Seed coating agent, coated seeds, and seed coating method

Abstract

To provide a seed coating agent capable of increasing seed density while preventing damage of the seed caused by oxidation heat generation of metallic iron, coated seed and seed coating method.SOLUTION: A seed coating agent containing iron-based powder and used for coating a seed surface is characterized in that one or more types of ascorbic acid, erythorbic acid and their compounds are added as antioxidant, and an addition amount of the antioxidant to a mass of the iron-based powder is 0.02 mass% or more and 15 mass% or less. Alternatively, a coated seed is characterized in that the seed surface is coated with the seed coating agent. Further alternatively, a seed coating method is characterized in that a seed surface is coated with the seed coating agent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a seed coating agent containing an iron-based powder for coating a seed surface, a coated seed whose surface is coated with the seed coating agent, and a seed coating method for coating a seed surface using the seed coating agent. [Background technology]

[0002] With the aging of agricultural workers and the globalization of agricultural product distribution, labor-saving in farming and reduction of agricultural production costs have become issues that need to be resolved. To address these issues, for example, in rice cultivation, direct seeding, in which seeds are sown directly in the field, is becoming more common, with the aim of eliminating the labor of raising seedlings and transplanting. Among these methods, a technique using coated seeds coated with iron powder to increase seed density has attracted attention because it has the advantages of preventing seeds from drifting or being washed away in paddy fields and preventing bird damage. Examples of coated seeds coated with iron powder as described above are disclosed in Patent Documents 1 and 2. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-192458 [Patent Document 2] Japanese Patent Application Publication No. 2017-153427 Summary of the Invention [Problem to be solved by the invention]

[0004] Coated seeds like those mentioned above can remain in place where they are sown by increasing their seed density (specific gravity). However, in actual fields, they are exposed to various water currents, and strong currents can cause them to be washed away. Therefore, coated seeds with a higher seed density were needed. In the coated seeds described in Patent Documents 1 and 2, the seed density can be increased by increasing the proportion of iron-based powder per unit mass of seed. However, there is a problem in that increasing the seed density increases the risk of seeds being damaged due to heat generated by oxidation of metallic iron contained in the iron-based powder.

[0005] The present invention has been made to solve the above-mentioned problems, and aims to provide a seed coating agent, coated seeds, and seed coating method that can increase the seed density per mass of iron-based powder while preventing damage to seeds caused by heat generation due to oxidation of metallic iron contained in the iron-based powder. [Means for solving the problem]

[0006] In order to solve the above problems, the inventors investigated various coatings of iron powder on seeds, and as a result, they discovered that coating the seed surface with a seed coating agent containing ascorbic acid, erythorbic acid, or these compounds as antioxidants can prevent damage to the seeds caused by heat generated by the oxidation of metallic iron and increase seed density. The present invention has been made based on the above findings and has the following configuration.

[0007] (1) The seed coating agent according to the present invention contains an iron-based powder and is used to coat the surface of seeds, The present invention is characterized in that ascorbic acid, erythorbic acid, and one or more of these compounds are added as antioxidants, and the ratio of the antioxidant to the mass of the iron-based powder is 0.02 mass% or more and 15 mass% or less.

[0008] (2) The coated seeds according to the present invention are characterized in that the surface of the seeds is coated with the seed coating agent described in (1) above.

[0009] (3) The seed coating method according to the present invention is characterized in that the seed surface is coated with the seed coating agent described in (1) above. [Effects of the Invention]

[0010] According to the present invention, coated seeds having a high seed density per mass of iron-based powder can be obtained while preventing damage to the seeds caused by heat generated by oxidation of metallic iron contained in the iron-based powder. DETAILED DESCRIPTION OF THE INVENTION

[0011] Before describing the seed coating agent, coated seeds, and seed coating method according to the embodiment of the present invention, the seeds to which the present invention is applied will be described. In the following description, "mass %" will be simply written as "%".

[0012] <seed> Rice is preferably used as the seed to be coated with the seed coating agent of the present invention. There is no particular restriction on the rice variety, and any of Japonica, Indica, and Javanica rice can be used. Rice is often cultivated in paddy fields in hot and humid regions, so the effects of the present invention can be achieved.

[0013] <Seed coating agent> Next, the seed coating agent according to the embodiment of the present invention will be described. The seed coating agent according to this embodiment contains iron-based powder and is used to coat the surface of seeds.

[0014] <Iron-based powder> The iron-based powder may be iron powder, iron oxide powder, or a mixture of iron powder and iron oxide powder. As the iron powder, powders such as pure iron and alloy iron can be used, and there are no particular limitations as long as the effects of the present invention can be obtained. The iron oxide powder can be iron oxide or partial iron oxide powder. Examples of iron oxide include magnetite (Fe3O4), hematite (Fe2O3), wustite (FeO), and amorphous iron. The proportion of iron oxide in these powders is not particularly limited, but from an economical standpoint, iron oxide powders such as mill scale and iron ore are preferably used.

[0015] Iron powder and iron oxide powder can be used in combination. From the viewpoint of rust prevention, it is preferable that the iron powder content of the mixed iron-based powder is 20% or more, and more preferably 40% or more.

[0016] The proportion (amount) of iron-based powder contained in the seed coating agent is not particularly limited, but the mass ratio to the seeds (dry rice grains) is preferably 5% or more and 800% or less, and more preferably 10% or more and 500% or less.

[0017] Although the particle size of the iron-based powder is not particularly specified, it is preferable for uniform coating that iron-based powder of 150 μm or less accounts for 80% or more of the total mass of the iron-based powder. The particle size distribution of the iron-based powder can be evaluated by sieving using the method specified in JIS Z2510-2004.

[0018] The iron-based powder may be a mixture of the above-mentioned iron powder, iron oxide powder, or a mixture of iron powder and iron oxide powder with other metal powder. However, from the viewpoint of rust formation, the metallic iron content of the iron-based powder is preferably 20% or more, more preferably 40% or more, based on the mass of the iron-based powder.

[0019] <Antioxidants> The seed coating agent according to the present embodiment contains ascorbic acid, erythorbic acid, and one or more of these compounds added as antioxidants.

[0020] The form in which the antioxidant is added is not limited as long as ascorbic acid or erythorbic acid is added. Ascorbic acid or erythorbic acid, salts thereof, or anhydrides, hydrates, or isomers thereof can be used, and two or more types can be used in combination.

[0021] Specific examples of ascorbic acid include L-ascorbic acid, sodium L-ascorbate, calcium L-ascorbate, L-ascorbic acid palmitate, and L-ascorbic acid stearate. Specific examples of erythorbic acid include erythorbic acid and sodium erythorbate.

[0022] The antioxidant is presumed to have the function of suppressing excessive oxidation of the high-density metallic iron contained in the iron-based powder and of facilitating the production of high-density iron oxides (magnetite, wustite, etc.) rather than low-density iron hydroxides. Therefore, it is thought that the addition of the antioxidant to the seed coating agent according to the present embodiment increases seed density while preventing seed damage due to heat generation by oxidation.

[0023] The amount of antioxidant is set to 0.01% or more and 15% or less based on the mass of the iron-based powder. If it is less than 0.01%, the effect of the present invention is reduced. If it exceeds 15%, the density decreases and the coating tends to become brittle.

[0024] When adding the antioxidant, it may be mixed with the iron-based powder in advance, or may be sprayed onto the iron-based powder as an aqueous solution or suspension at the time of powder coating, and either method can be suitably employed.

[0025] If coarse iron-based powder particles remain on the seed surface, they can be removed using a sieve or the like, and the removed iron-based powder can be reused as a raw material for seed coating. On the other hand, if fine iron-based powder is used, unevenness in the coating is reduced, resulting in a smoother surface.

[0026] <Binder> In the present invention, a binder may be used, which is composed of sulfates and / or chlorides. The sulfates include calcium sulfate, potassium sulfate, magnesium sulfate, and hydrates thereof. Chlorides include potassium chloride, calcium chloride, magnesium chloride, and their hydrates. Plaster of Paris (calcium sulfate hemihydrate) and gypsum (calcium sulfate dihydrate) are particularly preferred. Plaster of Paris and gypsum may be used in mixtures or as a mixture.

[0027] The mass ratio of the binder to the iron-based powder is not particularly limited, but is preferably 0.1% or more and 33% or less in order to facilitate the progression of rust.

[0028] The average particle size of the binder is not particularly specified, but is preferably 1 to 150 μm. If the average particle size of the binder is less than 1 μm, a large number of agglomerates will be generated during the coating process, significantly reducing workability. On the other hand, if the average particle size of the binder exceeds 150 μm, the adhesive strength to the iron-based powder will decrease, and the strength of the coating will tend to decrease.

[0029] <Finishing agent> A finishing agent is not required when coating the seed surface with the seed coating agent, but in order to further prevent the seeds from fusing together due to oxidation of the iron-based powder, it is preferable to use a finishing agent such as calcined gypsum, gypsum, silica gel, etc.

[0030] ≪Third component≫ The seed coating agent according to the present invention may contain a third component to the extent that the effect of the present invention is not impaired. The third component includes unavoidable impurities and additives intentionally added for some effect, and in either case, the amount of the third component contained is preferably up to about 30% of the seed coating agent.

[0031] <Coated seeds and seed coating method> Next, the coated seeds and seed coating method according to the embodiment of the present invention will be described below.

[0032] The coated seeds according to the present embodiment are seeds whose surfaces are coated with the seed coating agent according to the present embodiment described above.

[0033] The seed coating method according to the present embodiment involves coating the surface of a seed with the seed coating agent according to the present embodiment. The seed coating method according to the present embodiment includes, for example, a step of attaching the seed coating agent to the surface of a seed (hereinafter also referred to as "coating"), and a step of oxidizing the seed coating agent attached to the surface of the seed to form a coating layer.

[0034] There are no specific limitations on the method for coating the seed surface with the seed coating agent. For example, as shown in the "Iron-Coated Flooded Direct Seeding Manual 2010 (compiled by the Kinki-Chugoku-Shikoku Agricultural Research Center, National Agriculture and Food Research Organization)," any method may be used, including manual coating and a conventionally known method using a mixer.

[0035] Examples of mixers that can be used include impeller mixers (such as Henschel mixers and concrete mixers) and rotating container mixers (such as V-type mixers, double cone mixers, tilt-rotating pan mixers, and rotary hoe mixers). Concrete mixers without impellers are also preferred.

[0036] When applying the seed coating agent using these mixers, the iron-based powder and seeds, and optionally a binder, a separating agent, and an additive, may be placed in the mixer, and water may be added as needed. The water may be added by rotating the mixer while spraying water and / or a treatment solution mainly composed of water, or the antioxidant may be sprayed as an aqueous solution or suspension without being mixed with the iron-based powder.

[0037] Regarding the step of forming the coating layer, there is no limitation on the method for oxidizing the seed coating agent. For example, as shown in the "Iron-Coated Direct Seeding Manual 2010 (compiled by the Kinki-Chugoku-Shikoku Agricultural Research Center, National Agriculture and Food Research Organization)," seeds can be spread in seedling trays and watered, or an oxidation method using an oxidation regulator can be applied. Alternatively, a method may be used in which the seeds are oxidized while flowing in a mixer and supplying water and air into the mixer (hereinafter referred to as the "mixed oxidation method"). The mixed oxidation method is more preferable because it can generate more bivalent iron. The requirements for the mixed oxidation method are as follows:

[0038] Air can be supplied using an electric fan, a fan, various types of dryers, a hot air blower, etc. The temperature of the supplied air is not particularly limited as long as the effects of the present invention are obtained, but a temperature of -20 to 150°C is preferably applied, more preferably 0 to 100°C, and even more preferably 46 to 95°C. However, to maintain germination, the seed temperature should be 50°C or less, more preferably 40°C or less. Furthermore, to prevent the seeds from freezing and promote rusting, the seed temperature should be 0°C or higher, more preferably 10°C or higher.

[0039] The wind speed of the supplied air is not particularly limited as long as the effects of the present invention are obtained, but is preferably 0.1 to 15 m / s, and more preferably 0.5 to 10 m / s. If the wind speed is less than 0.1 m / s, oxidation and cooling do not proceed smoothly, and if the wind speed is more than 15 m / s, the seeds and coating agent may be scattered.

[0040] Water can be supplied either directly to the seeds or in the air, for example, by spraying, atomizing, or adding water to the seeds or the inside of a mixer using a container such as a cup, or by supplying water as humidified air.

[0041] The moisture content is not particularly limited, but is preferably 10 to 1000% of the mass of the iron-based powder, more preferably 20 to 500%, and even more preferably 50 to 200%. If it is less than 10%, rusting will be insufficient, which may cause the coating layer to peel off, and if it exceeds 1000%, there is a problem that the time required for drying will be long. Furthermore, if a large amount of water is supplied at once, the seeds will clump together due to the moisture, so it is preferable to supply the water in multiple batches while keeping the amount to a level that allows the seeds to flow within the mixer and keeping the seeds wet.

[0042] The oxidation treatment by the mixed oxidation method is preferably carried out after coating the seed surface with the seed coating agent, but it is also possible to supply air together with water to the flowing seeds in the process of coating the seeds with the seed coating agent, and carry out the coating treatment and the oxidation treatment simultaneously.

[0043] After supplying water and air to the mixer, air is supplied to the mixer and the seeds are taken out after they have dried to a certain extent.The seeds are then transferred to a tray or the like and spread out to remove excess moisture and dry for storage.

[0044] As described above, according to the seed coating agent, coated seeds, and seed coating method of this embodiment, it is possible to obtain coated seeds that have an increased seed density per unit mass of the iron-based powder coated on the seed surface while preventing damage to the seeds caused by heat generated by oxidation of metallic iron.

[0045] Although the amount of the seed coating agent according to the present invention to be applied to the surface of a seed is not particularly limited, it is preferable to set the amount of the seed coating agent so that the iron-based powder is 5 to 800 parts by mass per 100 parts by mass of dry seeds. More preferably, to obtain a seed density (specific gravity) sufficient to sink the coated seeds to the bottom of water, the iron-based powder should be about 10 to 500 parts by mass. In the present invention, even if the proportion of iron-based powder is increased, as long as it is within the above-mentioned range, coated seeds with an even higher seed density can be obtained while preventing damage to the seeds caused by the heat generated by oxidation of metallic iron. [Example]

[0046] An experiment was conducted to confirm the effects of the present invention, and the results will be described below. In the experiment, rice seeds were coated with the seed coating agent according to the present invention, and the coated seeds were subjected to an evaluation test.

[0047] The coating with the seed coating agent was carried out by a step of coating (dusting) the seed surface with the seed coating agent and a step of oxidizing the seed coating agent coated on the seed surface. The coating of the seed coating agent (dust dressing) was carried out according to the method described in the aforementioned "Iron-Coated Direct Seeding Manual 2010." The oxidation of the seed coating agent was carried out using two methods: the mixed oxidation method and the tray oxidation method. Specifically, the methods are as follows:

[0048] When using the mixed oxidation method, first, a seed coating agent was prepared by mixing rice seeds in advance, and then, using an inclined rotating pan mixer, an appropriate amount of water (or an L-ascorbic acid aqueous solution) was sprayed onto 100 g of seeds, with the seed coating agent being coated in several batches. Next, air at approximately 60°C was supplied to the seeds using a hot air blower, while approximately 40 to 50 g of water was sprayed onto the seeds. Unless otherwise specified, tap water was used. In Example 14 of the present invention shown in Table 1 below, a finishing agent was applied last. The coated seeds were then spread on a tray and allowed to dry naturally.

[0049] In the tray oxidation method, rice seeds were first mixed with a seed coating agent, and then 100 g of seeds were coated with the seed coating agent in several batches using an inclined rotating pan mixer while spraying an appropriate amount of water. Finally, the seeds were coated with a finishing agent. The coated seeds were then spread on a tray, sprayed with water six times, and allowed to oxidize sufficiently before being air-dried.

[0050] In the experiment, rice seeds were coated by changing the type and amount of each ingredient contained in the seed coating agent and the seed coating method, as shown in Table 1. Tables 2 to 5 show each ingredient (Table 2: iron powder, Table 3: iron oxide, Table 4: binder, Table 5: antioxidant).

[0051] [Table 1]

[0052] [Table 2]

[0053] [Table 3]

[0054] [Table 4]

[0055] [Table 5]

[0056] In Table 1, inventive examples 1 to 21, seeds were coated using the seed coating agent according to the present invention. In addition, in all of inventive examples 1 to 21, the ratio of the antioxidant to the mass of the iron-based powder was 0.02 mass% or more and 15 mass% or less.

[0057] Furthermore, for comparison, seeds were coated using the seed coating agents of Comparative Examples 1 and 2 shown in Table 1. Comparative Examples 1 and 2 are based on the prior art, which does not contain an antioxidant. In Comparative Example 1, the seed coating was performed by the mixed oxidation method, and in Comparative Example 2, the seed coating was performed by the tray oxidation method.

[0058] The coated seeds coated with the seed coating agents according to the above-mentioned invention examples 1 to 21 and comparative examples 1 and 2 were subjected to evaluation tests for seed density and coating strength. These evaluation tests were carried out as follows. Note that in the iron-based powder ratios in invention examples 1 to 21 and comparative examples 1 and 2, no damage to the seeds due to oxidation heat was observed.

[0059] <Seed density> The seed density of each coated seed was measured using an electronic hydrometer EW-300SG (manufactured by Alpha Mirage Co., Ltd.).

[0060] <Coating strength> 100g of coated seeds were shaken for 1 minute using a 2mm sieve in a Rotap sieve shaker, and the weight loss rate was measured. The weight loss rate was judged as follows: ◎: 1% or less, ○: over 1% to 5% or less, △: over 5% to 20%, ×: over 20%.

[0061] As shown in Table 1, the seed densities of the coated seeds of Comparative Examples 1 and 2 were 1.50 and 1.49. In contrast, the seed densities of the coated seeds of Invention Examples 1 to 21 were 1.52 to 1.60, which was an improvement over Comparative Examples 1 and 2. Here, in all of Invention Examples 1 to 21 and Comparative Examples 1 and 2, the iron-based powder was contained in a ratio of 50 parts by mass per 100 parts by mass of seeds. Therefore, from the seed density results shown in Table 1, it can be seen that in Invention Examples 1 to 21, the seed density per unit mass of the coated iron-based powder was increased even without increasing the proportion of iron-based powder.

[0062] Furthermore, the coating strength of the coated seeds of Examples 1 to 21 was equivalent to that of Comparative Examples 1 and 2. These results demonstrate that the seed coating agent of the present invention, to which ascorbic acid, erythorbic acid, or a mixture of one or more of these compounds is added as an antioxidant, can produce coated seeds with improved seed density without reducing coating strength.

Claims

1. A seed coating agent containing an iron-based powder and used to coat a seed surface, A seed coating agent characterized in that erythorbic acid and one or more of its compounds are added as antioxidants, and the ratio of the antioxidant to the mass of the iron-based powder is 0.02 mass% or more and 15 mass% or less.

2. A coated seed, the surface of which is coated with the seed coating agent according to claim 1.

3. A seed coating method, comprising coating the surface of a seed with the seed coating agent according to claim 1.

Images