Chelated salt-alkali soil conditioner and preparation method thereof

Abstract

The application provides a chelated saline-alkali soil improver which is prepared from raw materials including polymeric ferric sulfate and EDDHA chelated iron. Through a special preparation process of constant-temperature deep chelation and low-temperature microbial embedding, the industry pain points of existing improvement products, such as rapid failure in high-saline-alkali environment, single function and effect rebound, are solved. The product has multiple effects of flocculation and soil improvement, alkali and salt adjustment, long-acting iron supply and bacterium inhibition and land nurturing, and can quickly reduce the pH and salt content of saline-alkali soil, break the hardening, correct the yellowing and stunted seedlings of crops, repair the degraded saline-alkali farmland year by year, and greatly improve the yield and quality of various crops. The preparation process is stable, and is suitable for industrial large-scale production and large-area saline-alkali land popularization and application.

Description

Technical Field

[0001] This invention belongs to the field of saline-alkali land ecological restoration and soil improvement technology, specifically relating to a chelated saline-alkali soil conditioner and its preparation method. Background Technology

[0002] Currently, developing and utilizing saline-alkali arable land is a core reserve of arable land resources for ensuring food security. Saline-alkali soils generally suffer from typical problems such as high pH, ​​high salinity, extreme iron passivation, collapse of granular structure, poor aeration, and lack of beneficial microorganisms. When the pH of saline-alkali soil is greater than 8.5, more than 95% of the iron ions in the soil are fixed and locked, and ordinary iron fertilizers quickly become ineffective after application, resulting in widespread yellowing of new leaves, stunted seedlings, seedling death, and significant yield reduction in crops.

[0003] Traditional methods of alkali improvement (high-volume water treatment to reduce salt content, single-ingredient gypsum, and simple organic fertilizer) have long cycles, only address the symptoms and not the root cause, and salt levels are prone to rebound. They also cannot simultaneously solve the problems of nutrient activation and microecological reconstruction. Commercially available EDDHA chelated iron products have limited functions, only supplementing iron and failing to reduce salt content and adjust alkali levels; ordinary polyferric sulfate products only have the ability to flocculate and reduce alkali levels, and their long-term absorption and utilization rate by crops is extremely low.

[0004] Most existing soil conditioners are physically formulated without chelation stabilization processes, resulting in poor acid-base compatibility. Their effectiveness rapidly diminishes in high-salt-alkali environments, and long-term application can easily lead to secondary soil compaction and acidification. Patent CN109233787B discloses a single polyferric sulfate formulation, focusing only on flocculation and alkalinity reduction, without addressing the issues of long-term micronutrient chelation and efficient crop absorption. Patent CN105237286B discloses a single EDDHA chelated iron fertilizer, targeting only iron supplementation and yellowing in crops, without functions for salinity reduction, soil improvement, breaking up compaction, or microbial restoration. Most compound soil conditioner patents fail to solve core technical challenges such as microbial inactivation during high-temperature granulation, mutual incompatibility within chelation systems, and component antagonism, resulting in poor mass production stability.

[0005] Based on the above-mentioned shortcomings of existing technologies, it is necessary to innovate and design an integrated preparation process of polymerization chelation and low-temperature encapsulation, and develop a long-lasting soil conditioner that combines chemical alkali adjustment, physical soil improvement, nutrient activation and bioremediation to fill the technological gap in the industry. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a chelated saline-alkali soil conditioner that deeply chelates polyferric sulfate and EDDHA-chelated iron, significantly improving stability and ensuring that iron remains undeactivated and unpassivated even under extreme high-salt and alkaline conditions. When used in conjunction with organic fertilizer, magnesium fertilizer, pH buffers, and synergists, it rapidly reduces soil pH and salinity, breaks up soil compaction, effectively activates iron, rebuilds beneficial soil micro-ecology, and continuously improves soil fertility. This product is suitable for large-scale industrial production and widespread application.

[0007] The purpose of this invention is to provide a chelated saline-alkali soil conditioner, which is made from raw materials including polyferric sulfate and EDDHA chelated iron.

[0008] The polyferric sulfate and EDDHA are chelated. Preferably, the chelation is carried out under heating conditions, with a heating temperature of 35~70℃.

[0009] The raw materials of the chelated saline-alkali soil conditioner also include organic fertilizer, salt-tolerant functional bacteria, magnesium fertilizer, acid-base buffer regulator and synergist.

[0010] The raw materials of the chelated saline-alkali soil conditioner also include a carrier, selected from one or more mineral powders, preferably natural bentonite and / or attapulgite.

[0011] The present invention also aims to provide a method for preparing the chelated saline-alkali soil conditioner, wherein the method first chelates polyferric sulfate and EDDHA chelated iron under heating conditions. Preferably, organic fertilizer, magnesium fertilizer, acid-base buffer regulator and synergist are then added, and finally salt-tolerant functional bacteria are inoculated.

[0012] The method specifically includes the following steps: Step 1: The pretreated polyferric sulfate and EDDHA chelated iron are chelated under heating conditions; Step 2: While maintaining the stirring and constant temperature conditions of Step 1, add organic fertilizer, magnesium fertilizer, acid-base buffer regulator and synergist to obtain the mixture; Step 3: Inoculate the mixture with salt-tolerant functional bacteria, granulate, and dry to obtain the chelated saline-alkali soil conditioner.

[0013] Another objective of this invention is to provide the use of the chelated saline-alkali soil conditioner for in-situ remediation of moderately to severely saline-alkali soils, secondary salinized soils, soils with continuous cropping, compacted and degraded farmland, and lightly heavy metal contaminated soils. It is widely suitable for planting various crops such as wheat, corn, rice, cotton, sugar beets, vegetables, medicinal herbs, fruit trees, and forest trees.

[0014] The dosage of the chelated saline-alkali soil conditioner is 9-80 kg / mu.

[0015] The present invention has the following beneficial effects: (1) This invention is the first to use a deep chelation process of polyferric sulfate and EDDHA chelated iron, which is different from the simple physical mixing products on the market. The chelation stability is improved by more than 3 times. The iron element does not fail or passivate under the extreme environment of high salt and alkali. It can improve the soil in multiple dimensions and treat both the symptoms and the root cause.

[0016] (2) The chelated saline-alkali soil conditioner provided by the present invention can quickly neutralize soil alkalinity. The soil pH can be reduced by 0.8 to 1.5 units in 30 days, achieving physical salt reduction, breaking up compaction, reconstructing granular structure, accelerating surface salt leaching, and reducing salt content by 35% to 45%.

[0017] (3) The chelated saline-alkali soil conditioner provided by this invention not only improves salinity and alkalinity but also activates nutrients, provides long-term and stable iron supply, completely solves the problem of iron deficiency, yellowing, and stunted seedlings in crops, and continuously restores the soil microecology. Long-term continuous application can gradually reduce soil alkalinity, steadily improve arable land fertility, and prevent salinity and alkalinity from rebounding.

[0018] (4) The chelated saline-alkali soil conditioner provided by this invention is safe, environmentally friendly, and widely adaptable. The raw materials are green and residue-free, with no toxic heavy metals added, making it safe and friendly to crops, humans, livestock, and the surrounding environment. It is perfectly compatible with all planting modes, including dryland farming, paddy farming, drip irrigation, flood irrigation, and dry sowing with wet emergence. Detailed Implementation

[0019] The present invention will now be described in detail through specific embodiments, and the features and advantages of the present invention will become clearer and more explicit with these descriptions.

[0020] This invention provides a chelated saline-alkali soil conditioner, which is prepared using raw materials including polyferric sulfate and EDDHA chelated iron.

[0021] Polyferric sulfate contains a basicity of 18-25 wt% and water-insoluble matter ≤0.5 wt%. EDDHA chelated iron is ethylenediamine di-o-hydroxyphenyl ferric acetate sodium (EDDHA-FeNa), with a total available iron ≥6 wt%, ortho-chelated iron content ≥4.8 wt%, and a pH stability range of 3-11.

[0022] Polyferric sulfate possesses excellent charge neutralization capacity and stronger adsorption bridging effect, effectively removing heavy metal ions and organic pollutants from soil. Through hydrolysis, it produces various hydroxyl iron complexes, which can co-precipitate or adsorb heavy metal ions (such as Cd, Pb, As, etc.) in the soil, thereby reducing the bioavailability of heavy metals. Furthermore, its strong oxidizing properties can decompose some organic pollutants, such as polycyclic aromatic hydrocarbons (PAHs) and pesticide residues, converting them into low-toxicity or non-toxic small molecules. In addition, polyferric sulfate can improve soil physical structure, promote the formation of soil aggregates, and enhance soil water retention and permeability, creating favorable conditions for subsequent phytoremediation or microbial remediation. EDDHA chelated iron can regulate soil pH, improve nutrient utilization, adsorb and precipitate heavy metals, improve soil compaction, and enhance moisture and fertilizer retention capacity.

[0023] The polyferric sulfate and EDDHA chelated iron are chelated. Preferably, the chelation is carried out under heating conditions, with a heating temperature of 35~70℃, more preferably 40~65℃, and even more preferably 45~60℃. This invention deeply complexes the high molecular weight iron ions in polyferric sulfate with the chelating groups of EDDHA to form a highly stable polyferric chelated iron composite masterbatch, significantly improving the overall system's alkali and salt resistance. It solves the problem of poor mass production stability caused by mutual repulsion and component antagonism in the chelation system. This invention is the first to propose an integrated deep chelation process for polyferric sulfate and EDDHA chelated iron, which is different from the simple physical mixing products on the market. The chelation stability is improved by more than 3 times, and the iron element does not fail or passivate under extreme high salt and alkali environments.

[0024] The polyferric sulfate is present in an amount of 15-50 parts by weight. When the amount of polyferric sulfate is less than 15 parts, the flocculation and alkali reduction capacity is insufficient, the soil pH decreases slowly, and the effect of aggregate structure reconstruction is poor. When the amount is more than 50 parts, the system is too acidic, which can easily lead to local soil acidification and inhibit the activity of subsequent salt-tolerant functional bacteria, while also increasing production costs.

[0025] The EDDHA chelated iron content ranges from 6 to 28 parts by weight. When the EDDHA chelated iron content is less than 6 parts, the long-term iron supply capacity is insufficient and cannot completely solve the problem of iron deficiency chlorosis in crops; when the content is more than 28 parts, the cost increases significantly, and excessive iron will antagonize elements such as phosphorus and zinc in the soil, affecting the absorption of other nutrients.

[0026] The raw materials of the chelated saline-alkali soil conditioner also include organic fertilizer, salt-tolerant functional bacteria, magnesium fertilizer, acid-base buffer regulator and synergist.

[0027] The organic fertilizer is selected from one or more of the corrosive acid fertilizers, preferably from one of ammonium humate, sodium humate, nitrohumic acid, humic acid phosphate fertilizer, and potassium humate, and more preferably potassium humate. The organic fertilizer has a weight of 6 to 30 parts, preferably 9 to 25 parts, and more preferably 12 to 20 parts.

[0028] The salt-tolerant functional bacteria are selected from one or more of *Bacillus licheniformis*, *Bacillus mucilaginosus*, and *Bacillus megaterium*. These salt-tolerant bacteria can effectively reduce soil salinity, improve saline-alkali soil environments, decompose insoluble inorganic and organic matter in the soil, and release nutrients that can be absorbed by plants, thereby improving soil fertility. The various bioactive substances they produce can regulate crop growth and metabolic processes, and enhance crop resistance to adverse conditions. The salt-tolerant functional bacteria are present in an amount of 6-25 parts by weight, preferably 7-20 parts, and more preferably 8-15 parts.

[0029] The magnesium fertilizer is selected from one or more of magnesium sulfate, magnesium chloride, and magnesium nitrate, preferably magnesium sulfate and / or magnesium nitrate, and more preferably magnesium sulfate. Magnesium fertilizer can supplement key nutrients, improve soil structure, regulate pH, and remediate and improve heavy metal pollution in the soil. The magnesium fertilizer is present in parts by weight of 1-12 parts, preferably 2-10 parts, and more preferably 3-8 parts.

[0030] The acid-base buffer regulator is selected from one or more of the following: citrate-sodium citrate composite buffer, potassium dihydrogen phosphate-dipotassium hydrogen phosphate buffer system, and humic acid buffer, preferably citrate-sodium citrate composite buffer and / or potassium dihydrogen phosphate, and more preferably citrate-sodium citrate composite buffer. The acid-base buffer regulator has a weight ratio of 3 to 14 parts, preferably 4 to 12 parts, and more preferably 5 to 10 parts.

[0031] The synergist is selected from one or more of polyaspartic acid, fulvic acid, polyacrylamide, rhamnolipid, and γ-polyglutamic acid, preferably one or more of polyaspartic acid, fulvic acid, and γ-polyglutamic acid, and more preferably γ-polyglutamic acid. The synergist can achieve the functions of water and fertilizer retention, promoting nutrient absorption, improving soil structure, and enhancing crop stress resistance. The synergist has a weight ratio of 1-9 parts, preferably 2-7 parts, and more preferably 2-5 parts.

[0032] The raw materials of the chelated saline-alkali soil conditioner also include a carrier, selected from one or more mineral powders, preferably natural bentonite and / or attapulgite.

[0033] This invention provides a method for preparing the chelated saline-alkali soil conditioner, wherein polyferric sulfate and EDDHA chelated iron are chelated under heating conditions. Preferably, organic fertilizer, magnesium fertilizer, acid-base buffer regulator, and synergist are then added, and finally, salt-tolerant functional bacteria are inoculated.

[0034] The method specifically includes the following steps: Step 1: The pretreated polyferric sulfate and EDDHA chelated iron are chelated under heating conditions.

[0035] The pretreatment involves grinding polyferric sulfate and drying it until the moisture content is ≤5wt%. After grinding, the polyferric sulfate particle size is 60~120 mesh, preferably 70~110 mesh, and more preferably 80~100 mesh. The drying temperature is 60-80℃, preferably 65-70℃, and more preferably 70℃.

[0036] Under stirring conditions, EDDHA chelated iron is added to polyferric sulfate and heated to a constant temperature for reaction. The stirring speed is 40~120 r / min, preferably 50~100 r / min, more preferably 60~80 r / min. The heating temperature is 35~70℃, preferably 40~65℃, more preferably 45~60℃. The reaction time is 30~80 min, preferably 35~70 min, more preferably 40~60 min. In the above process, the polymeric iron ions of polyferric sulfate deeply complex with the EDDHA chelating groups to form a highly stable polymeric chelated iron composite masterbatch, which significantly improves the overall system's alkali and salt resistance.

[0037] The polyferric sulfate is 15-50 parts by weight, preferably 20-45 parts, and more preferably 25-40 parts.

[0038] The EDDHA chelated iron is present in 6 to 28 parts by weight, preferably 8 to 23 parts, and more preferably 10 to 18 parts.

[0039] Step 2: While maintaining the stirring and constant temperature conditions of Step 1, add organic fertilizer, magnesium fertilizer, acid-base buffer regulator and synergist to obtain the mixture.

[0040] The organic fertilizer is 6 to 30 parts by weight, preferably 9 to 25 parts, and more preferably 12 to 20 parts by weight.

[0041] The magnesium fertilizer is 1 to 12 parts by weight, preferably 2 to 10 parts, and more preferably 3 to 8 parts.

[0042] The acid-base buffer is present in parts by weight of 3 to 14, preferably 4 to 12, and more preferably 5 to 10.

[0043] The synergist is present in parts by weight of 1 to 9 parts, preferably 2 to 7 parts, and more preferably 2 to 5 parts.

[0044] After adding organic fertilizer, magnesium fertilizer, pH buffer, and synergist, the constant temperature stirring time is 15-45 minutes, preferably 20-40 minutes, and more preferably 25-35 minutes. After addition, the pH of the system is neutralized and pre-adjusted, controlling the overall pH of the mixture to be stable at 5.5-7.0. The components fully complex, eliminating elemental antagonism and forming a synergistic effect system.

[0045] Step 3: Inoculate the mixture with salt-tolerant functional bacteria, granulate, and dry to obtain the chelated saline-alkali soil conditioner.

[0046] The salt-tolerant functional bacteria are present in a weight ratio of 6 to 25 parts, preferably 7 to 20 parts, and more preferably 8 to 15 parts.

[0047] The salt-tolerant functional bacteria are introduced by spraying them into the mixture when it has naturally cooled to no higher than 30°C, and then stirring for 10-30 minutes, preferably 10-30 minutes, more preferably 15-25 minutes. The stirring speed is 25-55 r / min, preferably 30-50 r / min, more preferably 35-45 r / min, such as 40 r / min. This stirring process utilizes a dual process of powder adsorption and membrane encapsulation of the salt-tolerant functional bacteria, maximizing the viability of beneficial microorganisms, with a viable bacteria retention rate ≥90%.

[0048] After mixing, the mixture is fed into a granulator and sprayed with water to bind it together, forming uniform spherical particles with a particle size of 2-4 mm. Then, it is air-dried (air-drying temperature ≤40℃), and the moisture content of the finished product is strictly controlled to ≤8%, thus obtaining a chelated saline-alkali soil conditioner.

[0049] This invention achieves deep chelation between polyferric sulfate and EDDHA, increasing chelation stability by more than 3 times. Iron remains unaffected and unpassivated even in high-salt and alkaline environments, providing multi-dimensional synergistic soil improvement and addressing both the symptoms and root causes. It rapidly forms a flocculated gel, neutralizing soil alkalinity; soil pH can decrease by 0.8-1.5 units within 30 days. It achieves physical desalination, breaking up soil compaction, reconstructing granular structure, and accelerating surface salt leaching, reducing salt content by 35%-45%. Nutrient activation provides long-term, stable iron supply, completely resolving iron deficiency-induced yellowing and stunted seedlings in crops. Using the 15N tracer method, iron absorption and utilization rates in crops reach 42%-48%, 6-8 times higher than ordinary physical soil conditioners. It also facilitates bioremediation, rapidly colonizing salt-tolerant beneficial bacteria, inhibiting soil-borne diseases, and continuously restoring the soil microecology. The effects are long-lasting, stable, and without rebound. Field trials show that the fertilizer's effectiveness and soil-improving effect can last for 150-180 days, with a single application taking effect for the entire season; long-term continuous application can gradually reduce soil alkalinity, steadily improve soil fertility, and prevent salinity from rebounding.

[0050] Safe and environmentally friendly, with wide applicability, the raw materials are green and residue-free, with no added toxic heavy metals, and meet national agricultural fertilizer safety standards; it is safe and friendly to crops, humans, livestock and the surrounding environment; it is perfectly compatible with all planting modes such as dryland farming, paddy farming, drip irrigation, flood irrigation, dry sowing and wet emergence.

[0051] The chelated saline-alkali soil conditioner provided by this invention can rapidly reduce soil pH and salinity, break up soil compaction, activate iron elements for a long time, rebuild beneficial soil micro-ecology, and continuously improve soil fertility. It is suitable for modern saline-alkali land planting models such as original soil and water, dry sowing and wet emergence, and slightly saline water irrigation, and greatly improves the survival rate and yield of crops in saline-alkali arable land.

[0052] The preparation process of the chelated saline-alkali soil conditioner is simple and controllable, with low production energy consumption, strong product stability, resistance to clumping, and long shelf life, making it suitable for large-scale industrial mass production and application.

[0053] This invention also provides the uses of the chelated saline-alkali soil conditioner for in-situ improvement and remediation of moderately to severely saline-alkali soils, secondary salinized soils, soils continuously cropped in the same location, compacted and degraded farmland, and lightly heavy metal contaminated soils. The soil conditioner is widely suitable for planting various crops such as wheat, corn, rice, cotton, sugar beets, vegetables, medicinal herbs, fruit trees, and forest trees.

[0054] Key indicators for various applicable soil types: Slightly saline-alkali soil: Total salt content of soil is 0.1~0.2wt%, and pH value is 7.5~8.5; Moderately saline-alkali land: Soil total salt content is 0.2~0.4wt%, pH value is 8.5~9.5; Severely saline-alkali land: Soil total salt content greater than 0.4wt%, pH value greater than 9.5; Secondary salinized soils: caused by improper irrigation and excessive fertilization, with a total salt content of 0.15~0.5wt%, pH value of 7.8~9.0, soil EC (electrical conductivity) value >2.0mS / cm, and nitrate content >200mg / kg; Continuous cropping soil: The same crop has been planted on the same plot of land for more than 3 consecutive years, and the number of soil pathogens is >10. 6 CFU / g, number of beneficial microorganisms <10 5 CFU / g, soil-borne disease incidence rate >30%, crop autotoxic substance accumulation >5mg / kg; Compacted and degraded farmland: soil bulk density > 1.35 g / cm³, porosity < 45%, aggregate content < 20%, topsoil thickness < 15 cm, soil permeability < 10 ml / (cm²・h); Slightly heavy metal contaminated soil: The heavy metal content in the soil is within the range of risk screening values ​​and control values ​​in GB15618-2018, namely cadmium ≤ 0.6 mg / kg, mercury ≤ 3.4 mg / kg, arsenic ≤ 40 mg / kg, lead ≤ 170 mg / kg, and chromium ≤ 250 mg / kg.

[0055] The dosage of the chelated saline-alkali soil conditioner is 9-80 kg / mu, preferably 12-75 kg / mu, and more preferably 15-70 kg / mu.

[0056] The chelated saline-alkali soil conditioner can be applied by broadcasting, drip irrigation, or fertigation.

[0057] For moderately and severely saline-alkali soils, the application rate is 15-50 kg per acre for moderately saline-alkali soils, preferably 20-45 kg, and more preferably 25-40 kg; for severely saline-alkali soils, the application rate is 40-70 kg per acre, preferably 45-65 kg, and more preferably 50-60 kg. After even application, the soil should be deeply tilled to a depth of 20-30 cm and thoroughly watered.

[0058] For moderately and severely saline-alkali soils, when applying via drip irrigation or fertigation, mix the chelated saline-alkali soil conditioner with water at a mass ratio of 1:(800~1700), preferably 1:(900~1600), and more preferably 1:(1000~1500). Apply the mixture with the integrated water and fertilizer drip irrigation system and supplement it every 10~15 days. Example

[0059] Example 1 (1) Pulverize and grind industrial grade polyferric sulfate (total iron ≥19wt%, basicity 18%~25%), pass through an 80-mesh standard sieve, and dry at 70℃ until the moisture content is ≤5wt%.

[0060] Potassium humate (fulvic acid ≥ 50 wt%), natural bentonite carrier, magnesium sulfate heptahydrate, and citric acid-sodium citrate composite buffer were air-separated to remove impurities (sand, weeds, etc.), dried at 70℃ for 2.5 h until the moisture content was ≤ 6 wt%, and passed through an 80-mesh standard sieve for later use; the salt-alkali resistant composite functional bacterial agent was stored in a cool, dark place at 4℃ in a sealed container to avoid premature inactivation.

[0061] (2) Add 32 parts of the above-treated polyferric sulfate to a sealed corrosion-resistant reactor, start low-speed stirring (60~80r / min), and slowly and uniformly add 14 parts of ethylenediamine di-o-hydroxyphenyl ferric acetate sodium EDDHA-FeNa chelated iron powder (total effective iron ≥6wt%, ortho-chelated iron content ≥4.8wt%, pH stable range 3~11); raise the temperature and control the internal temperature of the reactor to stabilize at 50℃, and continuously stir the chelation reaction for 50min. In the above process, the high molecular iron ions of polyferric sulfate and the chelating groups of EDDHA are deeply complexed to form a highly stable polymeric chelated iron composite masterbatch, which greatly improves the overall system's alkali and salt resistance stability.

[0062] Then, add 17 parts of potassium humate (fulvic acid ≥50wt%), 12 parts of natural bentonite, 5 parts of magnesium sulfate heptahydrate, 7 parts of agricultural-grade citric acid-sodium citrate composite buffer (manufacturer: Shandong Luxi Biotechnology Co., Ltd., model: NY / T 1107-2010), and 3 parts of γ-polyglutamic acid (bio-fermentation grade, manufacturer: Jiangsu Tiankai Bioengineering Co., Ltd., model: PGA-10000, molecular weight 8000~15000Da) as a synergist to the reactor in sequence. Mix and stir continuously at a constant temperature of 50℃ for 30 minutes to complete the pH neutralization and pre-adjustment of the system, and control the overall pH of the mixture to be stable at 6.2.

[0063] Stop heating and allow the mixture to cool naturally to below 30℃. Then, evenly spray 12 parts of a salt-alkali tolerant compound functional microbial agent (salt-tolerant Bacillus licheniformis + Bacillus mucilaginosus compound, manufacturer: Shandong Lvlong Biotechnology Co., Ltd., model: LL-YJ-02, effective viable count ≥20 billion / gram) into the mixture. Gently stir and mix at a low speed of 40 r / min for 20 minutes to achieve the dual effects of powder adsorption and film encapsulation, maximizing the activity of beneficial microorganisms, with a viable bacteria retention rate ≥90%. Finally, a uniformly mixed compound material is obtained.

[0064] (3) The composite material obtained above is fed into a disc granulator and sprayed with a small amount of water for bonding. The mass ratio of water to composite material is 1:28. Then it is air-dried at 38~40℃, and the moisture content of the finished product is strictly controlled to be ≤8wt%. The powder and oversized unqualified particles are removed by grading and screening through a vibrating screen to obtain a chelated saline-alkali soil conditioner.

[0065] The total iron content of the chelated saline-alkali soil conditioner was tested to be ≥8.2wt%, the proportion of chelated iron was ≥92%, the number of effective viable bacteria was ≥2.2 billion / gram, the moisture content was ≤7.2wt%, the pH value was 6.1, the salt content was ≤3.5wt%, and the heavy metal limits met the requirements of GB / T 23349-2020 "Ecological Indicators for Arsenic, Cadmium, Lead, Chromium and Mercury in Fertilizers".

[0066] Example 2 An experiment was conducted in a severely saline-alkali cotton field in Binzhou, Shandong Province. The experimental plot had a pH of 9.3 and a total salt content of 0.68%. The yellowing rate of cotton seedlings exceeded 80%.

[0067] Apply 55 kg of the chelated saline-alkali soil conditioner prepared in Example 1 of this invention and 55 kg of commercially available soil conditioner (gypsum + humic acid type, manufacturer: Hebei Wotu Agricultural Technology Co., Ltd., model: SG-2024) per mu. Conventional planting management: Use the mulch film cultivation mode, sow in mid-April, with a row spacing of 60 cm and a plant spacing of 25 cm, and a sowing rate of 4.5 kg per mu; irrigate after sowing and apply topdressing twice during the growing season (15 kg / mu of urea and 10 kg / mu of diammonium phosphate), and control cotton bollworm and aphids twice each.

[0068] The soil samples were tested before application, 30 days after application of the chelated saline-alkali soil conditioner prepared in Example 1, 30 days after application of the commercially available soil conditioner, and 30 days after application of the blank control group without soil conditioner. The results are shown in Table 1.

[0069] Table 1

[0070] Production increase comparison: The product of this invention increased production by 26.7% compared to commercially available common improvers and by 41.2% compared to the blank control.

[0071] Example 3 A wheat field experiment in North China was conducted. The experimental plot had a pH of 8.8, indicating moderate salinity and alkalinity. In previous years, the wheat seedlings had been stunted and had poor tillering.

[0072] Apply 35 kg of the chelated saline-alkali soil conditioner prepared in Example 1 of this invention per mu as base fertilizer, and set up a blank control group (no conditioner was applied). Conventional planting management: Sow in early October, with a row spacing of 20 cm and a sowing rate of 12 kg per mu; irrigate the soil before sowing, apply 20 kg / mu of urea during the greening period, apply 15 kg / mu of urea + 5 kg / mu of potassium chloride during the jointing period, spray potassium dihydrogen phosphate foliar fertilizer once during the grain filling period, and control powdery mildew and aphids once each.

[0073] At the wheat harvest period (210 days after sowing), compared with the blank control without soil amendment, the wheat root length increased by 42%, the number of tillers per plant increased by 25%, the number of effective ears increased by 21%, the thousand-grain weight increased by 8.7%, and the yield increased by 18.3% compared with the conventional control.

[0074] Comparative Example Comparative Example 1 The experimental plot was the same as the severely saline-alkali cotton field in Binzhou, Shandong (pH=9.3, total salt content 0.68wt%) in Example 2. 55 kg of industrial-grade polyferric sulfate, 55 kg of EDDHA-FeNa chelated iron, and 55 kg of well-rotted sheep manure organic fertilizer (manufacturer: Shandong Quanlin Organic Fertilizer Co., Ltd., model: NY 525-2021) were applied per mu. The planting and management methods were completely consistent with Example 2.

[0075] The test results 30 days after application and at harvest time are as follows:

[0076] Comparative Example 2 The only difference between this comparative example and Example 1 is that the polyferric sulfate and EDDHA-FeNa were not subjected to a high-temperature chelation reaction, but were instead directly mixed with other excipients at room temperature. The remaining raw material ratios, preparation processes, and parameters are completely consistent with those of Example 1.

[0077] Technical Effect Comparison: Under the same experimental conditions as Example 2, 55 kg of the soil conditioner prepared in Comparative Example 2 was applied per acre. After 30 days of application, the soil pH dropped to 8.6, the total salt content was 0.55%, the proportion of yellowed cotton seedlings was 52%, the seedling uniformity was 63%, and the final seed cotton yield increased by 9.7%. Compared with the product of Example 1, the pH decrease was 0.5 units less, the salt content reduction was 15 percentage points less, the proportion of yellowed seedlings was 44 percentage points higher, the seedling uniformity was 30 percentage points lower, and the yield increase was 17 percentage points lower. This fully demonstrates that the original deep chelation process of this invention is the core key to the high performance of the product.

[0078] The present invention has been described in detail above with reference to specific embodiments and / or exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A chelated saline-alkali soil conditioner, which is prepared using raw materials including polyferric sulfate and EDDHA chelated iron, wherein the polyferric sulfate and EDDHA chelated iron are chelated.

2. The chelated saline-alkali soil conditioner according to claim 1, characterized in that, The polyferric sulfate is present in parts by weight of 15 to 50 parts. The EDDHA chelated iron is present in parts by weight of 6 to 28. The chelation is carried out under heating conditions, with a heating temperature of 35~70℃.

3. The chelated saline-alkali soil conditioner according to claim 1, characterized in that, The raw materials for the chelated saline-alkali soil conditioner also include organic fertilizer, salt-tolerant functional bacteria, magnesium fertilizer, acid-base buffer regulator, and synergist. The organic fertilizer is selected from one or more types of corrosive acid fertilizers. The salt-tolerant functional bacteria are selected from one or more of the following: salt-tolerant Bacillus licheniformis, Bacillus mucilaginosus, and phosphate-solubilizing Bacillus megaterium. The magnesium fertilizer is selected from one or more of magnesium sulfate, magnesium chloride, and magnesium nitrate. The synergist is selected from one or more of polyaspartic acid, fulvic acid, polyacrylamide, γ-polyglutamic acid, and rhamnolipid. The organic fertilizer is in the form of 6-30 parts by weight. The weight fraction of salt-tolerant functional bacteria is 6-25 parts. The magnesium fertilizer is 1-12 parts by weight. The acid-base buffer is present in parts by weight of 3 to 14 parts. The synergist is present in parts by weight of 1 to 9 parts.

4. The chelated saline-alkali soil conditioner according to claim 1, characterized in that, The raw materials of the chelated saline-alkali soil conditioner also include a carrier, selected from one or more mineral powders, preferably natural bentonite and / or attapulgite.

5. A method for preparing a chelated saline-alkali soil conditioner according to any one of claims 1 to 4, characterized in that, The method first chelates polyferric sulfate and EDDHA chelated iron under heating conditions, then adds organic fertilizer, magnesium fertilizer, acid-base buffer regulator and synergist, and finally inoculates salt-tolerant functional bacteria.

6. The preparation method according to claim 5, characterized in that, The method specifically includes the following steps: Step 1: The pretreated polyferric sulfate and EDDHA chelated iron are chelated under heating conditions; Step 2: While maintaining the stirring and constant temperature conditions of Step 1, add organic fertilizer, magnesium fertilizer, acid-base buffer regulator and synergist to obtain the mixture; Step 3: Inoculate the mixture with salt-tolerant functional bacteria, granulate, and dry to obtain the chelated saline-alkali soil conditioner.

7. The preparation method according to claim 6, characterized in that, In step 1, the pretreatment involves grinding polyferric sulfate and drying it until the moisture content is ≤5wt%. After grinding, the particle size of the polyferric sulfate is 60~120 mesh. The polyferric sulfate is present in parts by weight of 15 to 50 parts. The EDDHA chelated iron is present in parts by weight of 6 to 28.

8. The preparation method according to claim 6, characterized in that, In step 2, The organic fertilizer is in the form of 6-30 parts by weight. The magnesium fertilizer is 1-12 parts by weight. The acid-base buffer is present in parts by weight of 3 to 14 parts. The synergist is present in parts by weight of 1 to 9 parts.

9. The preparation method according to claim 6, characterized in that, In step 3, the salt-tolerant functional bacteria are introduced by spraying the salt-tolerant functional bacteria into the mixture when the mixture is naturally cooled to no higher than 30°C, and stirring for 10 to 30 minutes. The weight of the salt-tolerant functional bacteria is 6 to 25 parts.

10. The use of a chelated saline-alkali soil conditioner according to any one of claims 1 to 4, characterized in that, It is used for in-situ improvement and remediation of moderately to severely saline-alkali soils, secondary salinized soils, soils that have been continuously cropped, compacted and degraded farmland, and soils with mild heavy metal pollution.

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