one embodiment of the present invention will be described in detail. A growth-promoting method for promoting seed growth according to one embodiment of the present invention is a method including a soaking step of soaking seeds in a suspension containing a growth-promoting agent including calcium oxide (CaO) and silica (SiO2).

[0012] (growth promoter) The seed growth promoter is not particularly limited as long as it contains calcium oxide (CaO) and silica (SiO2), but it may be preferable for it to further contain at least one element selected from the group consisting of magnesium, phosphorus, iron, manganese, and boron, and more preferably at least two, three, four, or five (all) elements. Magnesium, phosphorus, iron, manganese, and boron may be contained as simple elements or in the form of compounds such as salts or oxides. Examples of compounds include magnesium oxide (MgO), diphosphorus pentoxide (PO5), iron oxide (FeO), iron(III) oxide (Fe2O3), manganese oxide (MnO), and boron oxide.

[0013] The proportion of each component contained in the growth promoter is not particularly limited, but calcium oxide is, for example, in the range of 30% by mass to 50% by mass, 40% by mass to 50% by mass, or 42% by mass to 50% by mass. Silica is, for example, in the range of 5% by mass to 15% by mass, 5% by mass to 13% by mass, or 5% by mass to 12% by mass. When magnesium oxide (MgO) is included, it is, for example, in the range of 1% by mass to 10% by mass, 1% by mass to 5% by mass, or 2% by mass to 5% by mass. When diphosphorus pentoxide (P2O5) is included, it is, for example, in the range of 1% by mass to 10% by mass, 1% by mass to 5% by mass, or 2% by mass to 4% by mass. When iron (III) oxide (Fe2O3) is contained, the content is, for example, in the range of 5% by mass to 20% by mass, 5% by mass to 15% by mass, or 7% by mass to 15% by mass. When magnesium, phosphorus, or iron is contained in a form other than MgO, P2O5, or Fe2O3, the content of these elements can be calculated from the content of the specific compounds exemplified above. For example, the content of magnesium can be calculated by multiplying the content (% by mass) of magnesium oxide (MgO) by approximately 0.6. When manganese is contained, the content is, for example, in the range of 1% by mass to 10% by mass, 1% by mass to 5% by mass, or 2% by mass to 4% by mass. When boron is contained, the content is, for example, 1 g / kg or less, 50 mg / kg to 1 g / kg, or 100 mg / kg to 600 mg / kg.

[0014] The form of the growth promoter is not particularly limited, but may be, for example, a solid, particularly a granular or powdery solid, and is used in the form of a suspension in water as described below. An example of a growth promoter is steel slag, such as blast furnace slag or steelmaking slag. The steel slag may be used as is, or may be selected using a sieve or other method to obtain a particle size within a predetermined range. Alternatively, the steel slag may be pulverized into a powder with a smaller particle size, or these may be mixed and used. Pulverization into a powder with a smaller particle size may facilitate suspension in water and may facilitate the exertion of its effects as a growth promoter. The steel slag powder may preferably have a particle size of 200 μm or less, more preferably 100 μm or less, or even 90 μm or less, 80 μm or less, 70 μm or less, 60 μm or less, or 50 μm or less. The lower limit of the particle size of the steel slag powder is not particularly limited and is determined appropriately depending on the desired handleability, etc., and is, for example, 1 μm or more, 5 μm or more, 10 μm or more, 20 μm or more, 30 μm or more, or 40 μm or more. In terms of average particle size, the steel slag powder may preferably have a particle size in the range of 20 μm or more to 200 μm or less, 30 μm or more to 100 μm or less, 30 μm or more to 70 μm or less, 40 μm or more to 60 μm or less, or 40 μm or more to 55 μm or less.

[0015] (Suspension of growth promoter) In one embodiment of the present invention, the growth promoter is used as an aqueous suspension in water. This aqueous suspension exhibits, for example, alkaline properties due to partial dissolution of the suspended components. More specifically, the aqueous suspension may exhibit an alkaline property of, for example, pH 9 or higher, pH 9.5 or higher, or pH 10 or higher, and pH 12.5 or lower, or pH 12 or lower. That is, this aqueous suspension exhibits, for example, a weak to strong alkaline property (pH 11 or higher).

[0016] Furthermore, when the growth promoter is steel slag, from the viewpoint of promoting seed germination, the steel slag is preferably suspended in the suspension at a concentration of 1 mg / mL or more, or 2 mg / mL or more. More preferably, the steel slag is suspended at a concentration of 5 mg / mL or more, or 10 mg / mL or more. The upper limit of the steel slag concentration is not particularly limited, but is, for example, 500 mg / mL or less, 250 mg / mL or less, 200 mg / mL or less, or 150 mg / mL or less.

[0017] When the growth promoter is steel slag, from the viewpoint of promoting cotyledon growth, it may be preferable that the steel slag be suspended in the suspension at a concentration of 2 mg / mL or more, 5 mg / mL or more, or 10 mg / mL or more. The upper limit of the steel slag concentration is not particularly limited, but is, for example, 500 mg / mL or less, 250 mg / mL or less, 200 mg / mL or less, or 150 mg / mL or less.

[0018] (Seeds, treatments on seeds, and seeds after treatment) The type of seed in one embodiment of the present invention is not particularly limited, and examples thereof include seeds used for industrial purposes including agriculture and horticulture. Typical examples include ungerminated rice seeds (particularly paddy rice), seeds of pulses such as wheat, corn, and soybean, seeds of other vegetables, and hard-seeded seeds. Other typical examples include seeds (the type of plant is not limited to rice) before sowing for seedling cultivation.

[0019] A preferred example of the seed treatment method using the above suspension includes a soaking step of soaking seeds in the suspension. The temperature conditions for performing the soaking step are not particularly limited and may be set appropriately depending on the type of seed, etc. The temperature conditions may be the same as the ambient temperature, or may be temperature-controlled within a facility, etc. Examples of temperature conditions for performing the soaking step include a range of 5°C or higher and 35°C or lower, a range of 10°C or higher and 35°C or lower, a range of 15°C or higher and 35°C or lower, a range of 15°C or higher and 25°C or lower, and a range of 25°C or higher and 35°C or lower. The period for performing the soaking step of soaking seeds in the suspension is also not particularly limited, and examples include a range of 5 hours to 100 hours, a range of 10 hours to 100 hours, a range of 15 hours to 100 hours, and a range of 20 hours to 100 hours.

[0020] This soaking step can also be carried out as one step in seed preparation. Seed preparation, particularly for rice (paddy rice) seeds, involves the steps of seed selection, disinfection, soaking, and germination to prepare seeds in a slightly germinated state called pigeon breast. The soaking step in one embodiment of the present invention can be carried out as a soaking step in seed preparation, resulting in, for example, a shortened seed soaking period and / or the omission of the germination step. Furthermore, shortening the seed soaking period also makes it possible to omit water changes during the soaking period. The soaking step in one embodiment of the present invention can be carried out as a germination step in seed preparation, resulting in growth-promoting effects such as promoting coleoptile elongation and root system development (e.g., root elongation, crown root development, root hair development, etc.). Both the soaking step and the germination step in seed preparation can also be carried out as this soaking step.

[0021] Seeds treated with the suspension can be used, for example, as seeds for raising seedlings or seeds for direct sowing. The treated seeds exhibit a significantly improved germination rate compared to untreated seeds, regardless of the intended use. Furthermore, as shown in the examples described below, by appropriately adjusting the treatment conditions, it is possible to prepare seeds in a desired state depending on the intended use, such as a dovetail state, a state in which coleoptile elongation has been promoted to a desired degree, or a state in which root system development has been promoted to a desired degree.

[0022] (Processes other than the immersion process) In one embodiment of the present invention, the method may further include a step of sowing the treated seeds for raising seedlings or a step of directly sowing the seeds in soil (in a paddy field in the case of paddy rice). The method of direct sowing is not particularly limited, and may be, for example, surface sowing or subsurface sowing.

[0023] (Rice seed growth promoter) One example of the growth promoter is a rice (particularly paddy rice) seed growth promoter containing steel slag. This growth promoter is used to prepare the following compositions for promoting rice seed growth: 1) an aqueous suspension in which steel slag is suspended in water, 2) the supernatant of the steel slag aqueous suspension, or 3) the supernatant and sediment of the steel slag aqueous suspension (steel slag). One example of the aqueous suspension does not contain a binder such as PVA (polyvinyl alcohol). Another example of the aqueous suspension contains essentially only water and steel slag. This rice seed growth promoter is used, for example, for preparing rice seeds in a pigeon-breasted state, for preparing rice seeds in a state in which coleoptile elongation has been promoted, or for preparing rice seeds in a state in which root system development has been promoted.

[0024] (summary) For example, the following inventions are also included in the scope of the present invention. (1) A method for promoting seed growth, comprising a soaking step of soaking the seeds in a suspension containing a growth promoter containing calcium oxide (CaO) and silica (SiO2). (2) The growth promotion method according to (1), wherein the growth promoter further contains magnesium oxide (MgO). (3) The growth promotion method according to (1) or (2), wherein the growth promoter contains calcium oxide in an amount of 30% by mass or more and 50% by mass or less, and silica in an amount of 5% by mass or more and 15% by mass or less. (4) The growth promotion method according to any one of (1) to (3), wherein the growth promoter is steel slag. (5) The growth promotion method according to (4), wherein the suspension contains the steel slag suspended at a concentration of 2 mg / mL or more. (6) The growth promotion method according to (4) or (5), wherein the steel slag is steel slag powder with a particle diameter of 200 μm or less. (7) A growth promotion method described in any one of (1) to (6), wherein the suspension is alkaline with a pH of 10 or more and a pH of 12 or less. (8) The method for promoting growth according to any one of (1) to (7), wherein the seeds are ungerminated rice seeds. (9) A growth promotion method described in any one of (1) to (8), wherein in the soaking step, the seeds are soaked in the suspension for 20 hours or more and 100 hours or less in an environment of 15°C or more and 35°C or less. (10) A rice seed growth promoter containing an iron and steel slag. A rice seed growth promoter containing a suspension of an iron and steel slag. The suspension of the iron and steel slag is, for example, one of the above (1) to (7).

[0025] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Example]

[0026] Example 1: Germination of seeds soaked in a slag suspension Slag A suspension (25 mg / mL) and slag B suspension (25 mg / mL) were prepared by adding 1 g of pre-pulverized slag A or slag B per 40 mL of distilled water. Slag A was converter slag (product name: S-Minecal, manufactured by Sangyo Shinko Co., Ltd.), and slag B was pre-treated slag (product name: Noryoku Up, manufactured by Sangyo Shinko Co., Ltd.). The compositional analysis results of the steel slags A and B are shown in Table 1. [Table 1]

[0027] The meaning of each component shown in Table 1 is as follows: T-CaO (total lime), CaO (exchangeable lime), T-MgO (total magnesium), MgO (exchangeable magnesium), T-P2O5 (total phosphate), P2O5 (available phosphate), T-Fe2O3 (total iron oxide), Fe2O3 (available iron oxide), T-SiO2 (total silicic acid), SiO2 (available silicic acid), T-Mn (total manganese), Mn (exchangeable manganese), TB (total boron), B (hot water soluble boron).

[0028] Of the components listed in Table 1 above, the calcium content in the slag A suspension was 159-212 mg / L, the ionic silica content was 3-4 mg / L, the soluble manganese content was 0.1 mg / L-0.2 mg / L, the boron content was 0.5 mg / L in terms of borate ions, the phosphate ions were less than 1.0 mg / L (below the detection limit), the Fe(II) ions and Fe(III) ions were less than 0.1 mg / L (below the detection limit), and the magnesium content was less than 0.1 mg / L (below the detection limit). The calcium content in slag B suspension was 305-333 mg / L, ionic silica content was 7 mg / L, soluble manganese content was 0.5 mg / L-0.6 mg / L, boron content was 0.6 mg / L (calculated as borate ions), Fe(II) ions content was 1 mg / L-1.2 mg / L, magnesium content was 0.1 mg / L, phosphate ions content was less than 1.0 mg / L (below the detection limit), and Fe(III) ions content was less than 1 mg / L (below the detection limit). Both slag A suspension and slag B suspension were alkaline, with pH values ​​generally ranging from 10 to 12. Furthermore, no oxygen generation was observed in either slag A suspension or slag B suspension.

[0029] Each slag suspension or distilled water used as a control was poured into a tube, and Kinuhikari seeds were placed in each tube and soaked at 20°C for 4 days. After soaking, the calcium content in slag A suspension was 71.4-85.8 mg / L, the ionic silica content was 10-13 mg / L, the soluble manganese content was 0.2-0.3 mg / L, the boron content (calculated as borate ions) was 0.9-1.0 mg / L, the Fe(II) ions content was 0.1-0.2 mg / L, the magnesium content was 2.7 mg / L, the phosphate ions content was less than 1.0 mg / L (below the detection limit), and the Fe(III) ions content was less than 0.1 mg / L (below the detection limit). After soaking, the calcium content in the slag B suspension was 206-225 mg / L, the ionic silica content was 85-97 mg / L, the soluble manganese content was 0.8 mg / L-1.1 mg / L, the boron content was 1.0 mg / L-1.1 mg / L in terms of borate ions, the Fe(II) ion content was 1.1 mg / L-1.3 mg / L, the magnesium content was 2.2-3.9 mg / L, the phosphate ion content was less than 1.0 mg / L (below the detection limit), and the Fe(III) ion content was less than 1 mg / L (below the detection limit).

[0030] Figure 1 shows a photograph of the seeds after soaking. Figure 1 compares the germination of seeds soaked in slag suspensions. As shown in Figure 1, seeds soaked in distilled water did not germinate, but seeds soaked in slag A suspension and slag B suspension both germinated to the pigeon breast size.

[0031] Example 2: Germination of seeds soaked in a slag suspension The seeds soaked in Example 1 were further placed in the suspension at 30°C for one day to stimulate germination. The results are shown in Figure 2. Figure 2 is a graph comparing the germination of seeds soaked in slag suspensions.

[0032] As shown in the first three images from the top of Figure 2, only a small portion of the seeds germinated in distilled water germinated, but both the seeds germinated in the slag A suspension and the seeds germinated in the slag B suspension showed more accelerated coleoptile elongation than the seeds germinated in distilled water.

[0033] Furthermore, similar tests were conducted under shallow water conditions (soaking and germinating seeds in a petri dish), which are not used in actual soaking and germination treatments. As a result, coleoptile elongation was confirmed even in distilled water, as shown in the bottom row of images in Figure 2. From these results, it can be said that growth can be ensured by using a slag suspension, even when the dissolved oxygen concentration is lower than in shallow water conditions.

[0034] Example 3: Rooting of seeds immersed in a slag suspension The dovetail seeds obtained in Example 1 were removed from the suspension and placed on a sieve in a thermo-hygrostat heated to 30°C for two days to undergo rooting treatment. The results are shown in Figure 3, which compares the rooting rate of seeds immersed in slag suspensions.

[0035] As shown in Figure 3, images A–F, the seeds rooted in slag A suspension and those rooted in slag B suspension showed enhanced coleoptile and seminal root elongation compared to seeds rooted in distilled water. Furthermore, the seeds rooted in slag A suspension and those rooted in slag B suspension also showed enhanced crown and lateral root development, which was not observed in seeds rooted in distilled water.

[0036] Example 4: Germination of seeds soaked in slag suspension by sowing method The pigeon-breasted seeds obtained in Example 1 were sown in pots by the following method, and the number of germinating seeds was counted. In method A, seedling raising, the seeds were sown in culture soil, covered with soil, and subjected to steam emergence treatment at 30°C for 2 days, followed by storage at 25°C. In method B, surface sowing, the seeds were sown on the surface of puddled paddy field soil and stored at 25°C without covering with soil. In method C, shallow subsurface sowing, the seeds were sown on the surface of puddled paddy field soil, covered with 2 mm of soil, and stored at 25°C. In method D, subsurface sowing, the seeds were sown on the surface of puddled paddy field soil, covered with 10 mm of soil, and stored at 25°C. In method E, Italian-style direct sowing, the seeds were sown on the surface of flooded paddy field soil, uncovered with soil, and maintained in 4 cm water for 2 days after sowing, followed by storage at 25°C.

[0037] The number of germinated seeds in pots sown using each method was counted 5, 10, and 15 days after sowing, and the percentage of germinated seeds per 100 seeds was calculated. The results are shown in Figures 4 and 5. Figures 4 and 5 are graphs comparing the number of germinated seeds immersed in slag suspension by sowing method.

[0038] As shown in Figures 4 and 5, in all sowing methods, the germination rate of seeds soaked in slag suspension was improved compared to seeds soaked in distilled water.

[0039] (Example 5: Relationship between slag particle size and number of germinated seeds) A slag suspension (25 mg / mL) was prepared by adding 1 g of slag A to 40 mL of distilled water. Four types of slag A with different particle shapes were prepared: a commonly available granular slag (S-Minecal (product name) manufactured by Sangyo Shinko Co., Ltd.; hereinafter, also referred to as "coarse-fine mixed slag"), coarse-grained slag and fine-grained slag obtained by sieving the coarse-fine mixed slag, and fine-grained slag obtained by pulverizing the coarse-fine mixed slag. Suspensions of each type were prepared. Images of each slag and their average particle diameters are shown in Figure 6. Figure 6 is a diagram showing the particle diameters of the slags used in the examples.

[0040] The average particle diameters of the coarse-fine mixed slag, coarse slag, and fine slag were measured by sieving. A rotary sieving device, DuraTap (manufactured by Advantech), was used for the measurements. The measurement conditions were a sieving time of 10 minutes and a particle diameter range of 9500 to 53 μm.

[0041] The average particle size of the finely powdered slag was measured using the laser diffraction and scattering method. A laser diffraction and scattering particle size distribution analyzer, LMS-2000e (manufactured by Seishin Enterprise Co., Ltd.), was used for the measurement. After a blank measurement using only the dispersion medium, an appropriate amount of sample was placed in a dispersion tank, and the sample was dispersed using ultrasonic waves, followed by measurement of the particle size distribution using a circulation system. The measurement conditions were a measurement range of 0.020 to 2000.00 μm, ion-exchanged water as the dispersion medium, and one minute of ultrasonic dispersion time.

[0042] Kinuhikari seeds were soaked in each slug suspension at 20°C for four days, and then germination was accelerated at 30°C for one day. The number of germinated seeds and average coleoptile length of seeds accelerated in each of the four slug suspensions were calculated, and the results are shown in Figure 7. Figure 7 is a graph showing the results of an investigation into the relationship between slug particle size and the number of germinated seeds and average coleoptile length.

[0043] As shown in Figure 7, the seeds grown in the suspension of finely powdered slag had the highest number of germinated seeds and the longest average coleoptile length. These results indicate that preparing the slag into a fine powder finer than the fine particles with an average particle size of 201 μm improves the growth-promoting effect.

[0044] Example 6: Relationship between slag suspension concentration and number of germinated seeds Slag A was added to 40 mL of distilled water to prepare a slag suspension. The slag suspension concentrations were adjusted to four levels: 2.5 mg / mL (0.1 g / 40 mL), 12.5 mg / mL (0.5 g / 40 mL), 25 mg / mL (1 g / 40 mL), and 125 mg / mL (5 g / 40 mL). Images of the suspensions at each concentration are shown in Figure 8. Figure 8 shows the slag suspensions used in the examples by concentration.

[0045] Kinuhikari seeds were soaked in each slag suspension at 20°C for four days, and then germination was accelerated at 30°C for one day. The number of germinated seeds and average coleoptile length of seeds accelerated in each of the four concentrations of slag suspension were calculated, and the results are shown in Figure 9. Figure 9 is a graph showing the results of an investigation into the relationship between slag suspension concentration and the number of germinated seeds.

[0046] As shown in Figure 9, the number of germinated seeds increased and coleoptile elongation was promoted in a slag concentration-dependent manner. The number of germinated seeds reached a plateau at slag concentrations of 12.5 mg / mL or higher. These results demonstrate that the seed growth-promoting effect can be controlled by adjusting the slag concentration. [Industrial Applicability]

[0047] The present invention can be used in the fields of agriculture, breeding, etc.

Claims

1. A method for promoting seed growth, comprising: Calcium oxide (CaO) and silica (SiO ２ a soaking step of soaking the seeds in a suspension containing a growth promoter containing A growth promotion method comprising:

2. The growth promotion method according to claim 1 , wherein the growth promoter further contains magnesium oxide (MgO).

3. 3. The growth promotion method according to claim 1, wherein the growth promoter contains 30% by mass or more and 50% by mass or less of calcium oxide and 5% by mass or more and 15% by mass or less of silica.

4. The growth promotion method according to claim 1 or 2, wherein the growth promoter is steel slag.

5. The growth promotion method according to claim 4 , wherein the suspension contains the steel slag suspended at a concentration of 2 mg / mL or more.

6. The growth promotion method according to claim 4, wherein the steel slag is steel slag powder having a particle diameter of 200 μm or less.

7. The growth promotion method according to claim 1 or 2, wherein the suspension is alkaline with a pH of 10 or more and a pH of 12 or less.

8. The method for promoting growth according to claim 1 or 2, wherein the seeds are ungerminated rice seeds.

9. 3. The growth promotion method according to claim 1, wherein in the soaking step, the seeds are soaked in the suspension for 20 hours or more and 100 hours or less in an environment of 15°C or more and 35°C or less.

10. A growth promoter for rice seeds containing steel slag.

Images