Organic foliar fertilizer for reducing cadmium and increasing yield of crops and preparation method thereof

Abstract

The present invention relates to the technical field of farmland soil contamination remediation, specifically disclosing an organic foliar fertilizer for reducing cadmium and increasing crop yields, and its preparation method. The organic foliar fertilizer is composed of a variety of raw materials, including plant organic selenium extract, an organosilicon additive, a biogas slurry extract, monosilicic acid, and a hydroxamic acid-type siderophore. It can effectively reduce cadmium and increase crop yields, and can be applied over large areas via drone spraying, greatly improving implementation efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of farmland soil pollution remediation, and in particular to an organic foliar fertilizer for reducing cadmium and increasing crop yield, and a preparation method thereof. Background Art

[0002] Currently, there are relevant technical products on the market to address the issue of cadmium reduction in crops, such as organic foliar inhibitors and inorganic foliar inhibitors. However, these basically use physical or chemical principles for repair, and there are few products that combine biological repair. There may be secondary pollution problems, and it is difficult for existing products to achieve cadmium reduction and increase production at the same time.

[0003] CN111646843A discloses a selenium-enriched, cadmium-reducing foliar fertilizer for rice and its preparation method. This invention uses liquid sodium silicate as the primary raw material, adds organosilicon-coupled selenium, zinc, manganese, titanium, and other trace elements, and chitosan as a composite synergist, to produce a highly efficient, selenium-enriched, cadmium-reducing foliar fertilizer for rice. This technology effectively reduces cadmium without significantly impacting rice yield.

[0004] CN114903049A discloses the application of hydroxamic acid siderophores as rice cadmium reduction preparations, and applying them to cadmium-contaminated paddy soils for growing rice can significantly reduce the cadmium content in rice grains. However, applying hydroxamic acid siderophores directly to cadmium-contaminated paddy soils may significantly affect crop yields, because the excessive presence of hydroxamic acid siderophores affects the coexistence of rhizospheric bacteria and bacterial wilt, increases the occurrence of crop diseases, and thus affects the growth and yield of crops; on the other hand, because siderophores chelate iron ions, they may reduce the absorption of iron by plants, thereby affecting the synthesis of chlorophyll, and thus affecting photosynthesis and yield. In addition, this technology is applied to the soil in any period or any several periods such as the soil tillering period, heading period, filling period, and wax ripe period to achieve the desired effect. In order to apply uniformly, supporting stirring measures may be required, and when the fields are uneven, manual application is required, and mechanical large-scale application cannot be adopted. If the farming season is missed, the effect may be poor, and the overall implementation efficiency is not high. Summary of the Invention

[0005] In view of the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide an organic foliar fertilizer for reducing cadmium and increasing yield of crops and a preparation method thereof. The organic foliar fertilizer is composed of a variety of raw materials such as plant organic selenium extract, organosilicon additives, biogas slurry extract, organosilicon, hydroxamic acid type iron carriers, etc. It integrates multiple principles such as physics, chemistry, and biology, can effectively achieve the reduction of cadmium and increase of crop yield, and can be spread over a large area by drone spraying, greatly improving the implementation efficiency.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] An organic foliar fertilizer for reducing cadmium and increasing crop yield is prepared from the following components, measured in parts by weight: 3-4 parts of plant organic selenium extract, 2.5-3.5 parts of organosilicon additive, 45-55 parts of biogas slurry extract, 140-160 parts of monosilicic acid, 150-170 parts of hydroxamic acid-type siderophore, and 550-650 parts of distilled water.

[0008] Preferably, the preparation is made from the following components in parts by weight: 3 parts of plant organic selenium extract, 3 parts of organosilicon additive, 50 parts of biogas slurry extract, 150 parts of monosilicic acid, 160 parts of hydroxamic acid type siderophore and 620-650 parts of distilled water.

[0009] The preparation method comprises the following steps:

[0010] (1) 3-4 parts by weight of plant organic selenium extract, 150-170 parts by weight of hydroxamic acid-type siderophore, and 60-80 parts by weight of distilled water were uniformly mixed, and then treated in a high-temperature and high-pressure sterilizer for 15-20 minutes at a temperature of 120-150° C. and a saturated vapor pressure of 0.100 MPa-0.520 MPa. The mixture was then placed in a microwave ultrasonic mixing reactor with an ultrasonic frequency of 25 kHz, and the mixture was kept at a constant temperature of 35-45° C. for 2-2.5 hours, and then cooled to room temperature to obtain Agent 1;

[0011] (2) Pour 140-160 parts by weight of monosilicic acid into the same parts by weight of distilled water, stir evenly, then add 45-55 parts by weight of biogas slurry extract and 2.5-3.5 parts by weight of organosilicon additive, place the resulting mixture in a microwave ultrasonic mixing reactor, set the ultrasonic frequency to 25 kHz, and react at a constant temperature of 40-45°C for 30-45 minutes, then cool to room temperature to obtain Agent 2;

[0012] (3) Mixing the reagent 1 and the reagent 2 prepared in steps (1) and (2), adding the remaining weight portion of distilled water, heating to 50-60° C., stirring at a speed of 800-1200 rpm for 2-3 h, then cooling to room temperature, filtering with a filter with a 100-mesh pore size, and measuring the pH value of 8-9 with a pH meter, thereby obtaining the organic foliar fertilizer for reducing cadmium and increasing yield of crops.

[0013] The plant organic selenium extract is obtained by extracting selenium-rich plant stems and leaves. The plant organic selenium element content in the plant organic selenium extract accounts for more than 85% of the total selenium element content, and the concentration of organic selenium in the plant organic selenium extract is more than 2500 mg / L.

[0014] Furthermore, the preparation method of the plant organic selenium extract comprises the following steps:

[0015] 1) Grind the stems and leaves of selenium-rich plants through a 100-mesh sieve;

[0016] 2) adding 15 times the mass of distilled water to the crushed and sieved selenium-rich plant stem and leaf powder, stirring to dissolve, then adding a certain amount of pectinase, and heating in a water bath at 50°C±2°C for 2-2.5 hours; then filtering, taking the filtrate, adding 2-4 times the volume of anhydrous ethanol thereto, centrifuging, collecting the alcohol precipitation solution, adding the aforementioned volume of anhydrous ethanol to the remaining alcohol precipitate, centrifuging, collecting the alcohol precipitation solution, repeating this process 2-3 times, combining the collected alcohol precipitation solutions, and concentrating by evaporation to obtain a plant organic selenium extract.

[0017] Furthermore, the selenium-rich plant is selected from at least one of rapeseed, seaweed, cabbage, and cardamine.

[0018] Furthermore, the pectinase is polygalacturonase, the concentration of the pectinase is 7wt%, and the added amount is 1 / 10 of the mass of the selenium-rich plant stem and leaf powder.

[0019] Furthermore, the method for preparing the biogas slurry extract comprises the following steps:

[0020] A certain amount of biogas slurry is collected and poured into a sedimentation tank. After the large suspended particles are removed by sedimentation in the sedimentation tank, it is then ultrafiltered under a pressure of 0.8-1.2 MPa, a sieve aperture of 0.002-0.1 μm, and a molecular weight cut-off of 300-1200 million Daltons to obtain a biogas slurry extract. The biogas slurry extract is rich in organic molecules such as amino acids, humic acid, gibberellins, and indoleacetic acid, and the organic matter content is >30%.

[0021] Furthermore, the organosilicon auxiliary agent is ethoxy-modified polytrisiloxane.

[0022] Furthermore, the monosilicic acid has a silicon content of ≥25%.

[0023] The application of the above-mentioned organic foliar fertilizer for reducing cadmium and increasing crop yield in reducing the cadmium content of brown rice and increasing rice yield is specifically as follows: the organic foliar fertilizer is diluted and sprayed on the leaves and backs of rice planted in cadmium-contaminated fields.

[0024] Furthermore, the cadmium pollution in the soil of the cadmium-contaminated field is moderate, with a pH value of ≤5.5 and an effective cadmium content in the soil of 0.9-1.5 mg / kg. The organic foliar fertilizer is used at a dosage of 0.6 L per mu, diluted with water at a volume ratio of 1:50-100, and then sprayed onto the leaves and backs of rice planted in the cadmium-contaminated field. The spraying period is the early tillering stage, the heading stage, and the filling stage, and a total of 3 sprayings are performed.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The present invention is based on the fact that foliar fertilizer has composite components such as iron carriers, silicon, and selenium, which can reduce the cadmium content in the leaves through the coupling effects of adsorption, complexation, and chelation. At the same time, it contains organic silicon additives, etc., which can achieve the effects of increasing efficiency and saving application amount.

[0027] (2) The organic foliar fertilizer of the present invention has a diversified ratio, and the raw materials are easily available and the cost is low. It can simultaneously meet the plant's needs for multiple nutrients such as iron, silicon, selenium, organic matter, etc., while achieving cadmium reduction and yield increase.

[0028] (3) The preparation and use methods of the organic foliar fertilizer of the present invention are simple to operate, can be operated mechanically using a plant protection machine, etc., have high implementation efficiency, and are suitable for large-scale promotion. DETAILED DESCRIPTION

[0029] The applicant further describes the technical solution of the present invention in conjunction with specific embodiments below, but the scope of protection requested by the claims of the present invention is not limited to these embodiments.

[0030] The components used in the examples and comparative examples are described as follows:

[0031] The preparation method of S1 plant organic selenium extract comprises the following steps:

[0032] 1) The selenium-rich plant stems and leaves (a mixture of rapeseed leaves and seaweed in equal mass ratio) are dried and then crushed through a 100-mesh sieve.

[0033] 2) adding 15 times the mass of distilled water to the crushed and sieved selenium-rich plant stem and leaf powder, stirring with a glass rod for 5 minutes at room temperature, then standing and dissolving for 40 minutes, then adding 7wt% of polygalacturonase (destroying plant cell walls to make organic selenium more easily released from plant tissues) with a mass of 1 / 10 of the selenium-rich plant stem and leaf powder, heating in a water bath at 50°C±2°C for 2 hours, then filtering with suction, taking the filtrate, adding 3 times the volume of anhydrous ethanol thereto, standing at room temperature for 24 hours, then centrifuging at 4000r / min for 10 minutes, collecting the alcohol precipitation solution, adding the aforementioned same volume of anhydrous ethanol to the remaining alcohol precipitation, standing at room temperature for 24 hours, then centrifuging at 4000r / min for 10 minutes, collecting the alcohol precipitation solution, repeating 3 times, combining the collected alcohol precipitation solutions, and concentrating by evaporation to obtain a plant organic selenium extract.

[0034] The total and inorganic selenium contents of the plant organic selenium extract were determined according to GB5009.93-2017 and DBS42 / 010-2018. The organic selenium content is the total selenium content minus the inorganic selenium content. Analysis revealed that the plant organic selenium extract accounted for over 85% of the total selenium content, with a concentration of 2500 mg / L.

[0035] The preparation method of S2 biogas slurry extract comprises the following steps: 2 The fluid flux of h is used to collect the biogas slurry in the biogas tank into the sedimentation tank. After the large suspended particles are removed by sedimentation in the sedimentation tank, the microfiltration separation technology (ultrafiltration is carried out under the conditions of pressure of 0.8-1.2MPa, sieve pore size of 0.002-0.1μm, and molecular weight cut-off of 300-1200 million Daltons) is used to remove organic macromolecules such as proteins and polysaccharides to obtain the biogas slurry extract. The biogas slurry extract is rich in organic molecules such as amino acids, humic acid, gibberellins, indoleacetic acid, and the organic matter content is greater than 30%.

[0036] S3 silicone additive: ethoxy-modified polytrisiloxane, purchased from Laiyang Zhongxing Silicone Technology Co., Ltd., critical micelle concentration (CMC) = 5.0×10 -4 g / mL.

[0037] S4 monosilicic acid: molecular formula (Si(OH)4, silicon content ≥ 25%, purchased from Zongyang County Sanjin Pigment Co., Ltd.

[0038] S5 hydroxamic acid siderophore: Hydroxamic acid siderophore was produced by Pseudomonas fluorescens and purchased from Jiangxi Ouke Ecological Technology Co., Ltd.

[0039] Example 1: A method for preparing an organic foliar fertilizer for reducing cadmium and increasing crop yield, comprising the following steps:

[0040] (1) After 3 parts by weight of plant organic selenium extract, 160 parts by weight of hydroxamic acid siderophore and 80 parts by weight of distilled water are uniformly mixed, the mixture is treated in a high temperature and high pressure sterilizer (150°C, saturated steam pressure 0.420MPa) for 20 minutes, and then placed in a microwave ultrasonic mixing reactor, the ultrasonic frequency is set to 25kHz, and the reaction is carried out at a constant temperature of 40°C for 2.5 hours, and then cooled to room temperature to obtain an organic foliar fertilizer semi-finished solution. In this step, high temperature and high pressure and ultrasonic treatment can increase the movement between molecules, thereby improving solubility, making it easier for hydroxamic acid siderophore to combine with plant organic selenium, and promoting the structural change of hydroxamic acid siderophore and the formation of organic selenium chemical bonds.

[0041] (2) Pour 150 parts by weight of monosilicic acid into 150 parts by weight of distilled water, stir evenly, add 50 parts by weight of biogas slurry extract and 3 parts by weight of organosilicon additive, place the mixture in a microwave ultrasonic mixing reactor, set the ultrasonic frequency to 25 kHz, react at 45°C for 40 minutes, and then cool to room temperature.

[0042] (3) The prepared agents of (1) and (2) are mixed, and 400 parts by weight of water are added, and the mixture is stirred at 55° C. for 2 h using a high-speed stirrer at a speed of 1200 rpm until all the substances are fully mixed. The mixture is then heated until it is cooled to room temperature, filtered using a filter with a pore size of 100, and the pH value is determined to be 8.5 using a pH meter, thereby obtaining the organic foliar fertilizer for reducing cadmium and increasing yield of crops.

[0043] Comparative Examples 1 to 5: Preparation method of organic foliar fertilizer

[0044] Prepare the components and their corresponding weight parts according to Table 1, and prepare comparative organic foliar fertilizer products 1 to 5 by referring to the method of Example 1.

[0045] The components and corresponding weight parts of the organic foliar fertilizers prepared in Example 1 and Comparative Examples 1 to 5 are shown in Table 1.

[0046] Table 1

[0047]

[0048] Test example

[0049] In Yonghe Town, Liuyang City, Changsha City, Hunan Province, a flat field with an area of ​​about 1 mu was selected for the verification test of the effects of organic foliar fertilizer and its components. The test set up 7 treatments, each with 3 replicates, for a total of 21 plots, arranged in random blocks.

[0050] The basic physical and chemical properties of the test soil are: soil pH is 5.14, cation exchange capacity is 15.44 cmol / kg, organic matter is 30.62 g / kg, total cadmium content in soil is 4.23 mg / kg, and available cadmium content is 1.23 mg / kg.

[0051] Seven treatments were set up: the dosage of each treatment product was based on the total spraying volume of organic foliar fertilizer 0.6L / mu, diluted with water at a volume ratio of 1:100, and the total spraying solution was 60L / mu, sprayed three times with the same spraying volume each time, sprayed at the early tillering stage, heading stage, and grain filling stage respectively;

[0052] Treatment 1: blank (CK), conventional fertilization, total spraying water 60L / mu;

[0053] Treatment 2: conventional fertilization + 0.6 L / mu of organic foliar fertilizer prepared in Example 1, with the total spray solution after dilution being 60 L / mu;

[0054] Treatment 3: conventional fertilization + 0.6 L / mu of organic foliar fertilizer prepared in Comparative Example 1, the total spraying solution after dilution was 60 L / mu;

[0055] Treatment 4: conventional fertilization + 0.6 L / mu of organic foliar fertilizer prepared in Comparative Example 2, the total spraying solution after dilution was 60 L / mu;

[0056] Treatment 5: conventional fertilization + 0.6 L / mu of organic foliar fertilizer prepared in Comparative Example 3, with a total spray solution of 60 L / mu after dilution;

[0057] Treatment 6: conventional fertilization + 0.6 L / mu of organic foliar fertilizer prepared in Comparative Example 4, with a total spray solution of 60 L / mu after dilution;

[0058] Treatment 7: conventional fertilization + 0.6 L / mu of organic foliar fertilizer prepared in Comparative Example 5, with a total spray solution of 60 L / mu after dilution;

[0059] The Shenliangyou 5814 rice variety is planted uniformly, and field water management and fertilization conditions are consistent with local management conditions.

[0060] How to use organic foliar fertilizer: Mix organic foliar fertilizer with water in a mass ratio of 1:100, stir evenly to obtain a diluted solution, and spray it on the rice leaves and back of the leaves at the early stage of tillering 20 days after rice transplanting, with a spraying solution of 20L / mu. Then spray it once at the heading stage and filling stage, 20L / mu each time, for a total of 3 spraying times.

[0061] Compared to existing heavy metal control products used in soil, the organic foliar fertilizer spraying method of this application can timely replenish the nutrients needed by crops and reduce the occurrence of pests and diseases. At the same time, this organic foliar fertilizer can be sprayed over large areas using unmanned plant protection machines, with a daily spraying volume of 300 to 500 mu, greatly improving implementation efficiency.

[0062] During rice harvest, individual rice plots are harvested, dried, and weighed to calculate yield. Randomly, diversely, and equally sampled agricultural products (approximately 1 kg) are collected from each plot to test for cadmium content. The rice samples are sent to Zhejiang Zhenong Testing and Certification Technology Co., Ltd. for testing.

[0063] Results and Analysis:

[0064] 1. Effects of different treatments on rice yield

[0065] The effects of different treatments on rice yield are shown in Table 2.

[0066] Table 2

[0067]

[0068] As shown in Table 2, Treatment 7 experienced a yield reduction of 23.7 kg / mu compared to Treatment 1 (CK), a yield reduction of approximately 5%. This indicates that applying hydroxamic acid siderophores as the active ingredient in combination with an organosilicon adjuvant (synergistic solvent) to foliage can result in yield reduction. This reduction may be due to the fact that while the organosilicon adjuvant improves the coverage and penetration of foliar fertilizers, facilitating better absorption of the active ingredient by plant leaves, hydroxamic acid siderophores can lead to excessive chelation of extracellular iron, hindering iron absorption and thus affecting chlorophyll synthesis. This, in turn, impacts photosynthesis efficiency, leading to yield reductions.

[0069] Treatment 5 increased rice yield by 10.5 kg / mu compared to Treatment 1 (CK), a relatively limited increase. This suggests that applying monosilicic acid and plant organic selenium extracts in combination with an organosilicon adjuvant to foliar application can increase rice yield to a certain extent. This is because the organic foliar fertilizer prepared in Comparative Example 3 contains beneficial elements such as silicon and selenium, which are beneficial to crop growth.

[0070] Treatment 4 increased rice yield by 8.4 kg / mu compared to Treatment 1 (CK), a relatively limited increase. This suggests that applying hydroxamic acid siderophores, monosilicic acid, and plant-organic selenium extracts to foliage in combination with an organosilicon adjuvant can still increase rice yield to a certain extent. This is because the organic foliar fertilizer prepared in Comparative Example 2 contains beneficial elements such as silicon and selenium, which are beneficial to crop growth. These beneficial effects outweigh the yield reduction caused by the hydroxamic acid siderophores. However, the overall yield increase was not significant, slightly inferior to that of Treatment 5.

[0071] Treatment 6 increased rice yield by 31.8 kg / mu compared to Treatment 1 (CK). This indicates that applying biogas slurry extract as the active ingredient combined with a silicone adjuvant to the leaves can significantly increase rice yield. This is because biogas slurry extract contains organic matter, such as humus, which can increase crop yield.

[0072] Treatment 3 increased rice yield by 44.7 kg / mu compared with treatment 1 (CK), which is a significant increase. This shows that monosilicic acid, plant organic selenium extract, and biogas slurry extract combined with organosilicon adjuvants applied to the leaves can greatly increase rice yield, and the yield-increasing effect is better than treatments 6 and 5.

[0073] Treatment 2 increased rice yield by 56.6 kg / mu relative to Treatment 1 (CK), achieving a yield-increasing effect superior to Treatment 3. This indicates that the application of hydroxamic acid siderophores, monosilicic acid, plant organic selenium extracts, and biogas slurry extracts to foliage in combination with organosilicon adjuvants can still significantly increase rice yield and reverse the yield-reducing effect of hydroxamic acid siderophores applied alone to foliage. This is because the organic foliar fertilizer prepared in Example 1 contains beneficial elements such as silicon and selenium, and the biogas slurry extract contains organic matter components such as humus, both of which can promote crop photosynthesis and thus increase crop yield.

[0074] 2. Effects of different treatments on cadmium content in brown rice

[0075] The effects of different treatments on the cadmium content in brown rice are shown in Table 3.

[0076] Table 3

[0077]

[0078]

[0079] As shown in Table 3, treatments 2 through 7 all reduced cadmium content in brown rice to varying degrees. Treatment 2 achieved the greatest reduction, reducing cadmium by 0.71 mg / kg compared to treatment 1 (CK), a 79.8% reduction. Furthermore, only the brown rice harvested from treatment 2 met the national food contaminant limit for cadmium in brown rice.

[0080] Treatment 7 showed a 50.6% reduction in cadmium content in brown rice compared to Treatment 1 (CK). This suggests that applying hydroxamic acid siderophores as the active ingredient in combination with an organosilicon adjuvant (synergistic solvent) to the leaves significantly reduced cadmium content in brown rice. This is consistent with the effects of applying hydroxamic acid siderophores directly to cadmium-contaminated paddy soil. Hydroxamic acid siderophores, through their powerful metal chelating ability, form stable complexes with cadmium ions in plants, effectively reducing cadmium bioavailability. They also regulate redox reactions in plants. By regulating redox reactions, they can alter the chemical form and distribution of cadmium ions in plants, thereby reducing their bioavailability and minimizing damage to plants. Furthermore, organosilicon adjuvants significantly improved pesticide wetting, spreading, and adhesion on plant leaves, significantly increasing the deposition and retention of pesticide droplets on leaves. This significantly enhanced the efficacy of the droplets on leaves, thereby increasing the cadmium reduction effect.

[0081] Treatment 6 showed an 11.2% reduction in rice cadmium content compared to Treatment 1 (CK). This suggests that applying biogas slurry extract as the active ingredient in combination with a silicone adjuvant to leaves can also reduce cadmium levels in brown rice to some extent. This is because biogas slurry extract contains organic matter, such as humus, which may reduce the toxic effects of cadmium on rice crops by increasing their antioxidant capacity, but the reduction is relatively small.

[0082] The cadmium content in rice from Treatment 5 was reduced by 26.9% compared to Treatment 1 (CK). This indicates that monosilicic acid, plant organic selenium extract, and organosilicon additives applied to the leaves can reduce the cadmium content of brown rice to a certain extent. This is because the organic foliar fertilizer prepared in Comparative Example 3 contains beneficial elements such as silicon and selenium, which can reduce the cadmium content of brown rice through complexation, antagonism, and adsorption. Organic selenium can antagonize heavy metals such as cadmium, inhibiting the absorption of cadmium by rice, thereby reducing the cadmium content in the plant. Furthermore, organic selenium can form stable complexes with cadmium in the plant, which reduces the free ion concentration of cadmium and mitigates its toxic effects. Organic selenium can also promote the synthesis of phytochelatin peptides, promoting the complexation of cadmium with phytochelatin peptides and reducing the content of harmful cadmium forms in rice. Monosilicic acid, on the other hand, forms stable silicates with cadmium ions, thereby inhibiting the activity and bioavailability of cadmium ions.

[0083] The cadmium content in rice from Treatment 4 was 60.6% lower than that in Treatment 1 (CK). This indicates that applying hydroxamic acid siderophores, monosilicic acid, and plant-organic selenium extracts to foliage in combination with an organosilicon additive can significantly reduce the cadmium content in brown rice. This is because the organic foliar fertilizer prepared in Comparative Example 2 contains beneficial elements such as iron, silicon, and selenium, which can significantly reduce the cadmium content in brown rice through chelation, antagonism, and complexation.

[0084] The cadmium content of rice in treatment 3 was reduced by 39.3% compared with treatment 1 (CK), which shows that monosilicic acid, plant organic selenium extract, and biogas slurry extract combined with silicone adjuvants applied to the leaves can still reduce the cadmium content of brown rice to a certain extent, and can fully exert the synergistic effect between them, and the cadmium reduction effect is better than treatment 6 and treatment 5.

[0085] Cadmium content in rice grains in Treatment 2 decreased by 79.8% compared to Treatment 1 (CK). This suggests that applying hydroxamic acid siderophores, monosilicic acid, plant organic selenium extract, and biogas slurry extract to the leaves in combination with an organosilicon adjuvant significantly reduced cadmium content in brown rice. This is because the hydroxamic acid siderophores can combine with monosilicic acid to compete with soil cadmium ions for binding sites, reducing cadmium ion transport within the grain. Furthermore, the combination of monosilicic acid and organic selenium can form stable complexes or silicates with cadmium through antagonism, complexation, and adsorption, inhibiting the activity and bioavailability of cadmium ions. The addition of biogas slurry extract may have enhanced the cadmium-reducing activity of the siderophore active ingredients and, through a synergistic effect with monosilicic acid and organic selenium, further reduced cadmium content in rice.

Claims

1. An organic foliar fertilizer for reducing cadmium and increasing crop yield, characterized in that: The preparation method is prepared from the following components, in parts by weight: 3-4 parts of plant organic selenium extract, 2.5-3.5 parts of organosilicon additive, 45-55 parts of biogas slurry extract, 140-160 parts of monosilicic acid, 150-170 parts of hydroxamic acid-type siderophore, and 550-650 parts of distilled water. The preparation method comprises the following steps: (1) 3-4 parts by weight of plant organic selenium extract, 150-170 parts by weight of hydroxamic acid-type siderophore and 60-80 parts by weight of distilled water are uniformly mixed, and then treated in a high-temperature and high-pressure sterilizer for 15-20 minutes at a temperature of 120-150°C and a saturated vapor pressure of 0.100 MPa-0.520 MPa. The mixture is then placed in a microwave ultrasonic mixing reactor with an ultrasonic frequency set to 25 kHz, and the mixture is kept at a constant temperature of 35-45°C for 2-2.5 hours, and then cooled to room temperature to obtain Agent 1; (2) Pour 140-160 parts by weight of monosilicic acid into the same parts by weight of distilled water, stir evenly, then add 45-55 parts by weight of biogas slurry extract and 2.5-3.5 parts by weight of organosilicon additive, place the resulting mixture in a microwave ultrasonic mixing reactor, set the ultrasonic frequency to 25 kHz, and react at a constant temperature of 40-45°C for 30-45 minutes, then cool to room temperature to obtain Agent 2; (3) Mixing the reagents 1 and 2 prepared in steps (1) and (2), adding the remaining weight portion of distilled water, heating to 50-60° C., stirring at 800-1200 rpm for 2-3 hours, then cooling to room temperature, filtering with a filter with a 100-mesh pore size, and measuring the pH value of 8-9 with a pH meter, thereby obtaining the organic foliar fertilizer for reducing cadmium and increasing yield of crops; The preparation method of the plant organic selenium extract comprises the following steps: 1) Crush the stems and leaves of selenium-rich plants through a 100-mesh sieve; 2) Add 15 times the mass of distilled water to the crushed and sieved selenium-rich plant stem and leaf powder, stir to dissolve, then add a certain amount of pectinase, and heat in a water bath at 50°C ± 2°C for 2-2.5 hours; then filter, take the filtrate, add 2-4 times the volume of anhydrous ethanol to the filtrate, centrifuge, collect the alcohol precipitation solution, add the aforementioned volume of anhydrous ethanol to the remaining alcohol precipitate, centrifuge, collect the alcohol precipitation solution, repeat 2-3 times, combine the collected alcohol precipitation solutions, and evaporate and concentrate to obtain a plant organic selenium extract; The plant organic selenium content in the plant organic selenium extract accounts for more than 85% of the total selenium content, and the concentration of organic selenium in the plant organic selenium extract is more than 2500 mg / L; The method for preparing the biogas slurry extract comprises the following steps: A certain amount of biogas slurry is collected and poured into a sedimentation tank. After sedimentation in the sedimentation tank to remove suspended particles, it is then ultrafiltered under a pressure of 0.8-1.2 MPa, a sieve aperture of 0.002-0.1 μm, and a molecular weight cut-off of 300-1200 million Daltons to obtain a biogas slurry extract. The biogas slurry extract is rich in organic molecules such as amino acids, humic acid, gibberellins, and indoleacetic acid, and has an organic matter content of >30%; The organosilicon additive is ethoxy-modified polytrisiloxane; The silicon content in the monosilicic acid is ≥25%.

2. The organic foliar fertilizer for reducing cadmium and increasing yield of crops according to claim 1, characterized in that: The preparation is made from the following components in parts by weight: 3 parts of plant organic selenium extract, 3 parts of organosilicon additive, 50 parts of biogas slurry extract, 150 parts of organosilicon, 160 parts of hydroxamic acid type siderophore and 620-650 parts of distilled water.

3. The organic foliar fertilizer for reducing cadmium and increasing yield of crops according to claim 1 or 2, characterized in that: The selenium-rich plant is selected from at least one of rapeseed, seaweed, cabbage, and cardamine; The pectinase is polygalacturonase, the concentration of the pectinase is 7wt%, and the added amount is 1 / 10 of the mass of the selenium-rich plant stem and leaf powder.

4. Use of the organic foliar fertilizer for reducing cadmium and increasing yield of crops according to any one of claims 1 to 3 in reducing the cadmium content of brown rice and increasing rice yield.

5. The use according to claim 4, characterized in that Specifically, the organic foliar fertilizer is diluted and sprayed onto the leaf surfaces and backs of rice grown in cadmium-contaminated fields.

6. The use according to claim 5, characterized in that The cadmium pollution in the soil of the cadmium-contaminated field is moderate, with a pH value of ≤5.5 and an effective cadmium content in the soil of 0.9-1.5 mg / kg. The organic foliar fertilizer is used at a dosage of 0.6 L per mu, diluted with water at a volume ratio of 1:50-100, and then sprayed onto the leaves and backs of rice planted in the cadmium-contaminated field. The spraying period is the early tillering stage, the heading stage, and the filling stage, and a total of 3 sprayings are applied.

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