Saline-alkali soil improver as well as preparation and use methods thereof

Abstract

The invention discloses a saline-alkali soil improver as well as a preparation method and a use method thereof. The saline-alkali soil improver is mainly prepared by mixing fly ash, dilute sulphuric acid, zeolite powder, sawdust, desulfurized gypsum / calcium phosphate, humic acid, a bio-organic fertilizer and a microbial fertilizer with water. The concentration of the dilute sulphuric acid is 1-3 mol / l; the saw dust does not comprise Chinese honeylocust tree saw dust and melia azedarach saw dust. The saline-alkali soil modifier is combined with irrigation and water conservancy engineering measures, crops are planted, the upper layer and the lower layer of saline-alkali soil jointly exert force, the concentration of harmful ions in the upper layer soil and the lower layer soil of the saline-alkali soil can be effectively reduced, the soil condition of the improved saline-alkali soil is close to the soil condition of a normal farmland, and the saline-alkali soil quality is improved. In addition, the saline-alkali soil improver can effectively improve the soil environment while improving the soil, and has important application value and significance compared with saline-alkali soil improvement technologies such as pure high polymer materials and the like.

Description

Technical Field

[0001] This invention relates to the field of agricultural and forestry saline-alkali land management technology, and in particular to a saline-alkali land soil conditioner and its preparation and application methods. Background Technology

[0002] According to statistics, the world's saline-alkali land area is approximately 1.4325 million mu (approximately 95.5 million hectares), and China's saline-alkali land area is approximately 500 million mu (approximately 33.3 million hectares). China has about 210 million mu (approximately 14.3 million hectares) of saline soil, about 50 million mu (approximately 3.3 million hectares) of alkaline soil, and about 270 million mu (approximately 18.3 million hectares) of various types of salinized and alkalized soils. In addition, China has 260 million mu (approximately 17.3 million hectares) of potentially saline-alkali soil, mainly distributed in northern my country. Saline and salinized soils contain water-soluble salts that are harmful to crop growth; alkaline and alkalized soils, although containing less water-soluble salts, have soil colloids containing a large amount of exchangeable sodium, exhibiting a strong alkaline reaction.

[0003] The main reason for the formation of saline-alkali land is the presence of Cl in the soil solution. - SO4 2- CO3 2- HCO3 - Na + ,K + Ca 2+ Mg 2+ When the concentration of harmful ions reaches a level that adversely affects soil properties and plant growth and development, the soil becomes saline-alkali land. The causes of this increased concentration of harmful ions include: seawater intrusion, decomposition of rocks and minerals with high ion content, soil movement, fertilization and irrigation, and decomposition products from plants and animals. Under normal circumstances, groundwater and topsoil water maintain a certain dynamic balance; the groundwater level is constant, and the ion content in the topsoil is relatively stable. During droughts, soil evaporation increases, soil moisture content decreases, causing groundwater to move upwards along soil capillaries. Salts in the soil also move with the water; after evaporation, salts accumulate in the soil surface. When the salt ion concentration reaches a certain high level, soil salinization occurs. Therefore, most saline-alkali soils are distributed in arid and semi-arid regions.

[0004] Currently, there are many saline-alkali soil amendment products available. Statistics show that most existing saline-alkali soil amendments are composed of biochar, organic fertilizer, microbial agents, and polymeric compounds. Theoretically, these amendments can significantly improve soil fertility and crop yield in saline-alkali areas. Through straw carbonization and return to the field, as well as the rational combination of organic and chemical fertilizers, they not only increase soil organic matter content and improve soil structure, but also effectively enhance the nutritional status of saline-alkali soil, providing richer and more balanced nutrient conditions for crop growth. They are suitable for coastal saline-alkali areas, but their effects on other types of saline-alkali soil (such as inland saline-alkali soil in arid and semi-arid regions) are poor. Furthermore, current saline-alkali soil amendment methods typically involve turning and compacting to a depth of 15-25 cm. This is insufficient to effectively break down the hardened layer of saline-alkali soil, ultimately causing salt from deeper soil layers (60-100 cm) to rise to the surface through capillary action. Simultaneously, harmful ions from the surface layer do not sink to the 60-80 cm underground layer with water, resulting in unsatisfactory actual improvement effects. Summary of the Invention

[0005] To address the shortcomings of existing saline-alkali land conditioners and meet the improvement requirements of saline-alkali land in arid and semi-arid regions, this invention provides a saline-alkali land conditioner and its preparation and application methods. The saline-alkali land conditioner is prepared by mixing fly ash, dilute sulfuric acid, sawdust, zeolite powder, desulfurized gypsum / calcium phosphate, bio-organic fertilizer, and microbial fertilizer in a specific mass ratio and following a specific process. Using this conditioner, combined with comprehensive measures such as farmland engineering and crop cultivation, can effectively improve saline-alkali land.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A saline-alkali land conditioner is characterized in that it is mainly composed of fly ash, dilute sulfuric acid, zeolite powder, sawdust, desulfurized gypsum / calcium phosphate, humic acid, bio-organic fertilizer and microbial fertilizer mixed with water; the concentration of the dilute sulfuric acid is 1-3 mol / L; the sawdust does not include sawdust from soapberry tree and sawdust from neem tree.

[0008] It should be noted that the present invention selects different formulations for different harmful substances in saline-alkali land. When the main harmful substance in saline-alkali land is Na2SO4, calcium phosphate is used instead of desulfurization gypsum. In other cases, desulfurization gypsum is used, such as when the main harmful substances in saline-alkali land are carbonates and / or chlorides.

[0009] Furthermore, the mass percentages of the above components are as follows: fly ash (45-50)%; dilute sulfuric acid (5-6)%; sawdust (10-12)%; zeolite powder (5-10)%; desulfurized gypsum or calcium phosphate (10-12)%; humic acid (10-11)%; bio-organic fertilizer (5-6)%; microbial fertilizer (2-3)%; and the balance is water.

[0010] Furthermore, the sawdust is preferably poplar sawdust.

[0011] Furthermore: fly ash should have a particle size of 100-120 mesh, sawdust 60-80 mesh, zeolite powder 100-120 mesh, desulfurized gypsum or calcium phosphate 100-120 mesh, humic acid 100-120 mesh, and bio-organic fertilizer and microbial fertilizer should have a particle size of 100-120 mesh, in accordance with the usual agricultural fertilizer standards.

[0012] Furthermore, the preparation method of the saline-alkali land conditioner of the present invention is as follows:

[0013] Step 1: First, mix fly ash with dilute sulfuric acid at room temperature to neutralize the fly ash and adjust its pH value.

[0014] Step 2: Mix the pH-adjusted fly ash and zeolite powder, add water and control the reaction temperature to ensure that the fly ash and zeolite powder are fully mixed and undergo an adsorption reaction. The purpose is to reduce the content of harmful heavy metal elements Pb, As, Cd, Cr, Hg and Ti in the fly ash so that it meets the standards for agricultural fly ash. After the reaction is completed, let it stand for a period of time.

[0015] Step 3: After settling, add desulfurized gypsum or calcium phosphate, sawdust, humic acid, bio-organic fertilizer and microbial fertilizer in sequence and mix evenly. Finally, granulate to obtain granular saline-alkali soil conditioner. The material temperature should be controlled below 40℃ when adding microbial fertilizer, preferably (20-30)℃, to facilitate the maintenance of the vitality of the microorganisms. Before use, the sawdust should be free of harmful microorganisms and pathogens.

[0016] Furthermore, the sawdust needs to be fumigated with steam at 80-100℃ for 0.5 hours.

[0017] Furthermore, the adsorption reaction in step two is preferably carried out in a rotary kiln.

[0018] Furthermore, the adsorption reaction temperature is controlled at (40-60)℃, with 50℃ being the preferred temperature. Under this temperature condition, with the increase of temperature, and given certain temperature conditions, the harmful heavy metal elements in the fly ash come into full contact with the zeolite powder. The adsorption effect of the zeolite powder reduces the content of harmful heavy metal elements in the fly ash.

[0019] The method of using the saline-alkali land conditioner of this invention is as follows:

[0020] First, determine the main harmful substances in the saline-alkali soil to be improved. If the main harmful substance is Na2SO4, use a saline-alkali soil conditioner formulated with calcium phosphate. If the main harmful substance is not Na2SO4 but carbonates or / and chlorides, select a saline-alkali soil conditioner formulated with desulfurized gypsum. Then, determine the dosage of the saline-alkali soil conditioner based on the content of the harmful substances. Finally, evenly spread the saline-alkali soil conditioner on the surface of the saline-alkali soil to be improved, and combine it with field management. The purpose of field management is to facilitate the discharge of harmful ions in the saline-alkali soil to the outside of the saline-alkali soil through irrigation, leaching, or natural precipitation.

[0021] Furthermore, field management measures include: (1) evenly and deeply tilling the soil with the amendment until the hard layer of saline-alkali land is broken; (2) preparing the saline-alkali land plots with a certain slope, and digging ditches at intervals in the saline-alkali soil, using the slope and ditches to drain salt irregularly, and the wastewater from the salt drainage is treated and recycled.

[0022] Furthermore, the application rate of the saline-alkali land conditioner of this invention is 1500kg-12000kg / hm². 2 The specific application rate is determined based on a combination of factors, including the type of crop planted on saline-alkali land, the intensity of saline-alkali land improvement, and the local precipitation during the same season.

[0023] The mechanism of action of each raw material in this invention is explained below.

[0024] Fly ash, a waste product from coal combustion, can be an excellent soil conditioner for saline-alkali land after activation treatment to reduce its harmful heavy metal content. It loosens saline-alkali soil, increases soil permeability, and acts as a barrier layer in soil improvement, facilitating the settling of harmful ions and preventing their ascent. Simultaneously, the porous and flocculent structure of fly ash has a dual function of water absorption and release, and it also contains medium-level elements such as Si and S, and trace elements such as Be and Zn. The pH value of fly ash is mostly around 12.4, but it can be lowered to around 8.5-7.5 through neutralization with dilute sulfuric acid. Harmful heavy metals such as Pb, Cd, Cr, As, Hg, and Ti in fly ash are adsorbed through zeolite powder, reducing their content to the range of harmful heavy metals found in agricultural fly ash. In the improvement of saline-alkali land, fly ash can also supplement the soil with a certain amount of medium elements such as S, Mg, Si and trace elements such as Be, Mo, Zn. Experiments show that in early spring, from March to April, fly ash is grayish-black, absorbs heat and light, and can increase the soil temperature of 5cm of saline-alkali land by 1.2-1.7 degrees Celsius.

[0025] Sawdust, the wood chips produced during timber processing, is preferably made from sawdust from northern trees. With a fineness of approximately 60-80 mesh, it has good water absorption properties when applied to saline-alkali soil. After absorbing water, it expands rapidly. As long as the topsoil moisture is retained, it will have a salinity control effect, preventing harmful ions at a depth of 40-60 cm from rising to the surface of the saline-alkali soil, thus suppressing the rise of deep soil salts. After fermentation, sawdust can also serve as organic matter, replenishing the soil's organic matter content. Poplar sawdust is best, as it contains salicylic acid, which is beneficial for water retention in saline-alkali soil and for the rooting of planted crops. Sawdust from soapberry and neem trees is not suitable. Furthermore, the degradation of sawdust in saline-alkali soil generates heat, which can raise the soil temperature at a depth of 5 cm by 1-2 degrees Celsius in early spring.

[0026] Zeolite powder has a unique porous structure and ion exchange properties, enabling it to absorb harmful heavy metals such as aluminum, arsenic, cadmium, chromium, and mercury from fly ash. It can also adsorb harmful sodium ions from saline-alkali soils. + ,Cl - CO3 2- HCO3 - SO4 2- Although zeolite powder can adsorb harmful heavy metal elements in fly ash, excessive use of zeolite powder in saline-alkali soil can easily disrupt the ion balance. Therefore, this invention controls the amount of zeolite powder used to be 5-10%, and should not exceed 10%. The specific amount used is adjusted according to the type and quantity of harmful heavy metal elements detected in the fly ash.

[0027] Gypsum (desulfurization) utilizes the Ca in gypsum 2+ Replace harmful Na in saline-alkali land + Reduce harmful Na+ cations in saline-alkali soil + The function of SO4 2- To reduce CO3 2- HCO3 - ,Cl - Its functions include regulating soil pH, improving soil aggregate structure in saline-alkali land, and replenishing trace elements such as Fe and Zn. When Na2SO4 is the main pollutant in saline-alkali land, calcium phosphate can be used instead of desulfurization gypsum to avoid SO4 emissions from the desulfurization gypsum. 2- The adverse effects on saline-alkali land improvement. These are the points to note regarding the formulation of soil amendments during the improvement of different types of saline-alkali land. Calcium phosphate can regulate soil pH, reduce alkalinity, provide phosphorus and calcium nutrients, and calcium ions can replace sodium ions on soil colloids, promoting microbial activity. It works synergistically with other amendment ingredients to improve saline-alkali land.

[0028] Humic acid is a natural organic weak acid that improves soil structure, increases nutrient utilization, enhances plant drought resistance, and promotes root growth. For calcium phosphate formulations, humic acid can also be used in combination with calcium phosphate. Calcium phosphate has low solubility; the addition of humic acid helps improve its effectiveness. The two work synergistically to enhance the activity of calcium phosphate.

[0029] Bio-organic fertilizers improve the structure of the topsoil in saline-alkali land, replenish organic matter, regulate soil pH, promote soil aggregate formation, and absorb harmful ions. Microbial fertilizers, primarily composed of Bacillus subtilis and nitrogen-fixing bacteria (the microbial agents in the fertilizer must contain at least 350 million live microorganisms / g), inhibit harmful microorganisms in saline-alkali land, create a favorable soil micro-ecological environment, and decompose harmful substances. Applying bio-organic fertilizers and microbial fertilizers to saline-alkali soils improves their physicochemical properties and, when used in conjunction with other soil conditioners, enhances their effectiveness. The preparation and application of saline-alkali soil conditioners, along with subsequent farmland engineering measures and the planting of crops, further contribute to soil improvement. Additionally, bio-organic fertilizers and microbial fertilizers also absorb and decompose harmful heavy metals in fly ash.

[0030] The saline-alkali land conditioner of the present invention has the following beneficial effects:

[0031] Both fly ash and sawdust in this invention have excellent soil moisture retention properties. By adsorbing excess water from the soil or mist from the air, they store the water in a porous or flocculent structure, possessing a certain surface area and strong water adsorption capabilities. When crops grown in saline-alkali land need water, they can slowly release the stored moisture to supply the needs of the crop roots. Bio-organic fertilizer and microbial fertilizer increase soil organic matter, which is beneficial for the formation of granular soil structure. Sawdust expands after absorbing water, and after decomposition, it increases soil organic matter and releases heat, which helps to raise the ground temperature in saline-alkali land in early spring. Fly ash, sawdust, and zeolite powder together form a "salt barrier" in saline-alkali land, disrupting the capillary action that contaminates soil water. The "salt barrier" formed by fly ash, sawdust, and zeolite powder has large pores, reducing capillary force and inhibiting the capillary rise of groundwater and the movement of salt with rising water in saline-alkali land. The salt barrier formed simultaneously loosens the topsoil layer of saline-alkali land. When irrigation water or natural rainfall is present, as the downward infiltration rate of water increases, the salt in the 0-30cm topsoil layer of saline-alkali land is more easily moved to deeper layers (60-100cm). On the other hand, it also inhibits the capillary rise of salt in the lower 60-100cm soil layer to the surface, as the salt barrier cuts off the pathway. This process is very important for the improvement of saline-alkali land.

[0032] The desulfurization gypsum in this invention, whose main component is CaSO4, utilizes the substitution sequence of metal elements in the soil solution, Ca... 2+ Na can be removed from saline-alkali soil solutions + The salts are displaced and washed away in ditches or sunk into the lower 60-100cm soil layer of saline-alkali land. Calcium phosphate replenishes phosphorus and calcium nutrients in saline-alkali soil, enhances the ability to displace harmful sodium ions, and supplements trace elements Fe and Zn. Because saline soils have strong water absorption, the salts in the soil dissolve upon contact with water, causing the soil to soften. After water evaporates, the soil shrinks and hardens, damaging its structure. The reduced porosity of saline-alkali soil intensifies capillary action, causing salts to rise through the capillaries. Simultaneously, evaporation further exacerbates soil salinization. The desulfurized gypsum in this invention, with its calcium ions, can promptly displace the sodium ions from the surface layer of saline-alkali land. + Displaced, Cl - SO4 2- The replacement reduced the degree of soil salinization. Attached Figure Description

[0033] Figure 1 This is a scanning electron microscope image (1500x) of the saline-alkali land conditioner of this invention. Detailed Implementation

[0034] The technical solution and application effects of the present invention will be described in detail below, in conjunction with the preparation method and usage method of the modifier of the present invention and two application examples.

[0035] The preparation method of the saline-alkali land conditioner of the present invention is as follows:

[0036] Step 1: Weigh out the following components according to the required proportions: fly ash, dilute sulfuric acid, zeolite powder, sawdust, desulfurized gypsum or calcium phosphate, bio-organic fertilizer, and microbial fertilizer. The concentration of the dilute sulfuric acid should be 1-3 mol / L. The particle size of the fly ash should be 100-120 mesh, the sawdust 60-80 mesh, the zeolite powder 100-120 mesh, the desulfurized gypsum or calcium phosphate 100-120 mesh, and the humic acid 100-120 mesh. The fineness of the bio-organic fertilizer and microbial fertilizer should conform to the standard for agricultural fertilizers or be 100-120 mesh. The sawdust should be fumigated with steam at 80-100℃ for 0.5 hours to eliminate harmful microorganisms and pathogens.

[0037] Step 2: Mix fly ash with dilute sulfuric acid and neutralize at room temperature for 1-2 hours to adjust the pH value of fly ash to 7.5-8.5.

[0038] Step 3: Thoroughly mix the pH-adjusted fly ash and zeolite powder with water at a temperature of 40-60℃, preferably 50℃. After 1-2 hours of thorough mixing, the fly ash and zeolite powder will be fully and evenly mixed to allow for an adsorption reaction, reducing the content of harmful heavy metals Pb, As, Cd, Cr, Hg, and Ti in the fly ash, thus meeting the standards for agricultural fly ash. To ensure a more complete adsorption reaction between the fly ash and zeolite powder, the above reaction should generally be carried out in a rotary kiln. Beforehand, the outer layer of the rotary kiln can be heated to 70-80℃, and the inner layer temperature can reach 40-60℃. Then, fly ash and zeolite powder are transported to the rotary kiln, and water is added to the rotary kiln. Alternatively, before adding the material to the rotary kiln, the fly ash and zeolite powder are thoroughly mixed and water is added. Then, the mixture is moved to the side of the rotary kiln by a loader and transported to the rotary kiln by a conveyor belt. After the reaction has reached 1-2 hours, the material is released from the other end of the rotary kiln and moved to a semi-enclosed environment to stand for 24-48 hours. The purpose is to allow the harmful heavy metal elements in the fly ash to undergo further adsorption reaction with the zeolite powder.

[0039] Step 4: After the material has settled, add desulfurized gypsum, fumigated sawdust, humic acid, bio-organic fertilizer, and microbial fertilizer in sequence and mix thoroughly. Finally, granulate to obtain granular saline-alkali land conditioner. Note that the material temperature should be controlled below 40℃ when adding microbial fertilizer, with an optimal temperature of 20-30℃. Suitable temperature conditions help maintain the activity of the microorganisms. An electron micrograph of the saline-alkali land conditioner obtained by the method of this invention is shown below. Figure 1 ,from Figure 1 It can be seen that the obtained soil conditioner has a porous flocculent structure. The range of harmful heavy metal elements in the saline-alkali soil conditioner conforms to the group standard T / CCEMA0001-2019 formulated by the China Chemical Industry Management Association in May 2019, and the pH is 6.8-7.5.

[0040] Method of using the saline-alkali land conditioner of the present invention:

[0041] Step 1: Based on the types of crops to be planted on the saline-alkali land and the intensity of soil improvement, and considering the surrounding environment, analyze local meteorological data such as natural rainfall to select and determine the type and dosage of the saline-alkali land conditioner. Determine whether to use a gypsum-free formula or a calcium phosphate formula for the saline-alkali land conditioner. The application rate of the saline-alkali land conditioner in this invention is generally controlled at 1500-12000 kg / hm². 2 The specific application rate is determined based on a combination of factors, including the type of crop planted on saline-alkali land, the intensity of saline-alkali land improvement, and the local precipitation during the same season.

[0042] Step 2: Evenly spread the soil conditioner on the surface of the saline-alkali soil to be improved. Use agricultural machinery to deeply till the soil conditioner to a depth of 40-80cm and break up the hard layer of 60-80cm in the saline-alkali soil, so that the soil conditioner is evenly distributed in the 0-60cm soil. To achieve this effect, the saline-alkali soil can be deeply tilled to a depth of 60cm-80cm first, then rotary tilled to a depth of 0-30cm, and then the saline-alkali soil can be leveled. At the same time, the whole plot should have a north-south or east-west slope of 3-5 degrees, so that after watering, the water will flow in one direction, enter the ditch and be discharged outside the saline-alkali soil.

[0043] Step 3: On the leveled saline-alkali soil, dig several ditches at intervals of 15-20 meters. Each ditch should be 1 meter wide and 50-80 cm deep. Fill the ditches with treated groundwater. This step is usually carried out in April each year. The purpose of digging the ditches is to promptly drain the wastewater from the saline-alkali land after leaching or natural rainfall. The drained water can be reused for irrigation after treatment. Generally, the treated water can be put back into the ditches to maintain a certain water level and suppress harmful ions in the saline-alkali land.

[0044] The wastewater treatment method involves mixing the wastewater to be treated with a saline-alkali soil conditioner at a ratio of 100:1 to 5:1, and filtering 2-3 times to remove and rinse the sodium from the wastewater. + and Cl - Harmful substances such as...

[0045] Step 4: Plant crops on the improved saline-alkali land. This is usually done in April or May each year. You can start by planting salt-tolerant plants such as reeds, ryegrass, alfalfa, salt-tolerant soybeans, and cotton. During their growth, these plants can absorb some of the salt in the saline-alkali land, improve the soil structure, and increase the organic matter content of the saline-alkali land.

[0046] Step 5: After rinsing or natural rainfall, promptly drain the wastewater from the ditches out of the field and treat it to remove harmful ions, using the same method as in Step 3. Generally, depending on natural rainfall, 3-4 rinsing operations per year are sufficient to reduce the concentration of harmful ions in saline-alkali land.

[0047] Step 6: In October, harvest the plants grown on the saline-alkali land and rotary till the plant stalks into the 0-30cm depth of the saline-alkali soil. At the same time, test the types and quantities of various ions in the 0-100cm depth of the saline-alkali soil.

[0048] Step 7: Repeat steps 2-6 above to improve the same saline-alkali land multiple times. For mildly and moderately saline-alkali land, after 1-3 years of improvement, the combined effect of "leaching" in the upper layer and "settling" in the lower layer effectively reduces the concentration of harmful ions in both the upper and lower soil layers, resulting in soil conditions close to those of normal farmland. Severely saline-alkali land, after 3-5 years of effective improvement, will also approach the soil conditions of normal farmland.

[0049] The following two examples illustrate the application and effects of the present invention, but are not intended to limit the scope of application of the present invention.

[0050] Example 1:

[0051] Table 1. Results of 3-Year Improvement of Saline-Alkali Land in the Chen Family Farmland of Tofucha Village, Yiliqi Township, Hotan, Xinjiang

[0052]

[0053] On March 23, 2022, the types and quantities of soil cations and anions were determined at different levels. Table 1 shows that the harmful cation Na+ in the saline-alkali soil of the experimental site in Hotan region, Xinjiang, was high. + High content, with Na2SO4 as the main hazardous substance, and Cl- as the main anion. - and SO4 2 - CO3 is the main hazardous substance. 2- HCO3 - The content of harmful substances is less than 20%, classifying them as secondary hazards. Therefore, the saline-alkali soil conditioner with calcium phosphate formulation of this invention is selected, with a dosage of 1000 kg / mu. The saline-alkali soil conditioner is evenly spread on the surface of the saline-alkali soil to be improved. First, the saline-alkali soil is deeply tilled to a depth of 60-80 cm, followed by rotary tillage to a depth of 0-30 cm. Then, the saline-alkali soil is leveled, with the entire plot having a north-south slope of 3-5 degrees. On April 6th, dig ditches at 15-20 m intervals on the leveled saline-alkali soil. Each ditch is 1 m wide and 60 cm deep, and filled with treated groundwater. On April 18th, sprinkler irrigation is carried out, and the wastewater in the ditches is promptly discharged from the saline-alkali land. The discharged water can be reused for irrigation after wastewater treatment; the treated water can also be put back into the ditches to maintain a certain water level, which helps to suppress harmful ions in the saline-alkali soil. The wastewater to be treated is filtered 2-3 times through a saline-alkali soil conditioner to remove and rinse away sodium from the wastewater. + and Cl -Harmful substances were removed. Cotton was planted on the improved saline-alkali land on April 30th. The cotton absorbed some of the salt and improved the soil structure, increasing the organic matter content. From June to September, leaching continued or natural rainfall occurred, and wastewater from the ditches was promptly drained from the fields, with harmful ion removal treatment carried out. Three to four leaching operations were sufficient to reduce the concentration of harmful ions in the saline-alkali land. Cotton was harvested on October 16th, and the cotton stalks were rotary tilled into the 0-30cm depth of the saline-alkali soil on October 25th. On November 5th, the types and quantities of various ions in the 0-100cm depth of the saline-alkali soil were tested. The saline-alkali land improvement work of 2022 was repeated in 2023 and 2024. In 2025, the effectiveness of the saline-alkali land improvement was evaluated. If it met farmland soil standards, a wider range of crops, such as wheat and vegetables, could be planted.

[0054] Table 1 shows that after three years of improvement, the total salt content, pH value, alkalinity, and harmful sodium content in the saline-alkali soil of the experimental site decreased. + Mg 2+ Harmful CO3 2- HCO3 - ,Cl - SO4 2- All of these have decreased significantly. Among them:

[0055] The total salt content of the surface soil in saline-alkali land was adjusted from 20.0 g / kg to 4.50 g / kg; the pH value decreased from 10.68 to 8.50; and the alkalinity was adjusted from 68.70% to 28.0%. Na... + Adjusted from 1.35 g / kg to 0.61 g / kg; SO4 2- The ion concentration was adjusted from 2.40 g / kg to 1.00 g / kg;

[0056] At a depth of 20-40cm, the total salt concentration was 18.0g / kg, adjusted to 6.58g / kg; Na + Adjusted from 1.15 g / kg to 0.68 g / kg; SO4 2- The ion concentration was adjusted from 2.0 g / kg to 1.2 g / kg;

[0057] At a depth of 40-60cm, the total salt concentration was 16.2g / kg, adjusted to 8.5g / kg; Na + Adjusted from 0.85 g / kg to 0.53 g / kg; SO4 2- The ion concentration was adjusted from 1.5 g / kg to 0.90 g / kg;

[0058] At a depth of 60-80cm, the total salt concentration was 11.5g / kg, adjusted to 7.6g / kg; Na + Adjusted from 0.56 g / kg to 0.26 g / kg; SO42- The ion concentration was adjusted from 1.0 g / kg to 0.65 g / kg;

[0059] At a depth of 80-100cm, the total salt concentration was 9.8g / kg, adjusted to 6.07g / kg; Na + Adjusted from 0.40 g / kg to 0.21 g / kg; SO4 2- The ion concentration was adjusted from 0.45 g / kg to 0.30 g / kg.

[0060] The results of ion determination in the stratified soil showed that the improvement of saline-alkali land achieved the expected results.

[0061] Example 1 illustrates that, in saline-alkali soil at a depth of 0-100cm, after improvement using the saline-alkali soil conditioner and method of this invention, comprehensive improvement measures, including "upper layer leaching," "lower layer sedimentation," wastewater treatment outside the field, farmland irrigation measures, and crop planting, reduce the total salt and harmful sodium content in each soil layer (20cm layer). + SO4 2- All of these have been effectively reduced.

[0062] Generally, for mildly and moderately saline-alkali land, after 1-3 years of improvement, the combined effect of "leaching" in the upper layer and "settling" in the lower layer can effectively reduce the concentration of harmful ions in both the upper and lower layers of the soil. The improved soil condition is close to that of normal farmland. Severely saline-alkali land, after 3-5 years of effective improvement, can also approach the soil condition of normal farmland.

[0063] It is evident that the saline-alkali land conditioner and method of this invention have a significant and effective effect on improving saline-alkali land in Hotan region of Xinjiang.

[0064] Example 2

[0065] Table 2. Three-year experiment on the improvement of saline-alkali land in Zhang's farmland in Wuyuan County, Hetao Region, Inner Mongolia.

[0066]

[0067] Table 2 shows the composition of salt ions in the saline-alkali land of the Hetao region in Inner Mongolia, with harmful cations mainly consisting of Na+. + Ca 2+ Mg 2+ Mainly, harmful anions CO3 2- HCO3 - Mainly, accounting for more than 50%, harmful Cl - and SO4 2- The proportion is 20%, pH>9.0, and alkalinity>30%. Therefore, the saline-alkali land conditioner of the desulfurized gypsum formula of this invention is selected.

[0068] In April 2022, 800 kg / mu of saline-alkali soil conditioner was applied to the surface layer of the saline-alkali land. The land was then deeply tilled to a depth of 60 cm, leveled, and irrigated with ditches spaced 15-20 m apart, each 80 cm deep and 1 m wide. Irrigation was carried out twice, on April 15th and April 25th, at a rate of 40-60 cubic meters / mu to wash away the salt. Sunflowers were sown on April 30th, with a plant spacing of 15 cm and a row spacing of 20 cm. Sunflower seedlings emerged on May 11th. Irrigation was carried out twice more, on May 23rd and June 27th, at a rate of 40-60 cubic meters / mu each time. The sunflowers matured and were harvested in early September. At the end of October, the land was irrigated with 40-60 cubic meters / mu of freezing water. Soil samples were taken from different soil layers regularly, and their ionic composition was measured. In April 2023, rotary tillage and land preparation were completed, with 800 kg / mu of saline-alkali soil conditioner applied. The same agricultural operations as in 2023 were performed, and soil samples were taken from different soil layers. After pretreatment in the laboratory, the soil ionic composition was measured.

[0069] In 2024, the third year of saline-alkali land improvement, 800 kg / mu of saline-alkali land conditioner was applied, and other procedures were the same as above. Soil samples were collected from different soil layers, pretreated in the laboratory, and the soil ionic composition was measured. The improvement effect of the test area was tested in May 2025. During this period, the effective precipitation was 21.3 mm, the evaporation was 950 mm, and the average daily evaporation was 30.65 mm.

[0070] After three years of improvement, the total salt content in the 0-20cm soil layer was adjusted from 19.10 g / kg to 2.48 g / kg; the pH value was adjusted from 10.40 to 8.30; and the alkalinity was adjusted from 67.60% to 25.80%. + Adjusted from 0.85 g / kg to 0.49 g / kg; CO3 2- Adjusted from 0.18 g / kg to 0.017 g / kg; HCO3 - The concentration of ions was adjusted from 0.40 g / kg to 0.02 g / kg; Cl - Adjusted from 2.56 g / kg to 0.44 g / kg; SO4 2- The ion concentration was adjusted from 1.40 g / kg to 0.86 g / kg. This demonstrates that the saline-alkali land conditioner and method of this invention are significantly effective in improving saline-alkali land in the Hetao region of Inner Mongolia.

[0071] The above are merely two application examples of the present invention and should not be construed as limiting the technical solutions of the present invention. Any modifications or refinements made based on the present invention without inventive effort are within the scope of protection of the present invention. Therefore, the scope of protection of the present invention is determined by the claims.

Claims

1. A soil conditioner for saline-alkali land, characterized in that, It is mainly composed of fly ash, dilute sulfuric acid, zeolite powder, sawdust, desulfurized gypsum / calcium phosphate, humic acid, bio-organic fertilizer and microbial fertilizer mixed with water; the concentration of the dilute sulfuric acid is 1-3 mol / L; the sawdust does not include sawdust from soapberry tree and sawdust from neem tree.

2. The saline-alkali land conditioner as described in claim 1, characterized in that, The mass percentages of each component are as follows: fly ash (45-50)%; dilute sulfuric acid (5-6)%; sawdust (10-12)%; zeolite powder (5-10)%; desulfurized gypsum or calcium phosphate (10-12)%; humic acid (10-11)%; bio-organic fertilizer (5-6)%; microbial fertilizer (2-3)%; and the balance is water.

3. The saline-alkali land conditioner as described in claim 1, characterized in that, The sawdust mentioned is poplar sawdust.

4. The saline-alkali land conditioner as described in claim 1, characterized in that, The particle size of fly ash is 100-120 mesh, the particle size of sawdust is 60-80 mesh, the particle size of zeolite powder is 100-120 mesh, the particle size of desulfurized gypsum or calcium phosphate is 100-120 mesh, and the particle size of humic acid is 100-120 mesh.

5. The method for preparing the saline-alkali land conditioner according to any one of claims 1-4, characterized in that: Step 1: First, mix fly ash with dilute sulfuric acid at room temperature to neutralize the fly ash and adjust its pH value. Step 2: Mix the pH-adjusted fly ash and zeolite powder, add water and control the reaction temperature to ensure that the fly ash and zeolite powder are fully mixed and undergo an adsorption reaction. After the reaction is complete, let it stand for a period of time. Step 3: After settling, add desulfurized gypsum or calcium phosphate, sawdust, humic acid, bio-organic fertilizer and microbial fertilizer in sequence and mix evenly. Finally, granulate to obtain granular saline-alkali soil conditioner. The material temperature should be controlled below 40℃ when adding microbial fertilizer, preferably (20-30)℃, to facilitate the maintenance of the vitality of the microorganisms. Before use, the sawdust should be free of harmful microorganisms and pathogens.

6. The method for preparing the saline-alkali land conditioner as described in claim 5, characterized in that, The sawdust needs to be fumigated with steam at 80-100℃ for 0.5 hours.

7. The method for preparing the saline-alkali land conditioner as described in claim 5, characterized in that, The adsorption reaction in step two is carried out in a rotary kiln.

8. The method for preparing the saline-alkali land conditioner as described in claim 5, characterized in that, In step two, the adsorption reaction temperature is controlled at (40-60)℃, with 50℃ being the preferred temperature.

9. A method of using the saline-alkali land conditioner as described in claim 1, characterized in that, First, determine the main hazardous substances in the saline-alkali soil to be improved. If the main hazardous substance is Na2SO4, use a saline-alkali soil conditioner formulated with calcium phosphate. If the main hazardous substance is not Na2SO4, choose a saline-alkali soil conditioner formulated with desulfurized gypsum. Then, determine the dosage of the saline-alkali soil conditioner based on the content of the hazardous substances, and control the application rate of the conditioner at 1500-12000 kg / hm². 2 Finally, the saline-alkali soil conditioner is evenly spread on the surface of the saline-alkali soil to be improved, and combined with field management. The purpose of field management is to facilitate the discharge of harmful ions in the saline-alkali soil to the outside of the saline-alkali soil through irrigation, leaching or natural precipitation.

10. The method of using the saline-alkali land conditioner as described in claim 9, characterized in that, Field management measures include: (1) evenly and deeply tilling the soil with the amendment until the hard layer of saline-alkali land is broken; (2) preparing the saline-alkali land plots with a certain slope, and digging ditches at intervals in the saline-alkali soil, using the slope and ditches to drain salt from the soil periodically, and the wastewater from the salt drainage is treated and recycled.

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