Chitosan-selenium compound foliar fertilizer, preparation method and application and application method thereof

Abstract

The invention discloses a chitosan-selenium compound foliar fertilizer as well as preparation and application thereof. The compound foliar fertilizer is prepared from the following raw materials: chitosan, selenium dioxide, glacial acetic acid and Tween 20 in a mass volume ratio of (0.2-1): (0.2-0.3): (30-80): 0.001 g / g / mL / g. According to the compound foliar fertilizer disclosed by the invention, the selenium element is enhanced to prevent and control the absorption and accumulation of the overground parts of the leaf vegetables on arsenic and cadmium; meanwhile, an environment-friendly natural polymer material chitosan is compounded with selenium, the biomass of the leaf vegetables can be remarkably improved by spraying the chitosan-selenium compound leaf fertilizer on the leaf surfaces, and the method is a prevention and control method with huge application prospects and potential.

Description

Technical Field

[0001] The present invention belongs to the technical field of compound fertilizers, and particularly relates to a chitosan-selenium composite foliar fertilizer for controlling the absorption and accumulation of arsenic and cadmium in the above-ground parts of leafy vegetables, a preparation method thereof, an application thereof, and an application method thereof. Background Art

[0002] The foliar spraying technology is to directly spray the spray agent on the plant leaves and enter the plant interior through leaf absorption, so as to achieve the purpose of fertilization or pest control. The foliar spraying technology makes full use of the physiological characteristics of plant leaves, that is, the leaf surface has rich stomata and epidermal cells, which can effectively absorb and transport nutrients. This technology has the advantages of improving fertilizer utilization rate, reducing environmental pollution, improving crop yield and quality, and saving labor. In application, the foliar spraying technology can be used to spray fertilizers, pesticides and growth regulators. In the future, the development direction of the foliar spraying technology includes high efficiency and environmental protection, precise fertilization, multi-functional integration and intelligent foliar spraying. Foliar spraying is an important means for sustainable crop production management and has important commercial significance worldwide. Especially when: the soil conditions limit the availability of applied nutrients or the applied nutrients may have a high loss rate, or during the plant growth stage, the interaction between the internal needs of the plant and the environmental conditions restricts the transport of nutrients to the key organs of the plant. In these cases, foliar spraying can significantly improve the nutrient deficiency conditions of the plant body. The nutrient components entering the plant through the leaves can interact with heavy metals such as arsenic and cadmium in the plant body, thereby possibly inhibiting the absorption, transport and accumulation of arsenic and cadmium by the plant. It is known that foliar spraying of mineral nutrient elements (such as Si, Se, Zn, etc.) can control the absorption of heavy metals such as arsenic or / and cadmium by plants and alleviate heavy metal toxicity. Using the foliar spraying technology is not only simple and convenient, economically effective, but also not easily restricted by the soil environment.

[0003] Selenium is an important trace element and plays a crucial role in human health. Selenium can alleviate oxidative stress caused by metal and metalloid stress and affect plant root morphology to inhibit the absorption of metals and metalloids. Chitosan is an environmentally friendly natural polymer material and has a large number of functions in the agricultural, biomedical and feed industries. Chitosan nanoparticles are used for various purposes around the world due to their biodegradability, high permeability, ecological friendliness and low price. Existing chitosan-rich selenium fertilizers have been widely developed, but most of them contain many types of components, and their purposes are mainly focused on increasing the selenium content in crops. There is less research on leafy vegetables, especially on blocking the absorption of arsenic and cadmium in leafy vegetables. Summary of the Invention

[0004] In view of the above problems, on the one hand, the present invention provides a chitosan-selenium compound foliar fertilizer with few component types, which can effectively absorb arsenic and cadmium in leafy vegetables. On the other hand, the present invention provides a simple and feasible preparation method of the chitosan-selenium compound foliar fertilizer. Another object of the present invention is to apply the chitosan-selenium compound foliar fertilizer to leafy vegetables in soil culture and hydroponic experiments for arsenic and cadmium absorption. Finally, the present invention provides a method for spraying the chitosan-selenium compound foliar fertilizer.

[0005] In view of the deficiencies of the prior art, the technical solution adopted by the present invention is as follows: The present invention provides a chitosan-selenium compound foliar fertilizer, which is prepared from the following raw materials in mass-to-volume ratio: chitosan: selenium dioxide: glacial acetic acid: Tween 20 = (0.2 - 1): (0.2 - 0.3): (30 - 80): 0.01 g / g / mL / g.

[0006] Preferably, the chitosan-selenium compound foliar fertilizer is prepared from the following raw materials in mass-to-volume ratio: chitosan: selenium dioxide: glacial acetic acid = 0.5: 0.22: 50 g / g / mL.

[0007] The preparation method of the chitosan-selenium compound foliar fertilizer of the present invention includes the following steps:

[0008] Dissolve chitosan in glacial acetic acid, add selenious acid solution, heat and stir for reaction, and then add Tween 20 and mix to obtain.

[0009] Preferably, the degree of deacetylation of chitosan is 95%.

[0010] Preferably, the selenious acid solution is obtained by dissolving selenium dioxide in water.

[0011] Preferably, the temperature of the heating and stirring reaction is 80 - 100 °C, and the time of the heating and stirring reaction is more than 30 min.

[0012] The present invention also includes the application of the chitosan-selenium compound foliar fertilizer in controlling the absorption and accumulation of arsenic and cadmium in leafy vegetables.

[0013] Preferably, the leafy vegetables are amaranth or lettuce, and most preferably amaranth.

[0014] The present invention also includes an application method for the chitosan-selenium compound foliar fertilizer to control the absorption and accumulation of arsenic and cadmium in leafy vegetables, including the following steps:

[0015] During the 20 - 30 days of the growth of leafy vegetables, dilute the chitosan-selenium compound foliar fertilizer described in claim 1 or 2 with water according to the selenium molar concentration to 10 - 50 μmol / L, and spray it on the leaf surface of leafy vegetables.

[0016] Preferably, the liquid spraying amount is based on the standard that the front and back sides of the leaves are covered with liquid droplets, once a day, and continuously sprayed for 7 days.

[0017] The chitosan-selenium compound foliar fertilizer provided by the present invention has only the following raw materials: chitosan, selenium dioxide, glacial acetic acid and Tween 20. It is prepared by compounding the natural material chitosan with elemental selenium and spraying it on leafy vegetables through Tween 20, which can significantly promote the absorption of selenium by leaves and reduce the contents of As and Cd in the above-ground parts of leafy vegetables, thereby achieving the purpose of efficiently reducing arsenic and cadmium.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages:

[0019] The present invention mainly uses heating and magnetic stirring to compound chitosan with selenium element, and adds the surfactant Tween 20 to prepare a foliar spraying material; spraying the chitosan-selenium compound foliar fertilizer on leafy vegetables can significantly control the contents of arsenic and cadmium in the above-ground parts of leafy vegetables. Description of the Drawings

[0020] Figure 1 It is a diagram comparing the differences in the biomass growth rates of amaranth after spraying the foliar fertilizers of Example 1, the examples and Comparative Examples 1-4 on amaranth;

[0021] Figure 2 It is a schematic diagram comparing the contents of arsenic and cadmium in the above-ground parts of amaranth after spraying the foliar fertilizers of Example 1, the examples and Comparative Examples 1-4 on amaranth;

[0022] Figure 3 It is a schematic diagram comparing the contents of arsenic and cadmium in the above-ground parts of lettuce after spraying the foliar fertilizers of Example 1, the examples and Comparative Examples 1-4 on lettuce. Detailed Embodiments

[0023] The technical solutions of the present invention will be further described below in conjunction with the drawings and embodiments. It should be noted that the protection scope of the present invention is not limited to the following embodiments, and these examples are listed only for illustrative purposes and do not limit the present invention in any way.

[0024] The materials, reagents, etc. used in the following embodiments can be obtained from commercial channels without special instructions.

[0025] Example 1

[0026] Dissolve 0.5 g of chitosan with a deacetylation degree of 95% in 50 mL of 1% glacial acetic acid solution, stir for 10 h, sonicate for 10 min, add 10 mL of selenious acid solution (0.22 g of selenium dioxide dissolved in 10 mL of ultrapure water) and mix, stir magnetically at 90 °C for 40 min to form an orange-red solution, dilute it with deionized water according to the selenium molar concentration of 50 μmol / L, and then add 0.001 g of Tween 20 to obtain the chitosan-selenium compound foliar fertilizer.

[0027] The chitosan-selenium composite foliar fertilizer prepared in this example was completed at a reaction temperature of 90 °C. The visual color of the reaction solution is an indicator of the particle size and light absorption of the material, while the reaction temperature is considered a key factor affecting particle size evolution and shape formation. As the temperature increases, the color of the chitosan-selenium composite material gradually darkens, from light yellow to orange, indicating the successful synthesis of the chitosan-selenium composite foliar fertilizer. At 90 °C, the average particle size is approximately 971 nm.

[0028] XRD analysis of the chitosan-selenium composite material prepared in this example found that the chitosan-selenium composite foliar fertilizer has a relatively broad peak at 2θ = 22.4°, without obvious Bragg reflections, which may indicate that the formation of chitosan-selenium presents an amorphous structure through the redox system.

[0029] Fourier transform infrared spectroscopy (FTIR) analysis of the chitosan-selenium composite material prepared in this example found that stretching vibration peaks of O—H (3363.86 cm -1 ), C—O (1079.77 cm -1 ), N—H (1580.91 cm -1 ), and Se—O (846.84 cm -1 ) were found in the FTIR spectrum. This indicates that selenium effectively binds to chitosan particles and the polymerization of composite material particles is successful. Combining with the XPS spectrum, the surface chemical composition of the chitosan-selenium composite foliar fertilizer was determined.

[0030] Zeta potential intensity distribution analysis of the chitosan-selenium composite foliar fertilizer prepared in this example shows that a colloidal suspension with a Zeta potential greater than 40 mV is generally considered to have good stability, while particles with a lower Zeta potential are prone to aggregation. The Zeta potential of the chitosan-selenium composite material prepared in this example is 51 mV, indicating that the composite material has good stability.

[0031] Example 2

[0032] The experimental procedure was the same as in Example 1, and it was diluted with deionized water according to a selenium molar concentration of 10 μmol / L to obtain the chitosan-selenium composite foliar fertilizer.

[0033] Examples 3 - 7

[0034] The experimental procedure was the same as in Example 1, except that the amounts of selenium dioxide were 0.1, 0.2, 0.3, 0.4, and 0.5 g respectively, and five groups of chitosan-selenium composite foliar fertilizers were prepared.

[0035] Comparative Example 1

[0036] The experimental procedure was the same as in Example 1, except that the foliar spray fertilizer was prepared without adding selenious acid solution.

[0037] Comparative Example 2

[0038] The experimental procedure was the same as that of Example 1, except that chitosan was not added to prepare the foliar fertilizer.

[0039] Comparative Example 3

[0040] The experimental procedure was the same as that of Example 1, except that Tween 20 was not added to obtain the chitosan-selenium compound fertilizer.

[0041] Comparative Example 4

[0042] The experimental procedure was the same as that of Example 1, except that Tween 80 was used instead of Tween 20.

[0043] Example 8

[0044] The foliar fertilizers obtained in Examples 1-3 and Comparative Examples 1-5 were respectively used to spray amaranth and lettuce. Among them, the spraying liquid amount was appropriate when the front and back sides of the amaranth leaves were covered with mist droplets, and spraying clean water was used as a control.

[0045] The amaranth seeds were sown in contaminated soil (arsenic content was 75.40 ppm, cadmium content was 5.35 ppm). After growing for 20 days, a 7-day foliar spraying treatment was started. After growing for another 14 days, amaranth samples were collected to measure the arsenic and cadmium contents in the above-ground parts of the amaranth.

[0046] Determination of the total arsenic and total cadmium contents in the above-ground parts of plants: Determined by inductively coupled plasma mass spectrometry (ICP-MS). Weigh 0.05 - 0.2 g of the dried and pulverized plant sample, and use the HNO3-H2O2 system (10 mL of 1:1 (w / v) HNO3 and 1 mL of 30% H2O2) to carry out digestion in a graphite furnace at 105 °C.

[0047] The digestion process is as follows:

[0048] (1) Add 10 mL of 1:1 (w / v) HNO3 to the digestion tube and digest until the remaining digestion solution is about 1 mL;

[0049] (2) Add 1 mL of 30% H2O2 and continue to digest until the digestion solution is clear and transparent, without bubbles, and the remaining solution is about 1 mL. Take out the digestion tube and cool it to room temperature; Dilute the digestion solution to 50 mL with ultrapure water; After the digestion solution is diluted and fixed in volume, pass through a 0.22 μM filter membrane, and dilute it with 0.1 mol / L ultrapure nitric acid (Sigma) to less than 20 ppb; After adding the internal standard indium (Indium, In) to the arsenic standard solution, blank sample and sample, determine the contents of arsenic and cadmium by inductively coupled plasma mass spectrometry (ICP-MS).

[0050] Relative arsenic (cadmium) reduction rate = (1 - C T / C CK )×100%,

[0051] Where: C T As / Cd contents in the aerial parts of Amaranth in the treatment groups, C CK Arsenic / cadmium contents in the aboveground part of Amaranth in the control group (treated with clean water spraying).

[0052] Effects of chitosan-selenium compound foliar fertilizer on the biomass growth rate of Amaranth:

[0053] The chitosan-selenium composite foliar fertilizer prepared by the present invention was applied to soil-grown amaranth experiments, and the growth rate of plant fresh weight before and after spraying (growth rate = increase in fresh weight before and after spraying / initial fresh weight) was measured to measure the effect on biomass. Figure 1-2 shown.

[0054] Depend on Figure 1 It can be seen that compared with the treatment of spraying clear water, the high concentration of Example 1 and the low concentration of Example 2 chitosan-selenium composite foliar fertilizers showed a significant promoting effect on the biomass of amaranth, and the increase in the growth rate reached 64.7% and 48.6% respectively. It is shown that spraying the chitosan-selenium foliar fertilizer prepared by the present invention can effectively increase the biomass of amaranth. Comparative Examples 1-3 also contribute to the increase of amaranth biomass, wherein, without adding selenous acid solution to Example 1, only chitosan treatment increases the fresh weight growth rate of amaranth by 33%, Comparative Example 2 contains selenous acid solution but does not contain chitosan treatment and increases by 35.1%, Comparative Example 3 does not add Tween 20 to treat the fresh weight of amaranth and increases by 30%, while Comparative Example 4 replaces Tween 20 with Tween 80 and only increases by 14.8%, which shows that its effect is far lower than the effect of Tween 20. It can be seen from the above that the high concentration of Example 1 increases the fresh weight growth rate of amaranth by 31.7% compared with Comparative Example 1, and increases by 34.7% compared with Comparative Example 2. The low concentration of the embodiment increased the fresh weight of amaranth by 13.3% and 33.6% compared with the comparative example 2. It can be seen that the use of these three substances alone has a certain improvement on the biomass of amaranth. However, the effect is far lower than the combined use of the three substances, which shows that the combination of the three substances has a synergistic effect.

[0055] Depend on Figure 2 It can be seen that compared with the control of spraying clear water, both Example 1 and Example 2 significantly reduced the arsenic content in the aerial part of Amaranth. Example 1 has significant advantages over Comparative Example 1 and Comparative Example 2 used alone. Combined with Comparative Example 3 and Comparative Example 4, it is shown that the use of Tween 20 has more obvious advantages. It can be seen that the chitosan-selenium composite foliar fertilizer prepared in this application can significantly reduce the arsenic and cadmium contents in the aerial part of Amaranth.

[0056] Example 9

[0057] The experimental process was the same as in Example 8, except that lettuce was sprayed. Figure 3as shown

[0058] from Figure 3 It can be seen that the effect of spraying on lettuce is significantly inferior to that on amaranth. Moreover, compared with the control of spraying clear water, both Example 1 and Example 2 significantly reduced the cadmium content in the above-ground part of amaranth. Example 1 has certain advantages compared with Comparative Example 1 and Comparative Example 2. Among them, the relative cadmium and arsenic reduction rates of the high concentration of Example 1 are significantly higher than those of Comparative Example 1 and Comparative Example 2 used alone; at the same time, the effect of not using Tween 20 or replacing Tween 20 is significantly inferior to that of using Tween 20.

[0059] At the same time, the experimental process of Example 8 was used to spray the chitosan-selenium compound foliar fertilizer prepared in Examples 3-7 on amaranth. As a result, compared with the control of spraying clear water, the effects of Examples 3, 4, Example 1, Example 5, Example 6, and Example 7 first increased and then decreased, with an inflection point at Example 1. The effects of the chitosan-selenium compound foliar fertilizers prepared in Examples 4 and 5 are close to those of the chitosan-selenium compound foliar fertilizer prepared in Example 1. The effect of spraying the chitosan-selenium compound foliar fertilizer prepared in Example 3 on amaranth is similar to that of spraying clear water, and the effect is not obvious. The effects of Examples 6 and 7 are slightly decreased compared with Example 5 and then basically level off, indicating that the effect does not increase significantly after the dosage of selenium dioxide reaches a certain level.

Claims

1. A chitosan-selenium compound foliar fertilizer, characterized in that, It is made from the following raw materials in mass-to-volume ratio: chitosan: selenium dioxide: glacial acetic acid: Tween 20 = (0.2 - 1):(0.2 - 0.3):(30 - 80):0.001 g / g / mL / g.

2. The chitosan-selenium compound foliar fertilizer according to claim 1, wherein, It is made from the following raw materials in mass-to-volume ratio: chitosan: selenium dioxide: glacial acetic acid: Tween 20 = 0.5:0.22:50:0.001 g / g / mL.

3. The preparation method of the chitosan-selenium compound foliar fertilizer according to claim 1 or 2, characterized in that, It includes the following steps: Dissolve chitosan in glacial acetic acid, add selenious acid solution, heat and stir for reaction, and then add Tween 20 and mix to obtain it.

4. The preparation method according to claim 3, wherein The deacetylation degree of chitosan is 95%.

5. The preparation method according to claim 3, characterized in that, The selenious acid solution is obtained by dissolving selenium dioxide in water.

6. The preparation method according to claim 3, characterized in that, The temperature of the heating and stirring reaction is 80 - 100 °C, and the time of the heating and stirring reaction is more than 30 min.

7. Use of the chitosan-selenium composite foliar fertilizer described in claim 1 or 2 in blocking the absorption and accumulation of arsenic and cadmium in leafy vegetables.

8. The application according to claim 7, characterized in that, The leafy vegetables are amaranth or lettuce.

9. The application method of the chitosan-selenium compound foliar fertilizer described in claim 1 or 2 for controlling the absorption and accumulation of arsenic and cadmium in leafy vegetables, characterized in that, It includes the following steps: At 20 - 30 d of the growth of leafy vegetables, dilute the chitosan-selenium composite foliar fertilizer described in claim 1 or 2 with water according to the selenium molar concentration to 10 - 50 μmol / L, and spray it on the leaf surface of leafy vegetables.

10. The application method according to claim 9, characterized in that, The spraying amount is based on the standard that the front and back sides of the leaves are covered with liquid droplets, once a day, and continuously sprayed for more than 7 days.

Images