A method for improving saline-alkali soil

Abstract

The application discloses a saline-alkali soil improvement method and belongs to the field of agricultural technology. Total salt content and alkalinity in the saline-alkali soil are detected by sampling, then in March-April, a phosphoric acid solution is uniformly sprayed on the saline-alkali soil by spraying, then a PAM solution is uniformly sprayed, then ploughing is carried out, then the phosphoric acid solution is uniformly sprayed on the saline-alkali soil by spraying, the saline-alkali soil sprayed with the phosphoric acid solution is placed for 2-4 days, then the PAM solution is uniformly sprayed again, and the saline-alkali soil is placed for 1-2 days; then while ploughing, straw roots are scattered on the ploughed soil, then in July-September of the third year, a glyphosate solution is sprayed, an ammonium dihydrogen phosphate solution is sprayed, and coal ash is uniformly scattered, then ploughing is carried out, and sunflowers are planted in the second year, after 2-3 years of planting, other crops are planted. The application provides a saline-alkali soil improvement method, the method is simple, and the saline-alkali soil can be improved and crops can be planted, and the improvement effect is good.

Description

Technical Field

[0001] This invention belongs to the field of agricultural technology, specifically relating to a method for improving saline-alkali land. Background Technology

[0002] In the utilization process, saline-alkali land can be simply divided into lightly saline-alkali land, moderately saline-alkali land, and severely saline-alkali land. Lightly saline-alkali land refers to land with a germination rate of 70%-80% and a salt content of less than 0.3%. Severely saline-alkali land refers to land with a salt content of more than 0.6% and a germination rate of less than 50%. The middle area is moderately saline-alkali land (expressed by pH value: lightly saline-alkali land pH value: 7.1-8.5, moderately saline-alkali land pH value: 8.5-9.5, severely saline-alkali land pH value: above 9.5).

[0003] The root cause of saline-alkali soil formation lies in poor water conditions. Therefore, in the initial stages of improvement, the focus should be on improving soil moisture. This process generally involves several steps: first, draining and leaching salts to reduce soil salinity; then, planting salt-tolerant plants to enrich the soil; and finally, planting crops. Specific improvement measures include: drainage, irrigation to leach salts, silt removal for improvement, rice cultivation, soil enrichment, land leveling, and chemical treatment.

[0004] Saline-alkali soil is a general term for both saline and alkaline soils. Saline soil mainly refers to saline soils with high chloride or sulfate content, exhibiting alkalinity, although the pH value may not be very high. Alkaline soil refers to soils containing carbonates or diphosphates, with a higher pH value, exhibiting alkalinity. Saline-alkali soils have low organic matter content, low soil fertility, poor physicochemical properties, and contain more harmful anions and cations, making it difficult for crops to sprout. The fertilization principle for saline-alkali soils is to primarily apply organic fertilizers and high-efficiency compound fertilizers, while controlling the use of low-concentration chemical fertilizers. Organic fertilizers contain a large amount of organic matter, which acts as a buffer against harmful anions and cations in the soil, promoting root development and seedling growth. High-concentration compound fertilizers have fewer ineffective components and less residue, but the amount of chemical fertilizer applied each time should not be excessive to avoid aggravating secondary soil salinization. Irrigation should be combined with fertilizer application to reduce the soil solution concentration. Summary of the Invention

[0005] In view of the above-mentioned defects and deficiencies of the existing technology, the present invention provides a method for improving saline-alkali land. The method is simple and can realize the improvement of saline-alkali land and the planting of crops, with good improvement effect.

[0006] The present invention solves the above-mentioned technical problems through the following technical means:

[0007] The present invention provides a method for improving saline-alkali land, which includes the following steps:

[0008] (1) Sample and test the total salt and alkalinity in the saline-alkali soil. Then, in March-April, dissolve phosphoric acid in water to obtain a phosphoric acid solution, and then spray it evenly on the saline-alkali soil using a spraying method.

[0009] (2) Place the saline-alkali soil sprayed with phosphoric acid solution for 2-4 days, then spray PAM solution evenly and let it stand for 1-2 days;

[0010] (3) Then plow the soil to a depth of 6-10cm. Then spray the phosphoric acid solution evenly onto the saline-alkali land. Place the saline-alkali land that has been sprayed with phosphoric acid solution again for 2-4 days. Then spray the PAM solution evenly again and let it stand for 1-2 days.

[0011] (4) Cut fresh cogon grass roots into 5-10cm lengths, and then spread the cogon grass roots on the tilled land while plowing. Then, in July-September of the third year, spray glyphosate solution, and then spray ammonium dihydrogen phosphate solution 12-25 days later. Then spread coal ash evenly, and then plow to a depth of 6-10cm. Then plant sunflowers in the second year. After 2-3 years, plant other crops.

[0012] Sampling points were evenly distributed at 10-20 points per acre. Each sampling point used a cylindrical sampling tube with an inner diameter of 5cm and a depth of 10cm, vertically inserted into the soil. Soil samples from each acre were then mixed together, and hot pure water was added at a mass ratio of 1:5-8 at 80-95℃. The mixture was stirred and dispersed for 1-2 hours at a stirring speed of 100-200 r / min. The mixture was then filtered, and the filter residue was washed with hot pure water at 80-95℃ until the conductivity of the wash water was ≤50μS / cm. The mother liquor and wash water were then mixed thoroughly. The total salt content and alkalinity of the resulting solution were measured. The total salt content in the soil was then determined as follows:

[0013] S = m1S1 / m2;

[0014] Where: S is the total salt content of the soil, in g; m1 is the total mass of the mother liquor and washing water, in Kg; S1 is the total salt content in the solution, in g; m2 is the total mass of the soil sample, in kg;

[0015] The total salt content per acre is: 6.6667 * 10 4 ρs;

[0016] Where ρ is the soil density of saline-alkali land at a depth of 10cm, in kg / L;

[0017] The alkalinity of the soil is:

[0018] After mixing the above samples evenly, take 10g of the sample, add 100mL of deionized water, stir for 30min, filter, and measure the pH value Y of the supernatant with a pH meter to obtain the pH value.

[0019] Therefore, the number of moles of alkaline substances per acre is 6.6667 * 10. (Y-9) ρ

[0020] Where ρ is the soil density of saline-alkali land at a depth of 10cm, in kg / L;

[0021] In step (1), the number of moles of phosphoric acid in the phosphoric acid solution added per acre of saline-alkali land is 5-15 times the mass of soil alkalinity per acre of saline-alkali land.

[0022] In step (2), the mass of PAM in the PAM solution added per mu of saline-alkali land is 0.005-0.01 times the mass of total soil salt in per mu of saline-alkali land;

[0023] The amount of phosphoric acid added per mu in step (3) is 0.1-0.2 times the amount of phosphoric acid added per mu in step (1).

[0024] The concentration of the phosphoric acid solution in steps (1) and (3) is 0.005-0.01 mol / L.

[0025] The mass concentration of the PAM solution in steps (2) and (3) is 0.01%-0.1%.

[0026] In step (4), the amount of fresh cogon grass roots scattered per mu is 20-50 kg, the amount of glyphosate solution sprayed per mu is 20-50 kg, the mass concentration of glyphosate solution is 0.1-0.2%, the amount of 0.5-1 mol / L ammonium dihydrogen phosphate solution sprayed per mu is 50-100 kg, and the amount of coal ash scattered per mu is 10-50 kg.

[0027] In step (4), the spacing between sunflower plants is 20-30cm.

[0028] This invention uses phosphoric acid to neutralize alkaline substances in saline-alkali land, and PAM to flocculate and adsorb salts, thereby effectively improving and reducing alkalinity and salinity in saline-alkali land. In addition, the added phosphate ions will introduce phosphorus, thereby enhancing fertilizer efficiency.

[0029] This invention also achieves deep dealkalization and desalination by tilling followed by a secondary spraying of phosphoric acid and PAM, thereby further improving the soil. It also introduces cogongrass, generally referring to Imperata cylindrica, a perennial herbaceous plant belonging to the Poaceae family and the Imperata genus. The culms are erect, reaching up to 80 cm in height, with hairless nodes. Leaf sheaths are clustered at the base of the culm; the ligule is membranous; the culm leaves are narrowly linear, usually inrolled, with an acuminate, spiny apex, gradually narrowing towards the base, and are hard in texture, with soft hairs on the upper base. The panicles are dense; the first lemma is ovate-lanceolate, and the second lemma is nearly equal to its palea, ovate, with dentate lobes and cilia at the apex; the style is slender and purplish-black; the caryopsis is elliptical; the flowering and fruiting period is from April to June.

[0030] Imperata cylindrica has a strong regenerative ability; even after its roots have dried, they can still survive when buried in the soil. It is extremely difficult to remove and is a stubborn weed. Its rhizomes can be used medicinally.

[0031] Thatch grass has a strong reproductive capacity and is tolerant of saline-alkali soil and poor soil conditions. Its root system expands rapidly. Planting it can effectively improve the aeration of saline-alkali land and enhance its fertility. Furthermore, planting sunflowers, which are cash crops, can generate economic benefits and further improve saline-alkali land.

[0032] Meanwhile, this invention balances nitrogen, phosphorus, and potassium, cleverly using urea phosphate as an important component, which can improve fertilizer efficiency, and combines the characteristics of phosphate fertilizer and urea.

[0033] This invention provides a method for improving saline-alkali land. The method is simple and can achieve both the improvement of saline-alkali land and the planting of crops, with good improvement results. Detailed Implementation

[0034] The present invention will be described in detail below with reference to specific embodiments: A method for improving saline-alkali land according to this embodiment includes the following steps:

[0035] (1) Sample and test the total salt and alkalinity in the saline-alkali soil. Then, in March-April, dissolve phosphoric acid in water to obtain a phosphoric acid solution, and then spray it evenly on the saline-alkali soil using a spraying method.

[0036] (2) Place the saline-alkali soil sprayed with phosphoric acid solution for 2-4 days, then spray PAM solution evenly and let it stand for 1-2 days;

[0037] (3) Then plow the soil to a depth of 6-10cm. Then spray the phosphoric acid solution evenly onto the saline-alkali land. Place the saline-alkali land that has been sprayed with phosphoric acid solution again for 2-4 days. Then spray the PAM solution evenly again and let it stand for 1-2 days.

[0038] (4) Cut fresh cogon grass roots into 5-10cm lengths, and then spread the cogon grass roots on the tilled land while plowing. Then, in July-September of the third year, spray glyphosate solution, and then spray ammonium dihydrogen phosphate solution 12-25 days later. Then spread coal ash evenly, and then plow to a depth of 6-10cm. Then plant sunflowers in the second year. After 2-3 years, plant other crops.

[0039] Sampling points were evenly distributed at 10-20 points per acre. Each sampling point used a cylindrical sampling tube with an inner diameter of 5cm and a depth of 10cm, vertically inserted into the soil. Soil samples from each acre were then mixed together, and hot pure water was added at a mass ratio of 1:5-8 at 80-95℃. The mixture was stirred and dispersed for 1-2 hours at a stirring speed of 100-200 r / min. The mixture was then filtered, and the filter residue was washed with hot pure water at 80-95℃ until the conductivity of the wash water was ≤50μS / cm. The mother liquor and wash water were then mixed thoroughly. The total salt content and alkalinity of the resulting solution were measured. The total salt content in the soil was then determined as follows:

[0040] S = m1S1 / m2;

[0041] Where: S is the total salt content of the soil, in g; m1 is the total mass of the mother liquor and washing water, in Kg; S1 is the total salt content in the solution, in g; m2 is the total mass of the soil sample, in kg;

[0042] The total salt content per acre is: 6.6667 * 10 4 ρs;

[0043] Where ρ is the soil density of saline-alkali land at a depth of 10cm, in kg / L;

[0044] The alkalinity of the soil is:

[0045] After mixing the above samples evenly, take 10g of the sample, add 100mL of deionized water, stir for 30min, filter, and measure the pH value Y of the supernatant with a pH meter to obtain the pH value.

[0046] Therefore, the number of moles of alkaline substances per acre is 6.6667 * 10. (Y-9) ρ

[0047] Where ρ is the soil density of saline-alkali land at a depth of 10cm, in kg / L;

[0048] In step (1), the number of moles of phosphoric acid in the phosphoric acid solution added per acre of saline-alkali land is 5-15 times the mass of soil alkalinity per acre of saline-alkali land.

[0049] In step (2), the mass of PAM in the PAM solution added per mu of saline-alkali land is 0.005-0.01 times the mass of total soil salt in per mu of saline-alkali land;

[0050] The amount of phosphoric acid added per mu in step (3) is 0.1-0.2 times the amount of phosphoric acid added per mu in step (1).

[0051] The concentration of the phosphoric acid solution in steps (1) and (3) is 0.005-0.01 mol / L.

[0052] The mass concentration of the PAM solution in steps (2) and (3) is 0.01%-0.1%.

[0053] In step (4), the amount of fresh cogon grass roots scattered per mu is 20-50 kg, the amount of glyphosate solution sprayed per mu is 20-50 kg, the mass concentration of glyphosate solution is 0.1-0.2%, the amount of 0.5-1 mol / L ammonium dihydrogen phosphate solution sprayed per mu is 50-100 kg, and the amount of coal ash scattered per mu is 10-50 kg.

[0054] In step (4), the spacing between sunflower plants is 20-30cm.

[0055] Example 1

[0056] A method for improving saline-alkali land, comprising the following steps:

[0057] (1) Sampling and testing of total salt and alkalinity in saline-alkali soil.

[0058] Twenty sampling points were evenly distributed per acre. Each sampling point used a cylindrical sampling tube with an inner diameter of 5 cm and a depth of 10 cm, which was vertically inserted into the soil. Soil samples from each acre were then mixed together and hot pure water was added at a mass ratio of 1:8 at 95℃. The mixture was stirred and dispersed for 1 hour at a stirring speed of 200 r / min. The mixture was then filtered, and the filter residue was washed with 95℃ hot pure water until the conductivity of the wash water reached 48 μS / cm. The mother liquor and wash water were then mixed thoroughly. The total salt content and alkalinity of the resulting solution were measured. The total salt content of the soil was then determined as follows:

[0059] S=m1S1 / m2

[0060] The soil mass is 7.815 kg.

[0061] The total mass of mother liquor and washing water was 256.34 kg.

[0062] The total salt content of the mixed solution is 0.174g.

[0063] The final calculation shows that the total salt content of the soil is 5.7g, which is classified as moderately saline-alkali land.

[0064] The alkalinity of the mixed solution is:

[0065] Where: S is the total salt content of the soil, in g; m1 is the total mass of the mother liquor and washing water, in Kg; S1 is the total salt content in the solution, in g; m2 is the total mass of the soil sample, in kg;

[0066] The alkalinity of the soil is:

[0067] After mixing the above samples thoroughly, take 10g of the sample, add 100mL of deionized water, stir for 30min, filter, and measure the pH of the supernatant using a pH meter to find that it is 9.1.

[0068] The total salt content per acre is: 6.6667 * 10 4 ρs = 756.2 kg;

[0069] Where ρ is the soil density of saline-alkali land at a depth of 10cm, in kg / L. The soil density in Example 1 is 1.99 kg / L.

[0070] The alkalinity of the soil is:

[0071] After mixing the above samples evenly, take 10g of the sample, add 100mL of deionized water, stir for 30min, filter, and measure the pH value Y of the supernatant with a pH meter to obtain the pH value.

[0072] Therefore, the number of moles of alkaline substances per acre is 6.6667 * 10. (Y-9) ρ = 16.7 mol;

[0073] Where ρ is the soil density of saline-alkali land at a depth of 10cm, in kg / L;

[0074] In step (1), the number of moles of phosphoric acid in the phosphoric acid solution added per acre of saline-alkali land is 12 times the mass of soil alkalinity per acre of saline-alkali land.

[0075] In step (2), the mass of PAM in the PAM solution added per mu of saline-alkali land is 0.01 times the mass of the total salt content of the soil per mu of saline-alkali land;

[0076] The amount of phosphoric acid added per mu in step (3) is 0.2 times the amount of phosphoric acid added per mu in step (1).

[0077] Then in March, phosphoric acid was dissolved in water to obtain a phosphoric acid solution, which was then sprayed evenly onto the saline-alkali land using a spraying method.

[0078] (2) Place the saline-alkali soil sprayed with phosphoric acid solution for 4 days, then spray PAM solution evenly and let it stand for 2 days;

[0079] (3) Then plow the soil to a depth of 8cm, and then spray the phosphoric acid solution evenly onto the saline-alkali land. Place the saline-alkali land that has been sprayed with phosphoric acid solution again for 4 days, and then spray PAM solution evenly again and let it stand for 2 days.

[0080] (4) Cut fresh cogon grass roots into 5-10cm lengths, and then spread the cogon grass roots on the tilled land while plowing. Then, in September of the third year, spray glyphosate solution, and then spray ammonium dihydrogen phosphate solution 20 days later. Then, spread coal ash evenly, and then plow to a depth of 8cm. Then, plant sunflowers in the second year. After 3 years, plant other crops.

[0081] The concentration of the phosphoric acid solution in steps (1) and (3) is 0.01 mol / L.

[0082] The mass concentration of the PAM solution in steps (2) and (3) is 0.1%.

[0083] In step (4), the following steps are taken: 30 kg of fresh cogon grass roots are scattered per mu, 40 kg of glyphosate solution is sprayed per mu, the glyphosate solution concentration is 0.15%, 95 kg of 0.8 mol / L ammonium dihydrogen phosphate solution is sprayed per mu, and 50 kg of coal ash is scattered per mu.

[0084] In step (4), the spacing between sunflower plants is 25cm.

[0085] The improved land of this invention, i.e. land that has been planted with sunflowers for 3 years, is then planted with soybeans, and the yield is 190 kg per mu, which is basically close to the level of normal land.

[0086] Example 2

[0087] A method for improving saline-alkali land, comprising the following steps:

[0088] (1) Sample and test the total salt and alkalinity in the saline-alkali soil. Then in April, dissolve phosphoric acid in water to obtain a phosphoric acid solution, and then spray it evenly on the saline-alkali soil using a spray method.

[0089] (2) Place the saline-alkali soil sprayed with phosphoric acid solution for 2 days, then spray PAM solution evenly and let it stand for 1 day;

[0090] (3) Then plow the soil to a depth of 10cm, and then spray the phosphoric acid solution evenly onto the saline-alkali land. Place the saline-alkali land that has been sprayed with phosphoric acid solution again for 2 days, and then spray PAM solution evenly again and let it stand for 1 day.

[0091] (4) Cut fresh cogon grass roots into 5-10cm lengths, and then spread the cogon grass roots on the tilled land while plowing. Then, in July of the third year, spray glyphosate solution, and then spray ammonium dihydrogen phosphate solution 12 days later. Then, spread coal ash evenly, and then plow to a depth of 10cm. Then, plant sunflowers in the second year. After 3 years, plant other crops.

[0092] Ten sampling points were evenly distributed per acre. Each sampling point used a cylindrical sampling tube with an inner diameter of 5 cm and a depth of 10 cm, which was vertically inserted into the soil. Soil samples from each acre were then mixed together and hot pure water was added at a mass ratio of 1:5 at 80℃. The mixture was stirred and dispersed for 1 hour at a stirring speed of 100 r / min. The mixture was then filtered, and the filter residue was washed with 80℃ hot pure water until the conductivity of the wash water was ≤50 μS / cm. The mother liquor and wash water were then mixed thoroughly. The total salt content and alkalinity of the resulting solution were measured. The total salt content in the soil was then determined as follows:

[0093] S = m1S1 / m2;

[0094] Where: S is the total salt content of the soil, in g; m1 is the total mass of the mother liquor and washing water, in Kg; S1 is the total salt content in the solution, in g; m2 is the total mass of the soil sample, in kg;

[0095] The total salt content per acre is: 6.6667 * 10 4 ρs;

[0096] Where ρ is the soil density of saline-alkali land at a depth of 10cm, in kg / L;

[0097] The alkalinity of the soil is:

[0098] After mixing the above samples evenly, take 10g of the sample, add 100mL of deionized water, stir for 30min, filter, and measure the pH value Y of the supernatant with a pH meter to obtain the pH value.

[0099] Therefore, the number of moles of alkaline substances per acre is 6.6667 * 10. (Y-9) ρ

[0100] Where ρ is the soil density of saline-alkali land at a depth of 10cm, in kg / L;

[0101] In step (1), the number of moles of phosphoric acid in the phosphoric acid solution added per acre of saline-alkali land is 15 times the mass of soil alkalinity per acre of saline-alkali land.

[0102] In step (2), the mass of PAM in the PAM solution added per mu of saline-alkali land is 0.008 times the mass of the total salt content of the soil per mu of saline-alkali land;

[0103] The amount of phosphoric acid added per mu in step (3) is 0.15 times the amount of phosphoric acid added per mu in step (1), and the amount of phosphoric acid added per mu in step (3) is 0.1 times the amount of phosphoric acid added per mu in step (1).

[0104] The concentration of the phosphoric acid solution in steps (1) and (3) is 0.005 mol / L.

[0105] The mass concentration of the PAM solution in steps (2) and (3) is 0.03%.

[0106] In step (4), the following steps are taken: 50 kg of fresh cogon grass roots are scattered per mu, 50 kg of glyphosate solution is sprayed per mu, the glyphosate solution has a concentration of 0.2%, 100 kg of 1 mol / L ammonium dihydrogen phosphate solution is sprayed per mu, and 50 kg of coal ash is scattered per mu.

[0107] In step (4), the spacing between sunflower plants is 20cm.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for improving saline-alkali land, characterized in that, The following steps are required: (1) Sample and test the total salt and alkalinity in the saline-alkali soil. Then, in March-April, dissolve phosphoric acid in water to obtain a phosphoric acid solution, and then spray it evenly on the saline-alkali soil using a spraying method. (2) Place the saline-alkali soil sprayed with phosphoric acid solution for 2-4 days, then spray PAM solution evenly and let it stand for 1-2 days; (3) Then plow the soil to a depth of 6-10cm. Then spray the phosphoric acid solution evenly onto the saline-alkali land. Place the saline-alkali land that has been sprayed with phosphoric acid solution again for 2-4 days. Then spray the PAM solution evenly again and let it stand for 1-2 days. (4) Cut fresh cogon grass roots into 5-10cm lengths, and then spread the cogon grass roots on the tilled land while turning the soil. Then, in July-September of the third year, spray glyphosate solution, and then spray ammonium dihydrogen phosphate solution 12-25 days later. Then spread coal ash evenly, and then turn the soil to a depth of 6-10cm. Then plant sunflowers in the second year. After 2-3 years, plant other crops. Sampling points were evenly distributed at 10-20 points per acre. Each sampling point used a cylindrical sampling tube with an inner diameter of 5cm and a depth of 10cm, vertically inserted into the soil. Soil samples from each acre were then mixed together, and hot pure water was added at a mass ratio of 1:5-8 at 80-95℃. The mixture was stirred and dispersed for 1-2 hours at a stirring speed of 100-200 r / min. The mixture was then filtered, and the filter residue was washed with hot pure water at 80-95℃ until the conductivity of the wash water was ≤50μS / cm. The mother liquor and wash water were then mixed thoroughly. The total salt content and alkalinity of the resulting solution were measured. The total salt content in the soil was then determined as follows: S = m1S1 / m2; Where: S is the total salt content of the soil, in g; m1 is the total mass of the mother liquor and washing water, in Kg; S1 is the total salt content in the solution, in g; m2 is the total mass of the soil sample, in kg; The total salt content per acre is: 6.6667 * 10 4 ρs; Where ρ is the soil density of saline-alkali land at a depth of 10cm, in kg / L; The alkalinity of the soil is: After mixing the above samples evenly, take 10g of the sample, add 100mL of deionized water, stir for 30min, filter, and measure the pH value Y of the supernatant with a pH meter to obtain the pH value. Therefore, the number of moles of alkaline substances per acre is 6.6667 * 10. (Y-9) ρ; Where ρ is the soil density of saline-alkali land at a depth of 10cm, in kg / L; In step (1), the number of moles of phosphoric acid in the phosphoric acid solution added per acre of saline-alkali land is 5-15 times the mass of soil alkalinity per acre of saline-alkali land. In step (2), the mass of PAM in the PAM solution added per mu of saline-alkali land is 0.005-0.01 times the mass of total soil salt in per mu of saline-alkali land; The amount of phosphoric acid added per mu in step (3) is 0.1-0.2 times the amount of phosphoric acid added per mu in step (1).

2. The method for improving saline-alkali land according to claim 1, characterized in that: The concentration of the phosphoric acid solution in steps (1) and (3) is 0.005-0.01 mol / L.

3. The method for improving saline-alkali land according to claim 1, characterized in that: The mass concentration of the PAM solution in steps (2) and (3) is 0.01%-0.1%.

4. The method for improving saline-alkali land according to claim 1, characterized in that: In step (4), the amount of fresh cogon grass roots scattered per mu is 20-50 kg, the amount of glyphosate solution sprayed per mu is 20-50 kg, the mass concentration of glyphosate solution is 0.1-0.2%, the amount of 0.5-1 mol / L ammonium dihydrogen phosphate solution sprayed per mu is 50-100 kg, and the amount of coal ash scattered per mu is 10-50 kg.

5. The method for improving saline-alkali land according to claim 1, characterized in that: In step (4), the spacing between sunflower plants is 20-30cm.