Desert improvement agent, preparation method and application thereof

Abstract

The application discloses a desert improvement agent and a preparation method and application thereof, and belongs to the technical field of desert ecological restoration and soil improvement. The improvement agent is composed of calcined modified kaolin, acidified modified fly ash, a high-molecular water-retaining agent, biomass, a composite microbial agent and a compound fertilizer. The preparation method comprises the following steps: calcining kaolin at high temperature, modifying fly ash by acidification, mixing and maturing the modified kaolin and the modified fly ash with rotten biomass and a microbial agent, and uniformly mixing the mixture with a water-retaining agent and a compound fertilizer. Through the synergistic effect of the core structure material (calcined kaolin) and the functional auxiliary material (acidified fly ash), a stable "skeleton-filling" microstructure is constructed, and the water-retaining, organic carbon source and microbial activity components are introduced, so that the water-retaining, fertilizer-retaining, agglomeration and microbial activity of the desert soil can be simultaneously and significantly improved, and a soil microenvironment beneficial to plant growth is constructed. The product is environmentally friendly, low in cost and convenient to apply, and is suitable for the rapid treatment and ecological restoration of various desertification lands.

Description

Technical Field

[0001] This invention relates to the field of desert ecological restoration and soil improvement technology. Specifically, it relates to a desert soil conditioner prepared by composite modification of industrial solid waste (fly ash) and natural mineral materials (kaolin), as well as its preparation process and application. The aim is to simultaneously improve the water retention, fertilizer retention, aggregation performance and microbial activity of desert soil through multi-component ratio optimization and synergistic modification, construct a soil microenvironment for the synergistic growth of microorganisms and plants, and achieve effective management and ecological restoration of desertified land. Background Technology

[0002] Desertification is one of the major ecological and environmental problems facing the world. Traditional desertification control methods, such as simply planting trees or applying chemical amendments, often suffer from high costs, inconsistent results, and the potential for secondary pollution.

[0003] In recent years, the development of environmentally friendly desert soil conditioners using industrial waste and natural minerals has become a research hotspot. However, most existing conditioners are in granular or block form, which makes it difficult to meet the demand for lightweight and easily dispersible materials in desert environments. Furthermore, in practical applications, they suffer from drawbacks such as uneven bonding with sand and poor functional stability.

[0004] Therefore, it is particularly important to develop a soil conditioner that is low-cost, high-performance, easy to apply, and can significantly improve the quality of sandy land.

[0005] Based on this, the present invention is proposed. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a powdered desert soil conditioner based on the solid waste resource utilization of kaolin and fly ash. This desert soil conditioner uses specifically modified kaolin to provide durable structural support and, in conjunction with acidified fly ash, polymeric water-retaining agents, biomass, and composite microbial agents, can simultaneously improve the water retention, fertilizer retention, aggregation properties, and microbial activity of sandy soil, thereby constructing a soil microenvironment conducive to plant growth. This solves the core problems of traditional soil conditioners, such as high cost, unstable effects, and poor adaptability.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A desert amendment, comprising, by weight, the following components:

[0009] 50-100 parts by weight of calcined modified kaolin;

[0010] 10-50 parts by weight of acid-modified fly ash;

[0011] 1-5 parts by weight of polymeric water-retaining agent;

[0012] 5-20 parts by weight of biomass;

[0013] 0.1 to 2 parts by weight of compound microbial inoculant.

[0014] Furthermore, the desert amendment also includes 1 to 6 parts by weight of compound fertilizer.

[0015] Furthermore, the compound fertilizer is one of nitrogen-phosphorus-potassium compound fertilizer, potassium dihydrogen phosphate compound fertilizer, and ammonium nitrate-phosphate compound fertilizer.

[0016] Furthermore, kaolin, as a natural layered aluminosilicate mineral, has the following chemical composition in this invention: SiO2 77.5 wt%, Al2O3 20.3 wt%, Fe2O3 0.9 wt%, TiO2 0.6 wt%, MgO 0.2 wt%, CaO 0.2 wt%, K2O 0.1 wt%, and other components 0.2 wt%. The kaolin used in this invention exhibits a regular lamellar crystal structure, a large specific surface area, and is rich in hydroxyl active sites on its surface.

[0017] Furthermore, the calcined modified kaolin, serving as the core structural base of the desert soil conditioner of this invention, is prepared by calcining natural kaolin in air at 500–1000°C (e.g., 500°C, 600°C, 750°C, 850°C, or 1000°C) for 1–6 hours (e.g., 1, 2, 3, 4, 5, or 6 hours), with a heating rate of 5–10°C / min, transforming its crystal structure into highly active amorphous metakaolin. This modification significantly enhances its specific surface area, ion exchange capacity, and cementing properties. In the system, the calcined modified kaolin, through its activated surface sites and lamellar structure, embeds itself into the gaps between sand grains, acting as a key scaffold material for promoting the formation of soil micro-aggregates and enhancing structural stability and water retention capacity through adsorption, cementation, and intercalation. Simultaneously, its excellent ion exchange performance and chemical stability provide lasting physical support and microenvironment regulation for the soil, creating favorable conditions for the immobilization and slow release of other bioactive components in the system.

[0018] Furthermore, the fly ash originates from industrial solid waste emitted by coal-fired power plants. The composition of the fly ash used in this invention is as follows: SiO2 58.4 wt%, Al2O3 23.9 wt%, Fe2O3 7.9 wt%, SO3 2.5 wt%, K2O 2.4 wt%, CaO 1.5 wt%, MgO 1.4 wt%, TiO2 1.1 wt%, Na2O 0.5 wt%, P2O5 0.1 wt%, and other components 0.3 wt%. The fly ash particles used in this invention are mostly porous, with a porosity of 50%–80%.

[0019] Furthermore, the acid-modified fly ash, as a functional auxiliary component, is prepared by mixing fly ash and acid solution at a liquid-to-solid ratio (volume ratio) of 2-10:1, stirring at 10-700 rpm for 0.5-6 hours at 20-90℃, filtering, washing until pH ≥ 5.0, and drying at 50-150℃ for 1-24 hours until moisture content ≤ 3%, thus obtaining the acid-modified fly ash. Acidification treatment effectively removes impurities and activates the silica-alumina active sites on its surface, forming more silanol groups (Si-OH) and other functional groups. The porous structure of fly ash (porosity 50%-80%) increases the porosity and water storage capacity of the system; its contained mineral elements such as Ca, K, and Mg can be slowly released; and its residual carbon and humic acid-like substances can serve as organic carbon sources. It synergistically works with calcined kaolin to construct a water- and fertilizer-retaining microstructure.

[0020] Furthermore, the acid solution is one, two, or a combination of more of the following: sulfuric acid, hydrochloric acid, oxalic acid, citric acid, or glacial acetic acid.

[0021] Furthermore, the concentration of the acid solution is 0.01~5 mol / L.

[0022] Furthermore, the polymeric water-retaining agent is one, two, or more of polyacrylamide (PAM), sand ginger seed gum, and sodium carboxymethyl cellulose (CMC).

[0023] Furthermore, the polyacrylamide has a molecular weight of 8 million to 15 million and a degree of hydrolysis of 20% to 30%; the sodium carboxymethyl cellulose has a degree of substitution of 0.7 to 1.2 and a viscosity of ≥800 mPa·s (2% aqueous solution, 25℃); and the sand pine seed gum is a natural plant extract with a viscosity of ≥500 mPa·s (1% aqueous solution, 25℃).

[0024] Furthermore, the biomass of this invention primarily serves as an organic carbon source, improving soil organic matter content and providing habitats for microorganisms, thus promoting the development of soil microbial communities. The biomass includes, but is not limited to, one, two, or more types of straw selected from corn stalks, wheat stalks, rice stalks, and cotton stalks, obtained through crushing and subsequent composting. The length of the crushed straw particles is 0.1–1 mm. The biomass undergoes high-temperature aerobic composting for 30–60 days, achieving the following composting indicators: C / N ratio ≤ 20, seed germination index ≥ 80%, and moisture content ≤ 30%.

[0025] Furthermore, the compound microbial agent is a combination of two or more of Bacillus licheniformis, Bacillus subtilis, Bacillus mucilaginosus, and Bacillus megaterium, with a viable count ≥1×10⁻⁶. 8 CFU / g. This invention's compound microbial agent is used to activate soil, fix nitrogen and solubilize phosphorus, inhibit pathogens, and build a healthy soil microbial community.

[0026] A method for preparing a desert amendment includes the following steps:

[0027] (1) Calcinated modified kaolin, acidified modified fly ash, biomass, and compound microbial agent are mixed in proportion and matured for 10 to 60 days to obtain a mixture.

[0028] (2) Mix the polymer water-retaining agent, compound fertilizer and the above mixture evenly to obtain the desert amendment.

[0029] Application of a desert soil conditioner in improving desert soil.

[0030] Furthermore, the application involves applying the desert soil conditioner alone or mixed with fertilizer directly to the desert soil surface using a broadcasting device, followed by thorough mixing with the desert soil using a rotary tiller to a depth of 20–30 cm, planting drought-resistant plants, regularly replenishing water, and monitoring soil physicochemical indicators.

[0031] Furthermore, the dosage of desert amendment is 800–2000 kg / mu.

[0032] Furthermore, for mobile sand dunes or semi-fixed sandy land, the dosage of desert conditioner is 1200–2000 kg / mu; for fixed sandy land or slightly desertified soil, the dosage can be reduced to 800–1200 kg / mu.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] 1. This invention uses industrial solid waste fly ash and natural mineral kaolin as main raw materials to realize the resource utilization of solid waste, reduce raw material costs, and alleviate environmental burden. Through the synergistic effect of calcined modified kaolin and acidified modified fly ash, a "skeleton-filler" composite structure is constructed, which significantly enhances the agglomeration, water retention, and stability of sandy soil.

[0035] 2. The combination of polymeric water-retaining agent and biomass in this invention significantly enhances the soil's water absorption and retention capacity. Simultaneously, the mineral elements in fly ash are slowly released, providing long-lasting nutrients. The combination of compound microbial agents and organic biomass promotes the development of soil microbial communities, enhances soil biological activity, and improves the soil ecological environment.

[0036] 3. The product of this invention is in powder form, which is easy to spread and mix with sandy soil. It is suitable for soils with different degrees of desertification and significantly improves the survival rate of plants after use.

[0037] 4. All raw materials used in this invention are environmentally friendly and do not contain heavy metals or other harmful substances, and will not cause secondary pollution to soil and groundwater.

[0038] 5. The preparation process of this invention is simple, the raw materials are readily available, and it is suitable for industrial production and large-scale application, thus having good economic and social benefits. Detailed Implementation

[0039] The technical solution and effects of the present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0040] In the examples below, the polyacrylamide (PAM) has a molecular weight of 12 million and a degree of hydrolysis of 25%; sodium carboxymethyl cellulose has a degree of substitution of 1.0 and a viscosity of 1500 mPa·s; and sand ginger seed gum is a natural plant extract with a viscosity of 600 mPa·s (1% aqueous solution, 25°C).

[0041] The compound fertilizer used in the following examples is a 15-15-15 nitrogen-phosphorus-potassium compound fertilizer.

[0042] Example 1 (Combined effect of calcined modified kaolin and acid-modified fly ash)

[0043] The desert amendment in this embodiment includes: 10 parts of calcined modified kaolin, 30 parts of acidified modified fly ash, 1 part of polymer water-retaining agent, 10 parts of biomass (composted straw), 0.5 parts of compound microbial agent, and 2 parts of compound fertilizer.

[0044] The preparation method of calcined modified kaolin is as follows: natural kaolin is passed through a 100-mesh sieve and calcined at 850℃ for 2 hours.

[0045] The preparation method of acid-modified fly ash is as follows: fly ash is passed through a 100-mesh sieve and mixed with 0.1 mol / L oxalic acid solution at a liquid-to-solid ratio of 3. The mixture is stirred at 500 rpm for 2 hours at 25°C. After the reaction, the mixture is filtered, washed, and dried at 60°C for 12 hours.

[0046] The polymer water-retaining agent is polyacrylamide (PAM) and sand ginger seed gum in a mass ratio of 2:3.

[0047] The biomass consists of corn stalks and wheat stalks in a weight ratio of 1:2, which are then milled in a ball mill to a particle size of 0.15–0.3 mm and composted.

[0048] The compound microbial agent consists of Bacillus licheniformis, Bacillus subtilis, and Bacillus mucilaginosus in a mass ratio of 2:1:1.

[0049] Preparation method of desert amendment: Calcinated modified kaolin, acidified modified fly ash, biomass, and compound microbial agent are mixed in proportion and matured for 10 days to obtain a mixture; a polymer water-retaining agent, compound fertilizer and the above mixture are mixed evenly to obtain desert amendment A.

[0050] Example 2 (Modification of uncalcined kaolin)

[0051] The desert amendment in this embodiment includes: 10 parts kaolin, 45 parts acidified modified fly ash, 2 parts polymer water-retaining agent, 20 parts biomass (composted straw), 1 part compound microbial agent, and 6 parts compound fertilizer.

[0052] The preparation method of kaolin is as follows: natural kaolin is passed through a 100-mesh sieve.

[0053] The preparation method of acid-modified fly ash is as follows: fly ash is passed through a 100-mesh sieve, and then the fly ash is mixed with a 0.2 mol / L citric acid solution and a 1 mol / L glacial acetic acid solution. The volume ratio of the two acids is 2:1 and the liquid-solid ratio is 8. The mixture is stirred at 500 rpm for 4 hours at 25℃. After the reaction, the mixture is filtered, washed, and then dried at 100℃ for 8 hours to obtain deeply acidified fly ash.

[0054] The polymer water-retaining agent is polyacrylamide (PAM) and sand ginger seed gum in a mass ratio of 1:2.

[0055] The biomass consists of corn stalks and wheat stalks in a weight ratio of 3:1, which are then milled in a ball mill to a particle size of 0.15–0.3 mm and composted.

[0056] The microbial inoculant consisted of Bacillus licheniformis, Bacillus subtilis, and Bacillus megaterium in a mass ratio of 1:1:1.

[0057] Preparation method of desert conditioner: Kaolin, acidified modified fly ash, biomass and compound microbial agent are mixed in proportion and matured for 20 days to obtain a mixture; the polymer water-retaining agent, compound fertilizer and the above mixture are mixed evenly to obtain desert conditioner B.

[0058] Example 3 (Fly ash without acid modification)

[0059] The desert amendment in this embodiment includes: 10 parts of calcined modified kaolin, 40 parts of unacidified modified fly ash, 1.5 parts of polymer water-retaining agent, 15 parts of biomass (composted straw), 0.2 parts of compound microbial agent, and 4 parts of compound fertilizer.

[0060] The preparation method of calcined modified kaolin is as follows: natural kaolin is passed through a 100-mesh sieve and calcined at 650℃ for 3 hours.

[0061] The polymer water-retaining agent is polyacrylamide (PAM) and sand ginger seed gum in a mass ratio of 3:2.

[0062] The biomass consists of corn stalks and wheat stalks in a 1:1 weight ratio, which are then milled in a ball mill to a particle size of 0.15–0.3 mm and composted.

[0063] The microbial inoculant is Bacillus licheniformis and Bacillus subtilis in a mass ratio of 1:1.

[0064] Preparation method of desert conditioner: Calcinated modified kaolin, fly ash, biomass and compound microbial agent are mixed in proportion and matured for 60 days to obtain a mixture; a polymer water-retaining agent, compound fertilizer and the above mixture are mixed evenly to obtain desert conditioner C.

[0065] Example 4 (Kaolin without calcination modification, fly ash without acidification modification)

[0066] The desert amendment in this embodiment includes: 35 parts of kaolin that has passed through a 100-mesh sieve, 5 parts of fly ash that has passed through a 100-mesh sieve, 1 part of a polymer water-retaining agent, 12 parts of biomass (composted straw), 0.1 parts of compound microbial inoculant, and 3 parts of compound fertilizer.

[0067] The high-molecular water-retaining agent is polyacrylamide (PAM).

[0068] The biomass is corn stalks that are milled in a ball mill to a particle size of 0.15–0.3 mm and then composted.

[0069] The microbial inoculant is Bacillus megaterium and Bacillus maculatus in a mass ratio of 1:1.

[0070] Preparation method of desert conditioner: Calcinated modified kaolin, acidified modified fly ash, biomass, and compound microbial agent are mixed in proportion and matured for 50 days to obtain a mixture; a polymer water-retaining agent, compound fertilizer and the above mixture are mixed evenly to obtain desert conditioner D.

[0071] Example 5 (Synergistic Modification of All Components)

[0072] The desert amendment in this embodiment includes: 80 parts of calcined modified kaolin, 20 parts of acidified modified fly ash, 3 parts of polymer water-retaining agent, 20 parts of biomass (composted straw), 0.5 parts of compound microbial agent, and 5 parts of compound fertilizer.

[0073] The preparation method of calcined modified kaolin is as follows: natural kaolin is passed through a 100-mesh sieve and calcined at 750℃ for 1.5 hours.

[0074] The preparation method of acid-modified fly ash is as follows: fly ash is passed through a 100-mesh sieve and mixed with 1 mol / L oxalic acid solution and 0.5 mol / L glacial acetic acid. The volume ratio of the two acids is 3:1 and the liquid-solid ratio is 5. The mixture is stirred at 400 rpm for 6 hours at 25℃. After the reaction, the mixture is filtered, washed, and dried at 80℃ for 10 hours to obtain mildly acid-modified fly ash.

[0075] The polymer water-retaining agent is polyacrylamide (PAM) and sand ginger seed gum in a mass ratio of 2:1.

[0076] The biomass consists of corn stalks and wheat stalks in a weight ratio of 3:1, which are then milled in a ball mill to a particle size of 0.15–0.3 mm and composted.

[0077] The microbial inoculant consisted of Bacillus licheniformis, Bacillus subtilis, Bacillus mucilaginosus, and Bacillus megaterium in a mass ratio of 1:1:1:1:1.

[0078] Preparation method of desert conditioner: Calcinated modified kaolin, acidified modified fly ash, biomass, and compound microbial agent are mixed in proportion and matured for 40 days to obtain a mixture; a polymer water-retaining agent, compound fertilizer and the above mixture are mixed evenly to obtain desert conditioner E.

[0079] Comparative Example 1

[0080] Except for the absence of added biomass, the formula and preparation process are the same as in Example 3.

[0081] Comparative Example 2

[0082] Except for the absence of microbial agents, the formulation and preparation process are the same as in Example 2.

[0083] Comparative Example 3

[0084] The water-retaining agent in Example 5 was replaced with an equal amount of sodium carboxymethyl cellulose (CMC), while the rest remained unchanged.

[0085] Comparative Example 4

[0086] Based on Example 5, sodium carboxymethyl cellulose (CMC) was added.

[0087] Performance testing and structural function testing

[0088] I. Investigation into the Performance of Desert Conditioners

[0089] Weigh 5000 g of each example and comparative sample, place them in a water-permeable cloth bag, and put the bag into a water-filled container, ensuring the samples are completely submerged. Soak in a sealed container at 25°C for 24 hours to allow the samples to fully absorb water and become saturated. Then remove the cloth bag, hang it to drain until no obvious water droplets fall, and weigh its wet weight. Calculate the difference between the wet weight and the dry weight to determine the saturated water absorption rate of the sample.

[0090] Weigh 5000 g of each example and comparative sample and place them in a sealed container. Add 2000 g of water and mechanically stir at 60 rpm for 10 min to ensure uniform mixing. After standing for 24 h in a sealed container, transfer the mixture to a stainless steel square pan and spread it into a uniform layer 10–25 mm thick. Place the pan in a constant temperature and humidity chamber and keep it at 25°C and 30% relative humidity for 7 days. Weigh the samples on the initial day and the 7th day, and calculate the water retention rate based on the weight loss. Water retention rate (%) = (Sample mass on the 7th day - Sample dry weight) / (Initial saturated mass - Sample dry weight) × 100%.

[0091] Weigh 500 g of each example and comparative sample and place them in a sealed container. Add 1000 g of the prepared nutrient solution and mechanically stir at 200 rpm for 10 min to ensure uniform mixing. After standing for 24 h in a sealed container, take samples to determine the nitrogen, phosphorus, and potassium leaching amounts of the examples and comparative examples (nitrogen was determined using the Kjeldahl method, phosphorus using the molybdenum-antimony colorimetric method, and potassium using the flame photometry method). Then, calculate the fertilizer retention rate based on the total nitrogen, phosphorus, and potassium content. Fertilizer retention rate (%) = (Total nutrient content of initial nutrient solution - Total nutrient content of leached solution) / Total nutrient content of initial nutrient solution × 100%.

[0092] This test used a nutrient solution formula that simulates moderate fertility conditions in desert sandy areas, consisting of NH4Cl, KNO3, and KH2PO4 in proportions of 200 mg / L, 200 mg / L, and 100 mg / L.

[0093] The results of the above tests are shown in Table 1.

[0094] Table 1. Saturated water absorption rate, water retention rate, and fertilizer retention rate of each example and comparative sample.

[0095]

[0096] II. Performance Testing of Desert Conditioner and Sand-Soil Composite System

[0097] Take 500 g of each example and comparative sample and mix it evenly with 4500 g of local dry desert sand from Inner Mongolia Autonomous Region. Place the mixture in a water-permeable cloth bag and put it in a water-filled container. Add enough water to make the liquid level higher than the surface of the cloth bag, and let it stand for 24 hours to allow the sample to fully absorb water and become saturated. Then, remove the cloth bag and hang it to drain until no obvious water droplets fall, and weigh its wet weight. Calculate the difference between the wet weight and the dry weight to obtain the saturated water absorption rate of the sample.

[0098] Take 500 g of each example and comparative sample and mix it evenly with 4500 g of local dry desert sand from Inner Mongolia Autonomous Region. Add 200 g of water until the liquid level is above the surface of the mixture, and stir at 40 rpm for 15 min to ensure uniform water penetration. Transfer the mixture to a stainless steel square pan and spread it into a uniform layer of 25-40 mm thickness. Place the pan in a constant temperature and humidity chamber and leave it for 7 days at 25℃ and 30% relative humidity. Weigh the sample on the initial day and the 7th day, and calculate the water retention rate based on the weight loss. Water retention rate (%) = (Sample mass on the 7th day - Sample dry weight) / (Initial saturated mass - Sample dry weight) × 100%.

[0099] Take 50g of each example and comparative sample and mix it evenly with 450g of dry desert sand. Then, pack the mixture into an acrylic glass soil leaching experimental column. Next, perform a leaching operation. Under a constant temperature of 25℃, slowly inject 100mL of nutrient solution along the column wall to the top of the leaching column to simulate rainwater and collect all the leachate. Finally, calculate the nutrient retention rate by measuring the concentration of each nutrient in the leachate. Nutrient retention rate (%) = (Total nutrient content of initial nutrient solution - Total nutrient content of leachate) / Total nutrient content of initial nutrient solution × 100%.

[0100] This test used a nutrient solution formula that simulates moderate fertility conditions in desert sandy areas, consisting of NH4Cl, KNO3, and KH2PO4 in proportions of 200 mg / L, 200 mg / L, and 100 mg / L.

[0101] The results of the above tests are shown in Table 2.

[0102] Table 2. Saturated water absorption rate, water retention rate, and fertilizer retention rate of the sand-soil composite system for each embodiment and comparative sample.

[0103]

[0104] III. Performance Analysis of Desert Conditioners

[0105] Example 1 exhibited the highest saturated water absorption rate in its pure modifier state, thanks to the initial porosity advantage resulting from its high proportion of acidified fly ash. However, its long-term water retention capacity after combining with sand was weak, attributed to the low proportion of kaolin, which failed to provide sufficient structural support to maintain the water retention capacity of the sand.

[0106] Example 2 showed good water retention and fertilizer retention after being mixed with sand, but the water retention of the pure amendment was relatively low, indicating that the high proportion of fly ash affected its water retention capacity, resulting in insufficient initial water retention capacity.

[0107] In Example 3, the saturated water absorption and fertilizer retention rates of the fly ash mixed with sand remained high, but the water retention rate was relatively low. This is attributed to the fact that the fly ash was not acid-modified, resulting in insufficient surface activity, weak binding force with sand particles, and limited long-term water retention performance. Simultaneously, the low content of microbial inoculants prevented the formation of a sufficiently dense mycelial network to enhance soil structure.

[0108] Example 4, when mixed with sand, showed good water retention and fertilizer retention rates. However, the pure amendment exhibited extremely low water retention, indicating that the low proportion of fly ash severely weakened the initial water absorption capacity, and that a single PAM water-retaining agent could not form a stable water-retaining network. While a high proportion of kaolin could provide structural support, it could not compensate for the reduced water absorption capacity caused by insufficient fly ash.

[0109] Example 5 showed the best performance in the sand-soil composite system, with the highest values ​​for saturated water absorption, water retention, and fertilizer retention. This indicates that its formulation achieved a perfect synergy between the "skeleton-filler" structure and the "fast absorption-slow release" water management mechanism, resulting in a synergistic effect of "1+1>2" and a significant improvement in water and fertilizer retention performance.

[0110] Comparative Example 1 (without added organic matter) showed a significant decrease in both saturated water absorption and water retention rates of the pure soil conditioner. However, after mixing with sand, its water retention rate was close to that of Example 3. This demonstrates that while organic matter competes for water in the short term, in the long term, the lack of sufficient organic matter in the sand will lead to a decline in microbial activity, making it difficult to sustainably improve soil structure. This comparison verifies the dual role of biomass in desert soil conditioners: providing water-absorbing groups in the short term and serving as a carbon source for microorganisms to maintain the ecosystem in the long term.

[0111] The water retention and fertilizer retention rates of Comparative Example 2 (without added microbial inoculant) mixed with sand were significantly lower than those of Example 2, demonstrating that microbial inoculants have a decisive influence on the long-term performance of soil conditioners. Microorganisms significantly enhance soil aggregate stability and improve water and fertilizer retention capacity by secreting extracellular polymers and forming hyphal networks.

[0112] Although the water retention rate of Comparative Example 3 (CMC replacing PAM / Salix seed gum) mixed with sand was higher than that of Example 4, it was lower than that of Example 5. This indicates that although CMC has good initial water absorption capacity, its molecular structure is rigid and it is prone to irreversible shrinkage during wet-dry cycles, making it unable to form a stable three-dimensional network structure. In contrast, the PAM / Salix seed gum compound system achieves a dynamic balance of water absorption, water retention, and water release through synergistic effects.

[0113] Although Comparative Example 4 (with added CMC) showed a high water retention rate after mixing with sand, its saturated water absorption rate was lower than that of Example 5. This demonstrates that the addition of CMC disrupted the optimal ratio of PAM / sand pine seed gum, resulting in uneven distribution of the water-retaining agent and reducing the uniformity and stability of the overall network. This verifies the accuracy of the composite water-retaining agent formulation of this invention and proves that simply adding more water-retaining materials can actually reduce overall performance.

[0114] Application methods

[0115] The desert soil conditioner of this invention is applied either alone or mixed with fertilizers (including, but not limited to, one or more of nitrogen-phosphorus-potassium compound fertilizers (such as 15-15-15), potassium dihydrogen phosphate compound fertilizers, ammonium nitrate-phosphate compound fertilizers, organic fertilizers, and micronutrient fertilizers; the specific types and ratios can be adjusted according to the target plant species, soil fertility, and ecological restoration goals). It is then applied directly to the sandy surface using a broadcasting device, followed by thorough mixing with sand using a rotary tiller to a depth of 20-30 cm. Drought-resistant plants are planted, and regular watering and monitoring of soil physicochemical indicators are conducted. For the first 30 days after application, water is applied every 3-5 days, with each application providing 60%-80% of the field capacity. Afterward, water is applied every 7-15 days depending on rainfall. Monitoring indicators include: soil moisture content, pH value, electrical conductivity, organic matter content, microbial quantity, plant survival rate, plant height, and biomass. Suitable drought-resistant plants include local species such as sand willow, saxaul, sand fern, and purple locust.

[0116] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A desert amendment, characterized in that, By weight, it includes the following components: 50-100 parts by weight of calcined modified kaolin; 10-50 parts by weight of acid-modified fly ash; 1-5 parts by weight of polymeric water-retaining agent; 5-20 parts by weight of biomass; 0.1 to 2 parts by weight of compound microbial inoculant.

2. The desert conditioner according to claim 1, characterized in that, The desert amendment also includes 1 to 6 parts by weight of compound fertilizer.

3. The desert conditioner according to claim 1, characterized in that, The chemical composition of the kaolin is as follows: SiO2 77.5 wt%, Al2O3 20.3 wt%, Fe2O3 0.9 wt%, TiO2 0.6 wt%, MgO 0.2 wt%, CaO 0.2 wt%, K2O 0.1 wt%, and other components 0.2 wt%.

4. The desert conditioner according to claim 1, characterized in that, The preparation method of the calcined modified kaolin is as follows: natural kaolin is calcined at 500-1000℃ for 1-6 hours to transform its crystal structure into highly active amorphous metakaolin.

5. The desert conditioner according to claim 1, characterized in that, The composition of the fly ash is as follows: SiO2 58.4 wt%, Al2O3 23.9 wt%, Fe2O3 7.9 wt%, SO3 2.5 wt%, K2O 2.4 wt%, CaO 1.5 wt%, MgO 1.4 wt%, TiO2 1.1 wt%, Na2O 0.5 wt%, P2O5 0.1 wt%, and other components 0.3 wt%, with a porosity of 50%–80%.

6. The desert conditioner according to claim 1, characterized in that, The preparation method of the acid-modified fly ash is as follows: fly ash and acid solution are mixed at a liquid-to-solid ratio (volume ratio) of 2-10:1, stirred at 10-700 rpm for 0.5-6 hours at 20-90℃, filtered, washed, and dried at 50-150℃ for 1-24 hours to obtain acid-modified fly ash.

7. The desert conditioner according to claim 1, characterized in that, The polymeric water-retaining agent is one, two, or more of the following: polyacrylamide, sand ginger seed gum, and sodium carboxymethyl cellulose.

8. The desert conditioner according to claim 1, characterized in that, The biomass includes, but is not limited to, one, two or more types of straw selected from corn straw, wheat straw, rice straw and cotton straw, which are obtained by crushing and then composting, and the length of the crushed straw particles is 0.1 to 1 mm.

9. The desert conditioner according to claim 1, characterized in that, The compound microbial agent is a combination of two or more of Bacillus licheniformis, Bacillus subtilis, Bacillus mucilaginosus, and Bacillus megaterium, with a viable count ≥1×10⁻⁶. 8 CFU / g.

10. The application of the desert conditioner according to any one of claims 1 to 9 in improving desert soil.

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