Fertilizer and manufacturing method of fertilizer

Abstract

To provide a fertilizer that can upgrade a farming soil in a state more suitable for crop production without increasing workload on a farmer.SOLUTION: A fertilizer includes 35.0-45.0% CaO, 14.0-25.0% SiO2, 8.0-16.0% T-Fe, 15.0-25.0% MgO, 1.0-6.0% MnO, and 1.0-8.0% P2O5 in mass% such that a total weight thereof becomes 100% or less, and further has a chemical component composition with a CaO / SiO2 ratio of 1.80-2.50 and an MgO / (FeO+Fe2O3) ratio of 1.2-1.8. The fertilizer contains 20.0 mass% or more of FeO-MgO-MnO solid solution, a chemical component composition with the FeO-MgO-MnO solid solution includes MgO of 45.0-60.0% in mass%, where a total weight of FeO, MgO, and MnO is 90.0% or more.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to fertilizers and a method for manufacturing fertilizers.

Background Art

[0002] In agriculture, it is important to appropriately maintain a balance according to soil pH, the content of essential nutrients that serve as nutrients, the nutrient requirements, and the interactions between nutrients. Soil pH and the nutrients in the soil are affected by rainfall and the removal by harvested crops, and gradually decrease. Therefore, it is necessary to apply fertilizers according to each soil to appropriately supplement these pH and nutrients and adjust the soil to a state suitable for crop growth. Such work is called soil improvement or soil preparation.

[0003] Generally, after applying a calcareous fertilizer having the effect of increasing soil pH, nitrogen, phosphorus, and potassium fertilizers are sprayed after leaving a gap of about 1 to 2 weeks. Leaving a gap of about 1 to 2 weeks after applying the calcareous fertilizer is to prevent the direct reaction between the calcareous fertilizer and the nitrogen fertilizer and the dissipation of nitrogen as ammonia into the air.

[0004] In addition, according to the state of the soil, in order to adjust the balance of calcium and magnesium in the soil, called the base balance of the soil, which is important in addition to soil pH, a magnesia fertilizer is sprayed together with the calcareous fertilizer. In addition, it is also necessary to apply a fertilizer for supplying nutrients called trace elements such as iron and manganese, which cannot be supplemented with calcareous fertilizers or nitrogen, phosphorus, and potassium fertilizers. Thus, it is obvious that the work of preparing the soil suitable for crop cultivation is a very laborious work that requires multiple fertilizer sprays.

[0005] By the way, in the agricultural field, the decrease in the number of agricultural workers is a serious problem. Under such circumstances, in order to maintain crop production, the intensification of farmland is being promoted. As a result, the cultivated area managed per person is on an increasing trend. Comparing 2010 with 2020, the cultivated area per agricultural worker has increased 1.4 times from 2.2 ha to 3.1 ha, and the amount of work required per producer has also increased.

[0006] As a result, due to time constraints, it is difficult to carry out sufficient soil improvement, and there is an increasing number of cases where only nitrogen, phosphoric acid, and potassium fertilizers, which have a great impact on yield, and the adjustment of soil pH by applying calcareous fertilizers are carried out. As a result, the number of soils showing magnesium deficiency due to the breakdown of the soil base balance and soils showing symptoms of trace element deficiency has increased, and it has had an adverse effect on the quality and yield of crops.

[0007] As a method of adjusting the above-mentioned soil base balance and further solving trace element deficiency without increasing the workload of agricultural workers, fertilizers that can supply various nutrients secondarily while adjusting the soil pH have been proposed so far.

[0008] As a fertilizer that can supply various nutrients while adjusting the soil pH, for example, in Non-Patent Document 1, there are shown a plurality of fertilizers containing magnesium, iron, manganese, phosphoric acid, silicon, etc. in addition to calcium, using steel slag, which is a by-product generated in the steel manufacturing process, as a raw material.

[0009] In addition, in Patent Document 1 below, a fertilizer that can supply calcium and magnesium in a well-balanced manner is proposed by setting the equivalent ratio of CaO to MgO contained in the fertilizer to be 2 or more and 3 or less, including the target value of 2.5 for the base balance of generally used soil.

[0010] In addition, in Patent Documents 2 and 3 below, a fertilizer that uses steel slag with a basicity (CaO content / SiO2 content) exceeding 1.5 and not exceeding 2.2 as a raw material and can simultaneously supply various elements such as phosphoric acid, manganese, boron, iron, calcium, silica, magnesium, and sulfur has been proposed.

[0011] In addition, in Patent Document 4 below, in rice cultivation, in order to suppress the infection of sesame leaf blight and increase the yield of rice, an iron-containing material for rice mainly composed of oxides of manganese, calcium, silicon, iron, and magnesium and excellent in supplying iron, manganese, and silicon has been proposed.

[0012] In addition, in Patent Document 5 below, a soil conditioner that can simultaneously supply calcium and magnesium and has persistence in the effects of calcium and magnesium after application, and a soil improvement method using the soil conditioner have been proposed.

[0013] In addition, as a fertilizer that can simultaneously supply calcium and magnesium, calcined magnesia lime obtained by pulverizing dolomite, which is a mineral mainly composed of magnesium carbonate and calcium carbonate, is also widely used.

Prior Art Documents

Patent Documents

[0014]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Non-Patent Documents

[0015]

Non-Patent Document 1

[0016] However, as a result of the study by the present inventors, as a method for adjusting the pH and base balance of the soil as described above, and supplying iron and manganese, which are trace elements, the materials proposed in Non-Patent Document 1 and Patent Documents 1 to 5, and the use of calcined magnesia lime, the following points have been revealed to be a concern.

[0017] Calcium and magnesium in the soil have the property of suppressing the absorption of the other element when the amount of either element becomes excessive. Therefore, it is necessary to maintain a balance so that the amount of each element does not become excessive. This is called the base balance of the soil. The target value of the base balance of the soil is generally CaO:MgO = 5:2 in terms of equivalent ratio. Each equivalent is 1 meq = 28 mg for CaO and 1 meq = 20 mg for MgO. For 8 types of fertilizers made from steelmaking slag described in Non-Patent Document 1, the base balance of calcium and magnesium is 3.3 to 7.5 in terms of equivalent ratio, which is higher than the equivalent ratio of CaO to MgO of 2.5, which is the target value. With the application of such fertilizers alone, it is not possible to properly maintain the base balance of the soil, and MgO deficiency gradually progresses. Therefore, it is considered necessary to separately apply fertilizers rich in MgO.

[0018] Among the components of the fertilizer, the components that contribute to the effect of increasing soil pH are called alkaline components, and are determined by the following formula (1) from the CaO content and MgO content of the fertilizer.

[0019] Alkaline component (%) = CaO content (mass%) + 1.39 × MgO content (mass%) ··· Formula (1)

[0020] In the standard of calcareous fertilizers used for soil pH improvement, the alkaline component content needs to be 50% or more. For calcium carbonate, which is a product widely used as the above calcareous fertilizer, 53% and for magnesia lime, 55% are generally used as guaranteed values.

[0021] On the other hand, the alkaline component content of the fertilizer proposed in Patent Document 1 above is 31 to 45%, and the alkaline component content of the iron-containing fertilizer for rice proposed in Patent Document 4 above is 27.7 to 35.2%, which is less than that of widely used calcium carbonate and magnesia lime. Therefore, it is considered that the application amount required to obtain the same pH increase effect increases, resulting in a large workload.

[0022] In addition, regarding the steelmaking slag for fertilizer raw materials described in Patent Documents 2 and 3 above, as a feature, it is described that the elution of Fe and Mn is promoted by having a FeO-MnO-CaO-SiO2 solid solution obtained by pouring molten steelmaking slag at 1300 to 1400 °C into a dish-shaped heat-resistant container and rapidly cooling it. However, providing the above-mentioned rapid cooling equipment in addition to ordinary equipment complicates the equipment structure and increases the manufacturing cost.

[0023] Also, since the soil conditioner described in Patent Document 5 above does not describe either the content and form of manganese and its effect, the supply effect of manganese among trace elements cannot be obtained.

[0024] In addition, when using calcined magnesia lime, which is a fertilizer capable of supplying calcium and magnesium simultaneously, since calcined magnesia lime contains almost no components other than calcium and magnesium, it is necessary to separately supply iron and manganese as trace elements.

[0025] Therefore, among the fertilizers proposed so far, there is no single fertilizer that can adjust the soil pH, adjust the base balance of the soil, and further solve the lack of trace elements without increasing the workload of farmers. In this regard, there is still room for improvement.

[0026] Therefore, the present invention has been made in view of the above problems, and the object of the present invention is to provide a fertilizer that can improve agricultural land soil to a state more suitable for crop production without increasing the workload of farmers, and has the effects of adjusting soil pH, adjusting the base balance of the soil, and supplying iron and manganese as trace elements, and a method for producing such a fertilizer.

Means for Solving the Problems

[0027] As a result of intensive studies in view of the above problems, the present inventors have succeeded in developing the following fertilizer and completed the present invention. The gist of the present invention is as follows.

[0028] (1) A fertilizer having a chemical composition containing, by mass%, CaO: 35.0 to 45.0%, SiO2: 14.0 to 25.0%, T-Fe: 8.0 to 16.0%, MgO: 15.0 to 25.0%, MnO: 1.0 to 6.0%, P2O5: 1.0 to 8.0% so that the total is 100% or less, and further having a CaO / SiO2 ratio of 1.80 to 2.50 and a MgO / (FeO + Fe2O3) ratio of 1.2 to 1.8, containing 20.0% by mass or more of an FeO-MgO-MnO solid solution, and the chemical composition of the FeO-MgO-MnO solid solution being, by mass%, MgO: 45.0 to 60.0% and the total of FeO, MgO, and MnO: 90.0% or more. (2) The method for producing a fertilizer according to (1), comprising a step of mixing raw materials containing at least calcium oxide, iron (II) oxide, magnesium oxide, manganese oxide, silicon dioxide, and phosphoric acid so as to satisfy the chemical component composition described in (1), and a melting step of heating the mixture of the raw materials to 1400 ° C or higher in an inert gas atmosphere. (3) The method for producing a fertilizer according to (2), further comprising a cooling step of cooling the molten product generated in the melting step in an inert gas atmosphere.

Advantages of the Invention

[0029] As described above, according to the present invention, it is possible to improve agricultural land soil to a state more suitable for crop production without increasing the workload of agricultural workers. Thereby, it becomes possible to increase the crop yield.

Brief Description of the Drawings

[0030]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0031] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0032] <Regarding the FeO-MgO-MnO solid solution> Prior to describing the fertilizer according to the embodiment of the present invention in detail, the relationship between the composition of a FeO-MgO-MnO solid solution called wustite, which is focused on in the embodiment of the present invention, and the fertilizer effect will be described.

[0033] Wustite may be found in slag, which is a by-product of the metal refining process, when the slag contains iron oxide, magnesium oxide, and manganese oxide. In addition, the ratio of FeO, MgO, and MnO that make up wustite does not take a fixed value and is a mineral that can take a free ratio. However, for reasons related to the metal refining process, in most cases, it has a composition mainly composed of FeO. Therefore, in the fertilizer obtained by pulverizing the slag generated in the metal refining process, there is only wustite mainly composed of FeO.

[0034] As a result of intensive studies to solve the supply of trace elements Fe and Mn, which is one of the problems of the present invention, the inventor has obtained the idea that the problem can be solved by changing the chemical composition of the above FeO-MgO-MnO solid solution. Specifically, in the conventional wustite mainly composed of FeO, FeO was difficult to dissolve in the soil. However, focusing on the fact that MgO is easily soluble in the soil, the inventor has obtained the idea that if wustite mainly composed of MgO is used, FeO will also be easily dissolved.

[0035] To verify the effects of the above idea, the inventor created wustite A to wustite F shown below as FeO-MgO-MnO solid solutions with different ratios of FeO and MgO. In the creation, a mixture of iron(II) oxide, magnesium oxide, and manganese oxide reagent was inserted into an iron crucible, and the crucible was placed in an electric furnace filled with argon gas and heated and melted at 1400 °C for 2 hours. As a result, the target wustite A to F were obtained. The compositions of the obtained wustite A to F are shown in Table 1 below.

[0036]

Table 1

[0037] Furthermore, the above wustite pulverized to a particle size of 212 μm or less was mixed with soil at a ratio of 0.2 g / 100 g of soil to obtain test soil. Also, as a control group, soil without the addition of wustite was also used as test soil.

[0038] For the test soil as described above, 12 Komatsuna seeds were sown, and after thinning out, leaving 4 well-growing plants, they were cultivated for about 40 days from sowing. Then, the leaves and stems of Komatsuna were harvested as the above-ground parts.

[0039] The above-ground parts of Komatsuna harvested as described above were subjected to a drying treatment and then used for component analysis in order to analyze the amounts of iron, manganese, and magnesium absorbed from the mixed wustite.

[0040] For the Komatsuna harvested in each test plot, the measurement results of their magnesium, iron, and manganese contents are shown in Table 2 below.

[0041]

Table 2

[0042] Furthermore, based on Table 1 and Table 2 above, for each of the test plots where wustite A to F were applied, according to the following formula (2), the increase rate of the magnesium, iron, and manganese contents relative to the control plot, and the correlation with the ratio of magnesium oxide (mass%) to iron oxide (mass%) in wustite (MgO / FeO+Fe2O3) are shown in Figures 1 to 3.

[0043] Increase rate of content (%) = {Content in Komatsuna in wustite A to F plots (mg / kg) / Content in Komatsuna in the control plot (mg / kg)} × 100 ··· Formula (2)

[0044] From Figures 1 to 3, when the ratio of magnesium oxide to iron oxide in wustite is in the range of 0 to 1, there is no significant increase in the absorption amounts of iron, manganese, and magnesium compared to the control plot. On the other hand, when the above ratio exceeds 1, the absorption rates of iron, manganese, and magnesium increase significantly. In particular, it is a peculiar result that the absorption rates of iron and manganese increase while the iron content contained in wustite decreases and the manganese content hardly changes.

[0045] Therefore, from the results shown in FIGS. 1 to 3, it was found that in the composition of the FeO-MgO-MnO solid solution, when the ratio of magnesium oxide to iron oxide exceeds 1, the iron, manganese, and magnesium supply effects increase specifically.

[0046] As described above, prior to the description of the fertilizer according to the embodiment of the present invention, the relationship between the composition of the FeO-MgO-MnO solid solution called wustite, which was focused on in the embodiment of the present invention, and the fertilizer effect was described.

[0047] <Regarding fertilizers> Hereinafter, the fertilizer according to the embodiment of the present invention will be described in detail.

[0048] The fertilizer according to the present embodiment contains, by mass%, CaO: 35.0 to 45.0%, SiO2: 14.0 to 25.0%, T-Fe: 8.0 to 16.0%, MgO: 15.0 to 25.0%, MnO: 1.0 to 6.0%, P2O5: 1.0 to 8.0% so that the total is 100% or less. Further, it has a chemical composition with a CaO / SiO2 ratio of 1.8.0 to 2.5.0 and a MgO / (FeO + Fe2O3) ratio of 1.2 to 1.8. In addition, such a fertilizer contains 20.0 mass% or more of the FeO-MgO-MnO solid solution in the fertilizer, and the chemical composition of such an FeO-MgO-MnO solid solution is, by mass%, MgO: 45.0 to 60.0%, and the total of FeO, MgO, and MnO: 90.0% or more.

[0049] In addition, the fertilizer according to the present embodiment may contain various impurities in addition to the above components. That is, the fertilizer according to the present embodiment may contain various impurities as the remainder of the chemical composition as described above. Hereinafter, each component contained in the fertilizer according to the present embodiment will be described in detail.

[0050] <Regarding CaO and MgO, and the alkali content> Both Ca and Mg are included in the group of elements called essential nutrients, which are essential for plant growth. In addition, Ca and Mg contained in fertilizers react with the moisture in the soil to exhibit alkalinity, so they have the effect of increasing the pH of the soil.

[0051] In fertilizers, conventionally, when expressing the content of Ca or Mg, the content is expressed in terms of CaO or MgO of the oxide. Therefore, hereinafter, the content of Ca and Mg will be expressed as the CaO conversion value and the MgO conversion value.

[0052] The effect of increasing the pH of the above soil can be evaluated from the value called the alkaline component, which is obtained from the contents of CaO and MgO.

[0053] The analysis method of the alkaline component is defined in the "Fertilizer Test Method" determined by the National Institute of Technology and Evaluation for Agricultural, Forestry and Fisheries Products, and it is an analysis item with a guaranteed value in the "Law Concerning the Assurance of the Quality of Fertilizers" that defines the standards of fertilizers in Japan. It is desirable to obtain the value of the alkaline component by analysis in accordance with the above-specified analysis method. Also, the value of the alkaline component can be approximately predicted from the contents of CaO and MgO in accordance with the formula (1) described above. The formula (1) is reproduced below.

[0054] Alkaline component = CaO content (mass%) + 1.39 × MgO content (mass%) ··· Formula (1)

[0055] Generally, in the standard of calcareous fertilizers used for improving the pH of soil, the content of the alkaline component needs to be 50% or more by mass. The alkaline component is contained at 53% in calcium carbonate, which is a product widely used for improving soil pH, and at 55% in calcined magnesite lime. Therefore, in the fertilizer according to this embodiment, in order to exhibit the soil pH increasing effect equal to or higher than that of general fertilizers, it is desirable to contain the alkaline component at 55% or more.

[0056] The fertilizer according to this embodiment contains 35.0% by mass or more and 45.0% by mass or less of CaO, and 15.0% by mass or more and 25.0% by mass or less of MgO from the above viewpoints. By the CaO and MgO contents satisfying the above ranges, from the above formula (1), the content of the alkaline component is 55.8% or more and 79.8% or less, and a soil pH increasing effect equal to or higher than that of general fertilizers can be realized, and a high soil pH increasing effect can be obtained with a smaller application amount than general fertilizers.

[0057] When the CaO content is less than 35.0% by mass or the MgO content is less than 15.0% by mass, the content of the alkaline component becomes low and the application amount required for soil pH improvement increases, which is not preferable. The CaO content is preferably 37.0% by mass or more, more preferably 40.0% by mass or more. Also, the MgO content is preferably 17.0% by mass or more, more preferably 19.0% by mass or more.

[0058] On the other hand, when the CaO content exceeds 45.0% by mass or the MgO content exceeds 25.0% by mass, in the fertilizer according to this embodiment, the content of fertilizer components other than CaO and MgO decreases, and as a result, the above FeO-MgO-MnO solid solution focused on in the present invention is not sufficiently formed and the Fe and Mn supply effects cannot be sufficiently exerted, which is not preferable. The CaO content is preferably 44.0% by mass or less, more preferably 43.0% by mass or less. Also, the MgO content is preferably 23.0% by mass or less, more preferably 21.0% by mass or less.

[0059] Note that the above CaO content and MgO content can be measured, for example, by X-ray fluorescence analysis.

[0060] <Regarding SiO2 and CaO / SiO2 ratio> Although Si is not an essential element for plants, it is a very important element for Gramineae plants called silicic acid plants such as rice, wheat, and corn. In particular, rice absorbs a large amount of Si such that SiO2 accounts for about 5% of the dry mass of the plant body, and the absorbed SiO2 contributes to the activation of photosynthesis and the acquisition of lodging resistance. Therefore, the fertilizer according to this embodiment preferably contains Si. In the fertilizer, when expressing the Si content, the content is expressed in terms of SiO2 of the oxide. Therefore, hereinafter, the Si content is represented as SiO2.

[0061] Furthermore, SiO2 can combine with CaO and exist as dicalcium silicate (2CaO·SiO2), which is a form that is easily dissolved in the soil. Since CaO and SiO2 contained in the form of dicalcium silicate are gradually supplied to the soil, the fertilizer components are not easily washed away by rainwater or the like, and excellent sustainability is exhibited. Therefore, in the fertilizer according to this embodiment, SiO2 and CaO in the fertilizer are preferably contained in the form of dicalcium silicate.

[0062] The forms of CaO and SiO2 in the fertilizer change depending on the mass ratio CaO / SiO2 ratio of the contents of CaO and SiO2. Therefore, from the above viewpoints, in this embodiment, the CaO / SiO2 ratio is set to be 1.80 or more and 2.50 or less. Thereby, from the above CaO content and the CaO / SiO2 ratio, in the fertilizer according to this embodiment, the SiO2 content is 14.0% by mass or more and 25.0% by mass or less.

[0063] When the CaO / SiO2 ratio is less than 1.80, monocalcium silicate CaO·SiO2 that is difficult to dissolve in soil, wollastonite CaO·FeO·SiO2, etc. are formed, and the pH-raising effect of CaO and the supply effect of SiO2 are not exerted. Therefore, considering the range of the above CaO content of 45.0 mass% or less, the content of SiO2 is 25.0 mass% or less. The CaO / SiO2 ratio is preferably 1.85 or more, more preferably 1.90 or more. As a result, the SiO2 content is preferably 24.0 mass% or less, more preferably 23.0 mass% or less.

[0064] Also, when the CaO / SiO2 ratio exceeds 2.50, CaO may take the form of calcium ferrite 2CaO·Fe2O3 or the like, which is a form of CaO that is difficult to dissolve in soil in addition to the dicalcium silicate. Therefore, considering the range of the above CaO content of 35.0 mass% or more, the SiO2 content is 14.0 mass% or more. The CaO / SiO2 ratio is preferably 2.30 or less, more preferably 2.10 or less. As a result, the SiO2 content is preferably 16.0 mass% or more, more preferably 19.0 mass% or more.

[0065] Incidentally, the content of such SiO2 can be measured, for example, by X-ray fluorescence analysis. Also, whether 2CaO·SiO2 is contained in the fertilizer according to the present embodiment can be determined by analyzing with an X-ray diffractometer and checking for the presence or absence of peaks attributed to the crystals of 2CaO·SiO2 or Ca2SiO4.

[0066] <Regarding T-Fe and MnO, MgO / (FeO + FeO3), and FeO-MgO-MnO solid solution> Fe and Mn are one of the groups of elements called essential nutrients essential for plant growth. As described above, in the present embodiment, Fe, Mn, and Mg are contained as the above FeO-MgO-MnO solid solution in order to supply Fe, Mn, and Mg.

[0067] In the case of fertilizers, when expressing the Mn content, the content is expressed in terms of the oxide MnO. Therefore, hereinafter, the Mn content is expressed as MnO. Also, since Fe takes various forms such as metallic iron, iron(II) oxide, and iron(III) oxide, in fertilizers, the content converted to Fe is expressed as total iron (T-Fe). Therefore, the amount of Fe contained in the fertilizer according to this embodiment is described as T-Fe hereinafter. On the other hand, since the Fe contained in the above FeO-MgO-MnO solid solution is only iron(II) oxide FeO or iron(III) oxide Fe2O3 excluding metallic iron (m-Fe), in the part regarding the description of the above solid solution, it is described as FeO and Fe2O3 respectively without conversion to T-Fe.

[0068] Only when the above CaO / SiO2 ratio is 1.80 or more and 2.50 or less by mass ratio, most of the FeO, MgO, and MnO contained in the fertilizer according to this embodiment can exist as the above FeO-MgO-MnO solid solution. Furthermore, as described above for the FeO-MgO-MnO solid solution, among the chemical component compositions of the above FeO-MgO-MnO solid solution, the ratio of magnesium oxide to iron oxide greatly affects the supply effects of Fe, Mn, and Mg of the above FeO-MgO-MnO solid solution.

[0069] As a result of the intensive studies by the present inventor, in the fertilizer according to this embodiment, the chemical component composition of the above FeO-MgO-MnO solid solution is, by mass%, MgO is 45.0% or more and 60.0% or less, the total content of FeO, MgO, and MnO is 90.0% by mass or more, and further, the above FeO-MgO-MnO solid solution is contained in the above fertilizer at a content of 20.0% by mass or more.

[0070] When the MgO content in the chemical composition of the FeO-MgO-MnO solid solution is less than 45.0% by mass, the FeO-MgO-MnO solid solution is difficult to dissolve in the soil, and the supply effects of Fe, Mn, and Mg may not be fully exerted. On the other hand, when the MgO content in the chemical composition of the FeO-MgO-MnO solid solution exceeds 60% by mass, the supply amounts of Fe, Mn, and Mg become excessive, inhibiting growth. Also, when the total content of FeO, MgO, and MnO is less than 90.0%, or when the content of the FeO-MgO-MnO solid solution in the fertilizer is less than 20.0% by mass, sufficient amounts of Fe, Mn, and Mg will not be supplied.

[0071] In the chemical composition of the FeO-MgO-MnO solid solution, the content of MgO is preferably 50.0 to 55.0% by mass. Also, in the chemical composition of the FeO-MgO-MnO solid solution, the total content of FeO, MgO, and MnO is preferably 95.0% by mass or more. Furthermore, the content of the FeO-MgO-MnO solid solution in the fertilizer is preferably 25% by mass or more, more preferably 30.0% by mass or more.

[0072] Note that in the chemical composition of the FeO-MgO-MnO solid solution, the upper limit value of the total content of FeO, MgO, and MnO is not particularly defined, but substantially 98.0% by mass is the upper limit. Also, for the content of the FeO-MgO-MnO solid solution in the fertilizer, the more the better, but substantially about 51.0% by mass is the upper limit.

[0073] In the fertilizer according to this embodiment, in order for the FeO-MgO-MnO solid solution satisfying the conditions regarding the chemical composition as described above to exist, in view of the above range of the MgO content, in terms of mass%, it is important that the content of T-Fe is 8.0% or more and 16.0% or less, and the content of MnO is 1.0% or more and 6.0% or less.

[0074] When the content of T-Fe is less than 8.0% by mass, due to the low content of Fe, not only can a sufficient Fe supply effect not be obtained, but also an FeO-MgO-MnO solid solution that satisfies the conditions regarding the chemical composition as described above cannot exist. When the content of T-Fe becomes 8.0% by mass or more, not only can a sufficient Fe supply effect be obtained, but also an FeO-MgO-MnO solid solution that satisfies the conditions regarding the chemical composition as described above can be realized. The content of T-Fe is preferably 9.0% by mass or more, and more preferably 10.0% by mass or more.

[0075] On the other hand, when the content of T-Fe exceeds 16.0% by mass, the proportion of FeO in the chemical composition of the above FeO-MgO-MnO solid solution increases, and the content of MgO in the chemical composition of the above FeO-MgO-MnO solid solution cannot be satisfied. When the content of T-Fe becomes 16.0% by mass or less, an FeO-MgO-MnO solid solution that satisfies the conditions regarding the chemical composition as described above can be realized. The content of T-Fe is preferably 15.0% by mass or less, and more preferably 14.0% by mass or less.

[0076] Also, when the content of MnO is less than 1.0% by mass, due to the low content of Mn, not only can a sufficient Mn supply effect not be obtained, but also an FeO-MgO-MnO solid solution that satisfies the conditions regarding the chemical composition as described above cannot exist. When the content of MnO becomes 1.0% by mass or more, not only can a sufficient Mn supply effect be obtained, but also an FeO-MgO-MnO solid solution that satisfies the conditions regarding the chemical composition as described above can be realized. The content of MnO is preferably 2.0% by mass or more, and more preferably 3.0% by mass or more.

[0077] On the one hand, when the content of MnO exceeds 6.0% by mass, the supply amount of Mn becomes excessive, which not only causes Mn excess in plants but also makes it impossible to form an FeO-MgO-MnO solid solution that satisfies the conditions regarding the chemical composition as described above. By setting the content of MnO to 6.0% by mass or less, while preventing the supply amount of Mn from becoming excessive, a sufficient Mn supply effect can be obtained, and an FeO-MgO-MnO solid solution that satisfies the conditions regarding the chemical composition as described above can be realized. The content of MnO is preferably 5.5% by mass or less, and more preferably 5.0% by mass or less.

[0078] In addition, in the fertilizer according to the present embodiment, the MgO / (FeO + Fe2O3) ratio is 1.2 or more and 1.8 or less.

[0079] When the MgO / (FeO + Fe2O3) ratio is less than 1.2, the proportion of MgO in the chemical composition of the above FeO-MgO-MnO solid solution becomes small, and the content of MgO in the chemical composition of the above FeO-MgO-MnO solid solution cannot be satisfied, so the supply effects of Fe, Mn, and Mg may not be fully exerted. By setting the MgO / (FeO + Fe2O3) ratio to 1.2 or more, the chemical composition of the above FeO-MgO-MnO solid solution is satisfied, and it becomes possible to appropriately supply Fe, Mn, and Mg. The MgO / (FeO + Fe2O3) ratio is preferably 1.3 or more, and more preferably 1.4 or more.

[0080] On the other hand, when the MgO / (FeO + Fe2O3) ratio exceeds 1.8, the proportion of MgO in the chemical composition of the above FeO-MgO-MnO solid solution becomes large, and the content of MgO in the chemical composition of the above FeO-MgO-MnO solid solution cannot be satisfied, so Fe, Mn, and Mg may be supplied in excess, which may inhibit growth. By setting the MgO / (FeO + Fe2O3) ratio to 1.8 or less, the chemical composition of the above FeO-MgO-MnO solid solution is satisfied, and it becomes possible to appropriately supply Fe, Mn, and Mg. The MgO / (FeO + Fe2O3) ratio is preferably 1.7 or less, and more preferably 1.6 or less.

[0081] Incidentally, the contents of T-Fe and MnO contained in such fertilizer can be analyzed, for example, by X-ray fluorescence analysis. Further, the FeO content can be determined by phenanthroline absorption photometry, the metallic iron content can be determined by bromine-methanol volumetric method, and the Fe2O3 content can be determined by subtracting the FeO content and the metallic iron content from the analytical value of total iron.

[0082] Furthermore, the presence of FeO-MgO-MnO solid solution in the fertilizer according to this embodiment can be determined from the presence or absence of a structure in which Fe, Mg, Mn, and O coexist by mapping the elemental distribution of the slag structure observed on the cross section at an acceleration voltage of 15 kV using a general EPMA apparatus. Also, the fact that the above FeO-MgO-MnO solid solution has a preferable chemical composition of this embodiment can be obtained by analyzing and semi-quantifying the counts of each element in the EPMA for a structure in which Fe, Mg, Mn, and O are all observed in a measurement region with a diameter of 100 μm by the ZAF method.

[0083] <Regarding P2O5> P is one of the elemental groups called essential nutrients essential for plant growth, and is also one of the three elements called the three major elements of fertilizers, which are particularly important as fertilizer components, along with nitrogen and potassium. In fertilizers, when expressing the content of P, the content is expressed in terms of P2O5 of the oxide, so hereinafter, the content of P is expressed as P2O5.

[0084] In the fertilizer according to this embodiment, the content of P2O5 is 1.0 mass% or more and 8.0 mass% or less. When the P2O5 content is less than 1% by mass, the amount of P2O5 is small and the fertilizer effect as P2O5 cannot be exerted. By making the P2O5 content 1.0% by mass or more, the fertilizer effect as P2O5 can be exerted. The P2O5 content is preferably 2.0% by mass or more, and more preferably 3.0% by mass or more. On the other hand, it has been reported that P2O5 dissolves in the above-mentioned dicalcium silicate, and when the amount of P2O5 dissolved in dicalcium silicate increases, the dicalcium silicate in which P2O5 is dissolved becomes difficult to dissolve. When the above phenomenon occurs, P2O5 that is solid-solved with CaO and SiO2 constituting dicalcium silicate changes to a property that is difficult to dissolve in the soil. Since the above phenomenon becomes prominent when the P2O5 content exceeds 6% by mass, in the fertilizer according to the present embodiment, the P2O5 content is set to 8.0% by mass or less. The P2O5 content is preferably 7.0% by mass or less, and more preferably 6.0% by mass or less.

[0085] Note that such a P2O5 content can be measured by, for example, fluorescent X-ray analysis.

[0086] The fertilizer according to the present embodiment has been briefly described above.

[0087] <Regarding the method for manufacturing the fertilizer> Subsequently, a method for manufacturing a fertilizer according to an embodiment of the present invention will be described. As described above, in the fertilizer according to the present embodiment, it is necessary to contain a FeO-MgO-MnO solid solution that satisfies the above chemical composition conditions. A fertilizer containing a FeO-MgO-MnO solid solution can be obtained by mixing raw materials containing fertilizer components, dissolving them at a high temperature, and cooling the obtained dissolved product.

[0088] [Regarding the raw materials] As the raw material of the fertilizer according to this embodiment, those containing at least one of calcium oxide, iron(II) oxide, magnesium oxide, manganese oxide, silicon dioxide, and phosphoric acid can be used. Specific examples include limestone as the raw material containing calcium oxide, steel slag generated in the steel refining process as the raw material containing iron(II) oxide, dolomite as the raw material containing magnesium oxide, manganese ore residue generated in the manufacturing process of ferromanganese as the raw material containing manganese oxide, waste glass as the raw material containing silicon dioxide, and sludge fertilizer as the raw material containing phosphoric acid. Further, not limited to the above specific examples, as long as it contains at least one of calcium oxide, iron(II) oxide, magnesium oxide, manganese oxide, silicon dioxide, and phosphoric acid and does not adversely affect the properties of the finally obtained fertilizer, the raw material is not particularly limited.

[0089] [Regarding the dissolution process] In the production of the fertilizer according to this embodiment, the mixture of the above raw materials may be put into a container and heated in an electric furnace or the like. Here, the container used for heating may be any as long as it does not adversely affect the properties of the finally produced fertilizer and can withstand the temperature for performing the treatment of melting and homogenizing at a high temperature. Specifically, for example, a metal container made of iron, a ceramic container such as an alumina crucible, and a furnace body lined with refractory used in the metal refining process are applicable.

[0090] Note that iron(II) oxide, which is essential as a raw material component in this embodiment, may change from iron(II) oxide to iron(III) when exposed to a high temperature under conditions of high oxygen partial pressure such as in the air, and as a result, it may be difficult to form a FeO-MgO-MnO solid solution. Therefore, during the dissolution process, the inside of the container is filled with an inert gas so that iron(II) oxide is not oxidized. Note that the inert gas specifically refers to a gas mainly composed of any of noble gases such as nitrogen, ammonia, carbon dioxide, helium, and argon.

[0091] Furthermore, in the above melting step, the temperature of the raw materials is raised to 1400 °C or higher. This is the temperature required to ensure that when the raw materials are mixed and heated to meet the chemical composition conditions of the fertilizer according to this embodiment, the raw materials are sufficiently melted and the FeO-MgO-MnO solid solution that is the focus of this embodiment appears. If the temperature is below 1400 °C, the raw materials will not be sufficiently melted, and some will remain undissolved, etc., and the effects brought about by the present invention cannot be exerted.

[0092] [Regarding the cooling step] In order to use the molten product generated in the above melting step as a fertilizer raw material, a step of cooling it to a solid is required. In the method for producing a fertilizer according to this embodiment, the container containing the molten product is taken out of the electric furnace and left to stand until it reaches room temperature, or the container can be tilted to pour the molten product onto the ground or into another container for cooling.

[0093] In addition, in the cooling method of taking out from the electric furnace and leaving it to stand until it reaches room temperature, or the cooling method of pouring the molten product onto the ground or into another container, a phenomenon occurs in a part of the molten product that is in contact with the air, where iron(II) oxide reacts with oxygen and is oxidized to iron(III) oxide. Iron(III) oxide is less soluble in soil compared to iron(II) oxide, and there is a possibility that the supply effect of Fe may be slightly reduced. Therefore, a cooling step of cooling the molten product in the above inert gas atmosphere is more preferable. Specifically, the molten product is not taken out of the electric furnace filled with the inert gas in which the melting step was performed, the heater of the electric furnace is stopped, and it is left to stand until it reaches room temperature, or the molten product is cooled by spraying a low-temperature inert gas onto it, so that it can be cooled in an inert gas atmosphere.

[0094] The method for producing a fertilizer according to this embodiment has been briefly described above.

Examples

[0095] Hereinafter, the fertilizer according to this embodiment and the method for producing such a fertilizer will be specifically described while showing examples and comparative examples. Note that the examples shown below are merely examples, and the present invention is not limited to the examples shown below.

[0096] First, fertilizers were produced by the method shown below.

[0097] As raw materials, a mixture of oxide reagents of calcium oxide, silicon dioxide, iron(II) oxide, calcium phosphate, and aluminum oxide was put into a crucible made of magnesium oxide, and the crucible was placed in an electric furnace. After filling with argon gas, the temperature was raised to 1550°C, heated for 2 hours, melted to be uniform, then the heating was stopped, and after waiting for the furnace temperature to reach room temperature, the crucible was taken out of the furnace. As a result, fertilizers A to C having the chemical compositions shown in Table 3 below were obtained. Among Table 3, only fertilizer A is an example that satisfies the requirements of the present invention, and fertilizers B and C are comparative examples that partially do not satisfy the requirements of the present invention. Also, as a comparative example, a commercially available fertilizer D made from steelmaking slag generated in the ironmaking process, which has an effect of increasing soil pH and further contains magnesium, iron, and manganese, was also prepared.

[0098]

Table 3

[0099] Furthermore, the cross-sections of fertilizers A to D were observed by EPMA to analyze whether an FeO-MgO-MnO solid solution contained in the fertilizers exists and its composition. The composition analysis results of the FeO-MgO-MnO solid solution and the ratio of magnesium oxide to iron oxide in the FeO-MgO-MnO solid solution are shown in Table 4 below.

[0100]

Table 4

[0101] From the values shown in Table 4, the ratio of magnesium oxide to iron oxide in the iron oxide of the FeO-MgO-MnO solid solution present in Fertilizer A, which is an example of the present invention, is 1.5, exceeding 1.0, which is the value at which the iron, manganese, and magnesium supply effects of the FeO-MgO-MnO solid solution shown in FIGS. 1 to 3 change specifically. Such results indicate that an excellent fertilizer effect can be expected.

[0102] A cultivation test using the fertilizer and Komatsuna as described above was conducted to verify the effect of Fertilizer A, which is an example of the present invention.

[0103] First, the prepared Fertilizers A to C were pulverized and passed through a sieve with an aperture of 212 μm to obtain samples for evaluation.

[0104] Next, 400 g of black soil, superphosphate equivalent to 0.1 g each of nitrogen, phosphoric acid, and potassium, and 4 g of calcium nitrate, potassium nitrate, and Fertilizers A to C pulverized to 212 μm or less were measured and mixed well to obtain test soil, which was then put into a 1 / 10,000 a Neubauer pot. In addition, a control plot was prepared by mixing only superphosphate, calcium nitrate, and potassium nitrate with the black soil.

[0105] The soil pH of the black soil used for the test soil was 5.0, which is an acidic soil lower than the general soil improvement target value of 5.5 to 6.5. Furthermore, among the soil base balances, the equivalent ratio of calcium to magnesium was 5.9, indicating a tendency of magnesium deficiency in the soil, which is significantly higher than the general target value of 2.5 for the soil base balance.

[0106] Twelve Komatsuna seeds were sown in each of the above Neubauer pots containing the test soil, and after 10 days from sowing, thinning was carried out, leaving 4 plants with good growth. Furthermore, on the 40th day after sowing, the above-ground parts of the Komatsuna were harvested, dried, and the dry mass was measured.

[0107] The Komatsuna dried as described above and the soil after the cultivation test were sampled, and analyses were carried out to confirm the fertilizer effect respectively.

[0108] The dry mass of komatsuna in each test plot is shown in Table 5 below. Since the yield of Fertilizer A that meets the requirements of the present invention is higher than that of other control plots, Fertilizer B, and Fertilizer C, it was confirmed that the fertilizer obtained in the present invention has a favorable effect on crops.

[0109]

Table 5

[0110] Hereinafter, focusing on each fertilizer component, more specifically, the effect of the fertilizer obtained in the present invention will be verified.

[0111] To confirm that it has an effect of improving the pH of the soil, 250 mL of water was added to 100 g of air-dried soil, and after reciprocally shaking for 1 hour, the pH of the supernatant was measured. The obtained measurement results are shown in Table 6 below. It was confirmed that the soil pH increased for all fertilizers compared to the control plot, and they have an effect of improving the pH of the soil.

[0112]

Table 6

[0113] To confirm that the fertilizer proposed by the present invention can supply exchangeable lime and exchangeable magnesium in accordance with the target value of the soil base balance so as not to disrupt the soil base balance, the contents of exchangeable lime and exchangeable magnesia in each test soil after the cultivation test were measured. The obtained results are shown in Table 7 below.

[0114] The differences in exchangeable lime and exchangeable magnesia in each soil to which the control plot and Fertilizers A to C were applied, as determined by the following formulas (3) and (4), are the exchangeable lime and exchangeable magnesia supplied by the effects of Fertilizers A to C. Further, if the equivalent ratio of exchangeable lime to exchangeable magnesia supplied by the fertilizer, as determined by formula (5) shown below, is close to 2.5, which is the target value of the soil base balance, it indicates that the application of the fertilizer does not disrupt the soil base balance and an appropriate value is maintained. In this verification example, the equivalent ratio of exchangeable lime to exchangeable magnesia supplied was set within the range of 2 or more and 3 or less to appropriately maintain the soil base balance.

[0115] Amount of exchangeable lime supplied by the fertilizer = (Exchangeable lime in the plot where the fertilizer was applied - Exchangeable lime in the control plot) ··· Formula (3) Amount of exchangeable magnesia supplied by the fertilizer =(Exchangeable magnesia in the plot where the fertilizer was applied - Exchangeable magnesia in the control plot) ··· Formula (4) Equivalent ratio of exchangeable lime to exchangeable magnesia supplied by the fertilizer = (Amount of exchangeable lime supplied by the fertilizer ÷ 28) / (Amount of exchangeable magnesia supplied by the fertilizer ÷ 20) ··· Formula (5)

[0116] From Table 7, it was confirmed that the equivalent ratio of exchangeable lime to exchangeable magnesia supplied by Fertilizer A, which is an example of the present invention, is 2.3, and calcium and magnesium can be supplied in a balance close to 2.5, which is the target value of the soil base balance. On the other hand, the equivalent ratios of exchangeable lime to exchangeable magnesia supplied by Fertilizers B and C used as comparative examples were 7.3 and 13.3, respectively, showing values significantly higher than the target value of 2.5. The results regarding such Fertilizers B and C indicate that it is necessary to separately supply a fertilizer containing magnesium to compensate for the disruption of the soil base balance to calcium excess or magnesium excess. From the above, in this verification example, exchangeable lime and exchangeable magnesium are supplied in accordance with the target value of the soil base balance so as not to disrupt the soil base balance.

[0117]

Table 7

[0118] To confirm the iron supply effect, the results of measuring the available iron content in the soil after the test are shown in Table 8 below. The available iron content is the method described in Non-Patent Document 2 that summarizes the analysis methods of various nutrients in the soil. It is a method of extracting and measuring the iron in the form that can be utilized by plants from the iron present in the extracted soil using a 0.005 mol / L Na-EDTA solution. In the soil to which all fertilizers were applied, the available iron content increased compared to the control plot. However, the soil to which Fertilizer A, which is an example of the present invention, was applied exceeded the soils to which Fertilizers B and C, which are comparative examples, were applied, and it was determined that it had a high iron supply effect.

[0119]

Table 8

[0120] To confirm the manganese supply effect, the results of measuring the amount of Mn absorbed by Komatsuna are shown in Table 9 below. In the soil to which all fertilizers were applied, the manganese content increased compared to the control plot. However, the soil to which Fertilizer A, which is an example of the present invention, was applied exceeded the soils to which Fertilizers B and C, which are comparative examples, were applied, and it is determined that it has a high iron supply effect.

[0121]

Table 9

[0122] Therefore, as one of the embodiments of the present invention, as shown in Tables 6 to 9, Fertilizer A, which is an example of the present invention, although it is a single fertilizer, has an effect of improving the pH of the soil, and also has an effect of improving the base balance of the soil by supplying magnesium, an iron supply effect, and a manganese supply effect. As a result, the soil becomes suitable for cultivating crops, and as shown in Table 5, it has been clarified that the yield of the crops increases.

[0123] As described above, the preferred embodiments of the present invention have been described in detail, but the present invention is not limited to such examples. It is obvious that those having ordinary knowledge in the technical field to which the present invention pertains can conceive of various modification examples or correction examples within the scope of the technical idea described in the claims, and it is naturally understood that these also belong to the technical scope of the present invention.

[0124] The embodiments disclosed this time are illustrative in all respects and not restrictive. The above embodiments may be omitted, replaced, or changed in various forms without departing from the scope of the claims attached hereto and the configuration and the gist of the present invention as described hereinafter. For example, the constituent elements of the above embodiments can be arbitrarily combined within a range that does not impair their effects. Further, from such an arbitrary combination, the actions and effects of each constituent element related to the combination can be naturally obtained, and other actions and other effects obvious to those skilled in the art from the description of this specification can be obtained.

[0125] Also, the effects described in this specification are merely illustrative or exemplary and not restrictive. That is, the technology according to the present invention can exhibit other effects obvious to those skilled in the art from the description of this specification, together with or instead of the above effects.

Industrial Applicability

[0126] The fertilizer provided by the fertilizer and the manufacturing method of the present invention is a useful fertilizer that can simultaneously solve multiple problems of farmland as a single agricultural material, so that the number of times of fertilizer application, which was conventionally required multiple times, can be reduced. In addition, appropriately performing soil improvement while reducing the number of applications with the fertilizer of the present invention is particularly effective in the current situation of Japanese agriculture where the working time per unit area that can be allocated by intensifying farmland is decreasing, and by appropriately performing soil improvement, the crop yield can be increased.

Claims

1. By mass%, CaO: 35.0 - 45.0% SiO ２ : 14.0 - 25.0% T - Fe: 8.0 - 16.0% MgO: 15.0 - 25.0% MnO: 1.0 - 6.0% P ２ O ５ : 1.0 - 8.0% are contained so that the total is 100% or less, and further, CaO / SiO ２ ratio: 1.80 - 2.50, and MgO / (FeO + Fe ２ O ３ ) ratio: 1.2 - 1.8 has a chemical composition, and contains 20.0 mass% or more of a FeO - MgO - MnO solid solution, The chemical composition of the FeO - MgO - MnO solid solution is, by mass%, MgO: 45.0 - 60.0% Total of FeO, MgO, and MnO: 90.0% or more A fertilizer.

2. A method for producing the fertilizer according to Claim 1, comprising: A step of mixing raw materials containing at least calcium oxide, iron(II) oxide, magnesium oxide, manganese oxide, silicon dioxide, and phosphoric acid so as to satisfy the chemical composition according to Claim 1; A melting step of heating the mixture of the raw materials to 1400°C or higher in an inert gas atmosphere; A method for producing a fertilizer.

3. The method for producing a fertilizer according to Claim 2, further comprising a cooling step of cooling the molten product generated in the melting step in an inert gas atmosphere.

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