Method for repairing cadmium contaminated soil based on intercropping pepper and corn planting mode

Abstract

The present application relates to the technical field of cadmium contaminated soil remediation, and particularly relates to a method for remediation of cadmium contaminated soil based on a pepper intercropping corn planting mode; in the southern acidic soil, a Cd accumulation coefficient high pepper is first planted, and then a Cd accumulation coefficient low corn is intercropped, a double film covering measure is matched, crop root development is promoted, the difference in Cd accumulation of the roots and the competition relationship are utilized to amplify the hyperaccumulation of Cd by the pepper roots, so that the total Cd amount in the corn rhizosphere soil and the Cd absorption by the corn roots are reduced; then, 100 mg / L nano selenium is sprayed at the pepper budding stage and the corn jointing stage to further control the Cd absorption by the pepper and the corn kernels; meanwhile, the Cd contaminated soil is remediated by combining fertilization management during the whole growth period, and the method is green, high-yield, high-efficiency and sustainable.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of cadmium contaminated soil remediation, and particularly relates to a method for remediation of cadmium contaminated soil based on a pepper intercropping corn planting mode. BACKGROUND

[0002] At present, the methods for remediation of farmland soil Cd mainly include: (1) physical method: including soil stripping, covering, composting and the like. Soil stripping and covering can reduce the Cd content in soil by stripping the contaminated surface soil and covering clean soil, and the method is simple in operation, low in cost, and suitable for shallowly contaminated soil, but a large amount of soil covering material is needed, the cost is high, and the remediation effect is not thorough enough. Composting is to apply the composted organic fertilizer into the contaminated soil, mix with the soil, promote the increase of soil organic matter content, fix Cd in the organic matter, and reduce the biological availability of Cd. The composting treatment is environmentally friendly, does not introduce additional chemicals or pollutants; increases soil organic matter, improves soil structure and permeability; and has a long remediation period, high remediation cost and limited remediation effect. The physical method is greatly affected by soil properties and environmental conditions, and may damage the soil structure and affect the soil function, and is suitable for small-area and slightly contaminated soil remediation.

[0003] (2) Chemical remediation: adding soil conditioner to change the chemical form of soil Cd. For example, adding iron phosphate reducing agent to convert Cd in soil into insoluble or inactive state, so as to reduce the biological availability of Cd. The method can quickly reduce the biological availability of Cd in soil, and has obvious remediation effect. However, it may cause changes in soil pH value, affect the soil environment, and needs to add reducing agent repeatedly to maintain the remediation effect, and the cost is high.

[0004] (3) Phytoremediation: Phytoremediation is a new environmental pollution control method, which plants plants with Cd absorption and enrichment capacity (such as bracken fern, soybean, dogtail grass and the like) in contaminated soil, absorbs and accumulates Cd in soil through the root system of the plants, so as to reduce the content of Cd in soil. The method is environmentally friendly, can remediate soil pollution and protect the ecological system at the same time, is simple in operation and low in cost. However, it needs to stop farming, and the period is long.

[0005] Therefore, for the farmland with medium and light pollution, a kind of in-situ, clean, convenient, low-cost and sustainable repair method is needed, and the plant repair coupled with conditioner repair is an ideal repair method. Based on the theory of plant repair, two crops with different Cd enrichment abilities are interplanted. First, the hyperaccumulating crop (pepper) is planted to absorb part of Cd through the root system, and then the crop with low Cd enrichment coefficient (corn) is planted. Through the amplification of the root system of the hyperaccumulating crop (pepper) to the adsorption and competition of Cd, the accumulation of Cd in the rhizosphere soil and the root system of the low enrichment crop is finally reduced. In addition, the blocking agent is sprayed at a certain key growth stage to reduce the accumulation of Cd in the fruit of the crop, so as to achieve the effect of high yield and repair, which not only guarantees food safety, but also reduces the content of Cd in the soil. This is a green, low-cost, easy-to-operate, sustainable and safe effective way. SUMMARY

[0006] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a method for repairing cadmium-contaminated soil based on the interplanting mode of pepper and corn, which not only guarantees food safety, but also reduces the content of Cd in the soil,

[0007] The technical problem of the present application is solved by adopting the following technical scheme:

[0008] A method for repairing cadmium-contaminated soil based on the interplanting mode of pepper and corn, comprising the following steps:

[0009] S1. In the cadmium-contaminated south acidic dry land soil, the pepper with high cadmium enrichment coefficient and the corn with low cadmium enrichment coefficient are planted in the order of first planting pepper and then interplanting corn;

[0010] S2. The pepper is plug seedling in mid-to-late February, and is transplanted in mid-to-late April. The transplanted water is sufficient, and the field water holding capacity is 60%-80%. The row spacing of the pepper is 1.3 m, the plant spacing is 0.33 m, and the double-plant ridge planting is adopted. The corn is sown in mid-to-late May, the air temperature is kept above 12℃, the soil temperature is kept above 10℃, the field water holding capacity is between 60%-70%, the sowing depth is 4-5 cm, the corn is planted in wide and narrow rows, the large row spacing is 0.8 m, the small row spacing is 0.5 m, and the plant spacing is 0.25 m. The interplanted corn has a large row spacing of 0.8 m, a small row spacing of 0.5 m, and a plant spacing of 1 m;

[0011] S3. Nano-selenium with a particle size of ≤60 nm is sprayed at 100 mg / L at the pepper budding stage and the corn jointing stage;

[0012] S4. The fresh pepper is harvested in batches according to the ripening condition from June to September, the dried pepper is harvested from mid-to-late September to mid-to-late October, and the corn is harvested in mid-October;

[0013] S5, the second year of planting, the planting position of pepper and corn is transposed, and the content of cadmium in the soil is gradually and balancedly reduced.

[0014] Preferably, the variety of pepper is Xinhonghai with high cadmium enrichment coefficient and high yield, and the variety of corn is Quchen No.

[0015] Preferably, the pepper and corn are covered with mulch before planting, and 5-6 kg of film per mu is used.

[0016] Preferably, the preparation method of the nano selenium particles comprises the following steps:

[0017] A1, dissolving a selenium compound in water or an organic solvent to form a selenium compound solution;

[0018] A2, dissolving a precipitant in the selenium compound solution to form a precipitation reaction with selenium in the solution, the reaction temperature is 70°C, and the PH value is <8;

[0019] A3, centrifuging, filtering and separating the formed selenium precipitate at 3000-60000 r / min, washing with pure water or ethanol, freeze-drying, and grinding to obtain nano selenium particles.

[0020] Preferably, the selenium compound includes but is not limited to sodium selenate and ferrous selenate, the organic solvent includes but is not limited to ethanol and acetone, and the precipitant includes but is not limited to hydrogen sulfide, sodium hydroxide and sodium thiosulfate.

[0021] Preferably, the fertilization and field management method of pepper intercropped with corn comprises the following steps:

[0022] B1, base fertilizer: 30000 kg / hm of farmyard manure is applied in the pepper pond 2 , 1200 kg / hm of compound fertilizer 2 , 750 kg / hm of common calcium 2 , 4000 kg / hm of farmyard manure is applied in the corn pond 2 , 150 kg / hm of compound fertilizer 2 , 150 kg / hm of common calcium 2 ;

[0023] B2, topdressing: 150 kg / hm of high-potassium water-soluble fertilizer is applied at the present budding stage and fruiting stage of pepper 2 , and 75 kg / hm of urea is applied at the jointing stage of corn 2 ;

[0024] B3, field management is carried out in the single cropping mode, timely watering, removing weeds, selecting low-toxicity and low-residue pesticides for disease and pest control, and corn focuses on the prevention and control of Spodoptera exigua, corn borer and armyworm, and pepper mainly prevents and controls brown spot, black spot, powdery mildew, mole cricket, aphid and tobacco budworm.

[0025] The advantages and positive effects of the present application are:

[0026] 1、The present application makes full use of the coupling of agricultural measures and control agents, and combines with crop characteristics, to promote the growth of corn and pepper, reduce the content of Cd in medium and light Cd contaminated soil, promote the enrichment of Cd in high Cd-enriched pepper roots, and reduce the accumulation of Cd in low Cd-enriched corn roots. Meanwhile, the fruits of pepper and corn are high-yield and the Cd content meets the safety index, realizing an environment-friendly, high-value, sustainable and safe remediation method, effectively solving the problem of acid soil improvement and high-value utilization in the south.

[0027] 2、The present application plants pepper and corn by double film mulching, and couples with spraying of nano selenium, combined with fertilization management, which is convenient to manage and operate without complicated technology, greatly reduces the occurrence of diseases, pests and weeds, has low cost, is easy to be accepted by farmers and can be widely replicated and promoted, especially in the south of China.

[0028] 3、The present application uses two crops with large difference in Cd enrichment to plant by interplanting, in the south of China (Yunnan, Guizhou, Sichuan, Guangxi, Hunan, Guangzhou, etc. pH≤6.7 soil) Cd contaminated (total Cd content≤2mg / kg) soil, by interplanting Cd-enriched pepper with high Cd enrichment coefficient first and then interplanting Cd-enriched corn with low Cd enrichment coefficient, combined with double film mulching measures, to promote the development of crop roots, use the difference in Cd accumulation and competition relationship to amplify the hyperaccumulation of Cd by pepper roots, thereby reducing the total Cd content in the rhizosphere soil of corn and the absorption of Cd by corn roots; then spraying 100mg / L nano selenium at the pepper budding stage and the corn jointing stage to further control the absorption of Cd by pepper and corn seeds; at the same time, combining with fertilization management during the whole growth period to remediate Cd contaminated soil, which is green, high-yield, efficient and sustainable.

[0029] 4、The planting mode adopted in the present application is pepper interplanting corn: by interplanting Cd-enriched and high-yield "Xin Honghai" pepper first, allowing the pepper roots to enrich a part of Cd, and then interplanting Cd-enriched and high-yield "Qu Chen 11" corn, due to the competition effect of the roots, the absorption of Cd by the pepper roots is further amplified, the Cd content in the rhizosphere soil and roots of corn is reduced, double film mulching mode is adopted to inhibit weeds and diseases, promote root development, and strengthen the adsorption competition effect of the roots of the two crops to Cd.

[0030] 5、The present application further controls the absorption of Cd in the grains of peppers and corn by spraying 100mg / L nano (particle size ≤60nm) selenium at the present budding stage of peppers and the jointing stage of corn: As a selenium source, nano-selenium can be rapidly absorbed by plants when sprayed on the leaves, and can inhibit the absorption and transport of Cd in plants, thereby reducing the accumulation of Cd in plants; Nano-selenium can react with Cd in plants to form water-insoluble selenide precipitates or selenium compounds, thereby converting Cd into a poorly soluble form, reducing the solubility and biological activity of Cd in plants, and reducing its toxic effects on plants; Nano-selenium also participates in antioxidant reactions in plants, promotes the activity of antioxidant enzymes in plants, enhances the adaptability of plants to environmental stress, reduces the degree of Cd toxicity to plants, and reduces the damage of Cd to plants; Spraying nano-selenium on the leaves can also improve the soil environment, increase the soil pH, reduce the activity of Cd, and reduce the solubility and bioavailability of Cd in the soil, thereby reducing the migration and accumulation of Cd in plants. At the same time, the nano-selenium of the present application is simple to make: dissolve selenium compounds (such as sodium selenate, ferrous selenite, etc.) in water or organic solvents (such as ethanol, acetone, etc.) to form a solution of selenium compounds; Dissolve an appropriate amount of precipitant (such as hydrogen sulfide sodium hydroxide, sodium thiosulfate) in the selenium compound solution to form a precipitation reaction, and form under the conditions of a reaction temperature of 70℃ and a pH value of >8; The formed selenium precipitate is separated by centrifugation at 3000-60000r / min, and is washed with pure water or ethanol; The separated and washed selenium precipitate is freeze-dried and ground to obtain nano-selenium particles. The cost is low, and the yield of single plant is also promoted, without increasing the cost of repair.

[0031] 6、The nano-selenium used in the present application has high efficiency: The particle size of nano-selenium particles ≤60nm and high specific surface area make it easier to contact with crop leaves, improving the absorption and utilization rate of selenium elements; High permeability: Nano-selenium particles with a size of ≤60nm can better penetrate into the interior of crop tissues, improving the absorption and transport rate of selenium elements in crops; Uniformity: Uniform particle size, fast dissolution rate, and more uniform distribution in leaf tissues improve the stability of application effect; Environmental protection: Nano-selenium fertilizer has less impact on soil and environment, reducing the pollution risk of soil, and being beneficial to the protection of soil ecological environment; Strong controllability: The selenium fertilizer prepared by nano-technology can realize precise control of the release rate and amount of selenium elements, which helps to meet the demand of two crops for selenium elements.

[0032] 7、The fertilizer management of the present application adopts base fertilizer + topdressing fertilizer mode, which belongs to the conventional fertilizer management mode of peppers and corn, without additional management measures, but the fertilizer amount is appropriately adjusted: Base fertilizer: 30000kg / hm 2 of farmyard manure for peppers, 1200kg / hm 2 of compound fertilizer, and 750kg / hm 2, corn pond to apply 4000 kg / hm 2 , compound fertilizer 150 kg / hm 2 , common calcium 150 kg / hm 2 . Topdressing: Peppers present bud period, fruiting period, respectively, high potassium water soluble fertilizer 150 kg / hm 2 , corn period of jointing period of urea 75 kg / hm 2 . Can ensure the high yield and stable yield of two crops, greatly promote the competition of root system to Cd.

[0033] 8, the repair method of the application combines two conventional methods that are easy for farmers to accept, and the repair effect is good, which greatly promotes the absorption of high Cd accumulation pepper root system to Cd and inhibits the absorption of low Cd accumulation corn root system to Cd. Spraying 100 mg / L of selenium blocking agent with particle size ≤60 nanometers in the key growth period (pepper bud period, corn jointing period) can not only ensure food safety, but also be widely used in the repair of farmland soil contaminated by cadmium. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The figure shows the content of cadmium in the seeds of crops after coupling nano-selenium to repair cadmium-contaminated soil by pepper intercropping corn planting.

[0035] Figure 2 The figure shows the content of cadmium in the rhizosphere soil of different treatment groups after coupling nano-selenium to repair cadmium-contaminated soil by pepper intercropping corn planting in Yunnan dry land red soil field.

[0036] Figure 3 The figure shows the content of cadmium in the rhizosphere soil of different treatment groups after coupling nano-selenium to repair cadmium-contaminated soil by pepper intercropping corn planting in Yunnan dry land red soil field.

[0037] Figure 4 The figure shows the content of cadmium in the rhizosphere soil of different treatment groups after coupling nano-selenium to repair cadmium-contaminated soil by pepper intercropping corn planting in Yunnan dry land red soil field.

[0038] Figure 5 The figure shows the content of cadmium in the rhizosphere soil of different treatment groups after coupling nano-selenium to repair cadmium-contaminated soil by pepper intercropping corn planting in Yunnan dry land red soil field.

[0039] Figure 6 The figure shows the content of cadmium in the rhizosphere soil of different treatment groups after coupling nano-selenium to repair cadmium-contaminated soil by pepper intercropping corn planting in Yunnan dry land red soil field. DETAILED DESCRIPTION

[0040] The application will be further described in detail below by specific examples, which are only descriptive and not limiting, and cannot limit the protection scope of the application.

[0041] In the slightly polluted cadmium southern acid dry land soil, the content of Cd in the soil is less than or equal to 2 mg / kg, the southern acid dry land red soil refers to the soil with pH less than or equal to 6.7 in Yunnan, Guizhou, Sichuan, Guangxi, Hunan and Guangzhou, etc., the pepper (with high Cd enrichment coefficient) and the corn (with low Cd enrichment coefficient) with large difference in Cd enrichment coefficient are planted in the mode of double film covering by interplanting.

[0042] A method for repairing cadmium contaminated soil based on a pepper interplanting corn planting mode, comprising the following steps:

[0043] S1, in the slightly polluted cadmium southern acid dry land soil, the pepper with high Cd enrichment coefficient and the corn with low Cd enrichment coefficient are planted in the mode of first planting the pepper and then interplanting the corn;

[0044] S2, the pepper is plug seedling in the middle and late February, and is transplanted in the middle and late April, the transplanted pepper needs to be watered with enough root fixing water, the field water holding capacity is 60%-80%, the row spacing of the pepper is 1.3 m, the plant spacing is 0.33 m, and the double plants are planted by ridging; the corn is sowed in the middle and late May, the air temperature is kept above 12℃, the ground temperature is kept above 10℃, the field water holding capacity is between 60%-70% during sowing, the sowing depth is 4-5 cm, the corn is planted by wide and narrow row ridging, the large row spacing is 0.8 m, the small row spacing is 0.5 m, and the plant spacing is 0.25 m; the interplanting corn has the large row spacing of 0.8 m, the small row spacing of 0.5 m, and the plant spacing of 1 m;

[0045] S3, 100 mg / L nano selenium is sprayed at the pepper budding stage and the corn jointing stage, the particle size of the nano selenium particles is less than or equal to 60 nm;

[0046] S4, the fresh pepper is harvested in batches according to the ripening condition from June to September, the dried pepper is harvested from the middle and late September to the middle and late October, and the corn is harvested in the middle of October;

[0047] S5, the planting positions of the pepper and the corn are exchanged in the second year.

[0048] Example 1

[0049] A method for repairing cadmium contaminated soil based on a pepper interplanting corn planting mode, comprising the following steps:

[0050] 1, pepper interplanting corn double film covering planting:

[0051] Peppers, corn need to cover the film, each mu film 5-6 kg, according to the planting plan in advance with film planting machine; pepper hole tray seedlings in mid-February, in mid-April, transplanting, watering enough to follow the water, field water holding capacity to maintain 60%-80%; pepper row spacing is 1.3 m, plant spacing is 0.33 m, double row ridge planting; corn in mid-May sowing, air temperature stable at 12°C above, the ground temperature stable at 10°C above, field water holding capacity between 60%-70% when sowing, sowing depth of 4-5 cm, corn with wide and narrow row ridge planting, large row spacing is 0.8 m, small row spacing is 0.5 m, plant spacing is 1 m.

[0052] 2, pepper intercropping corn fertilization management:

[0053] Base fertilizer: pepper pond manure 30000kg / hm 2 , compound fertilizer 1200kg / hm 2 , general calcium 750kg / hm 2 ; corn pond manure 4000kg / hm 2 , compound fertilizer 150kg / hm 2 , general calcium 150kg / hm 2 .

[0054] Fertilizer: pepper present budding period, fruiting period, respectively, high potassium water soluble fertilizer 150kg / hm 2 , corn period of urea 75kg / hm 2 .

[0055] 3, nano selenium particles preparation (particle size ≤ 60nm):

[0056] Dissolve 10g selenium compounds (such as sodium selenate, ferrous selenite, etc.) in 1L water or organic solvent (such as ethanol, acetone, etc.), forming a solution of selenium compounds; 20mL of precipitant-hydrogen sulfide sodium hydroxide is dissolved in the selenium compound solution to form a precipitation reaction, the reaction temperature is 70℃, pH>8; the selenium precipitate is separated by centrifugation at 3000-60000r / min, filtration, and washed with pure water or ethanol; the separated and washed selenium precipitate is freeze-dried at-60℃, and ground into nano selenium particles with a particle size of ≤60nm.

[0057] 4, nano selenium spraying:

[0058] Pepper present budding period, corn jointing period, spray 100mg / L nano selenium, according to the amount of 15L / mu pepper, corn leaf. At the same time, set up no nano selenium as control.

[0059] Field management is carried out in a single mode, timely watering, removing weeds, selecting low-toxicity and low-residue pesticides for disease and pest control, corn focuses on the prevention and control of Spodoptera litura, corn borer, armyworm and the like, and pepper mainly prevents and controls brown spot, black spot, powdery mildew, mole cricket, aphid, tobacco greenworm and the like.

[0060] 5. Harvesting:

[0061] Fresh peppers are picked in batches according to the ripening condition from June to September, dried peppers are picked from the middle and late September to the middle of October, and corn is picked in the middle of October.

[0062] From Figure 1 It can be seen that spraying 100mg / L nano-selenium at the present budding stage of pepper and the jointing stage of corn can control the migration of Cd in the root system to the grain.

[0063] Example 2

[0064] The pepper selected in the application is a high-yield variety 'Xin Honghai' with a high Cd enrichment coefficient, and the corn is a high-yield variety 'Qu Chen 11' with a low Cd enrichment coefficient. The test soil is a red soil in a dry land in Yunnan, the Cd content in the soil is 0.56mg / kg, and the pH is 6.2. A same land block of 10m*9m is divided into 3 parts of 10m*3m, which are marked as corn monoculture, pepper monoculture and pepper intercropping corn respectively.

[0065] A method for repairing cadmium contaminated soil based on a pepper intercropping corn planting mode, comprising the following steps:

[0066] 1. Planting method:

[0067] Pepper is plug seedling in the middle and late February, and is transplanted in the middle and late April, and after transplanting, sufficient rooting water is needed, and the field water holding capacity is 60%-80%; corn is sown in the middle and late May, and is sown when the air temperature is stable at above 12℃, the ground temperature is stable at above 10℃, and the field water holding capacity is between 60-70%, and the sowing depth is 4-5cm; the row spacing of pepper is 1.3m, the plant spacing is 0.33m, and double-plant ridge planting is adopted; corn is wide and narrow row ridge planting, the large behavior of monoculture is 0.8m, the small behavior is 0.5m, and the plant spacing is 0.25m; the large behavior of intercropping corn is 0.8m, the small behavior is 0.5m, and the plant spacing is 1m; both pepper and corn adopt mulching, and 5-6kg of mulching film is used per mu.

[0068] 2. Nano-selenium spraying:

[0069] 100mg / L nano-selenium is sprayed at the present budding stage of pepper and the jointing stage of corn, and 1L / mu of the nano-selenium is sprayed on the leaves of pepper and corn.

[0070] 3. Fertilization method:

[0071] (1) Single pepper fertilization method: Single pepper fertilization method: Pepper base fertilizer needs to apply farmyard manure 30000kg / hm 2 , compound fertilizer 1200kg / hm 2 , common calcium 750kg / hm 2 ; Present bud stage, fruiting stage, respectively, high potassium water soluble fertilizer 150kg / hm 2 .

[0072] (2) Single corn fertilization method:

[0073] Corn base fertilizer needs to apply farmyard manure 20000kg / hm 2 , compound fertilizer 600kg / hm 2 , common calcium 600kg / hm 2 ; 3-4 leaf time and timely station; Pre-emergence shallow cultivation and weeding; Corn earing period, ensure field water holding capacity is 60%-80%; Fertile for nitrogen 90.0kg / hm 2 .

[0074] (3) Pepper interplanting corn fertilization method: Corn is planted in the middle and late May, base fertilizer: Pepper pond farmyard manure 30000kg / hm 2 , compound fertilizer 1200kg / hm 2 , common calcium 750kg / hm 2 , corn pond farmyard manure 4000kg / hm 2 , compound fertilizer 150kg / hm 2 , common calcium 150kg / hm 2 ; Fertilizer: Pepper present bud stage, fruiting stage, respectively, high potassium water soluble fertilizer 150kg / hm 2 , corn node period of urea 75kg / hm 2 .

[0075] 4, Cultivation management:

[0076] Timely watering, remove weeds, choose low toxicity and low residual pesticides to carry out disease and pest control, corn focuses on the prevention of armyworm, corn borer, armyworm, etc., pepper mainly prevents brown spot, black spot, powdery mildew, mole cricket, aphid, tobacco greenworm, etc.

[0077] 5, Harvest:

[0078] Pepper fresh pepper 6-9 months according to the maturity of the batch, dry pepper 9 middle and late October-middle October, corn is harvested in mid-October.

[0079] From Figure 2It can be seen that the method of the application can reduce the content of Cd in the rhizosphere soil of the intercropped corn and activate the activity of Cd in the rhizosphere soil of the pepper by coupling with spraying nano selenium. Figures 3-5 It can be seen that the method of the application can significantly promote the absorption and accumulation of Cd in the roots, stems and leaves of the pepper, take away the Cd in the soil through the enrichment of the pepper plants, significantly reduce the accumulation of Cd in the roots, stems and leaves of the corn, and ensure the healthy growth of the food crops and the low accumulation of Cd. Figure 6 It can be seen from the above that although the method of the application promotes the enrichment of Cd in the super-accumulating pepper plants and reduces the content of Cd in the rhizosphere soil of the food crops corn through the competitive adsorption of the roots, spraying nano selenium in the key growth period blocks and controls the migration of Cd in the roots to the grains, and finally ensures that the grain part meets the food safety.

[0080] Although the embodiments of the application are disclosed for the purpose of illustration, those skilled in the art can understand that various substitutions, changes and modifications are possible without departing from the spirit and scope of the application and the appended claims, therefore, the scope of the application is not limited to the disclosed content of the embodiments.

Claims

1. A method for repairing cadmium contaminated soil based on a pepper intercropping corn planting pattern, characterized in that: It comprises the following steps: S1. In the slightly polluted cadmium in the southern acid dry land soil, the cadmium-rich coefficient of high pepper is planted, and the cadmium-rich coefficient of low corn is planted in the form of first planting pepper and then interplanting corn; S2. The pepper is hole-disk seedling in mid-to-late February, and is transplanted in mid-to-late April. The transplanted water is 60%-80% of the field water holding capacity, the pepper row spacing is 1.3 m, the plant spacing is 0.33 m, and the double-plant ridge planting is adopted. The corn is sown in mid-to-late May, the air temperature is kept above 12℃, the ground temperature is kept above 10℃, the field water holding capacity is between 60%-70%, the sowing depth is 4-5 cm, the corn is planted in wide and narrow rows, the single crop large row is 0.8 m, the small row is 0.5 m, and the plant spacing is 0.25 m; the intercropped corn large row is 0.8 m, the small row is 0.5 m, and the plant spacing is 1 m; S3. Spray 100 mg / L nano selenium at the pepper budding stage and the corn jointing stage, and the particle size of the nano selenium particles is ≤60 nm; S4. The fresh pepper is harvested in batches according to the maturity from June to September, the dried pepper is harvested from mid-to-late September to mid-to-late October, and the corn is harvested in mid-October; S5. The next year, the planting positions of the pepper and the corn are exchanged, and the content of cadmium in the soil is gradually and balancedly reduced; The preparation method of the nano selenium particles comprises the following steps: A1. Dissolve the selenium compound in water or an organic solvent to form a selenium compound solution; A2. Dissolve the precipitant in the selenium compound solution to form a precipitation reaction with selenium in the solution, and the reaction temperature is 70℃ and the PH value is <8; A3. Centrifuge, filter and separate the formed selenium precipitate at 3000-60000 r / min, wash with pure water or ethanol, freeze-dry, and grind to obtain nano selenium particles; The selenium compound includes but is not limited to sodium selenate and ferrous selenate, the organic solvent includes but is not limited to ethanol and acetone, and the precipitant includes but is not limited to hydrogen sulfide, sodium hydroxide and sodium thiosulfate.

2. The method for repairing cadmium contaminated soil based on the pepper intercropping maize planting mode according to claim 1, characterized in that: The pepper variety is Xinhonghai with high cadmium-rich coefficient and high yield, and the corn variety is Quchen No. 11 with low cadmium-rich coefficient and high yield.

3. The method for repairing cadmium contaminated soil based on the pepper intercropping maize planting mode according to claim 1, characterized in that: Both the pepper and the corn are covered with mulch before planting, and 5-6 kg of mulch is used per mu.

4. The method for repairing cadmium contaminated soil based on the pepper intercropping maize planting mode according to claim 1, characterized in that: The fertilization and field management method of the pepper interplanted with corn comprises the following steps: B1, base fertilizer: 30,000 kg / hm of farmyard manure in pepper pond 2 , 1,200 kg / hm of compound fertilizer 2 , 750 kg / hm of common calcium 2 , 4,000 kg / hm of farmyard manure in corn pond 2 , 150 kg / hm of compound fertilizer 2 , 150 kg / hm of common calcium 2 ; B2, topdressing: hot pepper present bud period, fruiting period respectively after high potassium water soluble fertilizer 150 kg / hm 2 , corn period of dislocation node after urea 75 kg / hm 2 ; B3. The field management is carried out in the form of single cropping, timely watering, removing weeds, and selecting low-toxicity and low-residue pesticides for disease and pest control. The corn focuses on the prevention and control of Spodoptera exigua, corn borer and armyworm, and the pepper mainly prevents and controls brown spot, black spot, powdery mildew, mole cricket, aphid and tobacco budworm.

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