Modified fly ash, desert soil conditioner, soil water-retaining agent and preparation and use methods

Abstract

The invention discloses modified fly ash, a desert soil conditioner, a soil water-retaining agent and a preparation and use method thereof, the preparation method comprises the following steps: firstly, carrying out complexation reaction on fly ash and an ammonia carboxylic complexing agent under the conditions that the temperature is controlled at 60-85 DEG C and the water content of a material is 20-30wt% to modify the fly ash so as to reduce the content and pH value of main harmful heavy metals in the fly ash; and then adding a proper amount of organic matters or inorganic matters on the basis, thereby respectively obtaining the less-touch soil conditioner suitable for desert improvement and the soil water-retaining agent suitable for arid regions. The comprehensive treatment cost of desert soil improvement is reduced, the defects existing in the manufacturing process of an existing agriculture and forestry soil water-retaining agent are overcome, industrialization of the fly ash-based soil conditioner is promoted, the digestibility of fly ash is improved, and the method has good industrialization prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of soil conditioners, and specifically relates to a technology for ecological restoration of desert soil and soil in arid regions using fly ash. Background Art

[0002] Currently, the area of desertified land in China is increasing every year. Located deep in the interior of the country and far from the ocean, the northwest region of China has less precipitation and strong evaporation, laying the climatic conditions of aridity and little rain for the formation of desertification. Especially in recent years, under the influence of global warming, the aridification trend in the northwest region has continued to develop. Therefore, desertification control and ecological environment protection are the main environmental problems faced by the arid regions in the northwest of China.

[0003] From existing literature and on-site desert improvement sites, it can be found that most of the existing desert control methods mainly focus on wind prevention and sand fixation, and when it comes to improving desert soil, inorganic chemical products are mostly filled, and there are few methods for organic transformation of desert soil. Due to the poor water and fertilizer retention capacity, large evaporation, and little precipitation of desert soil, during the process of crop planting, frequent watering and fertilization are required, which not only consumes a large amount of manpower and material resources, but also, for the already water-scarce desert areas, this improvement method has extremely high costs and is unacceptable to local farmers. At the same time, most of the fertilizers used cannot be absorbed and utilized by crops due to drought and water shortage, resulting in waste of resources, and at the same time, excessive accumulation of nitrogen fertilizers in desert soil; furthermore, the fertilizers seeping into the ground with water are bound to cause pollution in the desert area and pollute the groundwater, thus causing greater pollution and damage in the western region. The most important thing is that the effect of desert improvement is not good, and the technologies used cannot be truly implemented, are unrealistic, and do not meet the needs of modern agricultural ecological development. Therefore, an effective method for improving desert soil is needed. Currently, there are many known methods for improving desert soil. The main practice of improving desert soil is to divide the desert into sand fixation control areas and planting control areas, apply plant straws or humus soil, fly ash, gypsum, decomposed cow dung, etc. into the desert soil for improvement, plant some Chinese medicinal materials or plant shelter forests, and gradually push towards the desert hinterland, achieving some desert control effects. However, due to the aridity, little rain, large evaporation, and high fluidity of the desert in desert areas, this brings great difficulties to desert improvement. In addition, in the arid and semi-arid regions of China, water shortage and soil infertility are important obstacles restricting the development of agriculture in arid areas, and water shortage is also the main factor restricting the improvement of soil productivity in arid areas.

[0004] In order to improve desert soil and solve the problem of water shortage in arid areas, soil conditioners (collectively referred to as soil conditioners), including soil conditioners and soil water retainers, have been widely introduced into desertification control and soil water conservation work. Among them, fly ash-based soil conditioners are one of them. Fly ash is a solid waste generated by the coal-fired industry, and its main source is coal-fired power plants. There is a honeycomb-like pore structure inside fly ash particles. It can store water by relying on physical pores. At the same time, it also has surface adsorption and penetration ability. Therefore, it is often used as a raw material for soil conditioners. At present, most technologies directly mix crushed fly ash raw materials with inorganic or organic substances. However, the content of harmful heavy metals in untreated fly ash exceeds the standard. After being directly applied to the soil, it may enter the food chain through plant absorption, threatening human health, posing significant ecological risks, and easily causing soil acid-base imbalance. Physicochemical modification of fly ash can well solve this problem. Among them, high-temperature calcination of fly ash is a modification method. For example, Chinese Patent Application No. CN201910776721.4 discloses a soil water-retaining conditioner based on fly ash and its preparation and use methods. It is composed of fly ash calcined clinker and two or more auxiliary materials that can balance nitrogen, phosphorus, potassium and various trace elements in the soil. It is undeniable that this modification method has expanded the application of fly ash in soil remediation, but it has also brought new problems. First, fly ash generally contains heavy metals such as lead, cadmium, and arsenic. Although high-temperature calcination can solidify some elements, it may activate volatile heavy metals such as antimony and selenium, increasing the pollution risk. Second, the volume change rate of ettringite generated at high temperature during wet-dry cycles is >8%. The long-term use of the soil structure degradation rate requires artificial additional repair. In addition, more complex inorganic substances generated by high-temperature calcination are difficult to decompose in the soil and difficult for crops to absorb, and the energy metabolism is slow, polluting the groundwater. For the above reasons, on the one hand, a large amount of accumulated fly ash cannot be digested, and on the other hand, the fly ash soil conditioner developed at the laboratory stage cannot be widely promoted. Facing the current predicament, it is urgent to seek a fly ash treatment method that is both ecologically safe and efficient and economical. On this basis, a water-retaining agent product suitable for use in farmland soil in arid and semi-arid areas of the western region, which has sufficient raw materials, an energy-saving and environmentally friendly manufacturing process, a high organic matter content, and good water retention, fertilizer enhancement, air permeability, and a simplified production process suitable for large-scale production, and a soil conditioner product for comprehensive desert soil treatment Summary of the Invention

[0005] In order to reduce the comprehensive treatment cost of desert soil improvement, solve the defects existing in the manufacturing process of existing agricultural and forestry soil water retainers, promote the industrialization of fly ash soil conditioners, and improve the digestion rate of fly ash, the present invention provides a modified fly ash.

[0006] The present invention also provides a desert soil conditioner and a soil water retainer including the above-mentioned modified fly ash.

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

[0008] A modified fly ash, characterized in that it is obtained by reacting fly ash with an aminocarboxylic acid complexing agent under hydrothermal conditions; the hydrothermal conditions refer to simultaneously controlling the reaction temperature and the water content of the material during the reaction.

[0009] Furthermore, the reaction temperature is controlled at 60°C - 85°C, and the water content of the material is controlled at 20 - 30 wt%. The preferred reaction temperature is 70°C - 80°C.

[0010] Furthermore, the aminocarboxylic acid complexing agent is an EDTA sodium salt, preferably EDTA-2Na·2H2O.

[0011] The desert soil conditioner provided by the present invention is prepared by adding loam, Bacillus subtilis composite microbial fertilizer and Tenebrio molitor manure sand to the above-mentioned modified fly ash, mixing them and granulating them, and then obtaining the desert soil conditioner after standing for a period of time.

[0012] Furthermore, the mass parts of each component in the desert soil conditioner are as follows: fly ash raw material: complexing agent; loam: Bacillus subtilis composite microbial fertilizer: Tenebrio molitor manure sand = 1:(0.002 - 0.004):(0.1 - 0.2):(0.001 - 0.003):(0.002 - 0.004).

[0013] The preparation method of the desert soil conditioner provided by the present invention is as follows:

[0014] S1: Mix fly ash and the complexing agent in the required proportion and place them in a reaction tank. Control the temperature in the reaction tank at (60 - 85)°C, and at the same time, spray water on the reaction material in a timely manner to control the water content of the material at (20 - 30) wt%. After reacting for a period of time, the modified fly ash is obtained. The purpose of the reaction is: one is to reduce the content of the main harmful heavy metals lead, chromium, cadmium, arsenic and mercury in the fly ash to ensure the normal growth of agriculture, forestry and plants; the other is to reduce the pH value of the fly ash.

[0015] S2: After the modified fly ash is dried for a period of time until the water content reaches 15 - 25 wt% (preferably 20 wt%), add loam, Bacillus subtilis composite microbial fertilizer and Tenebrio molitor manure sand, mix them evenly and granulate them, and then obtain the desert soil conditioner after standing for a period of time.

[0016] The comprehensive management method for desert soil improvement using the above-mentioned desert soil conditioner is as follows: The selected desert area is divided into three treatment areas that are advanced sequentially. According to the principle of proximity to farmland, the three treatment areas are successively called the planting improvement area, the sand fixation improvement area, and the protection improvement area from near to far. Then, the desert soil conditioner is used to improve the three areas in sequence; among them:

[0017] The method for improving the desert soil in the planting improvement area is: fully mix the desert conditioner with the surface desert soil in the planting improvement area or apply the soil conditioner in strips in the planting improvement area. Then, when the humidity of the surface sandy soil in the planting improvement area is less than 15 - 20% at 0 - 30 cm after spraying irrigation on the desert soil in the planting improvement area, short-stemmed plants such as crops or vegetables are planted;

[0018] The method for transforming the desert soil in the sand fixation improvement area is: in the sand fixation improvement area, apply the desert soil conditioner by trenching at intervals, and then spray irrigation in the strips where the conditioner is applied. When the water content of the improved sandy soil reaches about 20% at the 0 - 40 cm layer and more than 35% of the sandy soil has formed a loamy soil with a granular structure, crops can be planted;

[0019] The method for transforming the desert soil in the protection improvement area is: divide the desert in the protection improvement area into several square-shaped areas in a grid pattern with branches or straw stalks. Apply the desert conditioner per mu and spray water in the squares for sand fixation and maintenance. The surrounding branches and straw stalks are used to block the wind and fix the sand, and the desert in the small squares is improved. When the organic matter content of the sand layer reaches 3 - 5 wt% and the granular structure reaches 7 - 10% at 0 - 30 cm after improvement, crops can be planted;

[0020] The application rate of the desert soil conditioner per mu in the above-mentioned planting improvement area, sand fixation improvement area, and protection improvement area is all 1000 - 2000 Kg.

[0021] Further, the method of spray irrigation in the strips in the sand fixation improvement area is: bury rod-shaped straw bales at intervals in the strips, and the straw bales protrude above the sand surface.

[0022] Further, in the planting improvement area, when using the strip planting method, porous pipes can also be inserted into the strips, and the lower ends of the pipes can contact the soil in the lower layer of the desert.

[0023] In addition to the arid and semi-arid areas in the west, there is also a type of land in China with soil on the top and sand on the bottom. The improvement method uses the strip trench method to apply the desert conditioner into the strip trenches, which can also well improve this type of desert land.

[0024] It should be noted that: The improvement methods given for the planting improvement area, sand fixation improvement area, and protection improvement area of the present invention are basic operation methods. In actual operation, if the sandy soil or soil after improvement is to reach the level suitable for growing crops, it requires years of improvement.

[0025] The soil water retainer provided by the present invention is prepared by adding potassium sulfate, humic acid, organic fertilizer, and Bacillus subtilis compound microbial fertilizer to the above-mentioned modified fly ash, mixing them, and making them into granules.

[0026] Furthermore, the mass fractions of each component in the soil water retainer are as follows: fly ash raw material: complexing agent: potassium sulfate: humic acid: organic fertilizer: Bacillus subtilis compound microbial fertilizer = 1:(0.002 - 0.004):0.02:(0.002 - 0.005):(0.2 - 0.4):(0.001 - 0.003).

[0027] The preparation method of the soil water retainer provided by the present invention is as follows:

[0028] The first step: Mix fly ash and the complexing agent in the required proportion and place them in a reaction tank. Control the temperature in the reaction tank, and at the same time, spray hot water on the reaction materials in a timely manner to control the water content of the materials at (20 - 30)wt% and the temperature at (60 - 85)°C for a period of reaction to obtain modified fly ash. The purpose of the reaction is, firstly, to reduce the content of the main harmful heavy metals lead, chromium, cadmium, arsenic, and mercury in fly ash to ensure the normal growth of agriculture, forestry, and plants; secondly, to reduce the pH value of fly ash.

[0029] The second step: Add auxiliary materials such as humic acid, potassium sulfate, organic fertilizer, and Bacillus subtilis compound microbial fertilizer to the modified fly ash obtained in the first step in the required proportion, mix them evenly, and then place them in a rotating rotary kiln. Control the temperature of the rotary kiln, and at the same time, spray hot water on the materials in the rotary kiln in a timely manner to make the materials react for a period of time under the conditions of (70 - 80)°C and a water content of (20 - 30)%. Then, discharge the materials from the rotary kiln and let them stand for 24 - 48 hours under semi-closed, light-proof, and room temperature conditions to allow the harmful heavy metals in the materials to continue to react chemically with the components in the auxiliary materials, obtaining a semi-finished soil water retainer.

[0030] The third step: Wait until the water content of the semi-finished soil water retainer produced in the second step reaches the time when it can be granulated, and then granulate it. The particle size of the granulation is 1mm - 4mm, and finally, a granular soil water retainer with a pH of 6.5 - 7.5 (optimally 6.8 - 7.2) is obtained.

[0031] The fly ash described in the present invention is an industrial by-product, with a fineness requirement of passing through a 200-mesh sieve. The loam soil is the 0-45 cm surface soil in farmland where crops, fruit trees or vegetables have been planted. The Bacillus subtilis compound microbial fertilizer is a compound microbial fertilizer containing Bacillus subtilis. The yellow mealworm feces sand is the feces produced during the breeding process of yellow mealworms, which forms feces sand after drying in the sun and has no bacteria or viruses. The potassium sulfate is an inorganic substance and an agricultural chemical fertilizer, with a K2O content of 46%, in powder form and a fineness of less than 0.5 mm. The humic acid is a finished product of agricultural humic acid, an organic substance formed by the microbial fermentation of plant stems, leaves and branches; the EDTA-2Na·2H2O is a derivative of EDTA and has the ability to complex heavy metals; the organic fertilizer is an organic material, mainly the organic material obtained after the harmless treatment of manure from animals such as cows, sheep, pigs, etc. or the powder obtained by mechanically crushing plant straws, branches and withered leaves.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] (1) The fly ash raw material of the present invention is detected for its effective components by XRD diffraction method, and reacts with EDTA sodium salt for a period of time under the conditions of 60 degrees - 85 degrees and controlled water content, which can effectively reduce the contents of the main harmful heavy metals such as lead, chromium, cadmium, arsenic, mercury, etc. in the fly ash and the pH value of the fly ash, meeting the national standard requirements for agricultural fly ash. At the same time, a large amount of flocculants are formed, improving the water storage capacity. When the fly ash-based desert improver with the above indicators is applied to the desert in a large dose, a large amount of fly ash can wrap the sand grains into larger particles of different sizes. When the desert temperature drops at night and there is floating water mist in the air, the fly ash can adsorb and fix the water mist in the air in the desert. The set straw bales and porous pipes can also assist in adsorbing and storing the floating water mist, playing a role in fixing the desert, increasing and maintaining the water in the desert, thus playing a significant role in gradually improving the desert soil. Although the amount of fly ash used is large, the treatment cost of fly ash is low and is completely within the acceptable range. At the same time, a large amount of industrial by-products are consumed, which is a method that serves two purposes and is effective. In addition, the fly ash in the desert improver of the present invention has not been treated at high temperature and will not produce substances that damage the soil structure, and has no harm to the soil in the long term, so it is more suitable for the long-term improvement of desert soil. In addition, through the optimized configuration and treatment of fly ash, loam soil, Bacillus subtilis compound microbial fertilizer, yellow mealworm feces sand, etc., the application effect of desert soil improvement can be further optimized.

[0034] (2) The conditioner produced by the present invention in the way of combining inorganic and organic is applied to farmland, making the farmland soil elements more comprehensive. The soil is healthy, which is convenient for crops to absorb more comprehensive nutrient elements and produce healthier agricultural products. Combining with the current national industrial support policies, the manufacturing process is simplified, water-saving, power-saving, environmentally friendly and pollution-free, meeting the requirements of large-scale industrial production.

[0035] (3) In the present invention, the desert soil improvement is implemented in a progressive manner in different regions, realizing the comprehensive use of various sand control measures such as desert soil improvement, sand fixation and improvement, and windbreak area treatment. It can effectively fix and improve the sandy soil in the regional desert, and also provides a new idea for the comprehensive treatment and soil improvement of deserts in arid and semi-arid regions in the western part of China.

[0036] (4) In the present invention, the mixture constituting the soil water retainer is placed in a rotary kiln to control the reaction temperature and the moisture content of the material, so that the water retainer mixture is rotated and stirred under humid and hot conditions. On the one hand, it promotes the more sufficient complexation reaction and further reduces the content of harmful heavy metals; on the other hand, the porous structure of fly ash is fully combined with organic fertilizer and humic acid to form a complex with a high specific surface area, enhancing the adsorption performance of the water retainer. A small amount of potassium sulfate is added under humid and hot conditions to undergo an ion exchange - complexation reaction with humic acid to form a K + -humic acid complex, enabling the slow release of potassium ions. The added humic acid undergoes physical dehydration, colloidal loosening, and increased solubility under humid and hot conditions. The role of the added Bacillus subtilis complex microbial fertilizer in the soil water retainer is a multi-dimensional synergistic process, promoting microbial metabolism, soil structure improvement, and organic matter regulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a laboratory picture of the desert soil improver of the present invention, where 1a shows the state of sand plus the improver, and 1b shows the state of the original sand.

[0038] Figure 2 It is a scanning electron microscope image of fly ash, where 2a is the scanning electron microscope image of fly ash raw material, and 2b is the scanning electron microscope image of fly ash after treatment.

[0039] Figure 3 It is a physical picture of desert soil, where 3a shows the desert soil without the improver, and 3b shows the desert soil with the improver.

[0040] Figure 4 It is a schematic diagram of the improved plot with soil on the top and sand on the bottom in Example 4, where 4a shows the state of the plot before improvement, 4b shows the sand layer presented after digging 40 cm downward before improvement, 4c shows the state of applying the improver by digging trench in the field, and 4d shows the effect picture after 3 years of improvement. DETAILED DESCRIPTION OF THE INVENTION

[0041] The following combines examples to describe the implementation scheme of the present invention in detail. However, those skilled in agricultural technology in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. The auxiliary materials mentioned in the examples are all conventional products that can be obtained through commercial purchase.

[0042] The modification treatment of fly ash in the desert improver and soil water retainer of the present invention is the same. The specific method is as follows: Grind 1000 Kg of fly ash raw material to a fineness requirement of passing through a 200-mesh sieve, add (2-4) Kg of EDTA-2Na·2H2O, mix evenly, and put it into a reaction tank (semi-closed, with an air outlet and a feeding port) for reaction for 1-2 h. During the reaction process, the temperature in the reaction tank should be controlled at 60°C - 85°C, and the water content of the material should be (20-30) wt%. Once it is found that the water content is lower than (20-30) wt%, hot water should be added to the material in the reaction tank in a timely manner. Figure 1 Figure a shows the electron micrograph of the untreated fly ash raw material. Figure 1 Figure b shows the electron micrograph of the fly ash after hydrothermal reaction with the complexing agent. Comparing Figure 1 a and Figure 1 b, it can be seen that before the fly ash was treated, the particles were basically spherical and quasi-spherical, and the sphere diameters were basically in the range of 1-50 um. After being treated by the modification method of the present invention, there are fewer small crystal balls in the finished product, and a large number of flocs beneficial to water storage are formed. The pH value of the modified fly ash is reduced to 7.0-8.5 (optimally 7-8).

[0043] In order to prove that the content of harmful heavy metals and the pH value in the fly ash treated by the present invention meet the agricultural standards, the contents of harmful heavy metals such as lead, chromium, cadmium, arsenic, and mercury elements and the pH value in the fly ash raw material and the treated fly ash were measured respectively. The measurement results are shown in Table 1. The fly ash raw material was taken from Dingzhou Power Plant in Hebei Province, and the measurement unit is the National Key Laboratory of Wheat Breeding of Shandong Agricultural University. The results in the table are the results of treating with a mass ratio of fly ash raw material to complexing agent of 1:0.002, a water content of the material of 25%, a reaction control temperature of about 75 degrees, and a reaction time of 1.5 hours.

[0044] Table 1 (the unit of the content of harmful heavy metals in the table is mg / Kg)

[0045] Item \ Heavy metal content and pH value Hg As Cd cr Pb pH Fly ash raw material 4.31 44.93 16.45 57.53 56.16 12.14 Treated fly ash 1.3 4.90 2.95 21.16 16.95 7.2

[0046] It can be seen from Table 1 that the contents of the five heavy metals and the pH value in the treated fly ash have been greatly reduced, and are far lower than the contents specified in the national standard GB / T8196-2003 for agricultural fly ash. It also meets the group standard - Soil Water Retention Conditioner (Fly Ash Based) issued on April 26, 2019 and implemented on May 26 by the China Chemical Industry Enterprise Management Association, and is suitable for acidic, neutral, and alkaline soils.

[0047] The desert soil conditioner of the present invention is prepared by adding (100-200) Kg of loam, (1-3) kg of Bacillus microbial fertilizer and (2-4) Kg of Tenebrio molitor feces and sand to the modified fly ash after it is air-dried for a period of time until the water content reaches about 20 wt%. After mixing evenly, it is made into granular desert soil conditioner products (see Figure 2 ). After passing the laboratory inspection, it can be safely used in the improvement of deserts or farmlands.

[0048] The soil water retainer of the present invention is prepared by adding 20 kg of potassium sulfate, (2-5) kg of humic acid, (200-400) kg of organic fertilizer and (1-3) kg of Bacillus subtilis compound microbial fertilizer to the modified fly ash after it is air-dried for a period of time. Then it is placed in a rotary kiln, and the rotary kiln rotates at a constant speed. The temperature in the kiln is controlled at 70°C - 80°C. The mixed materials are evenly mixed and react for 0.5 - 2 hours under the drive of rotation in the kiln. During this process, the water content of the mixed materials in the furnace is monitored in real time. When it is found that the water content of the materials is lower than 20 - 30%, hot water is timely added to the furnace with a high-pressure gun, and the temperature of the added hot water should ensure that the temperature in the furnace is maintained at 70 - 80 degrees. The rotary kiln involved in the present invention is the equipment used in the compound fertilizer production line. There is a return pipe inside the rotary kiln, and the hot gas is transported to the return pipe at the kiln mouth. The materials are directly in contact with the return pipe and are heated. The rotary kiln is provided with a feeding port and an exhaust port. After reacting for 0.5 - 2 hours, the materials are discharged from the rotary kiln. Under the conditions of semi-closed, light-proof, room temperature, etc., they are left standing for 24 - 48 hours to enable the harmful heavy metals in the materials to continue to chemically react with the components in the auxiliary materials. When the water content of the reacted materials reaches the opportunity to form particles, granulation is carried out, and the particle size of granulation is 1 mm - 4 mm, and finally a granular soil water retainer with a pH value of 6.5 - 7.5 is obtained.

[0049] The following uses Examples 1 - 4 to illustrate how the present invention uses the desert soil conditioner to improve three treatment areas, and uses Examples 5 and 6 to illustrate the usage method and water retention effect of the soil water retainer of the present invention.

[0050] The improvement of desert areas is a gradual process. Generally, the areas close to farmland are improved first, and then gradually advanced towards the center of the desert. Based on this, when implementing the present invention, the desert area to be improved is first divided into three treatment areas that are advanced in sequence. The three treatment areas are successively called the planting improvement area, the sand fixation improvement area, and the protection improvement area from near to far. Among them, the area close to farmland is the planting improvement area, and the area farthest from farmland is the protection improvement area. Since the phenomenon of drought and water shortage is relatively serious in the desert improvement area, and considering the requirements of crop planting, growth and development for fertilizer and water, as well as the cost required for water transmission, in the desert area to be improved that is far from the water source (more than 50 km), the area of the planting improvement area should not exceed 100,000 hm2. After the crops in the planting area grow well and gradually form a relatively stable agricultural ecosystem, the area of the planting improvement area can be appropriately expanded to a scale of more than 1 million hm2. In the planting improvement area, through the planting of crops, the roots of the crops penetrate deep into the soil, which can play a certain role in wind prevention and sand fixation. At the same time, the crop residues fall into the soil and can also be programmed into organic matter, thereby forming nutritious soil, which can also play a role in improving the soil quality of the desert. The most important thing is that the desert improver of the present invention can absorb water, retain water, and nourish the soil, which provides convenience for further enriching the plant community of the agricultural ecosystem in the desert area.

[0051] Example 1: Taking the treatment of the planting improvement area as an example

[0052] The implementation location is within the economic and technological development zone of Kuche City, Aksu Region, Xinjiang Uygur Autonomous Region. It is a 10-acre square desert area established within the factory area of Beijing Zhonghe Hengrui Technology Development Co., Ltd. This plot is a desert wasteland where the farmland of several years ago was eroded by wind and sand. The sand in this desert wasteland was dug to a depth of 2.12 m, and the lower part of the sand is ancient soil. The desert soil improver of the present invention is used to improve this planting improvement area. The improvement method is as follows:

[0053] In May 2019, the desert improver was applied in strips in this planting improvement area at a rate of 1504 Kg per mu, and irrigation was sprayed to make the soil humidity of the sandy soil surface layer in the planting improvement area less than 15 - 20% at 0 - 30 cm. Then, cowpeas, variety Zhijiang 28, were planted in the strip trenches in the same year. At the same time, multi-hole pipes with a depth of 2 m were inserted into the strip trenches, and the lower end of the pipes could reach the ancient soil in the lower layer of the desert. Through the addition of irrigation water, microbial bacterial fertilizer, fertilizers and other external stimuli, the ancient soil in the lower layer of the desert can be activated. Coupled with the downward displacement of the upper soil improver, the desert in the planting area can be formed into a state similar to a sandwich sandwich, and the upper and lower parts work together to effectively improve the desert in the planting area into the granular structure state of farmland soil and harvest in the same year. According to the above method, it was improved for three years, and the data of the sand grain changes were investigated in the field every year. The investigation results are shown in the mechanical composition of the soil in the desert improvement planting area in Table 2.

[0054] Table 2

[0055] Particle category Particle size range (um) Desert (initial) (%) 2019 (%) 2022 (%) 2023 (%) Clay <2um 0.00 0.03 0.25 0.60 Silt 2 - 50um 3.30 0.4 10.37 12.10 Very fine sand 50 - 100um 6.20 6.50 12.5 14.45 Fine sand 100 - 250um 59.0 58.65 42.3 38.33 Medium sand 250 - 500um 25.5 24.65 26.5 25.40 Coarse sand 500 - 1000um 7.15 8.85 7.20 8.00 Very coarse sand >1000um 0.85 0.92 0.88 1.12

[0056] As can be seen from Table 2, by applying the desert soil conditioner of the present invention for three years (interrupted for 2 years due to force majeure), the mechanical composition of the soil in the desert improvement planting area has changed significantly, the volume of soil particles has increased significantly, achieving the purpose of fixing the desert. By excavating the desert soil layer of 0 - 35 cm, it is found that there is an additional 10.5% of soil with aggregate structure in the current year, the proportion of soil with aggregate structure is 18.4% in the second year, and 36.3% in the third year. By excavating the soil profile with a depth of 2.5 m, it is found that the effect of improving the desert in the sandwich layer of the planting improvement area is obvious. It is feasible to improve the upper 0 - 35 cm of desert soil into loam type. About 0.30 m of the sand layer at 1.7 - 1.8 m in the sandwich layer has been transformed, and the ancient soil layer more than 2 m below at the bottom has developed upward by 0.32 m.

[0057] In Example 1, the method of applying the conditioner in strips is used. In practice, the conditioner can also be directly mixed with Figure 3 the surface sandy soil shown in Figure 3 a. The mixing result is shown in

[0058] Example 2: Taking the fixed sand improvement area as an example

[0059] The implementation location is in Kekesayi Village, Ruokeya Township, Minfeng County, Hotan Prefecture, Xinjiang Uygur Autonomous Region. There is the Niya River in the northwest, the G0612 National Highway in the south, and the G315 National Highway in the east. The transportation is convenient, close to the water source. The sand excavation thickness exceeds 2 m and is less than 5 m. The specific improvement method is as follows:

[0060] In the first year, in this desert area, according to the dosage of 1000 - 2000 Kg / mu, use a wheat seeder to deeply spread the desert conditioner in the strip trenches. The strip trenches are spaced 10 m apart, the strip trenches are 0.5 m deep and 0.5 m wide. Inside the strip trenches, at intervals of 10 m, bundle plant straws into rod-shaped with a dot diameter of 0.4 m, bury them 0.45 m deep, and expose 0.15 - 0.25 m above the sand surface. Water can be regularly applied to the straw part.

[0061] In the second year, at the adjacent position of the strip trenches in the first year, open strip trenches at intervals, apply the conditioner in the strip trenches, with 1504 Kg of desert conditioner per mu. Inside the strip trenches, at intervals of 10 m, bundle plant straws into rod-shaped with a dot diameter of 0.4 m, bury them 0.45 m deep, and expose 0.15 - 0.25 m above the sand surface. Water can be regularly applied to the straw part.

[0062] In the third year, at the adjacent position of the strip trenches in the second year, open strip trenches and carry out improvement in the same way as in the second year. After about 3 years of desert improvement in the fixed sand improvement area, crops can be normally planted.

[0063] Example 3: Taking the protection improvement area as an example

[0064] The implementation location is located in Yilaikebuyi Village, Aksaray Township, Moyu County, Xinjiang Uygur Autonomous Region. There is the Karakax River to the east, Pishan County to the west, Langru Township and the G3012 National Highway to the south. The thickness of the desert in the desert protection and improvement area is more than 2m.

[0065] In the first year, use straw and branches to divide the reform area into several plots. Apply 1000 - 2000 Kg of desert conditioner per mu in the plots, directly mix the conditioner with the surface sand, and spray water for sand fixation and maintenance. The straw can also adsorb the fog water in the desert at night. By improving in this way for 3 - 5 years, drought-tolerant crops or Chinese medicinal materials can be normally planted basically.

[0066] Example 4: To improve the plot with soil on the upper layer and sand on the lower layer

[0067] The implementation location is in the large field within the Agronomy Experiment Station of Shandong Agricultural University, Shanggao Sub-district, Taishan District, Tai'an City, Shandong Province. The land of farmers is requisitioned. The thickness of the upper soil layer is 40 - 50 cm, and the thickness of the lower sand layer is about 2m (see Figure 4 a and 4b). This plot is for normal winter wheat planting. Before planting winter wheat, at the end of September, apply the conditioner by opening ditches when applying the base fertilizer for improvement.

[0068] Apply 504 Kg of desert conditioner per mu in the first year. Dig strip ditches in the field and apply the desert soil conditioner using the strip ditch method (see Figure 4 c). The interval between strip ditches is 10m, the depth is 0.5m, and the width is 0.5m.

[0069] Apply 504 Kg of desert soil conditioner per mu in the second year. Open strip ditches at the adjacent positions of the strip ditches in the previous year and apply the conditioner in the strip ditches.

[0070] Apply 504 kg of desert soil conditioner per mu in the third year. The method steps are the same as above.

[0071] After 3 years of improvement of the sandy soil layer at the bottom of the loam layer, the thickness of the loam soil layer increases by 20 - 30 cm (see Figure 4 d). Deep-rooted crops such as fruit trees can be normally planted, and significant effects of fertilizer and water conservation are also achieved during the planting process of other crops. This type of soil is also more in Inner Mongolia region, and similar improvement methods of the above-mentioned desert soil conditioner can also be adopted for desert soil improvement.

[0072] Example 5: Application example of soil water retainer

[0073] The implementation site is located in the large field of the Agronomy Experiment Station of Shandong Agricultural University, Shanggao Sub-district, Taishan District, Tai'an City, Shandong Province. In the large field of the Agronomy Experiment Station, the crop planted is winter wheat, variety Jimai 22. The soil is gray-brown loam, and the groundwater depth is 3m. At the end of September 2024, according to the control without application, 50 Kg per mu, and 100 Kg per mu, there are two treatments, with three replicates, a total of 9 plots. The agricultural and forestry soil water-retaining agent is plowed into the ground to a depth of 30-40 cm by machine tillage, and the soil is leveled. Wheat is sown on October 9. At the same time, soil cores are taken with a soil drill to a depth of 0-80 cm. After returning to the laboratory, the oven drying weight-loss method is used to measure the soil moisture. The experiment ends on December 26. The water-retaining effect of the water-retaining agent is shown in Table 3.

[0074] Table 3 Relative Humidity of Winter Wheat Farmland Soil %

[0075]

[0076] Example 6: Application Example of Soil Water-Retaining Agent

[0077] The implementation site is located in the farmland within the courtyard of Zhongcang Ecological Agriculture Technology Co., Ltd., Mingyuedian Town, Dingzhou City, Hebei Province. The crop planted is corn, variety Zhengdan 958. The soil is brown loam, and the groundwater depth is 3.5m. At the beginning of March 2024, according to the control without application, 50 Kg per mu, and 100 Kg per mu, there are two treatments, with three replicates, a total of 9 plots. The agricultural and forestry soil water-retaining agent is plowed into the ground to a depth of 30-40 cm by machine tillage, and the soil is leveled. Spring corn is sown on March 15. At the same time, soil cores are taken with a soil drill to a depth of 0-80 cm. After returning to the laboratory, the oven drying weight-loss method is used to measure the soil moisture. The experiment ends on June 22. The water-retaining effect of the water-retaining agent is shown in Table 4

[0078] Table 4 Relative Humidity of Spring Corn Farmland Soil %

[0079]

[0080] The above embodiments are only examples to illustrate the usage methods and effects of the desert improver and soil water-retaining agent of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be thought of without creative work should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope defined by the claims.

Claims

1. A modified fly ash, characterized in that, It is obtained by the reaction of fly ash and aminocarboxylic complexing agent under hydrothermal conditions; the hydrothermal conditions refer to controlling the reaction temperature and the water content of the materials during the reaction process.

2. The modified fly ash according to claim 1, wherein, The reaction temperature is 60°C - 85°C, the water content of the materials is 20 - 30 wt%, and preferably the reaction temperature is 70°C - 80°C.

3. The modified fly ash according to claim 1 or 2, characterized in that, The aminocarboxylic complexing agent is sodium salt of EDTA, preferably EDTA-2Na·2H2O.

4. A desert soil conditioner comprising the modified fly ash according to any one of claims 1-3, characterized in that, It is based on the product obtained from the complexation reaction of fly ash and aminocarboxylic complexing agent, and then loam, Bacillus subtilis compound microbial fertilizer and Tenebrio molitor feces and sand are added, mixed and made into granules.

5. The desert soil conditioner according to claim 4, wherein The mass parts of each component in the desert soil conditioner are: fly ash raw material: complexing agent; loam: Bacillus subtilis compound microbial fertilizer: Tenebrio molitor feces and sand = 1:(0.002 - 0.004):(0.1 - 0.2):(0.001 - 0.003):(0.002 - 0.004).

6. A preparation method of the desert soil conditioner as described in claim 4 or 5, characterized in that S1: Mix fly ash and complexing agent in the required proportion and place them in a reaction tank, control the temperature in the reaction tank at (60 - 85)°C, and at the same time spray water on the reaction materials in a timely manner to control the water content of the materials at (20 - 30) wt%, and after reacting for a period of time, obtain modified fly ash; S2: After the modified fly ash is dried for a period of time until the water content reaches 15 - 25 wt%, add loam, Bacillus subtilis compound microbial fertilizer and Tenebrio molitor feces and sand, mix evenly and make into granules, and after standing for a period of time, obtain the desert soil conditioner.

7. A comprehensive management method for desert soil improvement using the desert soil conditioner described in claim 4 or 5, characterized in that, Before improvement, first divide the selected desert area into three treatment areas that are advanced in sequence. According to the principle of the distance from the farmland, the three treatment areas are called the planting improvement area, the sand fixation improvement area and the protection improvement area from near to far in sequence, and then use the desert soil conditioner to improve the three areas in sequence; among them: The method for improving the desert soil in the planting improvement area is: fully mix the desert conditioner with the surface desert soil in the planting improvement area or apply the soil conditioner in strips in the planting improvement area, and then, when the surface sand humidity of the desert soil in the planting improvement area is less than (15 - 20)% at 0 - 30 cm, plant short-stemmed crops or vegetables; The method for transforming the desert soil in the sand fixation improvement area is: in the sand fixation improvement area, apply the desert soil conditioner in ditches at intervals, and then spray irrigation in the strips where the conditioner is applied. When the water content of the improved sand at the 0 - 40 cm layer reaches about 20% and more than 35% of the sand has formed a granular loam soil, crops can be planted; The method for desert soil improvement in the protected improvement area is as follows: The desert in the protected improvement area is separated into several square-shaped fields in a grid pattern using branches or straw stalks. Desert improver is applied at a rate of per mu and water is sprayed in the squares for sand fixation and maintenance. The branches and straw stalks around are used for windbreak and sand fixation, and the desert in the small squares is used for soil improvement. After improvement, when the organic matter content in the sand layer (0 - 30) cm reaches 3 - 5 wt% and the aggregate structure reaches 7 - 10%, crops can be planted; The application rate of the desert soil improver in the above-mentioned planting improvement area, sand fixation improvement area, and protected improvement area is 1000 - 2000 Kg per mu.

8. A soil water retainer containing the modified fly ash according to any one of claims 1-3, characterized in that, It is a granular product with a pH of 6.8 - 7.5 and a particle size of 1 - 4 mm, which is obtained by adding potassium sulfate, humic acid, organic fertilizer, and Bacillus subtilis compound microbial fertilizer to the product obtained from the complex reaction of fly ash and aminocarboxylic acid complexing agent and mixing them.

9. The soil water retention agent according to claim 8, wherein, The mass fractions of the components in the soil water retainer are as follows: fly ash raw material: complexing agent: potassium sulfate: humic acid: organic fertilizer: Bacillus subtilis compound microbial fertilizer = 1:(0.002 - 0.004):0.02:(0.002 - 0.005):(0.2 - 0.4):(0.001 - 0.003).

10. A preparation method of the soil water retainer as described in claim 8 or 9, characterized in that, The steps are as follows: First step: Mix fly ash and complexing agent in the required proportion and place them in a reaction tank. Control the temperature in the reaction tank and spray hot water on the reaction materials in a timely manner so that the water content of the materials is controlled at (20 - 30) wt% and the temperature is at (60 - 85) °C for a certain period of reaction to obtain modified fly ash; Second step: Add humic acid, potassium sulfate, organic fertilizer, and Bacillus subtilis compound microbial fertilizer auxiliary materials to the modified fly ash obtained in the first step in the required proportions and mix them evenly. Then place them in a rotating rotary kiln, control the temperature of the rotary kiln, and spray hot water on the materials in the rotary kiln in a timely manner so that the materials react for a certain period of time under the conditions of (70 - 80) °C and a water content of (20 - 30)%. Then, discharge the materials from the rotary kiln and let them stand for 24 - 48 hours under semi-closed, light-proof, and room temperature conditions to allow the harmful heavy metals in the materials to continue to react chemically with the components in the auxiliary materials to obtain a semi-finished soil water retainer; Third step: Wait until the water content of the semi-finished soil water retainer produced in the second step reaches the time when it can be granulated, and then granulate it to finally obtain a granular soil water retainer.

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