A selenium-enriching and cadmium-reducing method for selenium-rich cadmium-contaminated soil

Abstract

The present invention belongs to the technical field of soil selenium enrichment and cadmium reduction, and specifically discloses a selenium enrichment and cadmium reduction method for selenium-rich cadmium-polluted soil. The selenium enrichment and cadmium reduction method includes the following steps: before planting crops in the selenium-rich cadmium-polluted soil, measuring the molar ratio A of bioavailable selenium to cadmium and the total cadmium content B in the selenium-rich cadmium-polluted soil; during the process of planting crops, applying a soil conditioner to adjust the soil pH and the pH of irrigation water, and at the same time judging whether to apply selenium-rich organic fertilizer and spray foliar fertilizer during the process of planting crops according to the values of A and B. Based on the discovery of the dual effects of selenium and cadmium at the root-soil interface of crops, the present invention proposes a selenium enrichment and cadmium reduction method for selenium-rich cadmium-polluted soil, which can effectively achieve the synchronization of cadmium reduction and selenium enrichment by adjusting the available selenium-cadmium ratio in paddy soil, and truly realizes precise selenium enrichment and cadmium reduction. The method of the present invention has lower treatment cost, better treatment effect and higher economic benefit.

Description

Technical Field

[0001] The present invention belongs to the technical field of soil selenium enrichment and cadmium reduction, and particularly relates to a method for selenium enrichment and cadmium reduction in selenium-rich cadmium-polluted soil. Background Art

[0002] Selenium is an essential trace element for the human body, which is closely related to human health. It is the source of human life and is known as the "life element". It has various biological functions such as antioxidant and enhancing immune system function, and is an anti-cancer substance recognized by the international medical community. According to statistics, 72% of counties and cities in China are deficient in selenium to varying degrees, and 1 / 3 of them are severely selenium-deficient areas. For selenium-deficient people, dietary selenium intake is one of the important ways to supplement selenium, and the safest and most effective way for the human body to supplement selenium is usually natural selenium-rich agricultural products. The selenium content of agricultural products mainly comes from the soil, and the parent material of soil formation is the key factor determining the soil selenium content.

[0003] A large number of studies have found that due to the influence of geological movements, selenium often coexists with cadmium in the soil, resulting in a threat of cadmium pollution in selenium-rich areas. Cadmium is one of the persistent pollutants in the environment, which is easy to enter the biological system and may thus pose a hazard to the health of humans and other organisms. There is a dual effect of selenium and cadmium in the root-soil interface of crops in the soil: that is, selenium at different concentrations may either inhibit the absorption of cadmium and play an antagonistic role; or promote the absorption of cadmium and play a synergistic role, enhancing the biological toxicity of cadmium. It is precisely due to the superposition effect of the cadmium coexistence phenomenon in selenium-rich soil and the selenium-cadmium synergistic effect that the risk of cadmium pollution in agricultural products in selenium-rich soil areas has been exacerbated. In order to ensure the high-quality development of selenium-rich agriculture, it is of great significance and urgency to carry out the prevention and control of cadmium pollution risk areas in selenium-rich soil.

[0004] At present, the commonly used cadmium passivators for paddy soil often passivate the activity of selenium in the soil while reducing the available cadmium in the soil and controlling the absorption of cadmium by crops, reducing the effectiveness of soil selenium and the absorption of selenium by crops. Therefore, how to achieve selenium enrichment in agricultural products while reducing the absorption of cadmium in selenium-rich cadmium-polluted soil has become a technical problem. Existing soil conditioners or foliar control agents are difficult to accurately prevent and control farmlands with different degrees of selenium-rich cadmium pollution, and only by combining the discrimination technology with the precise application technology for farmlands with different soil selenium contents and different degrees of cadmium pollution can the absorption of cadmium be effectively controlled while realizing the safe production of selenium-rich agricultural products. Summary of the Invention

[0005] The purpose of the present invention is to solve the deficiencies of the prior art and provide a method for selenium enrichment and cadmium reduction in selenium-rich cadmium-polluted soil, and specifically adopt the following technical solutions:

[0006] A selenium-enriched cadmium-reducing method for selenium-rich cadmium-polluted soil, comprising the following steps: before planting crops in the selenium-rich cadmium-polluted soil, measuring the bioavailable selenium-cadmium molar ratio A and the total cadmium content B in the selenium-rich cadmium-polluted soil; during the process of planting crops, applying a soil conditioner to adjust the soil pH to above 6.2 and the irrigation water pH to above 7.0, and simultaneously judging whether to apply selenium-enriched organic fertilizer and spray foliar fertilizer during the process of planting crops according to the values of A and B;

[0007] The specific judgment conditions are as follows: when A≤0.6 and B≥0.8mg / kg, apply selenium-enriched organic fertilizer and spray foliar fertilizer; when A≤0.6 and B<0.8mg / kg, apply selenium-enriched organic fertilizer; when A>0.6 and B≥0.8mg / kg, spray foliar fertilizer; when A>0.6 and B<0.8mg / kg, neither apply selenium-enriched organic fertilizer nor spray foliar fertilizer.

[0008] How to reduce the cadmium content in agricultural products in selenium-rich cadmium-polluted soil to below 0.2mg / kg while meeting the standards of selenium-enriched agricultural products is a technical problem, because existing cadmium-reducing products or technologies significantly reduce the selenium content while reducing the cadmium content in agricultural products, and it is difficult to achieve a win-win situation for both. The present invention discovers that when the molar ratio of available selenium to cadmium in paddy soil > 0.6, the cadmium content in rice will decrease as the molar ratio of available selenium to cadmium in the soil increases, and the selenium content in rice will increase as the molar ratio of available selenium to cadmium in the soil increases; when the molar ratio of available selenium to cadmium in the soil ≤ 0.6, the cadmium content in rice will increase as the molar ratio of available selenium to cadmium in the soil increases, and the selenium content in rice will not change significantly as the molar ratio of available selenium to cadmium in the soil increases; therefore, the present invention can effectively achieve synchronous cadmium reduction and selenium enrichment by adjusting the molar ratio of available selenium to cadmium in paddy soil.

[0009] First, the present invention raises the soil pH to above 6.2 by applying a soil conditioner and adjusting the pH of irrigation water (specifically, it can be a lime sedimentation tank), effectively passivating the available cadmium in the soil, reducing the content of available cadmium in the soil, significantly activating the selenium in the soil, increasing the content of available selenium, and achieving a molar ratio of bioavailable selenium to cadmium in the soil of 1 or more. The raw materials of the soil conditioner include, by weight: 50 parts - 70 parts of lime materials, 15 parts - 40 parts of nitro-humic acid calcium and magnesium, and 30 parts - 50 parts of calcium magnesium phosphate fertilizer; the lime materials are at least one of limestone powder, dolomite powder, and oyster powder. Adding nitro-humic acid calcium and magnesium and calcium magnesium phosphate fertilizer is to utilize the antagonistic effect of elements such as calcium and magnesium in them, which can more effectively reduce the absorption of cadmium in the soil by rice; in addition, the formed phosphate radicals can not only preserve the available selenium in the soil through ion exchange effects, but also effectively reduce the content of available cadmium in the soil through organic matter complexation, phosphate precipitation, and other effects. The application method of the soil conditioner is one-time basal application, and the dosage of the soil conditioner required to raise the pH of the soil from pHi to pHt is Q; when the organic matter content in the soil is not more than 30 g / kg, Q = EXP(1.52×(pHt - 4.8)) - EXP(1.52×(pHi - 4.8)); when the organic matter content in the soil is more than 30 g / kg, Q = EXP(1.39×(pHt - 4.4)) - EXP(1.39×(pHi - 4.4)). The soil conditioner is obtained by granulating the raw materials after mixing them under the action of a binder.

[0010] Secondly, the present invention further accurately discriminates selenium-rich cadmium-contaminated soil by detecting two parameters, namely the molar ratio of available selenium to cadmium and the total cadmium content in the soil, and determines the treatment process. Specifically: when the molar ratio of available selenium to cadmium in the soil > 0.6 and the total cadmium content < 0.8 mg / kg, according to the above findings, it can be known that the cadmium content in rice will decrease with the increase of the molar ratio of available selenium to cadmium in the soil, the selenium content will increase with the increase of the molar ratio of available selenium to cadmium in the soil, and the total cadmium content is not too high. Therefore, it is only necessary to adjust the soil pH to above 6.2 by applying a soil conditioner and adjust the pH of the irrigation water to above 7.0, and there is no need to apply selenium-rich organic fertilizer and foliar fertilizer. When the molar ratio of available selenium to cadmium in the soil > 0.6 and the total cadmium content ≥ 0.8 mg / kg, the cadmium content in rice will decrease with the increase of the molar ratio of available selenium to cadmium in the soil, and the selenium content will increase with the increase of the molar ratio of available selenium to cadmium in the soil. However, the total cadmium content in the soil is too high. Not only is it necessary to apply a soil conditioner to adjust it to above 6.2 and adjust the pH of the irrigation water to above 7.0, but also an additional foliar fertilizer needs to be sprayed to assist in reducing cadmium. When the molar ratio of available selenium to cadmium in the soil ≤ 0.6 and the total cadmium content < 0.8 mg / kg, the cadmium content in rice will increase with the increase of the molar ratio of available selenium to cadmium in the soil, and the selenium content shows no significant change with the increase of the molar ratio of available selenium to cadmium in the soil. This indicates that the content of available selenium in the soil is too low at this time, but the total cadmium content is not too high. Therefore, at this time, not only is it necessary to apply a soil conditioner to adjust it to above 6.2 and adjust the pH of the irrigation water to above 7.0, but also a selenium-rich organic fertilizer needs to be applied to additionally supplement the available selenium to increase the molar ratio of available selenium to cadmium in the soil and achieve true selenium enrichment and cadmium reduction. When the molar ratio of available selenium to cadmium in the soil ≤ 0.6 and the total cadmium content ≥ 0.8 mg / kg, at this time, the molar ratio of available selenium to cadmium in the soil is too low and the total cadmium content in the soil is too high. Therefore, on the basis of applying a soil conditioner to adjust it to above 6.2 and adjusting the pH of the irrigation water to above 7.0, not only is it necessary to apply a selenium-rich organic fertilizer to additionally supplement the available selenium to increase the molar ratio of available selenium to cadmium in the soil, but also an additional foliar fertilizer needs to be sprayed to assist in reducing cadmium.

[0011] Thus, it can be seen that the selenium enrichment and cadmium reduction method for selenium-rich cadmium-contaminated soil proposed by the present invention can achieve accurate discrimination in the treatment process. Actual growers can select different solutions according to the method of the present invention for different soil conditions, accurately judge whether it is necessary to apply selenium-rich organic fertilizer and foliar fertilizer, and accurately judge the dosage of soil conditioner and selenium-rich organic fertilizer, truly realizing accurate selenium enrichment and cadmium reduction. Compared with the mostly empirical practices of existing methods and products, the method of the present invention has lower treatment costs, better treatment effects, and higher economic benefits.

[0012] Among them, the selenium-rich organic fertilizer is prepared by the following process: its raw materials include, by weight: 20-50 parts of activated selenium ore powder, 30-70 parts of selenium-rich organic material, 10-25 parts of cinder powder, and 2-10 parts of binder; the particle size of the cinder powder is 0.01mm-0.15mm; the preparation method of the selenium-rich organic fertilizer is obtained by granulating the mixed raw materials under the action of the binder.

[0013] After the selenium fertilizer is applied to acidic soil, it is quickly fixed by iron and manganese oxides, reducing its biological activity. Therefore, how to preserve the activity of selenium in the soil is a technical problem. The inventor found that cinder powder with a particle size of 0.01mm-0.15mm (derived from the waste residue discharged from boiler coal combustion. If the particle size of the particles is too large, its specific surface area will become smaller accordingly, which will affect its adsorption efficiency and adsorption capacity) has strong adsorption characteristics for selenite anions. Each gram of cinder powder can adsorb 4.78g of selenite anions. After being mixed with activated selenium ore powder and selenium-rich organic materials and applied to the soil, it can effectively reduce the chemical fixation of selenium fertilizer in the soil, significantly increase the content of available selenium in the soil, thereby achieving the effects of improving the biological utilization efficiency of selenium fertilizer and reducing costs.

[0014] The selenium-rich organic material is prepared by the following process: Mix the crushed selenium-rich straw (preferably crushed to 1cm-2cm; generally, the selenium content is greater than 0.2mg / kg), selenium-rich livestock and poultry manure (generally, the selenium content is greater than 0.5mg / kg), urea, and activated selenium ore powder as a premix, and the C:N in the premix is 20-30:1; then spray the bacterial liquid into the premix, control the water content in the premix to be 30%-50%, and ferment for 3-4 weeks to obtain the selenium-rich organic material with a total selenium content ≥2mg / kg; the bacterial liquid is obtained by dissolving brown sugar and adding it to the original EM bacterial liquid; the mass ratio of the premix, the original EM bacterial liquid, and brown sugar is 500-1000:1:1.

[0015] The activated selenium ore powder is prepared by the following process: Crush selenium-rich slate or selenium-rich coal gangue (selenium content ≥50mg / kg), and then mix it with 10%-20% by weight of CaO adsorbent, roast it at 500°C-600°C for 3h, and cool it to obtain the activated selenium ore powder.

[0016] The selenium-rich straw used is at least one of crop straws such as selenium-rich rape straw and selenium-rich rice straw; the selenium-rich livestock and poultry manure used is at least one of selenium-rich chicken manure, selenium-rich pig manure, and selenium-rich duck manure. The original EM bacterial liquid is a composite bacterial agent original liquid composed of Lactobacillus delbrueckii, Streptococcus lactis, and Rhodopseudomonas palustris, and the effective viable bacteria count ≥10 6CFU / mL, with a pH value ≤ 3.5. On the one hand, the added EM bacteria original liquid can promote the decomposition of straw and livestock manure and accelerate the fermentation speed; on the other hand, it can provide a large number of beneficial bacteria, which is beneficial to regulating the soil microbial flora and increasing the soil organic selenium content. The selenium content in the activated selenium ore powder is relatively high, but its raw material source is relatively specific and the acquisition cost is relatively high; while the selenium-rich straw and selenium-rich livestock manure are widely sourced, but their selenium content is relatively low. If added alone, it will result in excessive dosage. Therefore, considering the above situation, the present invention combines the two after scientific compounding, which not only reduces the overall dosage but also avoids the problem of too high raw material acquisition cost.

[0017] The mu dosage of the selenium-rich organic fertilizer is calculated by the following formula: M ≥ [BD × L × 666.67 × (0.6 × Cd - Se)] / (C × 1.27); M is the mu dosage, with the unit of kg, BD is the soil bulk density measured before planting the selenium-rich cadmium-polluted crop, with the unit of g / cm 3 , L is the soil layer thickness measured before planting the selenium-rich cadmium-polluted crop, with the unit of cm, Cd is the bioavailable cadmium content in the soil measured before planting the selenium-rich cadmium-polluted crop, with the unit of μmol / kg, Se is the bioavailable selenium content in the soil measured before planting the selenium-rich cadmium-polluted crop, with the unit of μmol / kg, and C is the total selenium content in the selenium-rich organic fertilizer, with the unit of mg / kg.

[0018] Among them, the foliar fertilizer is prepared by the following process: Dissolve the residue extract of Cinnamomum camphora, EDTA-chelated zinc, and sodium selenite in an acidic silica sol solution, and then add a spreading agent and mix well to obtain the foliar fertilizer; the ratio of the residue extract of Cinnamomum camphora, EDTA-chelated zinc, sodium selenite, acidic silica sol, and spreading agent is (3 mL - 10 mL):(40 g - 90 g):(4 g - 10 g):1 L:(1 mL - 3 mL); in the acidic silica sol solution, the SiO2 content is greater than 25%, and the pH is less than 3.5. The inventor found that the residue extract of Cinnamomum camphora (i.e., the residue extract after steam distillation of Cinnamomum camphora to extract borneol) contains a large amount of borneol essential oil and a small amount of borneol, which can significantly promote the absorption of Si and Se by leaves, greatly improve the absorption efficiency, and thus achieve the purpose of efficiently reducing cadmium; at the same time, the waste of the residue of Cinnamomum camphora is also reused. The inventor found that not only is there an interactive synergistic effect between Si and Se, but there is also an interactive synergistic effect among Si, Se, and Zn, which can further improve the control effect on Cd (the effect of reducing cadmium in rice by the single substance of EDTA-chelated zinc is very limited); in addition, the inventor found that if inorganic zinc sulfate is directly added, the amount of Zn ions required to play a synergistic role is too large, which easily causes the acidic silica sol to form a gel. Therefore, the inventor innovatively chooses to add EDTA-chelated zinc, which not only avoids the failure of the gel formation due to the excessive addition of Zn ions but also realizes the interactive synergistic effect among Zn-Si-Se. The pH of the acidic silica sol solution being less than 3.5 can further improve the dispersibility of other raw materials in the acidic silica sol, and the acidic environment is more conducive to the absorption of cadmium-blocking elements; the choice of the SiO2 content greater than 25% is mainly to ensure the silicon content in the foliar fertilizer. If the concentration is lower than this, the silicon content in the foliar fertilizer is too low, which will affect the cadmium-blocking effect. When the crop is rice, the foliar fertilizer is sprayed 2 times respectively during the heading stage and the filling stage of rice. Each time, the foliar fertilizer is diluted 100 - 200 times with water before spraying; the spraying amount is based on the standard that the front and back sides of the rice leaves are covered with mist droplets.

[0019] The residue extract of Cinnamomum camphora var. borneolifera is prepared by the following process: mixing the residue of Cinnamomum camphora var. borneolifera with a mixed solvent of ethanol and water at a ratio of 1 g:(5 mL - 10 mL), performing microwave-ultrasound (preferably, the ultrasound power is 400 W - 600 W and the microwave power is 200 W - 300 W) for 5 min - 20 min under the condition of 20°C - 50°C, and obtaining the residue extract of Cinnamomum camphora var. borneolifera after filtering the filtrate and performing reduced pressure distillation. First, the residue of Cinnamomum camphora var. borneolifera is mixed with the mixed solvent of ethanol and water at a ratio of 1 g:(5 mL - 10 mL). This ratio has the best effect on extracting borneol essential oil and a small amount of borneol in it. If the ratio is too low, the extraction is incomplete; if the ratio is too high, the extraction concentration is too low and it is uneconomical. Second, performing microwave-ultrasound under the condition of 20°C - 50°C is mainly because too low temperature will lead to reduced extraction efficiency and longer time consumption, while too high temperature will cause a large amount of ethanol to volatilize easily, affecting the extraction quality.

[0020] The beneficial effects of the present invention are as follows: Based on the relevant discovery of the dual effects of selenium and cadmium at the root-soil interface of crops, the present invention proposes a selenium-enriching and cadmium-reducing method for selenium-rich cadmium-polluted soil. By adjusting the available selenium-cadmium ratio in paddy soil, the synchronization of cadmium reduction and selenium enrichment can be effectively achieved, and accurate selenium enrichment and cadmium reduction are truly realized. The method of the present invention has lower treatment cost, better treatment effect and higher economic benefit. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a flowchart of a selenium-enriching and cadmium-reducing method for selenium-rich cadmium-polluted soil proposed by the present invention.

[0022] The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings. SPECIFIC EMBODIMENTS

[0023] For the convenience of understanding the present invention, the present invention will be described more comprehensively with reference to the relevant drawings. Several embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present invention more thorough and comprehensive.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0025] Please refer to Figure 1, the present invention specifically discloses a selenium-enriching and cadmium-reducing method for selenium-rich cadmium-polluted soil. The selenium-enriching and cadmium-reducing method includes the following steps: before planting crops in the selenium-rich cadmium-polluted soil, collecting soil samples with excessive selenium and cadmium from the selenium-rich cadmium-polluted soil to measure the molar ratio A of bioavailable selenium and cadmium and the total cadmium content B in the selenium-rich cadmium-polluted soil; during the process of planting crops, applying a soil conditioner to adjust the soil pH and the pH of irrigation water, and at the same time judging whether to apply selenium-rich organic fertilizer and spray foliar fertilizer during the process of planting crops according to the values of A and B. The specific judgment process is as follows: when A ≤ 0.6 and B ≥ 0.8 mg / kg, apply selenium-rich organic fertilizer and spray foliar fertilizer; when A ≤ 0.6 and B < 0.8 mg / kg, apply selenium-rich organic fertilizer; when A > 0.6 and B ≥ 0.8 mg / kg, spray foliar fertilizer; when A > 0.6 and B < 0.8 mg / kg, neither apply selenium-rich organic fertilizer nor spray foliar fertilizer.

[0026] It should also be noted that the soil conditioner, selenium-rich organic fertilizer, and foliar fertilizer in the following examples are prepared by the following processes respectively:

[0027] (1) Preparation of soil conditioner

[0028] The soil conditioner, its raw materials by weight include: 40 parts of calcium magnesium phosphate fertilizer, 30 parts of nitrohumic acid calcium magnesium, 60 parts of limestone / dolomite powder, and 10 parts of binder.

[0029] The preparation process is as follows: Mix calcium magnesium phosphate fertilizer, nitrohumic acid calcium magnesium, and limestone / dolomite powder evenly, then add the binder in a granulator for granulation until the particles are completely formed, then dry and screen. Return the particles with a particle size greater than 5 mm and less than 1 mm to the pulverizer for re-pulverization and then re-granulation. Screen out the particles with a particle size of 2 - 5 mm, measure them, and package them to obtain the soil conditioner.

[0030] (2) Preparation of selenium-rich organic fertilizer

[0031] The selenium-rich organic fertilizer, its raw materials by weight include: 25 parts of activated selenium ore powder, 50 parts of selenium-rich organic material, 20 parts of cinder powder (with a particle size of about 0.1 mm), and 5 parts of binder (a mixture of bentonite and sesbania powder).

[0032] The preparation process is as follows: Mix the above raw materials evenly in a mixer and then granulate under the action of the binder. After the particles are formed, dry and screen. Return the particles with a particle size greater than 5 mm and less than 1 mm to the pulverizer for re-pulverization and then re-granulation. Screen out the particles with a particle size of 2 mm - 5 mm, measure them, and package them to obtain the selenium-rich organic fertilizer.

[0033] The activated selenium ore powder is prepared by the following steps: Crushing the selenium-rich slate (selenium content ≥ 50 mg / kg), then mixing it evenly with a CaO adsorbent accounting for 20% of its weight, roasting at 550 °C for 3 h, and cooling to obtain the activated selenium ore powder;

[0034] The selenium-rich organic material is prepared by the following steps: Mixing the crushed selenium-rich rice straw (particle size 1 cm - 2 cm, selenium content > 0.2 mg / kg) and selenium-rich livestock and poultry manure (selenium-rich pig manure, selenium-rich chicken manure or a mixture of the two, selenium content > 0.5 mg / kg) according to a mass ratio of 1:2, then adding an appropriate amount of urea and mixing well to obtain a premix, with the C / N in the premix being about 25; Then spraying the bacterial solution into the premix, controlling the water content in the premix to be about 45%, compacting in a strip stack, covering with a plastic film, and fermenting for 4 weeks to obtain the selenium-rich organic material; The bacterial solution is obtained by dissolving brown sugar and adding EM bacterial original solution (a composite bacterial original solution composed of Lactobacillus delbrueckii, Streptococcus lactis, and Rhodopseudomonas palustris, with the effective viable count ≥ 10 6 CFU / mL and pH value ≤ 3.5); The mass ratio of the premix, EM bacterial original solution, and brown sugar is 800:1:1.

[0035] (3) Preparation of foliar fertilizer

[0036] The foliar fertilizer, whose raw materials include: extract of Cinnamomum camphora residue, sodium selenite, EDTA-chelated zinc, acidic silica sol, and Tween 80. The foliar fertilizer is prepared by the following process:

[0037] The preparation process is as follows: Dissolve 8 mL of the extract of Cinnamomum camphora residue, 90 g of EDTA-chelated zinc, and 7 g of sodium selenite in 1 L of acidic silica sol (SiO2 content is 30%, pH is 3.0) solution, and after complete dissolution, add 1 mL of Tween 80 and mix well to obtain the foliar fertilizer.

[0038] The extract of Cinnamomum camphora residue is prepared by the following process: Mix 2 kg of Cinnamomum camphora leaf and twig powder with an ethanol-water mixed solvent according to a mass-volume ratio of 1:5, then perform microwave-ultrasound for 10 min under the conditions of a 500 W ultrasonic power, a 250 W microwave power, and 30 °C, filter, collect the filtrate, and continue to perform microwave-ultrasound extraction on the residue in the above manner 3 times, and after combining the filtrates, perform reduced pressure distillation to obtain it.

[0039] Example 1

[0040] Before planting crops in selenium-rich cadmium-polluted soil, measure the bioavailable selenium-cadmium molar ratio A and the total cadmium content B in the selenium-rich cadmium-polluted soil; During the process of planting crops, apply a soil conditioner to adjust the soil pH to above 6.2, adjust the pH of the irrigation water to above 7.0, and at the same time judge whether to apply selenium-rich organic fertilizer and spray foliar fertilizer during the process of planting crops according to the values of A and B;

[0041] The specific judgment conditions are as follows: when A ≤ 0.6 and B ≥ 0.8 mg / kg, apply selenium-rich organic fertilizer and spray foliar fertilizer; when A ≤ 0.6 and B < 0.8 mg / kg, apply selenium-rich organic fertilizer; when A > 0.6 and B ≥ 0.8 mg / kg, spray foliar fertilizer; when A > 0.6 and B < 0.8 mg / kg, neither apply selenium-rich organic fertilizer nor spray foliar fertilizer.

[0042] Specifically, in this example, before planting, a plough layer soil sample was collected, and the bioavailable selenium-cadmium molar ratio A of the selenium-rich cadmium-polluted soil was measured to be 0.83, the total cadmium content B of the soil was 0.66 mg / kg, the total selenium content was 0.58 mg / kg, the bioavailable selenium content of the soil was 0.093 mg / kg, the bioavailable cadmium content of the soil was 0.16 mg / kg, the soil pH was 5.11, and the soil organic matter content was 41.47 g / kg.

[0043] According to the judgment condition, when A > 0.6 and B < 0.8 mg / kg, neither apply selenium-rich organic fertilizer nor spray foliar fertilizer.

[0044] Only during the process of growing crops, use a lime sedimentation tank to adjust the pH of the irrigation water to about 7 and apply a soil conditioner to adjust the soil pH to above 6.2. The dosage of the soil conditioner is calculated according to the following formula:

[0045] Q = EXP(1.52×(pHt - 4.8)) - EXP(1.52×(pHi - 4.8)) (OM ≤ 30 g / kg)

[0046] Q = EXP(1.39×(pHt - 4.4)) - EXP(1.39×(pHi - 4.4)) (OM > 30 g / kg)

[0047] Q represents the dosage of the conditioner (t / ha) required to increase the soil pHi = 5.11 to pHt = 6.2.

[0048] The dosage of the soil conditioner calculated according to this formula is: 635 kg / mu for the soil conditioner of the present invention.

[0049] Comparative Example 1

[0050] The implementation method and process are the same as those in Example 1, except that the application of the soil conditioner of the present invention is replaced with Tebi calcium conditioner (provided by Xiamen Mata Ecology Co., Ltd.), and the dosage of Tebi calcium conditioner is calculated according to the following formula:

[0051] Q = EXP(1.387×(pHt - 5.154)) - EXP(1.387×(pHi - 5.154)) (OM ≤ 30 g / kg)

[0052] Q = EXP(1.2×(pHt - 4.658)) - EXP(1.2×(pHi - 4.658)) (OM > 30 g / kg)

[0053] Q represents the dosage of conditioner required to increase the soil pHi = 5.11 to pHt = 6.2.

[0054] The result calculated according to this formula is the dosage of Tebbe calcium conditioner: 309 kg / acre.

[0055] Example 2

[0056] Before planting crops in selenium-rich cadmium-contaminated soil, measure the molar ratio A of bioavailable selenium to cadmium and the total cadmium content B in the selenium-rich cadmium-contaminated soil; during the process of planting crops, apply soil conditioner to adjust the soil pH to above 6.2, adjust the pH of irrigation water to above 7.0, and at the same time judge whether to apply selenium-rich organic fertilizer and foliar fertilizer during the process of planting crops according to the values of A and B;

[0057] The specific judgment conditions are as follows: when A ≤ 0.6 and B ≥ 0.8 mg / kg, apply selenium-rich organic fertilizer and spray foliar fertilizer; when A ≤ 0.6 and B < 0.8 mg / kg, apply selenium-rich organic fertilizer; when A > 0.6 and B ≥ 0.8 mg / kg, spray foliar fertilizer; when A > 0.6 and B < 0.8 mg / kg, neither apply selenium-rich organic fertilizer nor spray foliar fertilizer.

[0058] Specifically, in this example, a plow layer soil sample was collected before planting, and the molar ratio A of bioavailable selenium to cadmium in the selenium-rich cadmium-contaminated soil was measured to be 0.52, the total cadmium content B of the soil was 0.74 mg / kg, the total selenium content of the soil was 0.47 mg / kg, the bioavailable selenium content of the soil was 0.071 mg / kg, the bioavailable cadmium content of the soil was 0.19 mg / kg, the soil pH was 5.47, and the soil organic matter content was 33.3 g / kg;

[0059] According to the judgment condition that when A ≤ 0.6 and B < 0.8 mg / kg, selenium-rich organic fertilizer needs to be applied, and the dosage of selenium-rich organic fertilizer is calculated according to the following formula: M ≥ [BD × L × 666.67 × (0.6Cd - Se)] / (C × 1.27), where M is the dosage of organic fertilizer per acre (kg), BD is the soil bulk density (g / cm 3 )), L is the soil layer thickness (cm), Cd is the bioavailable cadmium content in the soil (μmol / kg), Se is the bioavailable selenium content in the soil (μmol / kg), and C is the total Se content in the organic fertilizer (mg / kg). Before starting planting, by measuring the soil bulk density, plow layer thickness, bioavailable cadmium content in the soil and bioavailable selenium content in the soil, adjust the selenium-cadmium molar ratio to above 0.6, and apply selenium-rich organic fertilizer: 152 kg / acre.

[0060] During the process of growing crops, a lime sedimentation tank is used to adjust the pH of the irrigation water to about 7, and a soil conditioner is applied to adjust the soil pH to above 6.2. The dosage of the soil conditioner is calculated according to the following formula:

[0061] Q = EXP(1.52×(pHt - 4.8)) - EXP(1.52×(pHi - 4.8)) (OM ≤ 30 g / kg)

[0062] Q = EXP(1.39×(pHt - 4.4)) - EXP(1.39×(pHi - 4.4)) (OM > 30 g / kg)

[0063] Q represents the dosage of the conditioner required to increase the soil pHi = 5.47 to pHt = 6.2

[0064] The result calculated according to this formula is the dosage of the soil conditioner: 519 kg / mu

[0065] Comparative Example 2-1

[0066] The implementation method and process are the same as those in Example 2, except that the selenium-rich organic fertilizer applied in Example 2 is replaced with a selenium-rich organic fertilizer without adding cinder powder, and its dosage is the same as that of the selenium-rich organic fertilizer in Example 2, which is 152 kg / mu

[0067] The preparation method of the selenium-rich organic fertilizer without adding cinder powder is the same as that of the selenium-rich organic fertilizer, except that cinder powder is not added to its raw material composition

[0068] Comparative Example 2-2

[0069] The implementation method and process are the same as those in Example 2, except that the selenium-rich organic fertilizer applied in Example 2 is replaced with sodium selenite, and its dosage is calculated according to the following formula: M ≥ [BD × L × 666.67 × (0.6Cd - Se)] / (C × 1.27) to adjust the selenium-cadmium molar ratio of the soil to above 0.6, and 3.34 g / mu of sodium selenite is applied

[0070] Example 3

[0071] Before growing crops in selenium-rich cadmium-polluted soil, measure the bioavailable selenium-cadmium molar ratio A and total cadmium content B in the selenium-rich cadmium-polluted soil; during the process of growing crops, apply a soil conditioner to adjust the soil pH to above 6.2 and the irrigation water pH to above 7.0, and at the same time judge whether to apply selenium-rich organic fertilizer and foliar fertilizer during the process of growing crops according to the values of A and B

[0072] The specific judgment conditions are as follows: When A ≤ 0.6 and B ≥ 0.8 mg / kg, apply selenium-rich organic fertilizer and spray foliar fertilizer; when A ≤ 0.6 and B < 0.8 mg / kg, apply selenium-rich organic fertilizer; when A > 0.6 and B ≥ 0.8 mg / kg, spray foliar fertilizer; when A > 0.6 and B < 0.8 mg / kg, neither apply selenium-rich organic fertilizer nor spray foliar fertilizer.

[0073] Specifically, before planting, soil samples from the plow layer were collected, and the bioavailable selenium-cadmium molar ratio A of the selenium-rich cadmium-polluted soil was determined to be 0.9, the total cadmium content B of the soil was 1.14 mg / kg, the total selenium content was 0.62 mg / kg, the bioavailable selenium content of the soil was 0.13 mg / kg, the bioavailable cadmium content of the soil was 0.21 mg / kg, the soil pH was 5.92, and the soil organic matter content was 23.18 g / kg.

[0074] According to the judgment condition: when A > 0.6 and B ≥ 0.8 mg / kg, foliar fertilizer needs to be sprayed. The foliar fertilizer of the present invention is sprayed 2 times during the heading and filling stages of rice, and is diluted 150 times each time for spraying. The spraying amount of the liquid is preferably such that the front and back sides of the rice leaves are covered with mist droplets.

[0075] During the process of growing crops, a lime sedimentation tank is used to adjust the pH of the irrigation water to about 7 and a soil conditioner is applied to adjust the soil pH to above 6.2. During the process of growing crops, a lime sedimentation tank is used to adjust the pH of the irrigation water to about 7 and a soil conditioner is applied to adjust the soil pH to above 6.2. The dosage of the soil conditioner is calculated according to the following formula:

[0076] Q = EXP(1.52×(pHt - 4.8)) - EXP(1.52×(pHi - 4.8)) (OM ≤ 30 g / kg)

[0077] Q = EXP(1.39×(pHt - 4.4)) - EXP(1.39×(pHi - 4.4)) (OM > 30 g / kg)

[0078] Q represents the dosage of the conditioner (t / ha) required to adjust the soil pHi = 5.92 to pHt = 6.2.

[0079] According to the result calculated by this formula, the dosage of the soil conditioner is: 194 kg / mu.

[0080] Comparative Example 3-1

[0081] The implementation method and process are the same as those of Example 3, except that the foliar fertilizer in Example 3 is replaced with a foliar fertilizer without the addition of Cinnamomum camphora residue extract, and its dosage is the same as that of the foliar fertilizer in Example 3.

[0082] The preparation method of the foliar fertilizer without the addition of the extract of Cinnamomum camphora residues is the same as that of the foliar fertilizer, except that the extract of Cinnamomum camphora residues is replaced with distilled water. The specific preparation process is as follows:

[0083] Add 8 mL of distilled water, 90 g of EDTA-chelated zinc, and 7 g of sodium selenite to 1 L of acidic silica sol (SiO2 content is 30%, pH is 3.0) solution. After complete dissolution, add 1 mL of Tween 80 and mix well to obtain the foliar fertilizer.

[0084] Comparative Example 3-2

[0085] The implementation method and process are the same as those in Example 3, except that the foliar fertilizer in Example 3 is replaced with a cadmium-reducing foliar control agent (provided by Jiangxi Puruifeng Ecological Technology Co., Ltd., mainly composed of nearly 10 natural plant nutrients such as organosilicon, organic selenium, and organic active substances, SiO2 ≥ 20%, K2O ≥ 15%). Its dosage and application method are carried out according to the product instructions.

[0086] Example 4

[0087] Before planting crops in selenium-rich cadmium-polluted soil, measure the bioavailable selenium-cadmium molar ratio A and total cadmium content B in the selenium-rich cadmium-polluted soil; during the process of planting crops, apply a soil conditioner to adjust the soil pH to above 6.2 and the irrigation water pH to above 7.0, and at the same time judge whether to apply selenium-rich organic fertilizer and spray foliar fertilizer during the process of planting crops according to the values of A and B;

[0088] The specific judgment conditions are as follows: when A ≤ 0.6 and B ≥ 0.8 mg / kg, apply selenium-rich organic fertilizer and spray foliar fertilizer; when A ≤ 0.6 and B < 0.8 mg / kg, apply selenium-rich organic fertilizer; when A > 0.6 and B ≥ 0.8 mg / kg, spray foliar fertilizer; when A > 0.6 and B < 0.8 mg / kg, neither apply selenium-rich organic fertilizer nor spray foliar fertilizer.

[0089] Specifically, in this example, a plow layer soil sample was collected before planting, and the bioavailable selenium-cadmium molar ratio A of the selenium-rich cadmium-polluted soil was measured to be 0.41, the total cadmium content B of the soil was 1.33 mg / kg, the total selenium content of the soil was 0.76 mg / kg, the bioavailable selenium content of the soil was 0.11 mg / kg, the bioavailable cadmium content of the soil was 0.37 mg / kg, the soil pH was 4.61, and the soil organic matter content was 48.63 g / kg.

[0090] According to the judgment conditions: when A ≤ 0.6 and B ≥ 0.8 mg / kg, it is necessary to apply selenium-rich organic fertilizer and spray foliar fertilizer. The application rate of selenium-rich organic fertilizer per mu is calculated according to the following formula: M ≥ [BD × L × 666.67 × (0.6Cd - Se)] / (C × 1.27). Before planting, by measuring the soil bulk density, plough layer thickness, bioavailable cadmium content in the soil and bioavailable selenium content in the soil, adjust the selenium-cadmium molar ratio to more than 0.6, and apply selenium-rich organic fertilizer: 659 kg / mu.

[0091] The foliar fertilizer of the present invention is sprayed 2 times during the heading stage and filling stage of rice, diluted 150 times each time for spraying, and the liquid spraying amount is preferably such that the front and back sides of the rice leaves are covered with mist droplets.

[0092] During the process of growing crops, use a lime sedimentation tank to adjust the pH of the irrigation water to about 7 and apply a soil conditioner to adjust the soil pH to more than 6.2. The dosage of the soil conditioner is calculated according to the following formula:

[0093] Q = EXP(1.52 × (pHt - 4.8)) - EXP(1.52 × (pHi - 4.8)) (OM ≤ 30 g / kg)

[0094] Q = EXP(1.39 × (pHt - 4.4)) - EXP(1.39 × (pHi - 4.4)) (OM > 30 g / kg)

[0095] Q represents the dosage of the conditioner (t / ha) required to increase the soil pHi = 4.61 to pHt = 6.2.

[0096] The result calculated according to this formula is the dosage of the soil conditioner: 725 kg / mu.

[0097] Comparative Example 4

[0098] The implementation method and process are the same as those in Example 4, except that the selenium-rich organic fertilizer applied in Example 4 is replaced with sodium selenite, and its dosage is calculated according to the following formula: M ≥ [BD × L × 666.67 × (0.6Cd - Se)] / (C × 1.27), adjust the selenium-cadmium molar ratio of the soil to more than 0.6, and apply sodium selenite: 14.45 g / mu.

[0099] Replace the foliar fertilizer sprayed in Example 4 with a cadmium-reducing foliar control agent, and its dosage and application method are carried out according to the product instructions.

[0100] Replace the application of the soil conditioner of the present invention with Tebet calcium conditioner, and the dosage of Tebet calcium conditioner is calculated according to the following formula:

[0101] Q = EXP(1.387×(pHt - 5.154)) - EXP(1.387×(pHi - 5.154)) (OM ≤ 30 g / kg)

[0102] Q = EXP(1.2×(pHt - 4.658)) - EXP(1.2×(pHi - 4.658)) (OM > 30 g / kg)

[0103] Q represents the dosage of conditioner required to increase the soil pHi = 5.11 to pHt = 6.2.

[0104] The result calculated according to this formula is the dosage of Tebbe calcium conditioner: 361 kg / mu.

[0105] Effect experiment:

[0106] A selenium - rich cadmium - reducing method for selenium - rich cadmium - polluted soil of the present invention has carried out four groups of tests on middle - season rice and late - season rice, and achieved good application effects.

[0107] Test group 1

[0108] The test was set with three treatments: conventional fertilization planting (CK), Example 1, and Comparative Example 1 (Tebbe calcium soil conditioner). Each treatment had 3 replicates, with a total of 9 pots, and each pot was filled with 15 kg of soil (in terms of dry weight). Conventional fertilization planting was to plant rice with customary fertilization (generally without applying conditioner and organic fertilizer). Example 1 and Comparative Example 1 were to apply a certain amount of conditioner on the basis of conventional fertilization planting. After mixing the soil with chemical fertilizers and conditioner, they were filled into pots. After filling the pots, water was added and soaked for about 1 week before transplanting rice. Each pot was transplanted with 3 clumps of rice. After the harvest of middle - season rice and late - season rice, soil samples and plant samples were collected to measure indexes such as rice yield, soil available selenium, soil available cadmium, brown rice selenium, and brown rice cadmium content. The relative cadmium - reducing rate and relative selenium - enriching rate were calculated through the cadmium and selenium content in brown rice; the soil cadmium passivation rate and soil selenium activation rate were calculated through the soil available cadmium and available selenium content.

[0109] The tested soil type: paddy soil; Basic physical and chemical properties of the soil: The molar ratio of soil bio - available selenium to cadmium is 0.83, the total cadmium content of the soil is 0.66 mg / kg, the total selenium content is 0.58 mg / kg, the soil bio - available selenium content is 0.093 mg / kg, the soil bio - available cadmium content is 0.16 mg / kg, the soil pH is 5.11, and the soil organic matter content is 41.47 g / kg. According to the limit value of "Soil Environmental Quality Risk Control Standards for Agricultural Land Soils (Trial)" (GB 15618 - 2018) in China (pH < 6.5, cadmium is 0.30 mg / kg), the total cadmium content of the test soil is about 2 times the standard limit value, belonging to moderately and lightly polluted soil.

[0110] The application method of the soil conditioner is one-time basal application. The dosage of the soil passivator required to increase the soil pH from the pre-fertilization pHi to the preset pHt = 6.2 by applying the soil conditioner is Q. When the organic matter content in the soil is no more than 30 g / kg, Q = EXP(1.48×(pHt - 4.5)) - EXP(1.48×(pHi - 4.5)); when the organic matter content in the soil is greater than 30 g / kg, Q = EXP(1.6×(pHt - 4.37)) - EXP(1.6×(pHi - 4.37)). The result calculated according to this formula is: the application rate of Example 1 on middle-season rice and late-season rice is 63.49 g / pot. The application rate of Tebai calcium soil conditioner in Comparative Example 1 on middle-season rice and late-season rice is calculated according to the following formula. When the organic matter content in the soil is no more than 30 g / kg, Q = EXP(1.387×(pHt - 5.154)) - EXP(1.387×(pHi - 5.154)); when the organic matter content in the soil is greater than 30 g / kg, Q = EXP(1.2×(pHt - 4.658)) - EXP(1.2×(pHi - 4.658)), and the calculated result is 30.95 g / pot.

[0111] Experimental Group 2

[0112] The experiment was set with four treatments: conventional fertilization planting (CK), Example 2, Comparative Example 2-1 (selenium-rich organic fertilizer without adding cinder powder), and Comparative Example 2-2 (sodium selenite). Each treatment had 3 replicates, with a total of 12 pots, and each pot was filled with 15 kg of soil (in terms of dry weight). Conventional fertilization planting was to plant rice with conventional fertilization (generally without applying conditioner and organic fertilizer). Example 2 and Comparative Example 2-1 were respectively applied with a certain amount of selenium-rich organic fertilizer and selenium-rich organic fertilizer without adding cinder powder on the basis of conventional fertilization planting. Comparative Example 2-2 was applied with a certain amount of sodium selenite on the basis of conventional fertilization planting. Examples and comparative examples were both applied with a certain amount of the conditioner of the present invention on the basis of conventional fertilization planting. After mixing the soil, chemical fertilizers and the test materials used, they were filled into pots. After filling the pots, water was added and soaked for about 1 week, and then rice was transplanted. 3 clumps of rice were transplanted into each pot. After the middle-season rice and late-season rice were harvested, soil samples and plant samples were collected to measure indexes such as rice yield, soil available selenium, soil available cadmium, brown rice selenium, and brown rice cadmium content. The relative cadmium reduction rate and relative selenium enrichment rate were calculated through the cadmium and selenium content in brown rice; the soil cadmium passivation rate and soil selenium activation rate were calculated through the soil available cadmium and available selenium content.

[0113] Tested soil type: paddy soil; Basic physical and chemical properties of the soil: The molar ratio of biologically available selenium to cadmium in the soil is 0.52, the total cadmium content in the soil is 0.74 mg / kg, the total selenium content in the soil is 0.47 mg / kg, the biologically available selenium content in the soil is 0.071 mg / kg, the biologically available cadmium content in the soil is 0.19 mg / kg, the soil pH is 5.47, and the soil organic matter content is 33.3 g / kg, belonging to moderately polluted soil.

[0114] The application method of selenium-rich organic fertilizer and soil conditioner is a one-time base application. The application rate of selenium-rich organic fertilizer in Example 2 is calculated according to the formula M≥[BD×L×666.67×(0.6Cd - Se)] / (C×1.27) to be 15.22 g / pot. The application rate of the organic fertilizer without adding cinder powder in Comparative Example 2-1 is the same as that of the selenium-rich organic fertilizer. The application rate of sodium selenite in Comparative Example 2-2 is calculated according to the above formula to be 0.34 mg / pot.

[0115] The dosage of the selenium-rich cadmium-polluted soil passivator required to increase the soil pH from the pre-fertilization pHi to the preset pHt = 6.2 by applying the soil conditioner is Q; when the organic matter content in the soil is not more than 30 g / kg, Q = EXP(1.48×(pHt - 4.5)) - EXP(1.48×(pHi - 4.5)); when the organic matter content in the soil is greater than 30 g / kg, Q = EXP(1.6×(pHt - 4.37)) - EXP(1.6×(pHi - 4.37)). The results calculated according to this formula are: the application rates in medium rice and late rice in the comparative examples and examples are 51.88 g / pot.

[0116] Test Group Three

[0117] The experiment was set with four treatments: conventional fertilization planting (CK), Example 3, Comparative Example 3-1 (foliar fertilizer without the addition of Cinnamomum camphora residue extract), and Comparative Example 3-2 (cadmium-reducing foliar control agent). Each treatment had 3 replicates, for a total of 12 pots. Each pot was filled with 15 kg of soil (dry weight). Conventional fertilization planting was the customary fertilization for growing rice (generally without applying conditioner and foliar fertilizer). In Example 2 and Comparative Example 2-1, a certain amount of foliar fertilizer and foliar fertilizer without the addition of Cinnamomum camphora residue extract were sprayed on the leaves respectively on the basis of conventional fertilization planting. In Comparative Example 2-2, a certain amount of cadmium-reducing foliar control agent was sprayed on the leaves on the basis of conventional fertilization planting. In both the examples and the comparative examples, a certain amount of the conditioner of the present invention was additionally applied on the basis of conventional fertilization planting. The soil was mixed with chemical fertilizers and the conditioner and then filled into pots. After filling the pots, water was added and soaked for about 1 week before transplanting rice. 3 clumps of rice were transplanted into each pot. After the middle-season rice and late-season rice were harvested, soil samples and plant samples were collected to measure indexes such as rice yield, soil available selenium, soil available cadmium, brown rice selenium, and brown rice cadmium content. The relative cadmium reduction rate and relative selenium enrichment rate were calculated through the cadmium and selenium content in brown rice; the soil cadmium passivation rate and soil selenium activation rate were calculated through the soil available cadmium and available selenium content.

[0118] Tested soil type: paddy soil; Basic soil physical and chemical properties: The molar ratio of soil bioavailable selenium to cadmium was 0.9, total cadmium content was 1.14 mg / kg, total selenium content was 0.62 mg / kg, soil bioavailable selenium content was 0.13 mg / kg, soil bioavailable cadmium content was 0.21 mg / kg, soil pH was 5.92, and soil organic matter content was 23.18 g / kg, belonging to moderately polluted soil.

[0119] The foliar fertilizer in Example 3 and the foliar fertilizer without the addition of Cinnamomum camphora residue extract in Comparative Example 3-1 were each sprayed once during the heading and filling stages of rice, and were diluted 150 times each time before spraying. The cadmium-reducing foliar control agent was sprayed after being diluted according to the instructions. The spraying volume was preferably such that the front and back sides of the rice leaves were covered with mist droplets.

[0120] The application method of the soil conditioner was one-time basal application. The dosage of the soil passivator required to increase the soil pH from the pre-fertilization pHi to the preset pHt = 6.2 was Q; when the soil organic matter content was not more than 30 g / kg, Q = EXP(1.48×(pHt - 4.5)) - EXP(1.48×(pHi - 4.5)); when the soil organic matter content was more than 30 g / kg, Q = EXP(1.6×(pHt - 4.37)) - EXP(1.6×(pHi - 4.37)). According to the calculation result of this formula: the application amount of the comparative examples and the examples on the middle-season rice and late-season rice was 19.41 g / pot.

[0121] Experimental Group Four

[0122] The experiment was set up with three treatments: conventional fertilization planting (CK), Example 4, and Comparative Example 4. Each treatment had 3 replicates, for a total of 9 pots. Each pot was filled with 15 kg of soil (dry weight). In conventional fertilization planting, generally no conditioner, organic fertilizer, or foliar fertilizer was applied. In Example 4, a certain amount of selenium-rich organic fertilizer and the soil conditioner of the present invention were additionally applied on the basis of conventional fertilization planting, and the foliar fertilizer of the present invention was sprayed on the leaves. In Comparative Example 4, a certain amount of sodium selenite and Tebet calcium conditioner were additionally applied on the basis of conventional fertilization planting, and the cadmium-reducing leaf surface control agent was sprayed on the leaves. After mixing the soil with chemical fertilizers and test materials, the pots were filled, and after filling, water was irrigated. After soaking for about 1 week, rice was transplanted. 3 clumps of rice were transplanted into each pot. After the middle-season rice and late-season rice were harvested, soil samples and plant samples were collected to measure indexes such as rice yield, soil available selenium, soil available cadmium, brown rice selenium, and brown rice cadmium content. The relative cadmium reduction rate and relative selenium enrichment rate were calculated through the cadmium and selenium content in brown rice; the soil cadmium passivation rate and soil selenium activation rate were calculated through the soil available cadmium and available selenium content.

[0123] Soil type for testing: paddy soil; Basic physical and chemical properties of the soil: The molar ratio of biologically available selenium to cadmium in the soil was 0.41, the total cadmium content in the soil was 1.33 mg / kg, the total selenium content in the soil was 0.76 mg / kg, the biologically available selenium content in the soil was 0.11 mg / kg, the biologically available cadmium content in the soil was 0.37 mg / kg, the soil pH was 4.61, and the soil organic matter content was 48.63 g / kg, belonging to moderately polluted soil.

[0124] The application rate of the selenium-rich organic fertilizer in the examples for middle-season rice and late-season rice was calculated according to the formula M≥[BD×L×666.67×(0.6Cd-Se)] / (C×1.27) to be 65.89 g / pot. The foliar fertilizer in the examples was sprayed once each during the heading stage and filling stage of rice, and was diluted 150 times each time for spraying. The application method of the soil conditioner was one-time basal application. The amount of the selenium-rich cadmium-polluted soil passivator required to increase the soil pH from the pre-fertilization pHi to the preset pHt = 6.2 was Q; when the organic matter content in the soil was not more than 30 g / kg, Q = EXP(1.48×(pHt - 4.5)) - EXP(1.48×(pHi - 4.5)); when the organic matter content in the soil was more than 30 g / kg, Q = EXP(1.6×(pHt - 4.37)) - EXP(1.6×(pHi - 4.37)). According to the calculation result of this formula, the application rate for middle-season rice and late-season rice was 72.45 g / pot.

[0125] In the comparative example, the application rate of sodium selenite on middle-season rice and late rice was calculated according to the above formula as 1.45 mg / pot; the application method of the soil conditioner was a one-time base application, and the dosage of the Tebai calcium soil conditioner required to increase the soil pH from the pre-fertilization pHi to the preset pHt = 6.2 was Q; when the organic matter content in the soil was not more than 30 g / kg,

[0126] Q = EXP(1.387×(pHt - 5.154)) - EXP(1.387×(pHi - 5.154)); when the organic matter content in the soil was more than 30 g / kg, Q = EXP(1.2×(pHt - 4.658)) - EXP(1.2×(pHi - 4.658)). According to this formula, the application rate on middle-season rice and late rice was calculated as 36.12 g / pot; in Comparative Example 4, the cadmium-reducing foliar control agent was diluted according to the instructions and sprayed. The spraying volume should be appropriate to make the front and back sides of the rice leaves fully covered with mist droplets.

[0127] After the rice in each experimental treatment matured, the rice yield was measured. As can be seen from Table 1, Experimental Group 1: Compared with the conventional fertilization planting treatment (CK1), Example 1 showed significant yield increases on middle-season rice and late rice, with the increase rates being 12.79% and 8.45% respectively; compared with Comparative Example 1, Example 1 also showed a yield increase trend on middle-season rice and late rice, with the increase rates being 6.14% and 3.56% respectively, indicating that the conditioner of the present invention has a significant yield increase effect compared with the Tebai calcium soil conditioner.

[0128] Experimental Group 2: Compared with the conventional fertilization planting (CK2) treatment, both the examples and the comparative examples showed a yield increase trend. Compared with Comparative Example 2-1, the yield increase effect of Example 2 on middle-season rice and late rice was not obvious, indicating that whether cinder powder was added to the selenium-rich organic fertilizer had little effect on the rice yield. Compared with Comparative Example 2-2, Example 2 increased the yield by 2.89% and 4.84% on middle-season rice and late rice respectively, indicating that the selenium-rich organic fertilizer showed a certain yield increase effect due to its ability to improve soil fertility.

[0129] Experimental Group 3: Compared with the conventional fertilization planting (CK3) treatment, Example 3, Comparative Example 3-1, and Comparative Example 3-2 all showed significant yield increases on middle-season rice and late rice, indicating that applying a soil conditioner while spraying a foliar fertilizer can effectively increase the rice yield. Compared with Comparative Example 3-1 and Comparative Example 3-2, the yield increase effect of Example 3 on middle-season rice and late rice was not obvious, indicating that: (1) whether the extract of Cinnamomum camphora residues was added to the foliar fertilizer of the present invention had little effect on the rice yield; (2) the foliar fertilizer of the present invention had a limited yield increase effect compared with the cadmium-reducing foliar control agent sold on the market.

[0130] Experimental Group 4: Compared with the conventional fertilization planting (CK4) treatment, Example 4 showed significant yield increases in both middle-season rice and late-season rice, with the yield increase rates reaching 10.91% and 11.3% respectively; compared with Comparative Example 4, the yield increase rates of Example 4 in middle-season rice and late-season rice reached 8.39% and 7.81% respectively. This shows that the selenium-rich cadmium-blocking method of the present invention can significantly increase the rice yield compared with the conventional fertilization planting method and the cadmium-blocking and selenium-rich products sold on the market.

[0131] Table 1 Effects of Selenium-Rich Cadmium-Reducing Methods on Rice Yield

[0132]

[0133]

[0134] Note: When A ≤ 0.6 and B ≥ 0.8 mg / kg, apply selenium-rich organic fertilizer and spray foliar fertilizer; when A ≤ 0.6 and B < 0.8 mg / kg, apply selenium-rich organic fertilizer; when A > 0.6 and B ≥ 0.8 mg / kg, spray foliar fertilizer; when A > 0.6 and B < 0.8 mg / kg, neither apply selenium-rich organic fertilizer nor spray foliar fertilizer. The same applies hereinafter.

[0135] After the rice matured, the cadmium and selenium contents in the brown rice of each treatment were measured, and the relative cadmium-reduction rate and relative selenium-enrichment rate of each treatment were investigated. The calculation results are shown in Table 3. In Experimental Group 1, compared with Comparative Example 1, Example 1 showed obvious cadmium-reduction effects in middle-season rice and late-season rice, and the relative cadmium-reduction rates increased by about 23.88 and 22.92 percentage points respectively. Further measurement of the available cadmium content in the soil showed that (see Table 3), Example 1 significantly reduced the available cadmium content in the soil and increased the soil cadmium passivation rate, with the increase reaching about 20 percentage points. This is the main reason for reducing cadmium in rice. Example 1 can not only effectively reduce cadmium, but also significantly enrich selenium. The relative selenium-enrichment rate increased by about 15 percentage points in middle-season rice and late-season rice. The reason is that Example 1 mainly achieved the goal of selenium enrichment in rice by increasing the available selenium content in the soil and improving the selenium activation rate. This shows that the soil conditioner of the present invention has a significantly better effect on reducing cadmium and enriching selenium in selenium-rich cadmium-exceeding soil than the Tebet calcium conditioner.

[0136] Experimental Group 2. Compared with Comparative Example 2-1, Example 2 showed obvious cadmium reduction effects on middle-season rice and late rice, and the cadmium reduction rates increased by 17.44 and 22.53 percentage points respectively. The reason is that Example mainly achieved the cadmium reduction of brown rice by reducing the available cadmium content in the soil and increasing the cadmium passivation rate of the soil. While reducing cadmium, Example 2 showed obvious selenium enrichment effects, and the selenium enrichment rates increased by 24.07 and 26.09 percentage points respectively. The research on soil available selenium shows (see Table 3) that Example 2 mainly achieved the selenium enrichment effect of rice by increasing the available selenium content and selenium activation rate of the soil, indicating that adding a certain amount of cinder powder to the selenium-enriched organic fertilizer can not only effectively promote the conversion of organic selenium to available selenium in the selenium-enriched organic fertilizer, increase the duration of available selenium in the soil, but also enhance the passivation effect of soil available cadmium and effectively reduce the cadmium content in rice. Compared with Comparative Example 2-2, Example 2 had a relatively greater cadmium reduction range on middle-season rice and late rice, and the cadmium reduction rates increased by 26.74 and 30.99 percentage points respectively; the selenium enrichment effect was relatively better, and the selenium enrichment rates increased by 33.33 and 36.96 percentage points respectively. Thus, it shows that the cadmium reduction and selenium enrichment effects of the selenium-enriched organic fertilizer of the present invention are significantly better than those of sodium selenite, mainly because the selenium-enriched organic fertilizer of the present invention can effectively increase the molar ratio of available selenium to cadmium in the soil, and then effectively passivate the available cadmium in the soil under the action of the soil conditioner of the present invention, while activating the soil selenium.

[0137] Experimental Group 3. Compared with Comparative Example 3-1, the cadmium content in the brown rice of middle-season rice and late rice in Example 3 decreased significantly, and the relative cadmium reduction rates increased by 20.43 and 28.41 percentage points respectively; Example 3 showed a significant selenium enrichment effect, and the relative selenium enrichment rates increased by 25 and 20.41 percentage points respectively on middle-season rice and late rice. Thus, it shows that adding the extract of Cinnamomum camphora residue to the foliar fertilizer of the present invention can effectively reduce the cadmium content in brown rice and increase the selenium content by significantly promoting the absorption of Si and Se by the leaves. Compared with Comparative Example 3-2, the cadmium reduction and selenium enrichment effects of Example 3 on middle-season rice and late rice were relatively more obvious, among which the relative cadmium reduction rates increased by 12.91 and 20.45 percentage points respectively; the relative selenium enrichment rate increased by about 41 percentage points. Thus, it can be seen that the cadmium reduction and selenium enrichment effects of the foliar fertilizer of the present invention are significantly better than those of the marketed cadmium-reducing foliar inhibitor.

[0138] Experimental group 4, compared with Comparative Example 4, Example 4 significantly reduced the cadmium content in the brown rice of mid-season rice and late-season rice. The relative cadmium reduction rates increased by 31.79 and 29.88 percentage points respectively, because the soil cadmium passivation rates increased by 23.68 and 31.71 percentage points respectively (see Table 3). While achieving cadmium reduction, Example 4 showed an obvious selenium enrichment effect. Compared with Comparative Example 4, the relative selenium enrichment rates of mid-season rice and late-season rice increased by 40.3 and 50 percentage points respectively, mainly due to the increase in soil selenium activation rates by 15.79 and 19.74 percentage points. According to the provisions of "Selenium-enriched Paddy Rice" (GB / T 22499-2008), the selenium content of rice processed from selenium-enriched paddy rice should be 0.04 - 0.30 mg / kg. After the application of the present invention to rice, the cadmium content in the brown rice was reduced to less than 0.2, and the selenium content in the brown rice reached 0.09 mg / kg, meeting the standard of selenium-enriched rice and achieving the goal of selenium enrichment and green and safe production of rice in cadmium-polluted soil in selenium-rich areas.

[0139] Table 2 Effects of selenium-enriched cadmium reduction methods on cadmium, selenium contents, cadmium reduction rate and selenium enrichment rate of rice

[0140]

[0141]

[0142] Note: Relative cadmium reduction rate (RE) = (1 - C T / C CK ) × 100%, where: C T is the cadmium content in the brown rice of the passivator treatment area, C CK is the cadmium content in the brown rice of the control area (without applying the passivator); Relative selenium enrichment rate (SEE) = (S T / S CK - 1) × 100%, where: S T is the selenium content in the brown rice of the treatment area, S CK is the selenium content in the brown rice of the control area.

[0143] Table 3 Effects of selenium-enriched cadmium reduction methods on available cadmium, selenium contents, cadmium passivation rate and selenium activation rate of soil

[0144]

[0145] Note: 1) The cadmium passivation rate (IE) of heavy metal cadmium in the soil in the table = (1 - C T / C CK ) × 100%, where: C T is the available cadmium content (DTPA extractable state) of soil cadmium in the passivator treatment area, C CKTo repair the available cadmium content (DTPA-extractable state) in the soil of the control area; soil selenium activation rate (AE) = available selenium content in soil / total selenium content in soil × 100%. 2) For the available selenium and cadmium in the soil in the table, the AB-DTPA method is used for determination in the present invention. Under the condition of 25 °C, weigh 5 g of pretreated soil, then add 20 mL of 0.5 M NH4HCO3 and 0.005 M diethylenetriaminepentaacetic acid (DTPA), and shake on a constant temperature shaker for 2 h. After centrifuging at 3000 rpm for 20 min, take the supernatant to measure the selenium and cadmium contents as the bioavailable components in the soil.

[0146] As mentioned above, it is only the preferred embodiment of the present invention. The present invention is not limited to the above-mentioned implementation manners. As long as it achieves the technical effects of the present invention by the same means, it should fall within the protection scope of the present invention. Within the protection scope of the present invention, various different modifications and changes can be made to its technical solutions and / or implementation manners.

Claims

1. A selenium-rich cadmium-reducing method for selenium-rich cadmium-polluted soil, characterized in that, It includes the following steps: Before planting crops in selenium- and cadmium-polluted soil, determine the molar ratio A of bioavailable selenium to cadmium and the total cadmium content B in the selenium- and cadmium-polluted soil; during the process of planting crops, apply a soil conditioner to adjust the soil pH to above 6.2 and the irrigation water pH to above 7.0, and at the same time judge whether to apply selenium-rich organic fertilizer and spray foliar fertilizer during the process of planting crops according to the values of A and B; The specific judgment conditions are as follows: when A ≤ 0.6 and B ≥ 0.8 mg / kg, apply selenium-rich organic fertilizer and spray foliar fertilizer; when A ≤ 0.6 and B < 0.8 mg / kg, apply selenium-rich organic fertilizer; when A > 0.6 and B ≥ 0.8 mg / kg, spray foliar fertilizer; when A > 0.6 and B < 0.8 mg / kg, neither apply selenium-rich organic fertilizer nor spray foliar fertilizer; The raw materials of the selenium-rich organic fertilizer include, by weight: 20-50 parts of activated selenium ore powder, 30-70 parts of selenium-rich organic material, 10-25 parts of cinder powder, and 2-10 parts of binder; the particle size of the cinder powder is 0.01 mm - 0.15 mm; The foliar fertilizer is prepared by the following process: dissolve the extract of Cinnamomum camphora residue, EDTA chelated zinc, and sodium selenite in an acidic silica sol solution, and then add a spreading agent and mix evenly to obtain the foliar fertilizer; the ratio of the extract of Cinnamomum camphora residue, EDTA chelated zinc, sodium selenite, acidic silica sol, and spreading agent is (3 mL - 10 mL): (40 g - 90 g): (4 g - 10 g): 1L: (1 mL - 3 mL); in the acidic silica sol solution, the SiO2 content is greater than 25% and the pH is less than 3.

5.

2. The selenium-enriched cadmium-reducing method according to claim 1, wherein The raw materials of the soil conditioner include, by weight: 50 parts - 70 parts of lime materials, 15 parts - 40 parts of nitro humic acid calcium and magnesium, and 30 parts - 50 parts of calcium magnesium phosphate fertilizer; the lime materials are at least one of limestone powder, dolomite powder, and oyster powder.

3. The selenium-rich cadmium reduction method according to claim 2, characterized in that, The application method of the soil conditioner is one-time basal application, and the dosage Q of the soil conditioner required to raise the soil pH from pHi to pHt is as follows: when the organic matter content in the soil is not greater than 30 g / kg, Q = EXP(1.52×(pHt - 4.8)) - EXP(1.52×(pHi - 4.8)); when the organic matter content in the soil is greater than 30 g / kg, Q = EXP(1.39×(pHt - 4.4)) - EXP(1.39×(pHi - 4.4)).

4. The selenium-rich cadmium reduction method according to claim 1, characterized in that, The selenium-rich organic material is prepared by the following process: mix the crushed selenium-rich straw, selenium-rich livestock and poultry manure, and urea as a premix, and the C:N in the premix is 20 - 30:1; then spray the bacterial liquid onto the premix, control the water content in the premix to be 30% - 50%, and after fermentation for 3 - 4 weeks, obtain the selenium-rich organic material with a total selenium content ≥ 2 mg / kg; the bacterial liquid is obtained by dissolving brown sugar and adding EM bacterial original liquid; the mass ratio of the premix, EM bacterial original liquid, and brown sugar is 500 - 1000:1:

1.

5. The selenium-rich cadmium reduction method according to claim 1, characterized in that, The selenium-rich organic fertilizer is obtained by granulating the raw materials after mixing them evenly under the action of a binder.

6. The selenium-rich cadmium reduction method according to claim 1, characterized in that, The per-acre application rate of the selenium-rich organic fertilizer is calculated by the following formula: M ≥ [BD × L × 666.67 × (0.6 × Cd - Se)] / (C × 1.27); M is the per-acre application rate, in kg, BD is the soil bulk density measured before planting the selenium-rich cadmium-polluted crops, in g / cm 3 , L is the soil layer thickness measured before planting the selenium-rich cadmium-polluted crops, in cm, Cd is the bioavailable cadmium content in the soil measured before planting the selenium-rich cadmium-polluted crops, in μmol / kg, Se is the bioavailable selenium content in the soil measured before planting the selenium-rich cadmium-polluted crops, in μmol / kg, and C is the total selenium content in the selenium-rich organic fertilizer, in mg / kg.

7. The selenium-rich cadmium reduction method according to claim 4, characterized in that, The original EM bacteria solution is a composite bacteria agent original solution composed of Lactobacillus delbrueckii, Streptococcus lactis, and Rhodopseudomonas palustris.

8. The selenium-rich cadmium reduction method according to claim 1, characterized in that, The extract of Cinnamomum camphora residue is prepared by the following process: mixing the Cinnamomum camphora residue with a mixed solvent of ethanol and water at a ratio of 1 g:(5 mL - 10 mL), and carrying out microwave (microwave power: 200 W - 300 W) - ultrasound (ultrasound power: 400 W - 600 W) for 5 min - 20 min under the condition of 20 °C - 50 °C, and after filtration, the filtrate is distilled under reduced pressure to obtain the extract of Cinnamomum camphora residue.

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