Method for saline soil remediation by combined irrigation of saline soil conditioning compositions

Abstract

The present application relates to saline-alkali soil remediation technical field, specifically disclose a kind of saline-alkali soil conditioning composition and its combined irrigation repair method.The composition includes porous calcium-silicate salt fraction conditioner, nano iron modified biochar, organic matter nutrient, structure modifier and microbial inoculum.The porous calcium-silicate salt fraction conditioner is prepared by granulating and calcining diatomite and calcium carbonate, and the nano iron modified biochar is obtained by loading nano zero-valent iron on biochar through liquid phase reduction method.The repair method includes applying the composition to soil and mixing, installing drip irrigation system, planting salt-tolerant crops and conducting precise water and fertilizer management through drip irrigation.The present application simultaneously realizes reducing saline-alkali, improving structure, improving fertility and activating microbial activity through multi-component synergistic effect, and combines with drip irrigation precise salt control, effectively solves the problems of traditional improvement mode such as single function, easy to return salt, high water consumption and short-term effect, realizes the rapid, water-saving and long-acting management of saline-alkali soil.

Description

Technical fields: This invention belongs to the field of saline-alkali land remediation technology, specifically relating to a saline-alkali land conditioning composition and a method for saline-alkali land remediation by combining it with irrigation. Background technology: The Hetao Irrigation District in Inner Mongolia is an important commodity grain production base in my country. It has long relied on the Yellow River for large-scale flood irrigation, which, while maintaining grain yields, has also led to severe secondary salinization. The soil salinity in this region is mainly composed of sodium sulfate and sodium chloride, classifying it as a typical sulfate-chloride type saline soil. The soil generally exhibits a high pH value (above 8.5) and high sodium ion concentration (Na₂O₅). + The soil exhibits a complex set of obstacles, including excessive levels of certain nutrients, high saliency (ESP), compacted soil structure, low porosity, poor aeration and permeability, low organic matter content (often below 1.0%), and a monotonous and degraded microbial community. These obstacles are interconnected and exacerbate each other, severely restricting crop root development, nutrient absorption, and the sustainable productivity of the land.

[0001] Traditional saline-alkali land management methods, such as "large-scale water suppression" and the single application of desulfurized gypsum, well-rotted organic fertilizer, or biochar, can reduce surface soil salinity in the short term, but they suffer from the following deep-seated, systemic problems: First, commonly used soil conditioners are mostly designed for single obstacles, lacking multi-target synergistic effects. For example, desulfurized gypsum mainly works by reducing calcium ions (Ca... 2+ ) Replace sodium ions (Na) in soil colloids +While traditional flood irrigation can lower ESP (Effective Soil Estrus), its effects on improving soil organic matter and stimulating microbial activity are limited. Furthermore, it requires large quantities, has a slow effect, and long-term application may introduce excessive sulfate. Organic fertilizers primarily replenish organic matter and improve soil aggregate structure, but they do not directly lower pH and ESP. They decompose slowly in saline-alkali environments, resulting in a long improvement cycle. Biochar, while capable of adsorbing salt ions and improving pore structure, may exacerbate soil pH increases due to its alkaline properties and has limited specific adsorption capacity for sodium ions. Secondly, under traditional flood irrigation, the depth and uniformity of water infiltration are difficult to control, easily leading to temporary desalination of the surface soil and salt accumulation in the subsoil and surrounding areas. Due to the lack of precise dynamic monitoring and control of water and salt in the root zone, irrigation water often fails to effectively leach salt below the crop root layer (usually requiring a depth of 1.2 meters), instead raising the groundwater level and accelerating the rise of salt to the surface via capillary water, resulting in a prominent "spring salinization" phenomenon. Simultaneously, the contradiction between large-scale flood irrigation and the increasing scarcity of Yellow River water resources and the reduction in agricultural water quotas is intensifying, and water-saving and salt-control technologies are still immature. Furthermore, single physical or chemical amendment measures are often insufficient to activate the self-regulating capacity of the soil ecosystem. For example, sodium ions displaced by gypsum, if not adequately leached, are easily re-adsorbed by soil colloids after rainfall or irrigation; short-term additions of organic matter decompose rapidly under the action of microorganisms, making it difficult to maintain the amendment effect. Without an amendment process driven by biological activity (such as specific salt-tolerant microorganisms, root exudates, etc.), soil structure recovery is slow, and the amendment effect is prone to recurrence, especially under climatic conditions with large interannual fluctuations in precipitation and evaporation.

[0002] Therefore, the treatment of saline-alkali land in the Hetao Irrigation District needs to overcome the above-mentioned technical bottlenecks. It is urgent to develop a repair and conditioning agent that can simultaneously achieve chemical improvement, physical structure optimization and biological function activation, and to match it with a precise irrigation and water and salt regulation scheme, so as to form a new model of saline-alkali land treatment and ecological improvement that is operable, sustainable and effective. Summary of the Invention: To address the shortcomings of existing technologies, this invention proposes a saline-alkali land conditioning composition and a method for saline-alkali land restoration by combining it with irrigation.

[0003] Specifically, the first aspect of the present invention provides a saline-alkali land conditioning composition comprising the following components in parts by weight: 50-65 parts of porous calcium-silicon salt conditioner, 20-30 parts of nano-iron modified biochar, 10-20 parts of organic matter nutrients, 0.5-2 parts of structural modifier, and 0.5-2 parts of microbial agent; wherein the porous calcium-silicon salt conditioner is obtained by granulation and calcination of a mixed powder composed of diatomaceous earth and calcium carbonate; the nano-iron modified biochar is obtained by loading nano-zero valent iron onto biochar as a base material using a liquid-phase reduction precipitation method.

[0004] As a further illustration of the present invention, the preparation method of the porous calcium-silicon salt conditioner includes: S11: Mix diatomaceous earth and calcium carbonate at a dry weight ratio of (6-8):(4-2); S12: Mix the mixed powder obtained in S11 with binder and water, and granulate it by extrusion granulation; S13: Calcine the particles obtained in S12 at 500-600°C for 1-3 hours to obtain the porous calcium-silicon salt conditioner.

[0005] As a further explanation of the present invention, in step S11, the dry weight ratio of diatomaceous earth to calcium carbonate is 7:3.

[0006] As a further illustration of the present invention, the preparation method of the nano-iron modified biochar includes: S21: Biochar substrate is prepared by pyrolyzing biomass at 400°-600°C under oxygen-limited conditions; S22: The biochar obtained in S21 is immersed in ferrous sulfate solution and stirred for adsorption. Then, sodium borohydride solution is added in an inert atmosphere to carry out a reduction reaction, so that nano-zero valent iron is loaded on the biochar. After filtration, washing and drying, the nano-iron modified biochar is obtained.

[0007] As a further explanation of the present invention, in step S22, the concentration of the ferrous sulfate solution is 0.05-0.2 M, and the concentration of the sodium borohydride solution is 0.1-0.5 M.

[0008] As a further explanation of the present invention, the organic nutrients are selected from one or more of humic acid, weathered coal, organic fertilizer, and amino acid residue; the structure modifier is selected from one or more of polyacrylamide or carboxymethyl cellulose; and the microbial agent is selected from one or more of Bacillus subtilis, Bacillus licheniformis, and gelatinous Bacillus.

[0009] A second aspect of the present invention provides a method for remediating saline-alkali land, which employs the above-mentioned saline-alkali land conditioning composition in conjunction with irrigation, the method comprising the following steps: S31: The saline-alkali soil conditioning composition is evenly spread on the surface of the saline-alkali soil to be restored, and then the soil is tilled to mix the conditioning composition with the topsoil. S32: Install a drip irrigation system and set the drip tape spacing according to the crop row spacing; S33: To carry out crop planting and field management, and to irrigate through the drip irrigation system.

[0010] As a further explanation of the present invention, in step S31, the soil tillage is deep tillage of 25-30cm or rotary tillage of 15-20cm, and this step is completed 7-10 days before sowing.

[0011] As a further explanation of the present invention, in step S33, the specific method of irrigation through the drip irrigation system is as follows: irrigate once every 7-10 days during the seedling stage of crops, irrigate once every 5-7 days from the jointing to the grain-filling stage, and irrigate 10-15 times throughout the entire growth period, with each irrigation volume being 15-25 m³. 3 / mu.

[0012] As a further explanation of the present invention, in step S33, the crop planted is a salt-tolerant crop, preferably sunflower or corn.

[0013] Compared with the prior art, the present invention has the following beneficial technical effects: This invention achieves simultaneous salt reduction, alkali control, pH adjustment, structural improvement, and activation of biological activity through the synergistic effect of porous calcium-silicon salt conditioner, nano-iron modified biochar, organic matter, structural modifier, and microbial agent, overcoming the limitations of a single modifier.

[0014] The conditioner provided by this invention rapidly adsorbs and fixes salts and replaces sodium ions. Combined with structural modifiers and organic matter, it quickly constructs stable aggregates, creating a habitable environment for microorganisms and driving the system towards a healthy and self-sustaining ecological direction, with a stable improvement effect.

[0015] This invention combines drip irrigation technology to achieve precise water supply and targeted salt leaching, creating a low-salt micro-zone in the root zone to protect crop growth, while significantly inhibiting spring salt return and greatly improving water resource utilization efficiency.

[0016] The conditioning composition provided by this invention works synergistically with drip irrigation to jointly construct an optimized micro-ecosystem in the crop root zone, characterized by strong salt buffering capacity, coordinated water and air, and high biological activity, which significantly improves crop emergence rate and survival rate. Attached image description: Figure 1 (a) is a SEM image of the porous calcium-silicon salt conditioner in this invention; Figure 1 (b) is a SEM image of the nano-iron modified biochar (nZVI-BC) in this invention.

[0017] Figure 2 The results of soil EC and MWD measurements are shown in different treatment groups.

[0018] Figure 3 The results of soil SAR and pH measurements in different treatment groups are shown.

[0019] Figure 4 The results show the yield of maize kernels in different treatment groups. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Traditional saline-alkali land management methods, such as "large-scale water suppression" and the single application of desulfurized gypsum, well-rotted organic fertilizer, or biochar, can reduce surface soil salinity in the short term, but they suffer from the following deep-seated, systemic problems: First, commonly used soil conditioners are mostly designed for single obstacles, lacking multi-target synergistic effects. For example, desulfurized gypsum mainly works by reducing calcium ions (Ca... 2+ ) Replace sodium ions (Na) in soil colloids + While traditional flood irrigation can lower ESP (Effective Soil Estrus), its effects on improving soil organic matter and stimulating microbial activity are limited. Furthermore, it requires large quantities, has a slow effect, and long-term application may introduce excessive sulfate. Organic fertilizers primarily replenish organic matter and improve soil aggregate structure, but they do not directly lower pH and ESP. They decompose slowly in saline-alkali environments, resulting in a long improvement cycle. Biochar, while capable of adsorbing salt ions and improving pore structure, may exacerbate soil pH increases due to its alkaline properties and has limited specific adsorption capacity for sodium ions. Secondly, under traditional flood irrigation, the depth and uniformity of water infiltration are difficult to control, easily leading to temporary desalination of the surface soil and salt accumulation in the subsoil and surrounding areas. Due to the lack of precise dynamic monitoring and control of water and salt in the root zone, irrigation water often fails to effectively leach salt below the crop root layer (usually requiring a depth of 1.2 meters), instead raising the groundwater level and accelerating the rise of salt to the surface via capillary water, resulting in a prominent "spring salinization" phenomenon. Simultaneously, the contradiction between large-scale flood irrigation and the increasing scarcity of Yellow River water resources and the reduction in agricultural water quotas is intensifying, and water-saving and salt-control technologies are still immature. Furthermore, single physical or chemical amendment measures are often insufficient to activate the self-regulating capacity of the soil ecosystem. For example, sodium ions displaced by gypsum, if not adequately leached, are easily re-adsorbed by soil colloids after rainfall or irrigation; short-term additions of organic matter decompose rapidly under the action of microorganisms, making it difficult to maintain the amendment effect. Without an amendment process driven by biological activity (such as specific salt-tolerant microorganisms, root exudates, etc.), soil structure recovery is slow, and the amendment effect is prone to recurrence, especially under climatic conditions with large interannual fluctuations in precipitation and evaporation.

[0022] To address the aforementioned technical problems, this invention first proposes a saline-alkali land conditioning composition, comprising the following components in parts by weight: 50-65 parts of porous calcium-silicon salt conditioner, 20-30 parts of nano-iron modified biochar, 10-20 parts of organic matter nutrients, 0.5-2 parts of structural modifier, and 0.5-2 parts of microbial agent; wherein, the porous calcium-silicon salt conditioner is obtained by granulation and calcination of a mixed powder composed of diatomaceous earth and calcium carbonate; the nano-iron modified biochar is obtained by loading nano-zero valent iron onto biochar as a base material using a liquid-phase reduction precipitation method.

[0023] Furthermore, the aforementioned organic nutrients are preferably humic acid, weathered coal, organic fertilizer, amino acid residue, etc. The structural modifier is preferably an environmentally friendly polymer such as polyacrylamide or carboxymethyl cellulose. The aforementioned microbial agents are preferably Bacillus subtilis, Bacillus licheniformis, and Bacillus spp., which are used for improving saline-alkali land.

[0024] Furthermore, the preparation process of the above-mentioned porous calcium-silicon salt conditioner includes: S1: Raw materials and proportions: Diatomaceous earth and calcium carbonate are mixed at a dry weight ratio of (6-8):(4-2). The main component of the diatomaceous earth is amorphous SiO2; the calcium carbonate is agricultural grade light calcium carbonate. Calcium. The mixing ratio of diatomaceous earth and calcium carbonate can balance structural strength and alkalinity regulation ability, and is further preferably 7:3 by dry weight of diatomaceous earth and calcium carbonate.

[0025] S2: Granulation: The mixed powder obtained in S1 is mixed with an appropriate amount of binder and water, and then granulated by extrusion. The machine produces particles with a diameter of 3-5 mm.

[0026] The binder can be selected from environmentally friendly agricultural binders such as sodium carboxymethyl cellulose, bentonite, and kaolin. The mass ratio of mixed powder (diatomaceous earth + calcium carbonate) to binder (dry basis) is 100:(1~5). The total water added during granulation should be controlled within 15%-25% of the dry weight of the mixed powder.

[0027] S3: Calcine the particles obtained in S2 at 500-600°C for 1-3 hours to obtain a porous calcium-silicon salt conditioner.

[0028] Through this calcination process, calcium carbonate is partially decomposed into more active calcium oxide, making the diatomaceous earth structure more stable and forming abundant micropores.

[0029] Through the above granulation and calcination treatment, a porous particle with rich micropores, high specific surface area and certain alkalinity can be obtained. Its core components are active CaO and porous SiO2 framework.

[0030] Furthermore, the above-mentioned preparation process of nano-iron modified biochar (nZVI-BC) includes: S1: Biochar substrate preparation: Biochar is prepared by pyrolyzing biomass at 400°-600°C under oxygen-limited conditions.

[0031] The biomass used is agricultural biomass such as sunflower stalks or corn stalks, which are abundant in the Hetao region. The biochar obtained in S1 is pulverized and sieved to obtain a uniform biochar substrate. The pulverized biochar is preferably sieved through a 60-mesh sieve. The above pyrolysis process can be carried out, for example, in a tubular furnace. Before heating and throughout the pyrolysis process, an inert gas (such as high-purity nitrogen or argon) is continuously introduced to completely remove and isolate air, thereby achieving oxygen-limited conditions.

[0032] S2: Nano-zero valent iron supported modification: The biochar obtained from S1 was immersed in a ferrous sulfate solution and stirred thoroughly to allow Fe... 2+ Ions are adsorbed onto the pores and surface of biochar; under an inert atmosphere protected by nitrogen, sodium borohydride solution is slowly added, causing NaBH4 to adsorb the Fe... 2+ It is reduced to nano-zero valent iron and precipitated and loaded onto biochar in the form of nanoparticles to form a composite material.

[0033] The concentration of the ferrous sulfate solution is preferably 0.05-0.2 M; the concentration of the sodium borohydride solution is preferably 0.1-0.5 M.

[0034] Furthermore, the process after S2 includes product post-processing: after the S2 reaction is complete, the product is filtered, separated into solid and liquid phases, washed, and vacuum dried to finally obtain a dried nano-iron modified biochar product. The preferred vacuum drying temperature is 60°C.

[0035] The present invention also provides a method for saline-alkali land restoration by combining the above-mentioned saline-alkali land conditioning composition with irrigation, which includes the following steps: S1: The above-mentioned saline-alkali soil conditioning composition is evenly spread on the surface of the saline-alkali soil to be restored, and then the soil is tilled to make the conditioning composition fully mixed with the topsoil.

[0036] Furthermore, the preferred soil tillage methods are deep tillage (25-30 cm) or rotary tillage (15-20 cm). This step should be completed 7-10 days before sowing.

[0037] S2: Install a drip irrigation system and set the drip tape spacing according to the crop row spacing.

[0038] Furthermore, drip irrigation systems require the configuration of water source filtration devices, fertilizer tanks, control valves, and water meters.

[0039] S3: Crop planting and field management, irrigated via drip irrigation system. Irrigate every 7-10 days during the seedling stage, and every 5-7 days from jointing to grain filling stage, for a total of 10-15 irrigations throughout the growth period, with each irrigation providing 15-25 cubic meters of water. 3 / mu.

[0040] Furthermore, salt-tolerant crops, such as sunflowers or corn, should be selected, and the seed purity should be ≥98% and the germination rate ≥95%.

[0041] Furthermore, the field management process specifically includes necessary field management steps such as fertilization, pest and disease control, thinning and seedling establishment, and weeding.

[0042] The porous calcium-silicon salt conditioner in this invention can quickly absorb water from drip irrigation, preventing water from seeping down too quickly and prolonging the root zone's moisture time; simultaneously, the salts (Na) in the irrigation water... + , Cl - (e.g., salts) are adsorbed into its pores and temporarily fixed, reducing the accumulation of salts to the surface via capillary water. The micropores of nano-iron modified biochar can adsorb more water and ions, and its application itself can break up soil compaction and increase total soil porosity. When mixed, the two form a continuous multi-level pore network in the soil, from micropores to macropores. This network greatly improves the water-holding capacity and salt buffering capacity of the root zone soil, transforming the originally intense salt accumulation process on the surface into a buffering process with more uniform distribution and gentler concentration changes within the root zone. Secondly, the active CaO in the porous calcium-silicon salt conditioner reacts with water to generate Ca(OH)2, providing OH- - and Ca 2+ OH - It can moderately adjust the H in an alkaline environment + Activity; Ca 2+ It can then remove alkalizing sodium ions (Na+) from soil colloids through ion exchange. + It is replaced to form NaOH.

[0043] In this invention, the nano-zero-valent iron (nZVI) in the nano-iron modified biochar can react with water to produce hydroxide ions (OH-). - ) and ferrous ions (Fe 2+ It exerts its strong reducing effect, and more importantly, it can react with the NaOH produced in the previous step and the salts in the soil solution, promoting the formation of some harmful ions into precipitates or inert substances. Meanwhile, Fe... 2+ It can be oxidized to Fe 3+ This forms iron oxides, which further adsorb and fix salts and heavy metals. In summary, porous calcium-silicon salt conditioners provide Ca... 2+ Will Na +The sodium is displaced from soil colloids, while nano-iron-carbon reacts through reduction, adsorption, and co-precipitation to release the free Na. + and Cl - In-situ fixation or transformation of anions reduces the electrical conductivity and sodium adsorption ratio (SAR) of the soil solution. The combination of these two processes achieves simultaneous reduction of salinity, control of alkalinity, and stabilization of pH. The improved water, air, and salinity environment creates favorable conditions for soil microorganisms and crop roots. Biochar itself provides an excellent living environment for microorganisms, and the porous particles further optimize this environment, enabling healthy microbial communities to secrete organic acids and polysaccharides, further promoting soil aggregate formation and salt transformation.

[0044] The organic matter nutrients in this invention provide soil microorganisms with directly usable carbon and energy sources, stimulating their metabolic activity. In particular, humic acids, rich in functional groups (-COOH, -OH), can fix excess metal ions (such as Na+) in the soil through complexation. + Ca 2+ Mg 2+ This reduces the ionic strength of the soil solution, alleviating salt damage. Simultaneously, it possesses a large buffering capacity, stabilizing soil pH and mitigating pH fluctuations caused by soil conditioner reactions. This organic matter is the core cementing substance for forming soil aggregates; its decomposition products (such as polysaccharides and mycelia) and its own structure promote the formation of soil micro-aggregates, increasing porosity, particularly increasing capillary pores effective for plants, directly improving soil permeability, aeration, and water and fertilizer retention capacity.

[0045] The structural modifier in this invention belongs to the category of high-molecular-weight polymers in soil conditioners. It can bridge and adsorb soil particles through the active groups on its long chains, rapidly flocculating dispersed soil particles into stable aggregates. This is crucial in saline-alkali land, where high sodium ion content leads to highly dispersed soil particles and a compacted structure. The structural modifier can quickly break down this dispersion, forming water-stable aggregates. Furthermore, the structural modifier helps stabilize the initial pore network constructed from porous calcium silicate particles and biochar, preventing its collapse under irrigation or rainfall and ensuring long-term unobstructed passage of water and air.

[0046] The microbial agents in this invention can rapidly colonize the improved microenvironment. Through metabolic activities, they produce organic acids (such as lactic acid and acetic acid) and extracellular polysaccharides. The organic acids can directly neutralize soil alkalinity, dissolve insoluble nutrients such as calcium and phosphorus, and promote the desorption and leaching of sodium ions through proton exchange and complexation. The extracellular polysaccharides, acting as highly efficient bio-cementing agents, synergistically work with organic matter and structural modifiers to further stabilize soil aggregates. The biofilm formed protects microorganisms and improves the rhizosphere microenvironment.

[0047] In this invention, drip irrigation is not merely a water supply tool; it serves as a key lever for activating soil conditioners and regulating salt transport. Firstly, frequent, small-volume drip irrigation continuously provides moisture to the soil conditioner, allowing the hydration of CaO and the redox reaction of nZVI to proceed slowly and steadily. This avoids drastic local pH fluctuations or rapid material deterioration caused by a single, violent reaction, thus extending the conditioner's shelf life. Secondly, drip irrigation diffuses water downwards and outwards in a point-source manner, forming a moistened bulb below the dripper. The conditioner is primarily distributed within this moistened bulb, collectively constructing a root zone micro-domain with low salt concentration, loose structure, and abundant nutrients. Seeds are planted precisely at the center of this micro-domain, achieving localized salt avoidance and significantly improving germination and seedling survival rates. Thirdly, after traditional flood irrigation, groundwater carries salts to the surface layer, where evaporation is high, through capillary action. Drip irrigation, through high-frequency water supply, maintains a high moisture content in the surface soil for extended periods, weakening the upward evaporation of soil moisture. Meanwhile, the downward expansion trend of the drip irrigation wetting front is stronger, guiding salt to move laterally and downward or deeper into the root system with the water, thus effectively inhibiting the accumulation of salt on the surface. Finally, regular leaching irrigation through the drip irrigation system ensures uniform water distribution and more efficiently leaches accumulated salt in the root zone vertically to deeper soil layers. The leaching efficiency is higher than that of flood irrigation, and it significantly saves water resources.

[0048] In summary, the porous calcium-silicon salt conditioner and nano-iron modified biochar in this invention first rapidly adsorb salts, replace sodium ions, adjust pH, and form a preliminary porous network. Drip irrigation precisely delivers water at this stage, activating the chemical reactions of the conditioner (such as CaO hydration and nZVI reduction) and guiding salt transport away from the rhizosphere. Then, organic matter nutrients provide energy for the rapidly multiplying microorganisms, while the structural modifier quickly binds the dispersed soil particles, biochar, and porous particles together, forming a stable aggregate structure. This creates a stable, breathable, and water-retaining physical space for microbial activity and root growth. Finally, the introduced microbial agents can colonize the rich pores of these materials and are protected. Simultaneously, the acids produced by microbial metabolism promote the slow release of nutrients such as calcium and silicon from the porous particles, while the calcium ions provided by the particles provide bridging ions for the microbial polysaccharide aggregates.

[0049] The five components in the invention, together with drip irrigation technology, constitute a complete soil improvement system. The core conditioner (porous calcium silicon and nano iron carbon) quickly tackles the prominent problems of salt, alkali, and compaction; organic matter and structural improvers rapidly build a suitable physical structure for biological survival; microbial agents are then introduced and drive the system towards a healthy and self-sustaining ecological direction; drip irrigation acts as a precise water and salt regulator and reaction activator throughout the process, ensuring that all processes are carried out efficiently and synergistically in the crop root zone.

[0050] The following field trials provide a detailed explanation of the effects of the soil conditioning composition provided by this invention on the remediation of saline-alkali land: Site selection and baseline value survey Site selection: The following field experiment selected a representative moderately to severely saline-alkali plot (soil pH > 8.5, total salt content > 0.3%) in the Hetao region of Inner Mongolia, which has flat terrain and relatively uniform salinization. The plot was divided into 10 experimental plots. The area of ​​each plot was 6m × 5m = 30㎡.

[0051] Background value investigation: Before the experiment, the electrical conductivity (EC), sodium adsorption ratio (SAR), pH value, and mean weight diameter (MWD) of water-stable aggregates were collected from soil samples in the 0-20cm soil layer using a checkerboard sampling method.

[0052] II. Preparation of Experimental Conditioner The raw materials for the following experimental conditioners were sourced as follows: Diatomaceous earth (SiO2 content ≥85%), purchased from Shijiazhuang Kuangtuo New Material Technology Co., Ltd.; Agricultural-grade light calcium carbonate, purchased from Shijiazhuang Zhengyu New Material Technology Co., Ltd.; Binder (sodium carboxymethyl cellulose, CMC-Na), CAS 9004-32-4, purchased from Jiangsu Fushengde Bioengineering Co., Ltd.; Corn stalks collected from field waste corn stalks in the Hetao region; Ferrous sulfate (FeSO4·7H2O), industrial and agricultural grade ferrous sulfate heptahydrate, purity ≥90%, purchased from Shandong Xinyongrun Chemical Technology Co., Ltd.; Sodium borohydride (NaBH4), analytical grade, purchased from Sinopharm Chemical Reagent Co., Ltd.; Sodium humate powder, humic acid content ≥50%, purchased from Shijiazhuang Ruixiang Mineral Products Co., Ltd.; Anionic polyacrylamide (APAM), molecular weight between 12-15 million, used for soil improvement, purchased from Henan Saike Environmental Protection Technology Co., Ltd. Agricultural Bacillus subtilis wettable powder, with an effective viable count ≥20 billion / gram, was purchased from Shandong Yixiou Biotechnology Co., Ltd. Agricultural gypsum was purchased from Jinhai Gypsum Products Factory, Yicheng District, Zaozhuang City.

[0053] The preparation process of conditioner A is as follows: Step 1: Preparation of porous calcium-silicon salt conditioner: S1 Raw materials and proportions: Weigh diatomaceous earth and agricultural-grade light calcium carbonate in a dry weight ratio of 7:3 and mix them evenly in a mixer.

[0054] S2 Granulation: The above-mentioned mixed powder is mixed with the binder sodium carboxymethyl cellulose, wherein the amount of binder added is 3% of the dry weight of the mixed powder. While stirring, purified water is added to the mixture, with the amount of water controlled at 20% of the dry weight of the mixed powder. The material is kneaded to achieve a suitable moisture content. The wet material is fed into an extrusion granulator to produce cylindrical wet granules with a diameter of 3-5 mm.

[0055] S3 Calcination: The wet granules are evenly spread on a high-temperature resistant tray and placed in a muffle furnace for calcination at 550°C for 2 hours. After calcination, the mixture is allowed to cool naturally to room temperature to obtain a porous calcium-silicon salt conditioner rich in micropores and with an active CaO and porous SiO2 framework as its core.

[0056] Figure 1 (a) shows the SEM image of the porous calcium-silicon salt conditioner. As can be observed from the image, the surface of the calcined conditioner is rough and crisscrossed with grooves, and has an irregular porous and slit structure with interwoven distribution, which intuitively proves that the material has a loose and porous microstructure.

[0057] Step 2: Preparation of nano-iron modified biochar S1 Biochar Substrate Preparation: Corn stalks were crushed to a length of 2-3 cm as biomass feedstock. The biomass feedstock was placed in a tube furnace, and high-purity nitrogen was continuously introduced before and throughout the pyrolysis process to create and maintain oxygen-limited conditions. The temperature was increased to 500°C at a rate of 10°C / min and maintained at this temperature for 2 hours for pyrolysis. After pyrolysis, the mixture was cooled to room temperature under nitrogen protection to obtain crude biochar. This crude biochar was then crushed and passed through a 60-mesh sieve to obtain uniform biochar substrate powder.

[0058] S2 nano-zero-valent iron loading modification: Prepare a 0.1 M ferrous sulfate (FeSO4·7H2O) aqueous solution. Immerse the above biochar substrate in the 0.1 M ferrous sulfate solution and mechanically stir at room temperature for 2 hours to allow Fe... 2+ Sufficient adsorption was achieved. The mixture was transferred to a reactor equipped with a stirrer and nitrogen inlet, and nitrogen was continuously introduced to maintain an inert atmosphere. Under vigorous stirring, a 0.3 M aqueous solution of sodium borohydride (NaBH4) (molar ratio of sodium borohydride to ferrous sulfate approximately 3:1) was slowly added dropwise over a period of 1 hour. A color change and the formation of black particles were observed in the solution, and the reaction continued until no obvious bubbles were produced.

[0059] S3 Product Post-processing: After the reaction was complete, the solid-liquid mixture was separated by suction filtration using a Buchner funnel. The solid product was washed several times with deoxyethanol and deionized water alternately until the washing solution was neutral and free of sulfate ions. The washed wet solid product was placed in a vacuum drying oven and dried at 60°C for 12 hours. After drying, black nano-iron modified biochar (nZVI-BC) was obtained and stored in a sealed container away from light.

[0060] Figure 1 (b) is a SEM image of nano-iron modified biochar (nZVI-BC). As can be observed from the image, nZVI is relatively uniformly dispersed on the surface of biochar in an irregular spherical shape, and no obvious large-area aggregation phenomenon was observed.

[0061] Step 3: Combining the components: According to the formula ratio, accurately weigh the following: porous calcium-silicon salt conditioner: 60 kg; nano-iron modified biochar: 25 kg; humic acid: 15 kg; polyacrylamide: 1 kg; Bacillus subtilis inoculant: 1 kg; put all components into a double helix conical mixer and mix for 30 minutes until uniform to obtain the final saline-alkali land conditioner product. Pack the obtained product in a moisture-proof bag and store it in a cool, dry place.

[0062] The preparation process of conditioner B is as follows: the only difference between it and the preparation process of conditioner A is that the raw material agricultural grade light calcium carbonate is omitted when preparing porous calcium silicate conditioner.

[0063] The preparation process of conditioner C is as follows: the only difference between it and the preparation process of conditioner A is that the raw material diatomaceous earth is omitted when preparing porous calcium-silicon salt conditioner.

[0064] The preparation process of conditioner D is as follows: The only difference between conditioner D and conditioner A is that when preparing nano-iron modified biochar, the nano-zero-valent iron loading modification process is omitted, and the nano-iron modified biochar in conditioner A is directly replaced with biochar substrate.

[0065] The preparation process of conditioner E is as follows: the only difference between it and the preparation process of conditioner A is that the first step of preparing porous calcium-silicon salt conditioner is omitted, that is, the raw material porous calcium-silicon salt conditioner in conditioner A is omitted.

[0066] The preparation process of conditioner F is as follows: the only difference between it and the preparation process of conditioner A is that the second step of preparing nano-iron modified biochar is omitted, that is, the raw material nano-iron modified biochar in conditioner A is omitted.

[0067] The preparation process of conditioner G is as follows: the only difference between conditioner G and conditioner A is that the raw material Bacillus subtilis inoculant in conditioner A is omitted.

[0068] Conditioner H is a commonly used agricultural gypsum soil conditioner.

[0069] III. Field Trial Process Experiment 1: Effects of different conditioning agents on the remediation of saline-alkali land S1. Application of soil conditioner: Evenly spread 9 kg of the above-mentioned conditioner AH on the soil surface of the corresponding test plots, and then immediately perform rotary tillage (15-20 cm) to fully mix the conditioner with the topsoil. This step should be completed 7-10 days before sowing.

[0070] S2. Irrigation System Design: Install a drip irrigation system. The drip tape spacing should be 60-70cm. Include a water source filter, fertilizer tank, control valve, and water meter. Irrigation Schedule: Initiate irrigation when soil moisture content is below 60% of field capacity, using a small, frequent irrigation method, with each irrigation providing 20 cubic meters of water. 3 / mu, irrigate once every 8 days during the seedling stage, once every 6 days from the jointing stage to the grain filling stage, and irrigate 10-15 times throughout the entire growth period.

[0071] S3. Sowing: Select the "Jingke 968" salt-tolerant corn hybrid variety, ensuring seed purity ≥98% and germination rate ≥95%. When the soil temperature at 5cm depth is consistently above 10-12℃, use manual furrow sowing. The target density is set at approximately 4000 plants / acre, with row spacing of 60-70cm, plant spacing of approximately 25cm, and sowing depth of 4cm. After sowing, compact the soil appropriately.

[0072] S4. Fertilization: The total nutrient input of chemical fertilizers is the same for all plots, only the conditioner differs. Base fertilizer: Before sowing, during land preparation, evenly spread per acre: 15-20 kg of diammonium phosphate (N 18%, P2O5 46%) + 10-15 kg of potassium sulfate (K2O 50%). Incorporate into the 0-15cm soil layer through rotary tillage. Topdressing: Use fertigation, preparing urea into a stock solution and injecting it through the fertilizer tank. Apply in 2-3 applications with drip irrigation during the large bell-shaped tasseling stage and the tasseling stage. The total urea usage is the same as in flood-irrigated areas. Flush the pipes with clean water before and after each fertilization.

[0073] S5. Pest and Disease Control: The timing, pesticides, and concentrations for pest and disease control are completely consistent across all plots. Underground pests: Before sowing, treat seeds with 0.2% phoxim EC at the seed weight. Corn borer: During the whorl stage, apply 0.5-1 kg of 3% phoxim granules per acre into the whorl. Aphids and spider mites: When they occur, spray with a 2000-fold dilution of 10% imidacloprid WP. Large leaf spot and small leaf spot: At the initial stage of disease, spray with a 500-fold dilution of 50% carbendazim WP, repeating every 7-10 days for 2-3 applications.

[0074] S6. Other field management: Thinning and fixing seedlings: Thin seedlings at the 3-4 leaf stage and fix seedlings at the 5-6 leaf stage to ensure uniform seedlings, remove weak seedlings and retain strong ones to achieve the designed density. Cultivation and weeding: Cultivate 1-2 times during the seedling stage to loosen the soil, increase soil temperature and remove weeds.

[0075] Experiment 2: Blank Control Experiment A blank control group was set up for the control experiment. The only difference between this group and Experiment 1 was that no soil conditioner was applied in S1.

[0076] Experiment 3: The impact of different irrigation methods on the restoration of saline-alkali land The difference between this group of field trials and Experiment 1 is that: S1. When applying soil conditioner, use conditioner A. S2's irrigation system uses the traditional flood irrigation method, with each irrigation quota being approximately 70m³. 3 / mu. Ensure adequate irrigation for sowing and emergence, the large trumpet stage, tasseling and flowering, and grain filling. Irrigate 4-5 times throughout the entire growth period. Use a water meter to measure and irrigate until the soil surface is evenly covered with a layer of water, allowing it to seep in naturally. Topdressing stage in S4: During the large trumpet stage, combine with inter-cultivation and hilling, apply 28 kg of urea (N 46%) per mu in strips.

[0077] IV. Test Indicators and Test Methods: Soil electrical conductivity (EC, 1:5 soil-water ratio): Collect soil samples from the 0-20cm topsoil layer, air-dry them, and pass them through a 2mm sieve. Add deionized water at a soil:water ratio of 1:5 (by weight), shake for 30 minutes, let stand for 30 minutes, and then take the supernatant for electrical conductivity measurement.

[0078] Soil sodium adsorption ratio (SAR): Soil leachate was obtained using a saturated mud extraction method, and Na was determined using atomic absorption spectrometry. + Ca 2+ Mg 2+ Concentration (unit: mmol / L), calculate SAR = [Na + ] / √(([Ca 2+ ]+[Mg 2+ ]) / 2).

[0079] Soil pH value: Collect soil samples from the 0-20cm topsoil layer, air-dry, and grind them through a 2mm sieve. Add deionized water at a soil:water ratio of 1:2.5 (by weight), and stir with a glass rod for 2 minutes to fully disperse the soil particles. After standing for 30 minutes, stir or shake again until homogeneous, and immediately use a pH meter to measure the pH value of the upper suspension.

[0080] Mean weight diameter (MWD) of water-stable soil aggregates (>0.25 mm): Using the wet sieving method, 50 g of air-dried soil sample was placed on a set of sieves with apertures of 2 mm, 1 mm, 0.5 mm, and 0.25 mm from top to bottom, and shaken up and down in water at a rate of 30 times / minute for 30 minutes. Aggregates on each sieve were collected in stages, dried, weighed, and the MWD was calculated.

[0081] Corn kernel yield: Each experimental plot was harvested separately, threshed, dried and weighed, and the yield per mu was converted to the standard moisture content (14%).

[0082] V. Test Results Figures 2-4 The effects of different treatment groups on the improvement of saline-alkali land and maize yield were shown. Figure 2 The results of soil EC and MWD measurements in different treatment groups; Figure 3 Soil SAR and pH test results for different treatment groups; Figure 4 The figures show the maize kernel yield results in different treatment groups. As can be seen from the graph, the complete formula (conditioner A) + drip irrigation group performed best in all indicators. Significant reductions in EC and SAR demonstrate the synergistic salt-reducing and alkali-controlling capabilities of porous calcium silicate and nano-iron carbon under drip irrigation activation. The mild pH reduction is a result of the balance of multiple regulatory mechanisms including CaO, nZVI, and organic acids. The significant increase in MWD reflects the ability of the structure modifier, organic matter, and microorganisms to synergistically construct a stable aggregate structure based on good porosity. The highest final yield is a comprehensive reflection of all the aforementioned improvements.

[0083] Compared to the complete formula (conditioner A) + drip irrigation group: the EC and SAR of the calcium carbonate-free (conditioner B) + drip irrigation group showed limited decreases, but the yield was lower, indicating a lack of active calcium source and Na. + The severely insufficient replacement capacity underscores the crucial role of CaO in porous calcium silicate. The decrease in EC and SAR in the diatomaceous earth-free (conditioner C) + drip irrigation group was relatively limited, and the MWD value was low, indicating that the lack of a stable porous framework formed by diatomaceous earth affected the construction of the pore network and water retention capacity, thus impacting crop growth. The EC and pH improvement effects of the non-nano-iron modified (conditioner D) + drip irrigation group were slightly inferior to group A, indicating that the reduction, fixation, and subsequent transformation of nano-zero-valent iron significantly contribute to deep desalination and environmental stabilization. Furthermore, since the non-porous calcium silicate (conditioner E) + drip irrigation group and the non-nano-iron carbon (conditioner F) + drip irrigation group (lacking the two core conditioners respectively) showed significantly worse performance in all indicators compared to the complete formula (conditioner A) + drip irrigation group, especially in SAR and yield, this demonstrates the irreplaceable nature of porous calcium silicate and nano-iron carbon. The MWD and yield of the drip irrigation group without microbial inoculant (conditioner G) were slightly lower than those of the complete formula (conditioner A) + drip irrigation group, indicating that exogenous microbial inoculants have a positive effect on rapidly establishing healthy microbial communities, promoting aggregation and ecological transformation.

[0084] For drip irrigation, compared to flood irrigation, using the same conditioner A, drip irrigation significantly outperforms flood irrigation in terms of salt reduction (lower EC), alkali control (lower SAR), soil improvement (higher MWD), and yield increase. This demonstrates that the drip irrigation's frequent, small-volume water supply pattern continuously activates the conditioner's reaction, guides salt migration downwards, inhibits surface accumulation, and constructs a locally optimized root zone. Flood irrigation's large-volume flushing and evaporative salt return weaken the overall effectiveness of the conditioner.

[0085] Compared with traditional soil conditioners (agricultural gypsum + drip irrigation group), although agricultural gypsum can reduce SAR and EC to a certain extent, its effect on improving soil structure (low MWD) and overall yield increase is far less than that of the complete system of this invention, thus proving the limitations of single chemical improvement.

[0086] The above test results indicate that porous calcium-silicon salt conditioner and nano-iron modified biochar are the core components for rapidly improving saline-alkali soil conditions; organic matter and structural modifiers are the supporting structures for building and stabilizing habitable soil structures; microbial agents are the driving force for the system's healthy development; and drip irrigation is the control hub for precisely coordinating all processes. The saline-alkali soil conditioning composition and drip irrigation technology provided by this invention are indispensable and work synergistically to achieve rapid, lasting, and ecological improvement of saline-alkali soil.

[0087] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0088] 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 composition for conditioning saline-alkali land, characterized in that, It contains the following components in parts by weight: 50-65 parts porous calcium-silicon salt conditioner, 20-30 parts nano-iron modified biochar, 10-20 parts organic matter nutrients, 0.5-2 parts structural modifier, and 0.5-2 parts microbial inoculant; The porous calcium-silicon salt conditioning agent is obtained by granulation and calcination of a mixed powder composed of diatomaceous earth and calcium carbonate; the nano-iron modified biochar is obtained by loading nano-zero valent iron onto biochar as a substrate using a liquid-phase reduction precipitation method.

2. The saline-alkali land conditioning composition according to claim 1, characterized in that, The preparation method of the porous calcium-silicon salt conditioner includes: S11: Mix diatomaceous earth and calcium carbonate at a dry weight ratio of (6-8):(4-2); S12: Mix the mixed powder obtained in S11 with binder and water, and granulate it by extrusion. S13: Calcine the particles obtained in S12 at 500-600°C for 1-3 hours to obtain the porous calcium-silicon salt conditioner.

3. The saline-alkali land conditioning composition according to claim 2, characterized in that, In step S11, the dry weight ratio of diatomaceous earth to calcium carbonate is 7:

3.

4. The saline-alkali land conditioning composition according to claim 1, characterized in that, The preparation method of the nano-iron modified biochar includes: S21: Biochar substrate is prepared by pyrolyzing biomass at 400°-600°C under oxygen-limited conditions; S22: The biochar obtained in S21 is immersed in ferrous sulfate solution and stirred for adsorption. Then, sodium borohydride solution is added in an inert atmosphere to carry out a reduction reaction, so that nano-zero valent iron is loaded on the biochar. After filtration, washing and drying, the nano-iron modified biochar is obtained.

5. The saline-alkali land conditioning composition according to claim 4, characterized in that, In step S22, the concentration of the ferrous sulfate solution is 0.05-0.2 M, and the concentration of the sodium borohydride solution is 0.1-0.5 M.

6. The saline-alkali land conditioning composition according to claim 1, characterized in that, The organic nutrients are selected from one or more of humic acid, weathered coal, organic fertilizer, and amino acid residue; the structural modifier is selected from one or more of polyacrylamide or carboxymethyl cellulose; and the microbial agent is selected from one or more of Bacillus subtilis, Bacillus licheniformis, and gelatinous Bacillus.

7. A method for remediating saline-alkali land, characterized in that, The method involves combined irrigation with the saline-alkali land conditioning composition according to any one of claims 1 to 6, and includes the following steps: S31: The saline-alkali soil conditioning composition is evenly spread on the surface of the saline-alkali soil to be restored, and then the soil is tilled to mix the conditioning composition with the topsoil. S32: Install a drip irrigation system and set the drip tape spacing according to the crop row spacing; S33: To carry out crop planting and field management, and to irrigate through the drip irrigation system.

8. The method for remediating saline-alkali land according to claim 7, characterized in that, In step S31, the soil tillage is deep tillage to 25-30cm or rotary tillage to 15-20cm, and this step is completed 7-10 days before sowing.

9. The method for remediating saline-alkali land according to claim 7, characterized in that, In step S33, the specific method of irrigation through the drip irrigation system is as follows: irrigate once every 7-10 days during the seedling stage of crops, irrigate once every 5-7 days from the jointing stage to the grain filling stage, and irrigate 10-15 times throughout the entire growth period, with each irrigation volume being 15-25 m³ / mu.

10. The method for remediating saline-alkali land according to claim 7, characterized in that, In step S33, the crop planted is a salt-tolerant crop, preferably sunflower or corn.

Images