Slow-release compound agent for reducing cadmium in rice as well as preparation and application of slow-release compound agent

Abstract

The invention provides a slow-release compound for reducing cadmium in rice as well as preparation and application of the slow-release compound. The slow-release compound agent comprises calcium selenite and calcium-magnesium-based minerals, wherein the mass ratio of the calcium selenite to the calcium-magnesium-based minerals is (1-2): (800-2400); the calcium-magnesium-based minerals comprise dolomite minerals. In the slow-release compounding agent for reducing cadmium in rice, the calcium selenite is insoluble selenium. The calcium-magnesium-based natural minerals can improve the content of calcium and magnesium in the soil, so that the pH value of the soil is improved, the content of iron films at the roots of the rice is further increased, and the content of cadmium in rice grains is efficiently reduced. Indissolvable selenium and calcium-magnesium-based minerals are mixed to prepare a slow-release compound, and the slow-release compound is applied to soil once, so that effective components such as selenium, calcium and magnesium in the material can be slowly released, the activity of soil cadmium is reduced, and the absorption of rice to cadmium is reduced in a long-acting manner.

Description

Technical Field

[0001] The invention relates to the field of cadmium reduction in rice, and in particular to a slow-release compound for cadmium reduction in rice, and its preparation and application. Background Art

[0002] Cadmium is widely present in air, soil, sediments and water. It is the most environmentally harmful toxic pollutant among heavy metals. In farmland, high cadmium content will inhibit plant growth and development, leading to abnormal biological metabolism, such as reducing plant weight and root length, accelerating the death of root tip cells, and causing leaves to turn yellow and fall off, or even die. Therefore, it is urgent to develop a method to reduce rice's absorption of soil cadmium. Summary of the invention

[0003] The main purpose of the present invention is to provide a slow-release compound for reducing cadmium in rice, and its preparation and application, so as to solve the technical problem of rice absorbing soil cadmium.

[0004] To achieve the above-mentioned purpose, the present invention provides a slow-release compound for reducing cadmium in rice, comprising calcium selenite and calcium-magnesium-based minerals, wherein the mass ratio of the calcium selenite to the calcium-magnesium-based minerals is (1-2): (800-2400); the calcium-magnesium-based minerals include dolomite minerals.

[0005] According to an embodiment of the present application, the mass ratio of the calcium selenite to the calcium-magnesium-based mineral is 1:1200.

[0006] According to the implementation mode of the present application, the calcium content in the dolomite mineral is 70-75%, and the magnesium content is 25-30%; the mass proportion of MgCa(CO3)2 is 90-95%, and the mass proportion of CaCO3 is 5-10%.

[0007] The present application also provides a method for preparing a slow-release compound for reducing cadmium in rice, comprising the following steps:

[0008] Calcium selenite and calcium-magnesium-based minerals are mixed to obtain a slow-release compound for reducing cadmium in rice, wherein the mass ratio of the calcium selenite to the calcium-magnesium-based mineral is (1-2): (800-2400); and the calcium-magnesium-based mineral includes dolomite mineral.

[0009] According to an embodiment of the present application, the preparation method of calcium selenite comprises:

[0010] The calcium selenite is prepared by mixing a selenium dioxide solution and a calcium hydroxide suspension, wherein the mass ratio of Se to Ca is 1:0.7-0.75.

[0011] The present application also provides the use of a slow-release compound for reducing cadmium in rice, wherein the slow-release compound is applied to the soil in a rice-growing area.

[0012] According to the implementation of the present application, the application amount of the slow-release compound meets the following requirements: the application amount of calcium selenite is 0.25-0.5 mg / kg soil, and the application amount of calcium-magnesium-based minerals is 200-600 mg / kg soil.

[0013] According to an embodiment of the present application, the step of applying the slow-release compound to the soil in the rice-growing area comprises:

[0014] Before planting rice, the base fertilizer and the slow-release compound are mixed and applied to the soil in the rice planting area.

[0015] According to the implementation mode of the present application, the soil is tilled before and after the application of the slow-release compound.

[0016] According to an embodiment of the present application, before and after the application of the slow-release compound, the soil is kept in a flooded condition for two days.

[0017] In the above-mentioned slow-release compound for reducing cadmium in rice, calcium selenite is insoluble selenium. Calcium-magnesium-based natural minerals can increase the calcium and magnesium content in the soil, thereby increasing the soil pH, and further increase the iron film content in the rice roots, so as to achieve efficient reduction of the cadmium content in rice grains. The slow-release compound is prepared by mixing insoluble selenium with calcium-magnesium-based minerals. Once applied to the soil, it can slowly release the effective ingredients such as selenium, calcium, and magnesium in the material, reduce the activity of soil cadmium, and achieve long-term reduction of rice's absorption of cadmium. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0019] Figure 1 The data comparison diagram of rice yield after harvest of rice with different treatments in Example 1: (a) number of ears per plant (b) weight of single ear;

[0020] Figure 2 This is a data comparison diagram of the cadmium content of rice after harvesting rice with different treatments in Example 1;

[0021] Figure 3 This is a comparison diagram of soil pH after harvest of rice with different treatments in Example 1;

[0022] Figure 4 This is a data comparison chart of the cadmium content of rice after harvest of rice with different treatments in the second season in Example 2.

[0023] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with the implementation methods and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] It should be noted that all directional indications (such as up, down, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0026] In addition, in the present invention, the descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0027] Furthermore, the technical solutions between the various embodiments of the present invention may be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in the field. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0028] The invention provides a slow-release compound for reducing cadmium in rice, comprising calcium selenite and calcium-magnesium-based minerals, wherein the mass ratio of the calcium selenite to the calcium-magnesium-based minerals is (1-2): (800-2400); the calcium-magnesium-based minerals include dolomite minerals.

[0029] Selenium is an essential trace element for plants and animals, and plays an important role in their growth and development. Plants can absorb selenium through their roots or leaves. Appropriate concentrations of selenium can also enhance plants' tolerance to heavy metal stress. The mechanisms by which selenium enhances plant heavy metal stress mainly include enhancing plant photosynthesis and antioxidant enzyme activity, promoting ROS clearance in the body, and inhibiting the absorption and accumulation of heavy metals.

[0030] Calcium-magnesium-based natural minerals are gaining more and more attention in the remediation of heavy metal-contaminated soils due to their low cost, environmental friendliness, and ease of large-scale application. Dolomite is a typical calcium-magnesium-rich anhydrous carbonate non-metallic calcium-magnesium-based mineral, mainly composed of calcium carbonate and magnesium carbonate. It can reduce the bioavailability of heavy metals in the soil by affecting soil properties such as soil pH and cation exchange capacity. For example, Ca in the mineral crystal structure 2+ Mg 2+ , K + The cations can be exchanged with heavy metal cations in the soil to reduce the mobility of heavy metals in heavy metal-contaminated soil. In addition, calcium-magnesium-based minerals also have certain application potential in promoting plant growth, alleviating plant heavy metal stress, and reducing the accumulation of heavy metals in plants.

[0031] Based on this, the present invention proposes a long-term cadmium reduction method using a combination of insoluble selenium and calcium-magnesium-based minerals to achieve efficient and sustained-release reduction of the cadmium content in rice grains, and further provide a new method for the safe utilization of cadmium-contaminated farmland.

[0032] The invention uses calcium selenite, which is easy to obtain, as a source of insoluble selenium, and can prepare materials efficiently and quickly. In addition, while reducing the cadmium content in rice, the selenium content in rice can also be increased to obtain selenium-enriched rice, further increasing the economic value of rice.

[0033] The present invention adopts low-cost and environmentally friendly calcium-magnesium-based natural minerals to increase the calcium and magnesium content in the soil, thereby increasing the soil pH, and further increasing the iron film content of rice roots, so as to achieve efficient reduction of the cadmium content in rice grains.

[0034] The present invention uses insoluble selenium and calcium-magnesium-based minerals to prepare a slow-release compound for reducing cadmium in rice. Once applied to the soil, the effective ingredients such as selenium, calcium, and magnesium in the material can be slowly released, the activity of soil cadmium can be reduced, and the absorption of cadmium by rice can be reduced in a long term. The slow-release compound has a higher cadmium-reducing effect on rice than the effect of applying it alone, and the second season of rice still maintains a good cadmium-reducing effect.

[0035] Specifically, the selenium element in the high-efficiency slow-release compound for reducing cadmium in rice mainly reduces the absorption and accumulation of cadmium by rice through the following mechanisms: (1) reducing the bioavailability of cadmium; (2) regulating the antioxidant system and cell metabolites of rice; (3) repairing damaged cell membranes and promoting chloroplast regeneration; (4) increasing the absorption of essential nutrients; (5) reducing the expression of cadmium transporter genes. The root surface iron film is a layer of reddish-brown iron oxide film formed by the oxidation of iron ions and manganese ions in the rice root system. It has a specific adsorption effect on anions and cations (such as cadmium) in the soil, and is therefore considered to be an important barrier to prevent rice from absorbing heavy metals (cadmium, lead, arsenic, etc.). Selenium may also reduce the absorption of cadmium by rice by increasing the content of the root surface iron film. Dolomite is rich in minerals such as calcium and magnesium, which can provide beneficial cations and plant-usable nutrients necessary for rice growth. Studies have shown that dolomite can reduce the content of heavy metals in plants and the accumulation of heavy metals in plants by reducing the effectiveness and mobility of heavy metals in the soil. Calcium and magnesium ions can compete with cadmium ions for root binding sites and ion channels, thereby reducing the absorption of cadmium by rice. In addition, since calcium selenite and dolomite are both insoluble in water, the effective ingredients calcium, magnesium and selenium can be slowly released and will not become ineffective with the seepage and flow of interstitial water in the rice field.

[0036] The form of calcium selenite is not limited, such as a suspension state or a solid state, so the form of the sustained-release compound for reducing cadmium in rice exists in the corresponding suspension state or solid mixture state. When calcium selenite is in a suspension state, the mass of calcium selenite is calculated by the mass of calcium selenite contained in the suspension.

[0037] In order to improve the effect of the sustained-release compound, in some embodiments, the particle size of the calcium-magnesium-based mineral is about 600 meshes. For example, dolomite is crushed, such as by ball milling, to form particles of the above particle size, or dolomite powder of the above particle size is directly purchased.

[0038] Moreover, the research on single lime conditioners and selenium fertilizers mostly adopts the method of foliar spraying, which has the problems of poor cadmium reduction effect on rice and insufficient long-term effectiveness. The compound of insoluble selenium and calcium-magnesium-based minerals can continuously release effective ingredients, which can effectively solve the above problems. It also overcomes the shortcomings of the existing technology, such as how to control the cost of reducing cadmium in the process of rice planting, reduce the burden on farmers, and further improve the economic benefits of rice.

[0039] In the above-mentioned slow-release compound for reducing cadmium in rice, calcium selenite is insoluble selenium. Calcium-magnesium-based natural minerals can increase the calcium and magnesium content in the soil, thereby increasing the soil pH, and further increase the iron film content in the rice roots, so as to achieve efficient reduction of the cadmium content in rice grains. The slow-release compound is prepared by mixing insoluble selenium with calcium-magnesium-based minerals. Once applied to the soil, it can slowly release the effective ingredients such as selenium, calcium, and magnesium in the material, reduce the activity of soil cadmium, and achieve long-term reduction of rice's absorption of cadmium.

[0040] In some embodiments, the mass ratio of the calcium selenite to the calcium-magnesium-based mineral is 1:1200.

[0041] In some embodiments, the dolomite mineral has a calcium content of 70-75%, a magnesium content of 25-30%, a mass proportion of MgCa(CO3)2 of 90-95%, and a mass proportion of CaCO3 of 5-10%.

[0042] The content of calcium and magnesium in dolomite was measured by scanning X-ray fluorescence spectrometer, and the calcium content in dolomite was 71% and the magnesium content was 25%. In addition, dolomite is mainly composed of MgCa(CO3)2 and CaCO3. According to the spectrum obtained by scanning X-ray fluorescence spectrometer, the mass proportion of MgCa(CO3)2 and CaCO3 can be obtained, which is about 91.4% and 8.6% respectively.

[0043] The present application also provides a method for preparing a slow-release compound for reducing cadmium in rice, comprising the following steps:

[0044] Calcium selenite and calcium-magnesium-based minerals are mixed to obtain a slow-release compound for reducing cadmium in rice, wherein the mass ratio of the calcium selenite to the calcium-magnesium-based mineral is (1-2): (800-2400); and the calcium-magnesium-based mineral includes dolomite mineral.

[0045] For example, a suspension containing calcium selenite is mixed with a calcium-magnesium-based mineral, or solid calcium selenite is directly mixed with a calcium-magnesium-based mineral. Calcium selenite can be prepared by itself or purchased commercially.

[0046] In some embodiments, the method for preparing calcium selenite comprises:

[0047] The calcium selenite is prepared by mixing a selenium dioxide solution and a calcium hydroxide suspension, wherein the mass ratio of Se to Ca is 1:0.7-0.75.

[0048] In this embodiment, the prepared calcium selenite is in the form of a suspension. The preparation method of the selenous acid solution can be: dissolving SeO2 in water to obtain the selenous acid solution. The preparation method of the calcium hydroxide suspension can be: dissolving CaO in water to obtain the calcium hydroxide suspension.

[0049] The present application also provides the use of a slow-release compound for reducing cadmium in rice, wherein the slow-release compound is applied to the soil in a rice-growing area.

[0050] The rice planting process can refer to the existing planting method, the main difference is that the rice cadmium and arsenic reducing slow-release compound agent is applied during the rice planting in the present invention.

[0051] Since a slow-release compound for reducing cadmium in rice is used, the application of the slow-release compound in reducing cadmium in rice has the corresponding beneficial effects of the aforementioned slow-release compound, which will not be described in detail.

[0052] In some embodiments, the application amount of the sustained-release compound satisfies: the application amount of calcium selenite is 0.25-0.5 mg / kg soil, and the application amount of dolomite is 200-600 mg / kg soil.

[0053] Considering the transportation and use costs of dolomite and the ratio of the mixed application amount with selenium fertilizer, the application amount of calcium selenite is set at 0.25-0.5 mg / kg soil, and the application amount of dolomite is set at 200-600 mg / kg, and calcium selenite and dolomite minerals are mixed and uniformly applied to the soil.

[0054] Taking the slow-release compound in suspension state as an example, the concentration and dosage of calcium selenite and dolomite in the slow-release compound meet the conditions that the application amount of calcium selenite is 0.25-0.5 mg / kg soil and the application amount of dolomite is 200-600 mg / kg soil. If the concentration of calcium selenite and dolomite is low, the dosage is relatively increased; if the concentration of calcium selenite and dolomite is high, the dosage is relatively reduced.

[0055] When the application amount of the slow-release compound meets the above conditions, selenium can be maintained at an appropriate concentration, which is more conducive to enhancing the plant's tolerance to heavy metal stress.

[0056] Furthermore, when the efficient slow-release compound for reducing cadmium in rice is applied to the soil, a better ratio of the efficient slow-release compound for reducing cadmium in rice is to add 0.5 mg of calcium selenite and 600 mg of dolomite per kilogram of soil.

[0057] The slow-release compound can be added alone or mixed with other substances. In some embodiments, the step of applying the slow-release compound to the soil in the rice planting area includes:

[0058] Before planting rice, the base fertilizer and the slow-release compound are mixed and applied to the soil in the rice planting area.

[0059] Before planting rice, basal fertilizer (urea and potassium chloride, etc.), calcium selenite and dolomite minerals are mixed and applied to the soil in the rice planting area. By applying it to the soil together with the basal fertilizer, the burden of secondary spraying of pesticides by farmers is reduced and the simple application method is also easy to promote.

[0060] In some embodiments, the soil is tilled before and after applying the slow-release compound to allow the slow-release compound to be fully mixed with the soil.

[0061] Before and after applying the efficient slow-release compound for reducing cadmium in rice, the soil needs to be ploughed, and the ploughed soil should usually be kept flat to ensure the uniformity of applying the efficient slow-release compound for reducing cadmium in rice.

[0062] In some embodiments, the soil is kept flooded for two days before and after the application of the slow-release compound, which allows the compound to more evenly penetrate into the soil to achieve a better cadmium reduction effect.

[0063] Example 1

[0064] This embodiment uses paddy soil taken from Beishan Town, Changsha County, Changsha City, Hunan Province for potted experiments. 5 kg of naturally dried soil is placed in a pot. There are 12 groups of experiments, 3 repeated experiments in each group, numbered S-1, S-2, S-3, S-4, S-5, S-6, S-7, S-8, S-9, S-10, S-11, S-12. S-1 is the CK group. The amount of selenium added in the CK group is 0 mg / kg, and the amount of dolomite added is 0 mg / kg. The amount of each group added, the change in soil pH after application, the number of panicles per plant, and the weight of a single panicle are shown in Table 1:

[0065] Table 1 Addition amount of each group of substances, soil pH changes after application, number of ears per plant and weight of single ear

[0066]

[0067] Mix different gradients of calcium selenite and dolomite materials with base fertilizer evenly in the soil, then put them into pots and keep them watered for 2 days for later use.

[0068] Rice breeding: Wash the rice seeds with deionized water, select seeds with full grains and sterilize them in 30% hydrogen peroxide solution for 20 minutes, half immerse the sterilized seeds in deionized water, and germinate them in a dark environment for 2-3 days. After the seeds germinate, transfer them to a plastic box filled with 20-mesh quartz sand and culture them in 1 / 2 Hogland nutrient solution for 14 days. After the rice grows to two leaves and one heart, transplant the seedlings with the same growth conditions into pots, with 5 seedlings per pot.

[0069] After the rice matures, some physical and chemical properties of the soil are measured, and the mature rice is further collected to measure the cadmium and selenium content.

[0070] The five-point sampling method was used to collect soil from the surface and bottom of the potted plants with different treatments, air-dried and ground, mixed through a 20-mesh sieve, and the soil pH was measured. The results were as follows: Figure 3 As shown in Table 1:

[0071] Reference Figure 3 Compared with the control group (without dolomite and selenium), when 0.25 mg / kg soil selenium fertilizer was mixed and applied, different gradients of dolomite (200 mg / kg soil, 400 mg / kg soil, 600 mg / kg soil, corresponding to S-6, S-7, S-8 groups, respectively) increased the soil pH by 13.5%, 16.9%, and 20.7%, respectively; when 0.5 mg / kg soil / selenium fertilizer was mixed and applied, different gradients of dolomite (200 mg / kg soil, 400 mg / kg soil, 600 mg / kg soil, corresponding to S-10, S-11, S-12 groups, respectively) increased the soil pH by 14.5%, 17.6%, and 21.1%, respectively. Compared with the application of selenium fertilizer alone, the mixed application of selenium and dolomite has a better effect on increasing soil pH; compared with the application of dolomite alone, the mixed application of selenium and dolomite has an increasing trend in increasing the effect of increasing soil pH; and when the same amount of dolomite is applied, with the increase of selenium fertilizer dosage (0-0.5 mg / kg soil), the effect of increasing soil pH has an increasing trend, indicating that the effect of mixed application is generally better than that of single application. The increase in soil pH is conducive to reducing the bioavailability of cadmium in the soil and further reducing the accumulation of cadmium in rice. This phenomenon can be attributed to the correlation between soil adsorption and pH. With the increase of pH, the negative charge on the surface of clay minerals and organic matter in the soil increases at the same time, enhancing their adsorption capacity for cations. With the increase of pH, the formation of metal hydroxide (Me-OH) is promoted, making it an adsorption site with a strong affinity for cadmium. At the same time, the soil H + The reduction of Cd ions slows down 2+ The hydrolysis of cadmium reduces the solubility of hydroxides and carbonates, ultimately reducing the bioavailability of cadmium in soil.

[0072] All the mature millets were harvested, dried naturally, weighed, and the average number of ears per plant and the average weight of each ear were calculated. Figure 1 And as shown in Table 1.

[0073] Compared with the application of selenium fertilizer and dolomite alone, the combination of dolomite and selenium fertilizer has a more obvious increase in the number of rice panicles per plant and the weight of a single panicle. With the increase in the amount of selenium and dolomite, the number of rice panicles and the weight of panicles also increase. The application of 0.5 mg / kg of selenium fertilizer and 600 mg / kg of dolomite in the soil (corresponding to the S-12 group) increased the average number of panicles per plant by 39.78% and the average weight of each panicle by 113.86%, with the best effect. The compound agent increases the number of rice panicles and the weight of panicles. This is because the compound agent increases the content of exchangeable calcium and exchangeable magnesium in the soil, gradually releases soluble elements / soluble salts, has a positive effect on the microbial community and structure, and promotes root growth. It is also rich in minerals such as Si, Ca and Mg, providing beneficial cations and plant-available nutrients necessary for rice growth.

[0074] The rice harvested at maturity was dried, shelled, and crushed. A certain weight of the crushed rice was weighed for microwave digestion, and the cadmium content was measured by graphite furnace atomic absorption spectrometer. The results were as follows: Figure 2 And as shown in Table 2.

[0075] Table 2 Cadmium content in rice grains of each group of rice in the first season

[0076]

[0077]

[0078] The cadmium content of rice in the control group (no material was applied, corresponding to the S-1 group) was 0.37 mg / kg, which was higher than the food safety standard and was cadmium-contaminated rice. When dolomite and selenium fertilizer were applied together, the cadmium content of rice was around 0.15 mg / kg or less, and there was no risk of cadmium contamination in rice. At the same dolomite dosage, the cadmium reduction effect of applying 0.5 mg / kg soil selenium fertilizer was better than that of applying 0.25 mg / kg soil selenium fertilizer. Among them, the cadmium reduction effect of 600 mg / kg soil dolomite was better than that of 400 mg / kg soil and 200 mg / kg soil. When the same 0.25 mg / kg soil selenium fertilizer was applied, the effects of different amounts of dolomite on the Cd content of rice were not much different. When the same 0.5 mg / kg soil selenium fertilizer was applied, as the amount of dolomite increased, the cadmium reduction effect of rice became better and better. Among them, the cadmium reduction rate was the best when 600 mg / kg soil dolomite was applied, reaching 72.1%.

[0079] Example 2

[0080] After the first season rice samples were collected, the excess weeds and rice roots in the pots were removed, and the second season rice was planted on the basis of the first season pots. The amount of materials and base fertilizer was the same as the first season, and they were mixed evenly with the soil. The rice breeding used the same breeding method as the first season. After the rice grew to two leaves and one heart, the seedlings of the same variety and similar growth conditions were taken from the pots planted in the first season, and 5 seedlings were transplanted in each pot. The same water management and pest and disease control were used for the two plantings.

[0081] After the first season of rice is harvested, the second season of rice is planted in the potted plants planted in the first season. When the second season of rice is fully mature, the rice harvested at maturity is dried, shelled, and crushed. A certain weight of the crushed rice is weighed for microwave digestion, and the cadmium content is measured by graphite furnace atomic absorption spectrometer. The results are as follows: Figure 4 And as shown in Table 3.

[0082] Table 3 Cadmium content in rice grains of each group of second-season rice

[0083]

[0084] The cadmium content of rice in the control group still exceeded 0.2 mg / kg, which is higher than the limit of the national food safety standard, and there is a risk of cadmium contamination of rice. When the same amount of dolomite was applied, compared with no selenium application, the application of selenium fertilizer with a concentration of 0.5 mg / kg soil was better than that with a selenium fertilizer with a concentration of 0.25 mg / kg soil; when the same amount of selenium fertilizer with a concentration of 0.25 mg / kg soil was applied, the effects of different amounts of dolomite on the cadmium content of rice were not much different, and when the same amount of selenium fertilizer with a concentration of 0.5 mg / kg soil was applied, the cadmium reduction effect of rice increased slightly with the increase of dolomite dosage, among which, the cadmium reduction rate reached 44.28% when 600 mg / kg soil dolomite was applied compared with the control, which was the best effect.

[0085] In summary, the Cd content in rice in the second year was consistent with that in the first year. Insoluble selenium and calcium-magnesium-based minerals still had the effect of reducing cadmium and increasing yield in the second year, and the effect of their combination on reducing cadmium and increasing yield was better than the single application of insoluble selenium and calcium-magnesium-based minerals.

[0086] The above technical solutions of the present invention are only preferred embodiments of the present invention, and the patent scope of the present invention is not limited thereto. All equivalent structural changes made by using the contents of the present invention specification and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A sustained-release compound for reducing cadmium in rice, characterized in that: It comprises calcium selenite and calcium-magnesium-based minerals, wherein the mass ratio of the calcium selenite to the calcium-magnesium-based minerals is (1-2): (800-2400); the calcium-magnesium-based minerals comprise dolomite minerals.

2. The sustained-release compound according to claim 1, characterized in that: The mass ratio of the calcium selenite to the calcium-magnesium-based mineral is 1:1200.

3. The sustained-release compound according to claim 1, characterized in that: The dolomite mineral has a calcium content of 70-75% and a magnesium content of 25-30%; the mass proportion of MgCa(CO3)2 is 90-95%, and the mass proportion of CaCO3 is 5-10%.

4. A method for preparing a sustained-release compound for reducing cadmium in rice as claimed in any one of claims 1 to 3, characterized in that: The following steps are involved: Calcium selenite and calcium-magnesium-based minerals are mixed to obtain a slow-release compound for reducing cadmium in rice, wherein the mass ratio of the calcium selenite to the calcium-magnesium-based mineral is (1-2): (800-2400); and the calcium-magnesium-based mineral includes dolomite mineral.

5. The preparation method according to claim 4, characterized in that: The preparation method of calcium selenite comprises: The calcium selenite is prepared by mixing a selenium dioxide solution and a calcium hydroxide suspension, wherein the mass ratio of Se to Ca is 1:0.7-0.

75.

6. Use of the sustained-release compound for reducing cadmium in rice as claimed in any one of claims 1 to 3, characterized in that: The slow-release compound is applied to the soil in the rice-growing area.

7. The use according to claim 6, characterized in that: The application amount of the slow-release compound meets the following requirements: the application amount of calcium selenite is 0.25-0.5 mg / kg soil, and the application amount of calcium-magnesium-based minerals is 200-600 mg / kg soil.

8. The use according to claim 7, characterized in that: The step of applying the slow-release compound to the soil in the rice planting area comprises: Before planting rice, the base fertilizer and the slow-release compound are mixed and applied to the soil in the rice planting area.

9. The use according to claim 7, characterized in that: Before and after applying the slow-release compound, the soil is ploughed.

10. The use according to any one of claims 6 to 9, characterized in that: Before and after application of the slow-release compound, the soil was kept under flooding conditions for two days.

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