Method for improving farmland soil quality based on persulfate free radicals

Abstract

The invention discloses a method for improving the quality of farmland soil based on persulfate free radicals, which comprises the following steps: after the soil is turned over to be fluffy, uniformly spraying persulfate solutions with different concentrations on the surface, and controlling the water-soil ratio to be 1: 2. The invention further discloses application of the method in the process of improving basic physicochemical properties of farmland soil. The invention aims to add different low-concentration oxidants persulfate into the farmland soil to generate high-activity free radicals under the action of soil particles, so that the content of dissolved organic matters (DOC) in the soil, the content of bio-available iron, manganese, zinc and the like can be effectively increased, the number of harmful fungi is reduced, the microbial community structure of the soil is improved, and the soil quality is improved. And the recovery speed of the soil microbial community is accelerated.

Description

Technical Field

[0001] The invention relates to the technical field of improving farmland soil properties and enhancing soil fertility, and in particular to a method for improving farmland soil quality based on persulfate free radicals. Background Art

[0002] Soil is the material basis for human survival and development. In today's world where the contradiction between "people and land" is becoming increasingly acute, soil quality issues have become a hot topic of concern. Analyzing and evaluating soil quality and predicting the direction and trend of soil quality evolution are the basis for studying the mechanism of soil quality changes and regulating soil conservation capabilities. Soil quality mainly includes three aspects: soil fertility quality, environmental quality, and health quality. Factors affecting soil quality include natural factors and human factors. Among them, soil quality degradation (such as soil acidification, low fertility, etc.) caused by unreasonable human activities (such as agronomic measures such as greenhouse facilities) is much more serious than the impact of natural factors.

[0003] Many studies have shown that due to the special construction structure and the high temperature and humidity caused by the structure, no rainwater washing, high evaporation, etc., the ventilation conditions and water and fertilizer management measures are different from those of open field cultivation, resulting in many problems such as secondary salinization, soil acidification, nutrient imbalance, and weak fertility. In addition, improper production measures such as intensive production, continuous planting, and excessive fertilization of facility vegetable fields have caused soil salinization and soil-borne diseases to worsen, reducing the quality and yield of vegetables, reducing the income of vegetable farmers, and seriously affecting the promotion and cultivation of facility vegetables. Therefore, in order to promote the further development of the facility cultivation industry, it is particularly important to study the solutions to the maintenance of soil fertility and continuous cropping obstacles in facility vegetable fields. After long-term efforts by scientists, although a variety of methods have been developed to eliminate or alleviate the negative plant-soil feedback effect (PSF) to prevent and control crop soil-borne diseases, the frequent occurrence of crop soil-borne diseases in intensive agricultural production has not been fundamentally solved. The plant-soil feedback effect and the characteristics of farmland production determine the unsustainability of farmland soil productivity, so appropriate measures should be taken to keep the soil fertility fresh.

[0004] Oxidants (such as persulfates) are often used in the remediation of organic pollution in water bodies, soils, etc. because they have strong oxidizing properties and can be activated under certain conditions to produce strong oxidizing free radicals. Persulfates are easily ionized to produce persulfate ions (S2O8 2-), and has good stability, wide pH adaptability, oxidizes organic matter, and releases some small molecules. Therefore, as a chemical oxidant for in-situ soil remediation, it can oxidize a variety of environmental organic pollutants. Advanced oxidation treatment to remediate contaminated soil is to inject oxidants into the soil, remove organic pollutants in the soil or groundwater through redox reactions to produce free radicals and other processes, and degrade them into non-toxic or low-toxic substances. While high-concentration oxidants repair organic pollution on the site, they can also promote the release of soil dissolved organic matter and the diffusion of aggregates. Therefore, the application of low-concentration oxidants to farmland soil may significantly promote the increase of soil dissolved organic matter (including bioavailable parts), key nutrient content (nitrogen, phosphorus, potassium, etc.) and the improvement of soil structure (aggregate composition, porosity). In addition, the treatment effect of different oxidants on soil is affected by many factors, mainly including the type and dosage of oxidants, catalysts, pH, treatment time, and the concentration and composition of pollutants in the soil. Therefore, the treatment effect of oxidants under different conditions is not the same, and the impact on the physical and chemical properties of the soil and the biological community is also different.

[0005] Therefore, there are no reports on the research on improving farmland soil properties with low-concentration oxidants. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for improving farmland soil quality based on persulfate free radicals, which can solve the problems of low farmland soil fertility and pathogenic bacteria.

[0007] In order to solve the above technical problems, a technical solution adopted by the present invention is: to provide a method for improving farmland soil quality based on persulfate free radicals, after the soil is plowed and fluffed, persulfate solutions of different concentrations are evenly sprayed on the surface to control the water-soil ratio to 1:2.

[0008] In a preferred embodiment of the present invention, the persulfate solution is a room temperature aqueous solution, and the concentration is selected to be 1‰ to 5‰.

[0009] In a preferred embodiment of the present invention, the liquid oxidant is sprayed into the soil and then left to stand for 3-5 days.

[0010] In a preferred embodiment of the present invention, the improvement effect is mainly within 10 cm of the soil surface.

[0011] Furthermore, the soil is farmland dryland soil, such as farmland soil where corn is grown for a long time.

[0012] In order to solve the above technical problems, another technical solution adopted by the present invention is: to provide an application of the method for improving farmland soil quality based on persulfate free radicals as described above in the process of improving the basic physical and chemical properties of farmland soil.

[0013] Adding 1‰ and 5‰ persulfate to farmland soil will change the soil microbial community by changing the soil aggregate structure, oxidizing and decomposing organic matter, and killing pathogenic microorganisms, thereby promoting the accumulation of bioavailable active components such as Fe, Mn, and Zn.

[0014] Specifically, the improvement effects include increasing the content of available phosphorus, ammonium nitrogen, available Fe, Mn, Zn and DOC in the soil, increasing the content of beneficial microorganisms, and reducing pathogenic bacteria.

[0015] The beneficial effects of the present invention are:

[0016] (1) The present invention can promote the accumulation of bioavailable active components such as Fe, Mn, and Zn by adding an oxidant persulfate to farmland soil to change the soil physical and chemical properties and microbial community distribution, thereby having a good improvement effect on the soil physical and chemical properties;

[0017] (2) The oxidant of the present invention uses low-concentration persulfate, which has little secondary pollution to farmland soil on the basis of beneficial effects;

[0018] (3) Adding different concentrations of persulfate can change the physical and chemical properties of soil and have a significant impact on the microbial structure and content distribution of soil, beneficial bacteria, and harmful bacteria;

[0019] (4) The present invention is simple to operate, economically feasible, environmentally friendly, and suitable for improving farmland soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the result graph of the effect of pure water control group and 1‰ and 5‰ persulfate treatment groups on soil pH;

[0021] Figure 2 This is a graph showing the changes in the content of iron, manganese and zinc in the soil between the pure water control group and the groups treated with 1‰ and 5‰ persulfate.

[0022] Figure 3 This is the graph of the change of soil DOC content between the pure water control group and the groups treated with 1‰ and 5‰ persulfate addition;

[0023] Figure 4 This is a graph showing the changes in the abundance of different types of microorganisms in the soil between the pure water control group and the groups treated with 1‰ and 5‰ persulfate. DETAILED DESCRIPTION

[0024] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0025] The present invention collects farmland soil samples from Nanjing Liuhe where corn has been planted for a long time, explores the farmland soil after being treated with different concentrations of oxidant persulfate, measures the soil's physical and chemical properties, key nutrient content, DOC, microbial community structure, etc. to evaluate soil quality and pathogenic bacteria, explores the impact of oxidants on different soil indicators, and thus evaluates the beneficial improvement effects of different low-concentration oxidant treatment measures on the soil. On the one hand, the relevant research results can accumulate practical experience in the restoration and management of nutrient-poor soils in medium and low-yield fields; on the other hand, they can directly guide local agricultural production and serve local economic development. Embodiments of the present invention include:

[0026] Embodiment 1:

[0027] A 250mL round-bottom beaker was used as the reaction container. 220g of soil was weighed in each beaker. Persulfate was added to the treatment group at a concentration of 1‰ and 5‰. The persulfate was dissolved in 110mL ultrapure water, and the water-soil ratio was controlled to be 1:2. After the solution completely soaked the soil, it was left to stand for 3-5 days. At the same time, a control treatment of adding only pure water was set. After standing, the pH value was measured at 1, 5, 10, and 15 days, and the soil after standing was divided into three layers, upper, middle, and lower, dried, and sieved through a 10-mesh sieve to measure the physical and chemical properties of available phosphorus, available potassium, ammonium nitrogen, and nitrate nitrogen.

[0028] The results showed that the soil pH was less than 7, and the soil was slightly acidic. After adding persulfate, the pH value decreased, and after adding 5‰ sodium persulfate, the pH value dropped to about 4.3. Figure 1 shown.

[0029] Compared with the control group of pure water-treated soil, the content of available potassium in the persulfate-treated group remained almost unchanged, but the content of available phosphorus increased, as shown in Table 1. Phosphorus is an important factor affecting the accumulation of plant dry matter. Phosphorus fertilizer can significantly increase the dry matter accumulation of soybeans, and can also promote the yield of rice and cotton. Potassium is considered to be one of the three essential nutrients for plants, and an increase in potassium content is crucial for the growth and development of corn. It was found that the addition of 1‰ sodium persulfate treatment group significantly increased the ammonium nitrogen content in the soil; and the 5‰ sodium persulfate treatment group significantly increased the nitrate nitrogen content in the soil surface, which may be related to the oxidation of low-valent nitrogen compounds in the soil by oxidants, as shown in Table 1.

[0030] Table 1 Changes in soil ammonium nitrogen, nitrate nitrogen, available phosphorus and available potassium contents after treatment with different oxidants

[0031]

[0032] Embodiment 2:

[0033] A 250mL round-bottom beaker was used as the reaction container. 220g of soil was weighed in each beaker. Persulfate was added to the treatment group at a concentration of 1‰ and 5‰. The persulfate was dissolved in 110mL ultrapure water, and the water-soil ratio was controlled to be 1:2. After the solution completely soaked the soil, it was left to stand for 3-5 days. At the same time, a control treatment of adding only pure water was set. After standing, the soil was divided into three layers, upper, middle and lower, dried in the sun, and passed through a 10-mesh sieve to determine the content of iron, manganese and zinc. The results are as follows Figure 2 As shown in a, the results of the upper soil layer show that the bioavailable Fe content in the soil increased after the addition of oxidants compared with the control treatment, and the 5‰ persulfate treatment had the most obvious effect; the results of the middle soil layer show that the bioavailable Fe content in the soil also increased significantly after the addition of oxidants compared with the control treatment, among which the 1‰ persulfate treatment had the best effect. Overall, the 1‰ persulfate had the best beneficial effect.

[0034] like Figure 2 As shown in Figure b, the results of the upper soil layer show that the Mn content in the soil has changed significantly after the addition of oxidants. For the middle soil layer, the content of bioavailable Mn in the soil was the highest after the 1‰ persulfate treatment; and the results of the lower soil layer show that the content of bioavailable Mn in the soil was the highest after the 1‰ sodium persulfate treatment. In summary, the beneficial effect of the 1‰ persulfate treatment was the best.

[0035] like Figure 2 As shown in Figure c, the results of the upper soil layer show that compared with the control treatment, the content of bioavailable Zn in the soil after adding oxidants was the highest after 1‰ persulfate treatment, while the content of bioavailable Zn in the soil after 5‰ persulfate treatment was the lowest. The results of the middle soil layer show that compared with the control treatment, the content of bioavailable Zn in the soil after 1‰ and 5‰ treatments was significantly different, among which the content of bioavailable Zn in the soil after 1‰ persulfate treatment was the highest, while the content of bioavailable Zn in the soil after 5‰ persulfate treatment was the lowest. The application of zinc and iron fertilizers can increase the chlorophyll content and photosynthetic rate of leaves, and iron fertilizers can promote the good growth of soybeans; it also has a promoting effect on rice and wheat. Therefore, the application of low-concentration oxidant persulfate is beneficial to increase the content of bioavailable Fe, Mn, and Zn in the soil, thereby promoting the growth and yield of crops.

[0036] Embodiment 3:

[0037] A 250mL round-bottom beaker was used as the reaction container. 220g of soil was weighed in each beaker. Persulfate was added to the treatment group at a concentration of 1‰ and 5‰. The persulfate was dissolved in 110mL ultrapure water, and the water-soil ratio was controlled to be 1:2. After the solution completely soaked the soil, it was left to stand for 3-5 days. At the same time, a control treatment of adding only pure water was set. After that, the soil after standing was divided into three layers: upper, middle and lower, dried in the sun, passed through a 10-mesh sieve, and DOC was measured. The results are as follows Figure 3As shown in the figure, the upper soil data showed that after adding 5‰ persulfate, the DOC content increased significantly; the middle soil data showed that DOC increased significantly after 5‰ persulfate treatment; the DOC content of the lower soil also increased significantly. Therefore, compared with the 1‰ treatment group, 5‰ persulfate has the most significant beneficial effect on soil DOC. The increase in soil DOC content helps the colonization and reproduction of key microorganisms, promotes plant root growth and metabolism, and is of great significance for soil improvement and crop yield increase.

[0038] Embodiment 4:

[0039] A 250mL round-bottom beaker was used as the reaction container. 220g of soil was weighed in each beaker. Persulfate was added to the treatment group at a concentration of 1‰ and 5‰. The persulfate was dissolved in 110mL of ultrapure water. The water-soil ratio was controlled to be 1:2. After the solution completely permeated the soil, it was left to stand for 3-5 days. At the same time, a control treatment with only pure water and a treatment group without oxidant were set as the CK group. After standing, the soil was divided into three layers: upper, middle and lower. 2g of wet soil was taken from each layer and placed in a -80℃ refrigerator to be tested for microorganisms. Figure 4 , it was found that after adding persulfate, the content of beneficial bacteria in the soil, such as Myroderma, Trichoderma, and Bacillus, increased significantly;

[0040] Verrucosporium mycorrhizal fungi has a strong ability to colonize the rhizosphere, and has a good biological control effect on plant pathogenic fungi such as gray mold, bacteria and parasitic nematodes. The fungus can also be used as a biological herbicide for weeds, catalyzing the conversion of amino acids into urea and increasing nitrogen sources; it has a significant inhibitory effect on the growth of Arabidopsis and bluegrass, and also has a significant inhibitory effect on cucumber gray mold. Figure 4 a shows that after adding persulfate, the relative abundance of Mycorrhizal fungi increased significantly, among which 1‰ persulfate had the best effect. It was also found that the abundance in the upper layer was significantly higher than that in the lower layer. Figure 4 b shows that after persulfate treatment, the content of Trichoderma also increased significantly. Trichoderma has a strong colonization ability in the soil, which can effectively improve the physical and chemical environment of the soil, promote the establishment and maintenance of beneficial microbial communities in the soil, increase crop resistance, and thus promote crop growth and increase crop yields. Trichoderma can also effectively enhance the vitality of corn roots and increase aggregate content. Bacillus subtilis is also a rhizosphere growth-promoting bacterium widely present in terrestrial ecosystems, and plays an important role in plant growth and pest and disease control. In the figure, after the addition of the oxidant, the number of Bacillus increased significantly relative to CK ( Figure 4 c), indicating that persulfate significantly increased the content of soil Bacillus.

[0041] And it has a reducing effect on pathogenic bacteria such as Phytophthora and Alternaria; crop blight is one of the major diseases in global agricultural production, posing a serious threat to global food and ecological security, and causing economic losses of up to hundreds of billions of yuan to vegetable crops such as potatoes and tomatoes and cash crops such as soybeans in my country every year. As can be seen from Figure 4d, after the addition of the oxidant persulfate, the number of Phytophthora decreases with the increase in concentration, indicating that the oxidant has a certain killing effect on Phytophthora. Alternaria is a common, strongly parasitic pathogenic fungus of white clover, causing diseases and insect pests to cereal crops such as wheat, rice and sorghum, oil crops such as rapeseed and soybeans, vegetables and fruits such as tomatoes, potatoes, eggplants, peppers, apples, pears, ornamental flowers such as aloe vera and chrysanthemums; and cash crops such as cotton and tobacco. And from Figure 4 e It can be seen that after adding the oxidant persulfate, the relative content of Alternaria alternata was significantly reduced. As the concentration of the oxidant increased, the killing effect became stronger. And compared with CK, 5‰ persulfate had the best killing effect on harmful bacteria.

[0042] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0043] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for improving farmland soil quality based on persulfate free radicals, characterized in that: After the soil is plowed and fluffed, spray different concentrations of persulfate solution evenly on the surface to control the water-soil ratio to 1:

2.

2. The method for improving farmland soil quality based on persulfate free radicals according to claim 1, characterized in that: The persulfate solution is a room temperature aqueous solution, and the concentration is selected to be 1‰ to 5‰.

3. The method for improving farmland soil quality based on persulfate free radicals according to claim 1, characterized in that: Spray the soil with liquid oxidant and let it sit for 3-5 days.

4. The method for improving farmland soil quality based on persulfate free radicals according to claim 1, characterized in that: The improvement effect is mainly within the 10 cm range of the soil surface.

5. The method for improving farmland soil quality based on persulfate free radicals according to any one of claims 1 to 4, characterized in that: The soil is farmland dryland soil.

6. Use of the method for improving farmland soil quality based on persulfate free radicals as described in any one of claims 1 to 5 in the process of improving basic physical and chemical properties of farmland soil.

7. The use according to claim 6, characterized in that: The improvement effects include increasing the content of available phosphorus, ammonium nitrogen, available Fe, Mn, Zn and DOC in the soil, increasing the content of beneficial microorganisms, and reducing pathogenic bacteria.

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