A selenium-rich cadmium-reducing fertilizer special for alfalfa, its preparation method and application

Abstract

The present invention relates to a selenium-rich cadmium-reducing fertilizer special for alfalfa, which contains Se element, Fe element, Mn element, Zn element, B element, Mg element, Mo element, Co element, S element, chitosan, alkyl polyglycoside and chitosan quaternary ammonium salt, and the mass ratio is 1: 3.9-4.9: 21.3-22.3: 16.6-17.6: 12.1-13.1: 12.3-13.3: 45.4-46.4: 1.7-2.7: 40.2-41.2: 7.0-8.0: 1.5-2.5: 0.7-0.8. The present invention also relates to a preparation method of the selenium-rich cadmium-reducing fertilizer special for alfalfa. The present invention also relates to an application of the selenium-rich cadmium-reducing fertilizer special for alfalfa. The beneficial effects are that applying the fertilizer containing Se element to alfalfa can reduce the content of Cd element in the stems and leaves of alfalfa, and further reduce the content of Cd element in poultry fed with the stems and leaves of alfalfa, reduce the accumulation of Cd element in the human body, and can also increase the content of Se element in alfalfa, and further increase the content of Se element in poultry fed with alfalfa, and improve the content of Se element in the human body.

Description

Technical Field

[0001] The present invention relates to the technical field of fertilizers, and in particular to a selenium-rich cadmium-reducing fertilizer special for alfalfa, a preparation method and an application thereof. Background Art

[0002] Plants, especially alfalfa, grown on contaminated cultivated land will absorb and accumulate cadmium elements in the soil, resulting in a relatively high cadmium element content in alfalfa. As an important forage and green manure, if animals eat alfalfa with a relatively high cadmium element content for a long time, it is likely to affect the health of animals, and even cause the accumulation of cadmium elements in the human body due to biomagnification.

[0003] Therefore, there is an urgent need for a product that can reduce the cadmium element content in alfalfa leaves. Summary of the Invention

[0004] (I) Technical Problems to be Solved

[0005] In view of the above-mentioned disadvantages and deficiencies of the prior art, the present invention provides a selenium-rich cadmium-reducing fertilizer special for alfalfa, a preparation method and a usage method thereof, which solve the technical problem that alfalfa grown on contaminated cultivated land will absorb and accumulate cadmium elements in the soil, resulting in a relatively large cadmium element content.

[0006] (II) Technical Solutions

[0007] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0008] In the first aspect, the present invention also provides a selenium-rich cadmium-reducing fertilizer special for alfalfa, comprising:

[0009] A mixture containing Se element, Fe element, Mn element, Zn element, B element, Mg element, Mo element, Co element, S element, chitosan, alkyl polyglycoside and chitosan quaternary ammonium salt;

[0010] The mass ratio of the Se element, the Fe element, the Mn element, the Zn element, the B element, the Mg element, the Mo element, the Co element, the S element, the chitosan, the alkyl polyglycoside and the chitosan quaternary ammonium salt is 1: 3.9 - 4.9: 21.3 - 22.3: 16.6 - 17.6: 12.1 - 13.1: 12.3 - 13.3: 12.3 - 13.3: 45.4 - 46.4: 1.7 - 2.7: 40.2 - 41.2: 7.0 - 8.0: 1.5 - 2.5: 0.7 - 0.8.

[0011] According to the present invention, the mixture includes FeSO 4 ·7H 2 O, MnSO 4 ·H 2 O, ZnSO4 ·7H 2 O, H 3 BO 3 , MgSO 4 , (NH 4 ) 6 Mo 7 O 24 ·4H 2 O, CoSO 4 ·7H 2 O and Na 2 SeO 3 .

[0012] In a second aspect, the present invention also provides a method for preparing a selenium-rich cadmium-reducing fertilizer for alfalfa, comprising the following steps:

[0013] S1: After mixing the mixture and the chitosan, water is added to obtain formulation A;

[0014] S2: After mixing the alkyl polyglycoside and the quaternary ammonium salt of chitosan, water is added to obtain formulation B;

[0015] S3: After mixing formulation A and formulation B, water is added to obtain formulation C.

[0016] According to the present invention, step S1 further includes:

[0017] The mass ratio of the chitosan to the Se element, the Fe element, the Mn element, the Zn element, the B element, the Mg element, the Mo element, the Co element, and the S element in the mixture is 7.0 - 8.0:1:3.9 - 4.9:21.3 - 22.3:16.6 - 17.6:12.1 - 13.1:12.3 - 13.3:45.4 - 46.4:1.7 - 2.7:40.2 - 41.2:7.0 - 8.0:1.5 - 2.5;

[0018] After mixing the mixture and the chitosan, water is added to make the volume up to 1 L.

[0019] According to the present invention, step S2 further includes:

[0020] The mass ratio of the alkyl polyglycoside to the quaternary ammonium salt of chitosan is 1.5 - 2.5:0.7 - 0.8;

[0021] After mixing the alkyl polyglycoside and the quaternary ammonium salt of chitosan, water is added to make the volume up to 200 ml.

[0022] According to the present invention, step S3 further includes:

[0023] The volume of the preparation A is 500 mL, the volume of the preparation B is 100 mL, and the volume of the preparation C is 70 - 90 times the total volume of the preparation A and the preparation B.

[0024] In a third aspect, the present invention also provides an application of a selenium-rich cadmium-reducing fertilizer special for alfalfa, comprising the following steps:

[0025] SS1: Dilute the preparation C to obtain a stock solution, and add alkyl polyglycoside to the stock solution to obtain a spraying solution;

[0026] SS2: Spray the spraying solution onto the leaves of alfalfa.

[0027] According to the present invention, the step SS1 further includes:

[0028] Dilute the preparation C to 750 kg·hm -2 , to obtain the stock solution, and add 4 g of alkyl polyglycoside to every 50 L of the stock solution to obtain the spraying solution;

[0029] According to the present invention, the step SS2 further includes:

[0030] Spray the spraying solution onto the leaves of alfalfa with a plant height of 20 cm once a week for three consecutive weeks.

[0031] (III) Beneficial effects

[0032] The beneficial effects of the present invention are as follows: The special selenium-rich cadmium-reducing fertilizer for alfalfa proposed in the embodiments of the present invention can increase the antioxidant defense system by applying a fertilizer containing Se element to alfalfa, and keep lipid peroxidation at a low level under the condition of metal-induced oxidative stress inside alfalfa. Due to the reduced accumulation of reactive oxygen species, it plays a role in inhibiting the stress of Cd element, inhibits the transfer of Cd from the roots of alfalfa to the above-ground parts, thereby reducing the enrichment of Cd element in its above-ground parts, namely stems and leaves, achieving the effect of reducing the content of Cd element in the stems and leaves of alfalfa, and further being able to reduce the content of Cd element in poultry fed with the stems and leaves of alfalfa, thus reducing the accumulation of Cd element in the human body after consuming the poultry. At the same time, applying a fertilizer containing Se element to alfalfa can also increase the content of Se element in alfalfa, and further be able to increase the content of Se element in poultry fed with alfalfa. Using the biomagnification effect (the biomagnification effect refers to the phenomenon that organisms absorb certain elements or indigestible compounds from the surrounding environment, these pollutants accumulate in the body, and are passed down through the food chain, and the content in organisms increases with the increase of the trophic level of organisms, causing the concentration of certain elements or compounds in organisms to exceed the concentration in the environment), the content of Se element in the human body is increased. And Se element is one of the necessary components required for the human body to achieve antioxidant defense, regulate inflammation and produce thyroid hormones. Therefore, increasing the content of Se element in the human body helps to maintain human health.

[0033] At the same time, the Se element, Fe element, Mn element, Zn element, B element, Mg element, Mo element, Co element, S element, chitosan, alkyl polyglycoside and quaternary ammonium salt of chitosan in the special selenium-rich cadmium-reducing fertilizer for alfalfa of the present application are all nutritional components helpful for the growth of alfalfa. Moreover, adding B element to the special selenium-rich cadmium-reducing fertilizer for alfalfa can increase the content of B element in alfalfa leaves, so as to increase the photosynthetic rate and transpiration rate of alfalfa leaves and increase the chlorophyll content, and can effectively reduce the content of soluble sugar in alfalfa leaves; adding Mo element can increase the biomass of alfalfa; adding Co element can increase the content of protein, crude fat and crude ash in alfalfa; adding Fe element helps to increase the biomass of alfalfa; adding Mn element can significantly improve the absorption of nutritional elements such as Zn element, Mn element, P (phosphorus) element, Se element, Fe element and Mo (molybdenum) element helpful for the growth of alfalfa by alfalfa; adding Zn element can promote the absorption of N (nitrogen) element, P element and K (potassium) element helpful for its growth by alfalfa, and when Se element and Zn element are added simultaneously in the special selenium-rich cadmium-reducing fertilizer for alfalfa, compared with adding Se element or Zn element alone, the absorption ability of alfalfa for N element, P element and K element is better; adding Co element to supplement the content of Co element in alfalfa and solve the problem of the reduced absorption ability of alfalfa for Co element caused by adding Zn element.

[0034] Meanwhile, the alkyl polyglycoside, chitosan and chitosan quaternary ammonium salt in the selenium-rich cadmium-reducing fertilizer special for alfalfa of the present application. The alkyl polyglycoside is made from fatty alcohol and glucose, chitosan is a natural polysaccharide, and chitosan quaternary ammonium salt is prepared by modifying chitosan. And fatty alcohol, glucose and chitosan are all natural renewable resources. That is to say, the alkyl polyglycoside, chitosan and chitosan quaternary ammonium salt are all natural renewable resources or made from natural renewable resources. Preparing the selenium-rich cadmium-reducing fertilizer special for alfalfa with alkyl polyglycoside, chitosan and chitosan quaternary ammonium salt can reduce the raw material cost and is easy to obtain, thereby reducing the production cost of the selenium-rich cadmium-reducing fertilizer special for alfalfa and having a high yield, which is convenient for popularization and application.

[0035] The preparation method of the selenium-rich cadmium-reducing fertilizer special for alfalfa provided by the present invention is relatively simple and easy to operate.

[0036] The application method of the selenium-rich cadmium-reducing fertilizer special for alfalfa provided by the present invention is relatively simple and easy to operate. Description of the Drawings

[0037] Figure 1 It is a bar chart of the content of Se element in the roots, stems and leaves of Zhongmu No. 1 alfalfa cultivated with and without the selenium-rich cadmium-reducing fertilizer special for alfalfa;

[0038] Figure 2 It is a bar chart of the content of Cd element in the roots, stems and leaves of Zhongmu No. 1 alfalfa cultivated with and without the selenium-rich cadmium-reducing fertilizer special for alfalfa;

[0039] Figure 3 It is a bar chart of the content of Se element in the roots, stems and leaves of Caoyuan No. 3 alfalfa cultivated with and without the selenium-rich cadmium-reducing fertilizer special for alfalfa;

[0040] Figure 4 It is a bar chart of the content of Cd element in the roots, stems and leaves of Caoyuan No. 3 alfalfa cultivated with and without the selenium-rich cadmium-reducing fertilizer special for alfalfa;

[0041] Figure 5 It is a flow chart of the preparation method of the selenium-rich cadmium-reducing fertilizer special for alfalfa of the present invention. Detailed Embodiments

[0042] In order to better explain the present invention for easy understanding, the present invention will be described in detail below with reference to the drawings through specific embodiments.

[0043] The special selenium-rich cadmium-reducing fertilizer for alfalfa proposed in the embodiments of the present invention includes: a mixture containing Se (selenium), Fe (iron), Mn (manganese), Zn (zinc), B (boron), Mg (magnesium), Mo (molybdenum), Co (cobalt), and S (sulfur) elements, chitosan, APG (alkyl polyglycoside), and quaternary ammonium salt of chitosan.

[0044] By applying a fertilizer containing Se element to alfalfa, the antioxidant defense system can be enhanced through the Se element, and lipid peroxidation can be maintained at a low level under the condition of metal-induced oxidative stress inside alfalfa. Due to the reduced accumulation of reactive oxygen species, it plays a role in inhibiting the stress of Cd element, inhibits the transfer of Cd from the roots of alfalfa to the above-ground parts, thereby reducing the enrichment of Cd element in its above-ground parts, namely the stems and leaves, achieving the effect of reducing the content of Cd element in the stems and leaves of alfalfa, and further being able to reduce the content of Cd element in livestock that feed on the stems and leaves of alfalfa, thus reducing the accumulation of Cd element in the human body after consuming livestock. At the same time, applying a fertilizer containing Se element to alfalfa can also increase the content of Se element in alfalfa, and further increase the content of Se element in livestock that feed on alfalfa. Using the biomagnification effect (the biomagnification effect refers to the phenomenon that higher trophic level organisms on the same food chain enrich a certain element or refractory substance by consuming lower trophic level organisms, and its concentration in the organism increases with the increase of the trophic level number), the content of Se element in the human body is increased. And the Se element is one of the necessary components required for the human body to achieve antioxidant defense, regulate inflammation, and produce thyroid hormones. Therefore, increasing the content of Se element in the human body helps to maintain human health.

[0045] Meanwhile, the Se element, Fe element, Mn element, Zn element, B element, Mg element, Mo element, Co element, S element, chitosan, alkyl polyglycoside, and chitosan quaternary ammonium salt in the selenium-rich cadmium-reducing fertilizer for alfalfa of the present application are all nutrient components that contribute to the growth of alfalfa. Moreover, adding the B element to the selenium-rich cadmium-reducing fertilizer for alfalfa can increase the content of the B element in alfalfa leaves, thereby increasing the photosynthetic rate and transpiration rate of alfalfa leaves and increasing the chlorophyll content, and can effectively reduce the content of soluble sugar in alfalfa leaves; adding the Mo element can increase the biomass of alfalfa; adding the Co element can increase the contents of protein, crude fat, and crude ash in alfalfa; adding the Fe element helps to increase the biomass of alfalfa; adding the Mn element can significantly improve the absorption of nutrient elements such as Zn element, Mn element, P (phosphorus) element, Se element, Fe element, and Mo (molybdenum) element that contribute to the growth of alfalfa by alfalfa; adding the Zn element can promote the absorption of N (nitrogen) element, P element, and K (potassium) element that contribute to its growth by alfalfa. Moreover, when the Se element and the Zn element are added simultaneously to the selenium-rich cadmium-reducing fertilizer for alfalfa, compared with adding the Se element or the Zn element alone, alfalfa has a better absorption capacity for N element, P element, and K element; adding the Co element to supplement the content of the Co element in alfalfa and solve the problem of the reduced absorption capacity of alfalfa for the Co element caused by adding the Zn element.

[0046] Meanwhile, the alkyl polyglycoside in the selenium-rich cadmium-reducing fertilizer for alfalfa of the present application is made from fatty alcohol and glucose, chitosan is a natural polysaccharide, and chitosan quaternary ammonium salt is prepared by modifying chitosan. Fatty alcohol, glucose, and chitosan are all natural renewable resources. That is to say, alkyl polyglycoside, chitosan, and chitosan quaternary ammonium salt are all natural renewable resources or are prepared from natural renewable resources. Preparing the selenium-rich cadmium-reducing fertilizer for alfalfa with alkyl polyglycoside, chitosan, and chitosan quaternary ammonium salt can reduce the raw material cost and is easy to obtain, thereby reducing the production cost of the selenium-rich cadmium-reducing fertilizer for alfalfa and having a high yield, which is convenient for industrial-scale production.

[0047] Specifically, according to the comparative analysis of multiple test data, the mass ratio of the Se element, Fe element, Mn element, Zn element, B element, Mg element, Mo element, Co element, S element, chitosan, alkyl polyglycoside, and chitosan quaternary ammonium salt is set to 1:3.9 - 4.9:21.3 - 22.3:16.6 - 17.6:12.1 - 13.1:12.3 - 13.3:45.4 - 46.4:1.7 - 2.7:40.2 - 41.2:7.0 - 8.0:1.5 - 2.5:0.7 - 0.8. The selenium-rich cadmium-reducing fertilizer for alfalfa with this ratio can reduce the absorption of the Cd element by alfalfa and increase the content of the Se element in alfalfa. Moreover, the selenium-rich cadmium-reducing fertilizer for alfalfa with this ratio can provide the content of trace elements required during the growth process of alfalfa and can ensure that the wax layer of alfalfa leaves will not be damaged when spraying on alfalfa leaves.

[0048] Specifically, the mixture includes FeSO 4 ·7H 2 O, MnSO 4 ·H 2 O, ZnSO 4 ·7H 2 O, H 3 BO 3 、MgSO 4 、(NH 4 ) 6 Mo 7 O 24 ·4H 2 O, CoSO 4 ·7H 2 O and Na 2 SeO 3 。

[0049] Furthermore, the present invention also provides a preparation method for a selenium-rich cadmium-reducing fertilizer specifically for alfalfa. Refer to Figure 5 and it includes the following steps:

[0050] S1: Mix the mixture containing Se element, Fe element, Mn element, Zn element, B element, Mg element, Mo element, Co element, and S element with chitosan and then add water to obtain formulation A;

[0051] S2: Mix alkyl polyglycoside and chitosan quaternary ammonium salt and then add water to obtain formulation B;

[0052] S3: Mix formulation A and formulation B and then add water to obtain formulation C.

[0053] As can be seen from the above, the preparation method for the selenium-rich cadmium-reducing fertilizer specifically for alfalfa in this application is relatively simple and easy to operate.

[0054] Specifically, step S1 further includes:

[0055] The mass ratio of chitosan to Se element, Fe element, Mn element, Zn element, B element, Mg element, Mo element, Co element, and S element in the mixture is 7.0 - 8.0:1:3.9 - 4.9:21.3 - 22.3:16.6 - 17.6:12.1 - 13.1:12.3 - 13.3:45.4 - 46.4:1.7 - 2.7:40.2 - 41.2;

[0056] After mixing the mixture and chitosan, add water to make the volume up to 1 L.

[0057] Specifically, step S2 further includes:

[0058] The mass ratio of alkyl polyglycoside to quaternary ammonium salt of chitosan is 1.5 - 2.5:0.7 - 0.8;

[0059] After mixing alkyl polyglycoside and quaternary ammonium salt of chitosan, add water to make the volume up to 200 ml.

[0060] Specifically, step S3 further includes:

[0061] The volume of preparation A is 500 mL, the volume of preparation B is 100 mL. After mixing 500 mL of preparation A and 100 mL of preparation B, add water to make the volume up to 70 - 90 times of the total volume.

[0062] Specifically, the water in steps S1 - S3 is deionized water, distilled water or other unpolluted water.

[0063] Specifically, in step S1, a volumetric flask is used to hold the mixture and chitosan, and in step S2, a volumetric flask is used to hold alkyl polyglycoside and quaternary ammonium salt of chitosan. Using a volumetric flask to hold is for the purpose of facilitating the observation of the volume of the liquid held.

[0064] Specifically, in steps S1 - S3, water is added in a constant volume manner to more accurately ensure the concentration of the selenium - rich and cadmium - reducing fertilizer for alfalfa.

[0065] For better explanation, the following are specific examples of the preparation method of the selenium - rich and cadmium - reducing fertilizer for alfalfa of this application:

[0066] Example 1

[0067] It includes the following steps:

[0068] S1.1: Mix chitosan and the mixture. Among them, the mass ratio of chitosan to Se element, Fe element, Mn element, Zn element, B element, Mg element, Mo element, Co element and S element in the mixture is 7.5:1:4.5:21.8:17.1:12.6:12.8:45.9:2.2:40.7. After mixing, add water to make the volume up to 1 L to obtain preparation A;

[0069] S1.2: Mix alkyl polyglycoside and quaternary ammonium salt of chitosan according to the mass ratio of 2.0:0.7, and then add water to make the volume up to 200 ml to obtain preparation B;

[0070] S1.3: Mix 500 mL of preparation A and 100 mL of preparation B, and then add water to make the volume up to 80 times of the total volume after mixing to obtain preparation C.

[0071] Example 2

[0072] It includes the following steps:

[0073] S2.1: Mix chitosan with the mixture, where the mass ratio of chitosan to Se, Fe, Mn, Zn, B, Mg, Mo, Co, and S elements in the mixture is 7.0:1:4.0:21.5:16.5:12.1:12.3:45.5:1.8:40.3. After mixing, add water to make the volume up to 1 L to obtain Preparation A;

[0074] S2.2: Mix alkyl polyglycoside and chitosan quaternary ammonium salt in a mass ratio of 1.5:0.8, and then add water to make the volume up to 200 ml to obtain Preparation B;

[0075] S2.3: Mix 500 mL of Preparation A and 100 mL of Preparation B, and then add water to make the volume up to 90 times the total volume after mixing to obtain Preparation C.

[0076] Example 3

[0077] It includes the following steps:

[0078] S3.1: Mix chitosan with the mixture, where the mass ratio of chitosan to Se, Fe, Mn, Zn, B, Mg, Mo, Co, and S elements in the mixture is 8.0:1:4.8:22.2:17.5:13.0:13.2:46.3:2.6:41.0. After mixing, add water to make the volume up to 1 L to obtain Preparation A;

[0079] S3.2: Mix alkyl polyglycoside and chitosan quaternary ammonium salt in a mass ratio of 2.5:0.7, and then add water to make the volume up to 200 ml to obtain Preparation B;

[0080] S3.3: Mix 500 mL of Preparation A and 100 mL of Preparation B, and then add water to make the volume up to 70 times the total volume after mixing to obtain Preparation C.

[0081] Furthermore, the present invention also provides an application of the selenium-rich cadmium-reducing fertilizer special for alfalfa, including the following steps:

[0082] SS1: Dilute Preparation C to obtain the stock solution, and add alkyl polyglycoside to the stock solution to obtain the spraying solution;

[0083] SS2: Spray the spraying solution on the leaves of alfalfa.

[0084] Spraying the selenium-rich cadmium-reducing fertilizer special for alfalfa on the leaves of alfalfa enables Se to be enriched in the leaves and stems of alfalfa. When livestock eat the leaves and stems of alfalfa used as forage, the Se element provided by the selenium-rich cadmium-reducing fertilizer special for alfalfa in the leaves and stems can be absorbed by livestock for effective utilization. Therefore, in the application process of this application, the selenium-rich cadmium-reducing fertilizer special for alfalfa is sprayed on the leaves of alfalfa to enable the effective utilization of the Se element.

[0085] Specifically, step SS1 further includes:

[0086] Dilute formulation C to 750 kg·hm -2 , obtain the stock solution, and add 4 g of alkyl polyglycoside to every 50 L of the stock solution to obtain the spraying solution.

[0087] Specifically, step SS2 further includes:

[0088] Spray the spraying solution on the leaf surface of alfalfa with a plant height of 20 cm once a week for three consecutive weeks.

[0089] Among them, alkyl polyglycoside is a surfactant that can protect the leaf surface of alfalfa from corrosion by metal elements in the selenium-rich cadmium-reducing fertilizer special for alfalfa.

[0090] As can be seen from the above, the application method of the selenium-rich cadmium-reducing fertilizer special for alfalfa in this application is relatively simple and easy to operate.

[0091] For better explanation, the following are examples of the application of the selenium-rich cadmium-reducing fertilizer special for alfalfa in this application:

[0092] Example 4

[0093] It includes the following steps:

[0094] SS1.1: Dilute formulation C in Example S1 to 750 kg·hm -2 , obtain the stock solution, and add 4 g of alkyl polyglycoside to every 50 L of the stock solution to obtain the spraying solution;

[0095] SS1.2: Spray the spraying solution on the leaf surface of alfalfa with a plant height of 20 cm once a week for three consecutive weeks.

[0096] Example 5

[0097] It includes the following steps:

[0098] SS2.1: Dilute formulation C in Example S1 to 750 kg·hm -2 , obtain the stock solution, and add 4 g of alkyl polyglycoside to every 50 L of the stock solution to obtain the spraying solution;

[0099] SS2.2: Spray the spraying solution on the leaf surface of alfalfa with a plant height of 20 cm once a week for three consecutive weeks.

[0100] Example 6

[0101] It includes the following steps:

[0102] SS3.1: Dilute formulation C in Example S1 to 750 kg·hm -2, obtain a stock solution, add 4 g of alkyl polyglycoside to every 50 L of the stock solution to obtain a spray solution;

[0103] SS3.2: Spray the liquid on the leaves of alfalfa with a plant height of 20 cm for three consecutive weeks, once a week.

[0104] Specifically, the accompanying drawings Figure 1 and Figure 2 In the experiment on the alfalfa Zhongmu No. 1, except for the addition of Se element, the other component ratios and application methods of the fertilizer applied in the control group experiment were consistent with the selenium-rich cadmium-reducing fertilizer specially used for alfalfa in the present application.

[0105] Regarding the experimental results of Zhongmu No. 1 alfalfa, see the attached figure Figure 1 and Figure 2 It can be seen that compared with the alfalfa obtained in the control group, the Cd content in the roots, stems and leaves of the alfalfa cultivated according to the application conditions of Examples 4, 5 and 6 obtained by the preparation methods of Examples 1, 2 and 3 respectively are reduced, and the Se content is greatly increased, and the Se content and increase in the leaves of alfalfa are much higher than those in the roots and stems, indicating that the method of spraying the special selenium-rich cadmium-reducing fertilizer for alfalfa on the leaves of alfalfa can effectively improve the absorption of Se by the whole alfalfa, especially the leaves of alfalfa, and can improve the ability to inhibit the absorption of Cd by Se. At the same time, the content of Se element in the alfalfa obtained by the preparation methods of Example 1, Example 2 and Example 3 decreases successively, and the content of Cd element increases successively. That is to say, the combination of Fe element, Mn element, Zn element, B element, Mg element, Mo element, Co element and S element in the selenium-rich cadmium-reducing fertilizer for alfalfa obtained by spraying the preparation method of Example 1 is better, and the effect of selenium-enriched and cadmium-reducing on alfalfa is the best.

[0106] Regarding the experimental results of Grassland No. 3 alfalfa, see the attached figure Figure 3 and Figure 4It can be seen that compared with the alfalfa obtained in the control group, the content of Cd in the roots, stems and leaves of the alfalfa obtained by the preparation methods of Example 1, Example 2 and Example 3 respectively corresponding to the application conditions of Example 4, Example 5 and Example 6 is reduced or shows a decreasing trend (the content of Cd in the stem of alfalfa obtained by the preparation method of Example 2 and the application conditions of Example 5 is greater than that of the control group) and the Se content is greatly increased, and the content and increase of Se in the leaves of alfalfa are much higher than those in the roots and stems, indicating that the method of spraying the alfalfa-specific selenium-rich cadmium-reducing fertilizer on the leaves of alfalfa can effectively improve the absorption of Se by the alfalfa as a whole, especially the leaves of alfalfa, and can improve the inhibition of Cd absorption by Se. The reason for the appearance of "the content of Cd in the stem of alfalfa obtained by the preparation method of Example 2 and the application conditions of Example 5 is greater than that of the control group" is: studies have shown that a small amount of Zn and Mg elements will inhibit the absorption of Cd by alfalfa. It should be noted that there are interactions between Zn and Cd, and between Mn and Cd, and completely opposite results may occur under different nutritional environmental conditions.

[0107] At the same time, the content of Se in alfalfa obtained by the preparation methods of Example 1, Example 2 and Example 3 is reduced successively, and the content of Cd is relatively average, wherein the content of Cd in the root, stem and leaf of alfalfa obtained by the preparation method of Example 1 is the lowest, and the effect of selenium-enriched cadmium reduction on alfalfa is the best. After multiple comparisons and analyses of experimental data, it is concluded that the ratio of "Fe, Mn, Zn, B, Mg, Mo, Co and S" in the selenium-enriched cadmium reduction fertilizer for alfalfa obtained by the preparation method of Example 1 is better.

[0108] It should be noted that the characteristic of the special selenium-rich cadmium-reducing fertilizer for alfalfa of the present invention is that while increasing the Se content in alfalfa, its absorption of Cd element is greatly reduced. The applicant's research idea for obtaining the above-mentioned optimal embodiment ratio is: first, the ratio of foliar fertilizers of wheat, rice and sun-dried mushrooms is used as a prototype, but due to the large differences between alfalfa and rice, wheat or sun-dried mushrooms, major improvements must be made; secondly, the ratios of other cadmium-reducing fertilizers are introduced as reference values; thirdly, the influence of each element on alfalfa is studied and analyzed, and an analysis table of the influence of each element on alfalfa is obtained; finally, multiple experimental analyses are performed in combination with the data in the above three processes. Finally, the optimal ratio scheme of the present invention is obtained. The above research ideas also reflect that the research and development process of the ratio of each element in the special selenium-rich cadmium-reducing fertilizer for alfalfa of the present invention is not obtained by a limited number of experiments.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. Preparation method of selenium-rich cadmium-reducing fertilizer special for alfalfa, characterized in that, it comprises the following steps: S1: Mix the mixture and chitosan and then add water to obtain preparation A; the mixture is composed of Se element, Fe element, Mn element, Zn element, B element, Mg element, Mo element, Co element, S element; the mass ratio of the Se element, Fe element, Mn element, Zn element, B element, Mg element, Mo element, Co element, S element and the chitosan is 1: 3.9 - 4.9: 21.3 - 22.3: 16.6 - 17.6: 12.1 - 13.1: 12.3 - 13.3: 45.4 - 46.4: 1.7 - 2.7: 40.2 - 41.2: 7.0 - 8.0; after mixing the mixture and the chitosan, add water to make the volume up to 1 L; S2: Mix alkyl polyglycoside and quaternary ammonium salt of chitosan and then add water to obtain preparation B; the mass ratio of the chitosan, the alkyl polyglycoside and the quaternary ammonium salt of chitosan is 7.0 - 8.0: 1.5 - 2.5: 0.7 - 0.8; after mixing the alkyl polyglycoside and the quaternary ammonium salt of chitosan, add water to make the volume up to 200 ml; S3: Mix preparation A and preparation B and then add water to obtain preparation C; the volume of preparation A is 500 mL, the volume of preparation B is 100 mL, and the volume of preparation C is 70 - 90 times the total volume of preparation A and preparation B.

2. The preparation method of selenium-rich cadmium-reducing fertilizer special for alfalfa according to claim 1, characterized in that, The mixture includes FeSO 4 ·7H 2 O, MnSO 4 ·H 2 O, ZnSO 4 ·7H 2 O, H 3 BO 3 , MgSO 4 , (NH 4 ) 6 Mo 7 O 24 ·4H 2 O, CoSO 4 ·7H 2 O and Na 2 SeO 3 .

3. Application of the selenium-rich cadmium-reducing fertilizer special for alfalfa prepared by the preparation method according to any one of claims 1 - 2, characterized in that, it comprises the following steps: SS1: Dilute formulation C to 750 kg·hm -2 , to obtain a stock solution, and add 4 g of alkyl polyglycoside to every 50 L of the stock solution to obtain a spraying solution; SS2: Spray the spraying solution on the leaf surface of alfalfa.

4. The application of the selenium-rich cadmium-reducing fertilizer special for alfalfa according to claim 3, characterized in that, the step SS2 further comprises: spraying the spraying solution on the leaf surface of alfalfa with a plant height of 20 cm once a week for three consecutive weeks.

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