A selenium-rich cadmium-reducing foliar fertilizer, its preparation method and usage method

Abstract

The present invention belongs to the field of selenium-rich cadmium-reducing foliar fertilizers, and specifically relates to a selenium-rich cadmium-reducing foliar fertilizer, a preparation method thereof, and a usage method thereof. The raw materials of the selenium-rich cadmium-reducing foliar fertilizer include: residues extract of Cinnamomum camphora var. borneolifera, sodium selenite, and acidic silica sol. Compared with the existing inhibitors, the selenium-rich cadmium-reducing foliar fertilizer of the present invention can significantly improve the absorption efficiency of elements such as Si, Se, and Zn by leaves, and enhance the cadmium-blocking effects of elements such as Si, Se, and Zn; at the same time, it also reuses the discarded residues of Cinnamomum camphora var. borneolifera, which is a new means with great potential in application prospects.

Description

Technical Field

[0001] The present invention belongs to the field of selenium-rich cadmium-reducing foliar fertilizers, and particularly relates to a selenium-rich cadmium-reducing foliar fertilizer, a preparation method thereof, and a using method thereof. Background Art

[0002] In order to reduce the accumulation of cadmium in crops and soil and reduce the bioavailability of cadmium in soil, a great deal of efforts have been made, mainly including applying soil conditioners or cadmium passivators, regulating the water content in the field, and spraying foliar inhibitors, etc. Spraying a certain amount of chemical substances on the leaves to reduce cadmium toxicity and reduce the absorption of cadmium by plants may provide a strategy with low cost and strong practicability for food safety production. Research shows that foliar spraying of silicon (Si) and selenium (Se) is considered to be one of the effective methods to reduce the toxic effects of cadmium pollution in crops. However, the existing silicon (Si)- and selenium (Se)-containing foliar inhibitors have relatively poor effects on blocking cadmium absorption and reducing cadmium accumulation due to low absorption efficiency, and are unstable. Summary of the Invention

[0003] The purpose of the present invention is to solve the deficiencies of the prior art and provide a selenium-rich cadmium-reducing foliar fertilizer, and the following technical solutions are specifically adopted:

[0004] A selenium-rich cadmium-reducing foliar fertilizer, the raw materials of which include: residues extract of Cinnamomum camphora var. borneolifera, sodium selenite, and acidic silica sol.

[0005] The inventor found that the residues extract of Cinnamomum camphora var. borneolifera (i.e., the residues extract after steam distillation of Cinnamomum camphora var. borneolifera 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, so as to achieve the purpose of efficiently reducing cadmium; at the same time, the waste of Cinnamomum camphora var. borneolifera residues is also reused.

[0006] The residues extract of Cinnamomum camphora var. borneolifera is prepared by the following process: mixing the residues of Cinnamomum camphora var. borneolifera with a mixed solvent of ethanol and water in 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 at 20°C - 50°C, and after filtration, performing reduced pressure distillation on the filtrate to obtain the residues extract of Cinnamomum camphora var. borneolifera. First, mixing the residues of Cinnamomum camphora var. borneolifera with a mixed solvent of ethanol and water in a ratio of 1 g:(5 mL - 10 mL), this ratio has the best effect on extracting the 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 extracted concentration is too low and it is uneconomical. Secondly, performing microwave-ultrasound at 20°C - 50°C is mainly because too low temperature will lead to reduced extraction efficiency and longer time, and too high temperature will cause a large amount of ethanol to volatilize, affecting the extraction quality.

[0007] In some preferred embodiments, the raw materials of the above selenium-rich cadmium-reducing foliar fertilizer further include EDTA-chelated zinc. The inventors found that there is not only an interactive synergistic effect between Si and Se, but 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 EDTA-chelated zinc alone is very limited); in addition, the inventors 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 leads to the formation of gel in acidic silica sol. Therefore, the inventors innovatively chose to add EDTA-chelated zinc, which not only avoids the failure caused by the excessive addition of Zn ions to form gel, but also realizes the interactive synergistic effect among Zn-Si-Se.

[0008] Among them, in a preferred case, the pH of the acidic silica sol is less than 3.5, and the SiO 2 content is greater than 25%. Selecting a pH 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; while selecting a SiO 2 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.

[0009] Among them, the ratio of the residue extract of Cinnamomum camphora, sodium selenite, and acidic silica sol is (3 mL - 10 mL):(4 g - 10 g):1 L; the ratio of EDTA-chelated zinc to sodium selenite is (40 g - 100 g):(4 g - 10 g). Within the above range, the acidic silica sol is not easy to form gel, and the cadmium-reducing effect is relatively the best.

[0010] Generally speaking, the present invention first further extracts the residual borneol essential oil and borneol in the residue of Cinnamomum camphora under the conditions of ethanol-aqueous solution with microwave-ultrasound, which not only makes waste reused, but also the extract can significantly promote the absorption and transformation of silicon, selenium, and zinc elements by leaves, and effectively reduce the cadmium content in rice under the condition that the addition amounts of selenium, silicon, and zinc elements in the existing foliar fertilizer are greatly reduced. Secondly, the present invention also found that the effect of reducing cadmium in rice by EDTA-chelated zinc alone is limited, but adding EDTA-chelated zinc to acidic silica sol and sodium selenite solution can effectively enhance the cadmium-reducing effect of silicon and selenium elements; and compared with zinc sulfate, its dosage can be greatly reduced to effectively avoid the formation of gel in silica sol, and the cadmium-blocking effect is better. In addition, the present invention uses acidic silica sol, which not only helps the absorption and utilization of silicon elements, but also is conducive to the mutual dissolution of silicon elements with sodium selenite and EDTA-chelated zinc, effectively avoiding the precipitation and failure of silicon elements. Adopting the technical scheme of the present invention can not only effectively reduce the cadmium content in rice, but also greatly increase the selenium and zinc contents in rice, making the rice meet the standards of green, safe, and selenium-rich.

[0011] The raw materials of the above-mentioned selenium-rich cadmium-reducing foliar fertilizer also include a spreading agent (preferably Tween 80). And a preparation method of the selenium-rich cadmium-reducing foliar fertilizer is provided, including the following steps: dissolving the raw materials except for acidic silica sol in the acidic silica sol, and then adding the spreading agent and mixing evenly to obtain the foliar fertilizer.

[0012] The present invention also provides a method for using the above-mentioned selenium-rich cadmium-reducing foliar fertilizer, spraying it twice respectively during the heading stage and filling stage of rice, and taking the standard that the front and back sides of rice leaves are fully covered with mist droplets as the spraying liquid amount.

[0013] The beneficial effects of the present invention are as follows: Compared with the existing blocking agents, the selenium-rich cadmium-reducing foliar fertilizer of the present invention can significantly improve the absorption efficiency of elements such as Si, Se, and Zn by leaves, and enhance the cadmium-blocking effects of elements such as Si, Se, and Zn; at the same time, the waste Cinnamomum camphora residues are also reused, which is a new means with great potential in application prospects. Description of the Drawings

[0014] Figure 1 The figure shows the influence results of adding and not adding EDTA-Zn on the size of colloidal particles. Detailed Embodiments

[0015] The following will clearly and completely describe the concept and technical effects generated by the present invention in combination with the embodiments and drawings, so as to fully understand the purpose, scheme and effects of the present invention.

[0016] Example 1:

[0017] A selenium-rich cadmium-reducing foliar fertilizer, the raw materials of which include: Tween 80, Cinnamomum camphora residue extract, sodium selenite and acidic silica sol. The selenium-rich cadmium-reducing foliar fertilizer is prepared by the following process:

[0018] Dissolve 8 mL of Cinnamomum camphora residue extract, 90 g of EDTA-chelated zinc, and 7 g of sodium selenite in 1 L of acidic silica sol (SiO 2 content is 30%, pH is 3.0) solution. After complete dissolution, add 1 mL of Tween 80 and mix evenly to obtain the foliar fertilizer.

[0019] Among them, the Cinnamomum camphora residue extract is prepared by the following process:

[0020] Take 2 kg of Cinnamomum camphora leaf and twig powder and mix it with an ethanol-water mixed solvent according to a mass-volume ratio of 1:5. After microwave-ultrasonic treatment for 10 min under the conditions of a 500 W ultrasonic power, a 250 W microwave power, and 30 °C, filter and collect the filtrate. Then continue to perform microwave-ultrasonic extraction on the residue in the above manner for 3 times. After combining the filtrates, perform reduced pressure distillation to obtain it.

[0021] Example 2:

[0022] A selenium-rich cadmium-reducing foliar fertilizer, the raw materials of which include: Tween 80, the extract of Cinnamomum camphora residues, sodium selenite and acidic silica sol. The selenium-rich cadmium-reducing foliar fertilizer is prepared by the following process:

[0023] Dissolve 7 mL of the extract of Cinnamomum camphora residues, 80 g of EDTA-chelated zinc, and 6 g of sodium selenite in 1 L of acidic silica sol (SiO 2 with a content of 30% and a pH of 3.0). After complete dissolution, add 1 mL of Tween 80 and mix well to obtain the foliar fertilizer.

[0024] Among them, the extract of Cinnamomum camphora residues is prepared by the following process:

[0025] Take 2 kg of Cinnamomum camphora leaf and twig powder and mix it with an ethanol-water mixed solvent at a mass-to-volume ratio of 1:6. After microwave-ultrasonic treatment for 10 min under the conditions of a 500 W ultrasonic power, a 250 W microwave power, and 30 °C, filter and collect the filtrate. Then, continue the microwave-ultrasonic extraction of the residue in the above manner 3 times. After combining the filtrates, obtain it by reduced pressure distillation.

[0026] Example 3:

[0027] A selenium-rich cadmium-reducing foliar fertilizer, the raw materials of which include: Tween 80, the extract of Cinnamomum camphora residues, sodium selenite and acidic silica sol. The selenium-rich cadmium-reducing foliar fertilizer is prepared by the following process:

[0028] Dissolve 6 mL of the extract of Cinnamomum camphora residues, 70 g of EDTA-chelated zinc, and 5 g of sodium selenite in 1 L of acidic silica sol (SiO 2 with a content of 30% and a pH of 3.0). After complete dissolution, add 1 mL of Tween 80 and mix well to obtain the foliar fertilizer.

[0029] Among them, the extract of Cinnamomum camphora residues is prepared by the following process:

[0030] Take 2 kg of Cinnamomum camphora leaf and twig powder and mix it with an ethanol-water mixed solvent at a mass-to-volume ratio of 1:8. After microwave-ultrasonic treatment for 10 min under the conditions of a 600 W ultrasonic power, a 300 W microwave power, and 30 °C, filter and collect the filtrate. Then, continue the microwave-ultrasonic extraction of the residue in the above manner 3 times. After combining the filtrates, obtain it by reduced pressure distillation.

[0031] Example 4:

[0032] A selenium-rich cadmium-reducing foliar fertilizer, the raw materials of which include: Tween 80, the extract of Cinnamomum camphora residues, sodium selenite and acidic silica sol. The selenium-rich cadmium-reducing foliar fertilizer is prepared by the following process:

[0033] Dissolve 5 mL of the extract of Cinnamomum camphora residues, 60 g of EDTA-chelated zinc, and 4 g of sodium selenite in 1 L of acidic silica sol (SiO 2In a solution with a content of 30% and a pH of 3.0, after complete dissolution, add 1 mL of Tween 80 and mix well to obtain the foliar fertilizer.

[0034] Among them, the residue extract of Cinnamomum camphora is prepared by the following process:

[0035] Take 2 kg of Cinnamomum camphora leaf and twig powder and mix it with an ethanol-water mixed solvent at a mass-to-volume ratio of 1:5. After microwave-ultrasonic treatment for 10 min under the conditions of a 600 W ultrasonic power, a 300 W microwave power, and 30 °C, filter, collect the filtrate, and continue to perform microwave-ultrasonic extraction on the residue in the above manner 3 times. After combining the filtrates, perform reduced pressure distillation to obtain it.

[0036] Comparative Example 1:

[0037] A selenium-rich cadmium-reducing foliar fertilizer is prepared by the following process:

[0038] 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 (SiO 2 In a solution with a content of 30% and a pH of 3.0, after complete dissolution, add 1 mL of Tween 80 and mix well to obtain the foliar fertilizer.

[0039] Compared with Example 1, in Comparative Example 1, distilled water was used to replace the residue extract of Cinnamomum camphora.

[0040] Comparative Example 2:

[0041] A selenium-rich cadmium-reducing foliar fertilizer is prepared by the following process:

[0042] Add 8 mL of the residue extract of Cinnamomum camphora, 90 mL of distilled water, and 7 g of sodium selenite to 1 L of acidic silica sol (SiO 2 In a solution with a content of 30% and a pH of 3.0, after complete dissolution, add 1 mL of Tween 80 and mix well to obtain the foliar fertilizer.

[0043] Among them, the residue extract of Cinnamomum camphora is prepared by the following process:

[0044] Take 2 kg of Cinnamomum camphora leaf and twig powder and mix it with an ethanol-water mixed solvent at a mass-to-volume ratio of 1:5. After microwave-ultrasonic treatment 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-ultrasonic extraction on the residue in the above manner 3 times. After combining the filtrates, perform reduced pressure distillation to obtain it.

[0045] Compared with Example 1, in Comparative Example 2, distilled water was used to replace EDTA-chelated zinc.

[0046] Effect experiment:

[0047] A series of tests were conducted on selenium-rich cadmium-reducing foliar fertilizers of the present invention in middle-season rice and late-season rice, and good application effects were obtained.

[0048] The tests were set up with spraying clear water (CK), Comparative Example 1 (without adding Cinnamomum camphora extract), Comparative Example 2 (without adding EDTA-Zn), the strong 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, SiO 2 ≥20%, K 2 O≥15%) and Examples 1-4, a total of 8 treatments, with 3 replicates for each treatment, a total of 24 plots, and each plot had an area of 60m 2 . They were arranged in a randomized block design. Clear water and the selenium-rich cadmium-blocking foliar fertilizer were each sprayed once during the heading stage and filling stage of rice, diluted 150 times each time for spraying. The strong cadmium-reducing foliar control agent was sprayed after being diluted according to the instructions. The liquid spraying volume should be appropriate so that the front and back sides of the rice leaves were covered with mist droplets. After the middle-season rice and late-season rice were harvested, plant samples were collected to measure indexes such as rice yield, selenium in brown rice, and cadmium content in brown rice. The relative cadmium reduction rate and relative selenium enrichment rate were calculated based on the cadmium and selenium contents in brown rice.

[0049] 1. Influence of adding and not adding EDTA-Zn on the size of colloidal particles

[0050] First, add 7 g of sodium selenite to 1 L of acidic silica sol (SiO 2 content is 30%, pH is 3.0) solution. After complete dissolution, add 90 g of EDTA-chelated zinc. After complete dissolution, add 1 mL of Tween 80 as the "+Zn" treatment. Correspondingly, the EDTA-chelated zinc was not added as the "-Zn" treatment. Additionally, first add 7 g of sodium selenite to 1 L of acidic silica sol (SiO 2 content is 30%, pH is 3.0) solution. After complete dissolution, add 360 g of zinc sulfate heptahydrate. After complete dissolution, add 1 mL of Tween 80 as the zinc sulfate addition treatment. Each treatment had 5 replicates. After the solution was stable, a dynamic light scattering instrument was used to measure the particle size distribution. The measurement results are shown in Figure 1 .

[0051] As can be seen from Figure 1 (wherein, "-Zn" means not adding EDTA-Zn, and "+Zn" means adding EDTA-Zn), compared with not adding EDTA-Zn, adding EDTA-Zn promoted the aggregation of colloidal particles and increased the particle size of colloidal particles, but it was still within the range of colloidal particles and no gel was formed. This shows that adding a certain amount of EDTA-Zn in the present invention has no obvious effect on the effectiveness of silicon. The zinc sulfate addition treatment caused the acidic silica sol system to form a gel in a short time (the gel could not be used to measure the particle size), and the gel could hardly be dispersed into the water system and became ineffective.

[0052] 2. Effects of Selenium-Rich Cadmium-Resistant Foliar Fertilizer on Rice Yield

[0053] The selenium-rich cadmium-resistant foliar fertilizers prepared in the present invention (Example 1, Example 2, Example 3 and Example 4). As can be seen from Table 1, compared with the treatment of spraying clear water, Example 1, Example 2, Example 3 and Example 4 all showed significant yield increases in middle-season rice and late-season rice, with the increase rates reaching 6.93 - 9.03% and 5 - 7.14% respectively. This shows that spraying the selenium-rich cadmium-resistant foliar fertilizer prepared in the present invention can effectively increase the rice yield.

[0054] Compared with Comparative Example 1 (without adding Cinnamomum camphora residue extract), the yield increase of the examples in middle-season rice and late-season rice was relatively small; compared with Comparative Example 2 (without adding EDTA-Zn), the yield increase of the examples in middle-season rice and late-season rice was relatively large, being 5.42 - 7.49% and 1.63 - 3.7% respectively, indicating that adding a certain amount of EDTA-Zn to the selenium-rich cadmium-resistant foliar fertilizer is helpful for further improving the rice yield, while the effect of Cinnamomum camphora residue extract is limited.

[0055] Compared with the cadmium-reducing foliar control agent circulating in the market, the present invention also showed a certain yield increase effect in middle-season rice and late-season rice, with the increase rates being 1.59 - 3.58% and 1.06 - 3.12% respectively, indicating that the present invention has greater yield increase potential than the mainstream foliar control agents currently circulating in the market.

[0056] Table 1 Effects of Selenium-Rich Cadmium-Resistant Foliar Fertilizer on Rice Yield

[0057]

[0058]

[0059] 3. Effects of Selenium-Rich Cadmium-Resistant Foliar Fertilizer on Rice Quality

[0060] The results of measuring rice quality showed (see Table 2). Compared with the treatment of spraying clear water, the selenium-rich cadmium-resistant foliar fertilizers prepared in the present invention (Example 1, Example 2, Example 3 and Example 4) can significantly increase the brown rice rate, head rice rate, milled rice rate, alkali spreading value, and gel consistency of middle-season rice and late-season rice, and significantly reduce the chalkiness degree, amylose content, and protein content. This shows that the present invention can effectively improve the rice quality.

[0061] Compared with Comparative Example 1 (without adding Cinnamomum camphora residue extract) and Comparative Example 2 (without adding EDTA-Zn), the example treatment significantly increased the brown rice rate, head rice rate, milled rice rate, alkali spreading value, and gel consistency of middle-season rice and late-season rice, and significantly decreased the chalkiness degree, protein, and amylose content. This indicates that adding a certain amount of Cinnamomum camphora residue extract and EDTA-Zn in the present invention can further improve the rice quality.

[0062] Compared with the cadmium-reducing foliar inhibitor currently on the market, the head rice rate, milled rice rate, alkali spreading value, and gel consistency of medium-season rice treated with the selenium-enriched cadmium-blocking foliar fertilizer (Examples 1, 2, 3, and 4) prepared by the present invention increased by 0.76 - 1.52%, 0.45 - 1.05%, and 2.86 - 7.14% respectively, while the chalkiness degree and amylose content decreased by 19.05 - 33.3% and 1.89 - 4.72% respectively; for late-season rice, the head rice rate, milled rice rate, alkali spreading value, and gel consistency increased by 5.53 - 5.94%, 0.42 - 0.83%, 4.76 - 9.52%, and 11.11 - 15.28% respectively, and the chalkiness degree and amylose content decreased by 33.33 - 60% and 3.11 - 4.35% respectively. This shows that the selenium-enriched cadmium-blocking foliar fertilizer prepared by the present invention can further improve the quality of medium-season and late-season rice compared with the cadmium-reducing foliar inhibitor currently on the market, making the rice meet the standard of first-class high-quality rice.

[0063] Table 2 Effects of Selenium-Enriched Cadmium-Blocking Foliar Fertilizer on Rice Quality

[0064]

[0065]

[0066] 4. Effects of Selenium-Enriched Cadmium-Blocking Foliar Fertilizer on Selenium Content and Selenium-Enrichment Rate of Rice

[0067] Compared with Comparative Example 1 (without the extract of Cinnamomum camphora residue), the examples showed obvious selenium-enrichment effects on medium-season and late-season rice (see Table 3), and the relative selenium-enrichment rates increased by 69.23 - 100 percentage points and 90.91 - 109.09 percentage points respectively. Compared with Comparative Example 2 (without EDTA-Zn), the examples had less influence on the selenium content in the brown rice of medium-season and late-season rice, and the selenium-enrichment effect was not obvious. This indicates that adding a certain amount of the extract of Cinnamomum camphora residue in the present invention can further promote the absorption of selenium by rice leaves and increase the selenium content in brown rice, while the addition of EDTA-Zn has relatively less influence on the selenium-enrichment of rice.

[0068] As can be seen from Table 3, compared with the treatment of spraying clear water, the treatment of spraying selenium-rich cadmium-blocking foliar fertilizer (Examples 1, 2, 3, and 4) significantly increased the selenium content in the brown rice of middle-season rice and late rice. Among them, the selenium content in the brown rice of middle-season rice increased from 0.013 mg / kg in the treatment of spraying clear water to 0.04 - 0.044 mg / kg, and the selenium content in the brown rice of late rice increased from 0.022 mg / kg in the treatment of spraying clear water to 0.063 - 0.067 mg / kg. The relative selenium enrichment rates reached 207.69 - 238.46% and 186.36 - 204.55% in middle-season rice and late rice respectively. According to the "Hygienic Standard for Selenium Limits in Foods" (GB 13105-1991) and the "Selenium-Rich Paddy Rice" (GB / T 22499-2008), the selenium content of rice processed from selenium-rich paddy rice should be 0.04 - 0.30 mg / kg, and the selenium content of grains (finished grains) should be ≤ 0.30 mg / kg. After the application of the present invention on rice, the selenium-rich rice standard is achieved.

[0069] Compared with the cadmium-blocking foliar inhibitor for rapid reduction circulating in the market, the treatment of the selenium-rich cadmium-blocking foliar fertilizer (Examples) prepared by the present invention showed obvious selenium enrichment effects on both middle-season rice and late rice (see Table 3). The selenium enrichment rates increased by 30.77 - 61.54 percentage points and 68.18 - 86.36 percentage points respectively, indicating that the selenium enrichment effect of the present invention is better than that of the mainstream cadmium-blocking foliar inhibitors currently circulating in the market, and it has obvious market competitive advantages.

[0070] 5. Effects of Selenium-Rich Cadmium-Blocking Foliar Fertilizer on Cadmium in Rice and Cadmium Reduction Rate

[0071] As can be seen from Table 3, compared with Comparative Example 1 (without adding the residue extract of Cinnamomum camphora), the Examples significantly reduced the cadmium content in the brown rice of middle-season rice and late rice, and increased the relative cadmium reduction rate. The relative cadmium reduction rates of the brown rice of middle-season rice and late rice increased by 21.62 - 29.73 percentage points and 23.53 - 27.45 percentage points respectively. It shows that the residue extract of Cinnamomum camphora can effectively promote the absorption of Zn, Si, and Se elements, enhance the antagonistic effect of Zn, Si, and Se elements on cadmium, and significantly reduce the absorption of cadmium by rice. Compared with Comparative Example 2 (without adding EDTA-Zn), the Examples also showed obvious cadmium reduction effects on middle-season rice and late rice. The relative cadmium reduction rates of each Example increased by 8.11 - 16.22 percentage points and 9.8 - 13.73 percentage points respectively, indicating that adding a certain amount of EDTA-Zn can achieve the interactive synergistic effect among Zn, Si, and Se, and enhance the effect of the three elements of Zn, Si, and Se in synergistically blocking cadmium.

[0072] As can be seen from Table 3, compared with the treatment of spraying clear water, the cadmium content in the brown rice of medium-season rice and late-season rice treated with selenium-rich cadmium-blocking foliar fertilizer (Example 1, Example 2, Example 3, Example 4) decreased from 0.37 and 0.51 mg / kg in the treatment of spraying clear water to 0.15 - 0.18 and 0.17 - 0.19 mg / kg, and the relative cadmium reduction rates reached 51.35 - 59.46% and 62.75 - 66.67% respectively. This shows that the present invention can effectively block the absorption of cadmium by rice and greatly reduce the cadmium content in rice.

[0073] Compared with the cadmium-blocking foliar control agent circulating in the market, the present invention shows obvious cadmium reduction effects in both medium-season rice and late-season rice, and the relative cadmium reduction rates increase by 27.03 - 35.14 percentage points and 31.37 - 35.29 percentage points respectively, indicating that the cadmium reduction effect of the present invention is better than that of the similar products currently circulating in the market.

[0074] Table 3 Effects of selenium-rich cadmium-blocking foliar fertilizer on cadmium, selenium contents, cadmium reduction rate and selenium enrichment rate in rice

[0075]

[0076] 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.

[0077] The above are only the preferred embodiments 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, its technical solutions and / or implementation manners can have various different modifications and changes.

Claims

1. A selenium-rich cadmium-reducing foliar fertilizer, characterized in that, its raw materials include: residue extract of Cinnamomum camphora var. borneolifera, sodium selenite, acidic silica sol, and EDTA chelated zinc; 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 in a ratio of 1 g:(5 mL - 10 mL), performing microwave-ultrasound for 5 min - 20 min under the condition of 20°C - 50°C, and after filtration, subjecting the filtrate to reduced pressure distillation to obtain the residue extract of Cinnamomum camphora var. borneolifera; The ratio of the residue extract of Cinnamomum camphora var. borneolifera, the sodium selenite, and the acidic silica sol is (3 mL - 10 mL):(4 g - 10 g):1 L; The ratio of the EDTA chelated zinc to the sodium selenite is (40 g - 100 g):(4 g - 10 g).

2. The selenium-rich cadmium-reducing foliar fertilizer according to claim 1, characterized in that, the ultrasonic power is 400 W - 600 W, and the microwave power is 200 W - 300 W.

3. The selenium-rich cadmium-reducing foliar fertilizer according to claim 1, characterized in that, The pH of the acidic silica sol is less than 3.5, and the SiO 2 content is greater than 25%.

4. The raw materials of the selenium-rich cadmium-reducing foliar fertilizer according to claim 1 further include a spreading agent.

5. A preparation method of the selenium-rich cadmium-reducing foliar fertilizer according to claim 4, characterized in that, comprises the following steps: Dissolving the raw materials except the acidic silica sol in the acidic silica sol, and then adding the spreading agent and mixing evenly to obtain the product.

6. A using method of the selenium-rich cadmium-reducing foliar fertilizer according to any one of claims 1 to 4, characterized in that, spraying the selenium-rich cadmium-reducing foliar fertilizer twice respectively during the heading stage and the filling stage of rice, and the spraying liquid amount is based on the standard that the front and back sides of the rice leaves are covered with mist droplets.

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