Method for synergistically improving saline-alkali soil through organic and inorganic interlayers

Abstract

The invention discloses a method for synergistically improving saline-alkali soil through organic and inorganic interlayers. The method comprises the following steps: dissociating calcium bentonite capable of replacing sodium ions in the saline alkali soil by adopting sodium silicate and carrying out cross-linking reaction with sodium aluminate to obtain silica-alumina gel modified bentonite; organic fertilizer, silica-alumina gel modified bentonite and attapulgite are laid on the land to be improved in a layered mode, and an organic-inorganic interlayer is constructed; covering the earth surface with straws in successive years. Long-acting seepage reduction and salt resistance can be realized by reducing evaporation and increasing deep infiltration of irrigation water, and salt can be effectively inhibited from returning upwards in the middle and later growth periods of crops, so that water supply is provided; the soil pore structure is improved, the soil organic carbon stability is improved, the problems that salt is repeated and water and fertilizer in a root layer are difficult to supply in traditional coverage or a single interlayer are solved, and the multi-effect synergistic approach of salt inhibition, water retention and fertilization is achieved through organic and inorganic composite materials.

Description

Technical Field

[0001] The invention relates to a method for improving saline-alkali land, in particular to a method for improving saline-alkali land through the synergistic effect of organic and inorganic barriers. Background Art

[0002] Traditional methods of improving saline-alkali land mostly use single covering or interlayer salt-blocking technology, which has problems such as repeated return of salt, insufficient water and fertilizer supply in the root layer, and slow improvement of soil structure. In the existing technology, the use of organic materials (such as straw and manure) alone is easy to decompose and become ineffective, and although single inorganic materials (such as bentonite and attapulgite) can block salt, they lack fertilization function, making it difficult to achieve the synergistic goal of long-term salt control and soil quality improvement. In addition, traditional methods have limited effects on improving soil pore structure and organic carbon stability, resulting in long improvement cycles and high costs.

[0003] Based on existing research, saline-alkali land improvement technology mainly has the following problems:

[0004] Single function: Salt blocking, fertilization, conditioning and other links are separated and lack synergistic mechanism. For example, inorganic materials block salt but inhibit soil biological activity, and organic materials fertilize but accelerate salt leaching.

[0005] Lack of long-term effectiveness: Most technologies rely on short-term material investment (such as ground film, PAM) and lack periodic update design, resulting in a decline in effectiveness after 3 to 5 years.

[0006] Inefficient structural improvement: Traditional methods have limited effects on improving soil macropores (>50μm) and aggregate stability, and it is difficult to improve water conductivity and fertilizer retention capacity synergistically.

[0007] Poor economic efficiency: high-cost technologies (such as chemical mulching agents) require an average investment of more than 1,000 yuan per mu, while low-cost technologies (such as straw mulching) require frequent maintenance and have low overall benefits. Summary of the invention

[0008] In view of this, the present invention proposes a method for improving saline-alkali land through the synergistic mechanism of organic and inorganic interlayers, through the ternary synergistic mechanism of modified bentonite salt blocking, organic fertilizer fertilization and attapulgite tempering, combined with straw mulching to inhibit evaporation, to achieve directional salt control and rapid fertilization of saline-alkali land.

[0009] The method for improving saline-alkali land provided by the present invention comprises the following steps:

[0010] The calcium-based bentonite which can replace the sodium ions in the saline-alkali soil is dissociated by sodium silicate and cross-linked with sodium aluminate to obtain silica-alumina modified bentonite;

[0011] Spreading organic fertilizer, silica-alumina modified bentonite and attapulgite in layers on the land to be improved to construct an organic-inorganic interlayer;

[0012] Implement straw mulching on the ground surface year after year.

[0013] Optionally, the dissociation of calcium-based bentonite with sodium silicate and the cross-linking reaction with sodium aluminate are to immerse the calcium-based bentonite in an aqueous sodium silicate solution, add an aqueous sodium aluminate solution after dissociation, and adjust the pH value to 7.0 - 7.5, then let it stand to form silica-alumina gel modified bentonite.

[0014] Optionally, the silica-alumina gel modified bentonite forms a Si-O-Al network structure.

[0015] Optionally, the mass percentage concentration of the aqueous sodium silicate solution is 5% - 8%; the mass percentage concentration of the aqueous sodium aluminate solution is 2% - 5%; the molar ratio of sodium aluminate to sodium silicate is 1:(1.2 - 1.5).

[0016] Optionally, immerse the calcium-based bentonite in the sodium silicate solution and stir for 30 minutes - 60 minutes; the standing time is 18 hours - 24 hours.

[0017] Optionally, before constructing the organic-inorganic interlayer, it also includes the steps of plowing, harrowing, and rolling the land to be improved to form a finely leveled land with a surface elevation difference ≤ 5 cm.

[0018] Optionally, the dosage of the organic fertilizer is 200 - 300 kg / mu; the dosage of the silica-alumina gel modified bentonite is 100 - 200 kg / mu; the dosage of attapulgite is 100 - 200 kg / mu.

[0019] Optionally, after the layered application, it also includes the step of using a subsoiler to turn and press into the soil layer of 35 cm - 50 cm in 2 - 4 times; the interval between each turning and pressing is 3 - 5 days.

[0020] Optionally, for the year-after-year implementation of straw mulching on the ground surface, when plowing in autumn or preparing the land before sowing, crush the corn straw to a length of 5 - 10 cm, evenly spread it on the ground surface, with a coverage rate ≥ 90%, and an annual coverage amount of 0.8 - 2.5 tons / mu, and implement it year after year.

[0021] Optionally, after the year-after-year implementation of straw mulching on the ground surface, it also includes the step of washing salts with irrigation water, and the irrigation water volume is 1500 m³ / hm² 2 -1800 m³ / hm² 2 .

[0022] Beneficial effects:

[0023] The method for synergistically improving saline-alkali land by organic and inorganic interlayers provided by the present invention has the following beneficial effects:

[0024] (1) Salt control and efficiency increase: The salt return inhibition rate of the composite interlayer of the present invention reaches 76% - 85%, and the surface salt content is reduced by more than 10% on average.

[0025] (2) Rapid soil fertility improvement: The soil organic matter increases by more than 10% within 3 years.

[0026] (3) Structure improvement: Significantly increases the proportion of large soil pores (>50μm) and greatly improves the aggregate stability index.

[0027] (4) Synergistic and sustainable: The organic components provide carbon sources and nutrients, the inorganic components ensure pore stability, and straw mulching reduces evaporation by 20% - 30%, realizing the synergistic effect of salt inhibition - soil fertility improvement - texture modification.

[0028] The term "aggregate stability index" refers to a quantitative index of the resistance of soil aggregates to external force damage, reflecting the resistance of soil structure to external pressures such as water erosion and mechanical disturbance.

[0029] The term "sodium aluminosilicate modified bentonite" refers to a functional material with a sodium aluminosilicate-coated or intercalated structure obtained by subjecting bentonite to a composite modification treatment with sodium silicate (Na 2 SiO 3 ) and sodium aluminate (NaAlO 2 ) solutions. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] For purposes of illustration and not limitation, the present invention will now be described in accordance with preferred embodiments of the present invention, particularly with reference to the accompanying drawings, in which:

[0031] Figure 1 is a schematic diagram of the collaborative improvement of saline-alkali soil by organic and inorganic interlayers according to the present invention.

[0032] Figure 2 is the result of the influence of different treatments on the soil organic carbon content.

[0033] Figure 3 is the result of the influence of different treatments on the change of soil salt content.

[0034] Figure 4 is the result of the influence of different treatments on the change of soil moisture content.

[0035] Figure 5 is the result of the influence of different treatments on the change of soil total nitrogen content.

[0036] Figure 6 is the result of the influence of different treatments on crop yield.

[0037] Figure 7 is the result of the change of soil pore structure under different treatments. DETAILED DESCRIPTION OF THE INVENTION

[0038] The technical solution of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to illustrate and explain the present invention by way of example, and should not be construed as limiting the protection scope of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0039] Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods.

[0040] The test sites for the following examples and comparative examples of the present invention are located in Behaizi Village, Dalate Banner, Ordos City, Inner Mongolia (109.87°N, 40.48°E), with an average annual precipitation of 240 - 360 mm and an average annual temperature of 6.1 - 7.1 °C, belonging to a semi-arid monsoon climate.

[0041] The field test factors include 4 fertilization methods: (1) organic-inorganic composite interlayer combined with straw mulch (embodiment of the present invention), (2) organic interlayer (comparative example 1), (3) inorganic interlayer (comparative example 2), (4) no interlayer (control group). The organic material is cow dung, and the inorganic materials are bentonite and attapulgite. Each fertilization method is applied with conventional nitrogen, phosphorus, and potassium fertilizers (urea 450 kg / hm 2 , diammonium phosphate 375 kg / hm 2 , potassium sulfate 180 kg / hm 2 ) during sunflower sowing. For the above scheme, there are 4 treatments, each treatment is repeated 3 times, and there are a total of 12 plots. Other field management is the same as that of local farmers.

[0042] Experimental materials:

[0043] Cow dung: organic carbon content 16%, total nitrogen 1.6%, total phosphorus 0.57%, total potassium 6.2%, water content 32%.

[0044] Calcium-based bentonite: montmorillonite content ≥ 85%;

[0045] Attapulgite: Mohs hardness 2 - 3, when heated to 700 - 800 °C, hardness > 5. Specific gravity is 2.05 - 2.32.

[0046] Sodium silicate: Sinopharm chemical reagent, solid purity ≥ 95%. Slowly add 6 g of solid sodium silicate to 94 mL of deionized water, stir until completely dissolved (heating to 40 - 50 °C is required to accelerate dissolution), and prepare a 6% sodium silicate aqueous solution by mass percentage concentration. After cooling to room temperature, make up the volume to 100 mL and shake well for standby.

[0047] Sodium aluminate: from Guoyao Chemical Reagent, solid purity ≥ 95%. Slowly add 4 g of solid sodium aluminate to 96 mL of deionized water, stir until completely dissolved (heating to 40–50 °C is required to accelerate dissolution), and prepare an aqueous sodium aluminate solution with a mass percentage concentration of 4%. After cooling to room temperature, make up the volume to 100 mL and shake well for standby.

[0048] Example 1. Method for synergistically improving saline-alkali land through organic and inorganic interlayers

[0049] The method for synergistically improving saline-alkali land in this example includes the following steps:

[0050] (1) Bentonite modification: Take 100 kg of calcium-based bentonite (montmorillonite content ≥ 85%) and add it to an aqueous sodium silicate solution with a mass percentage concentration of 6%, stir for 30 minutes, add an aqueous sodium aluminate solution with a mass percentage concentration of 4% after standing and dissociation, adjust the pH to 7, and let it stand for 24 hours to form silica-alumina gel-modified bentonite. The silica-alumina gel-modified calcium-based bentonite forms a Si-O-Al network structure.

[0051] (2) Land leveling: Plow, harrow, and roll the land to be improved to form a fine-levelled land with a surface elevation difference ≤ 5 cm.

[0052] (3) Construction of organic-inorganic interlayers:

[0053] Layering and spreading: On the fine-levelled land in step (2) above, lay in sequence: organic fertilizer (cow dung) 250 kg / mu, silica-alumina gel-modified bentonite 150 kg / mu, attapulgite 150 kg / mu.

[0054] Inversion process: Use a subsoiler to invert to a 40-cm soil layer in 3 times, with a 7-day interval each time, and the total operation depth error ≤ 5 cm.

[0055] Cycle control: Repeat the construction of the interlayer every 3 years.

[0056] (4) Surface straw mulching: When plowing in autumn or preparing the land before sowing, crush crop straw (such as corn straw) to a length of 5–10 cm, evenly spread it on the surface of the land (coverage rate ≥ 90%), with an annual mulching amount of 2.5 tons / mu, and implement it continuously every year.

[0057] (5) Flushing and desalting: The flushing water volume is 1500 m³ / hm 2 ~1800 m³ / hm 2 .

[0058] (6) Cover the land with a film and apply fertilizer to plant sunflowers after rotary tillage and leveling. Urea 450 kg / hm 2 , diammonium phosphate 375 kg / hm 2 , potassium sulfate 180 kg / hm 2, planting density is 49,000 plants / hm 2 .

[0059] Figure 1 This is a schematic diagram of the collaborative improvement of saline-alkali soil by organic and inorganic interlayers in the present invention.

[0060] Effect: Measure soil salt content, organic matter and yield.

[0061] Method for measuring soil salt content: The conductivity of the soil extract (soil-water ratio is 5:1) is measured using a DDS-307 conductivity meter (Shanghai Teflon Electronics Co., Ltd., China).

[0062] The calculation formula for soil water-soluble salt content is as follows:

[0063] WSS = 3.0111×EC 1:5

[0064] (3 - 2)

[0065] Among them, WSS represents the water-soluble salt content (g·kg -1 ), EC 1:5 represents the conductivity of the soil solution (soil-water mass ratio is 5:1, ms·cm -1 ).

[0066] Method for measuring soil organic matter: Soil organic matter (SOM) is measured by the external heating method with potassium dichromate.

[0067] Aggregate fractionation method:

[0068] Aggregates in different soil layers are fractionated by the wet sieving method. Briefly, the operation process is as follows: Place 60 g of soil sample on a 2 mm sieve, soak it for 5 min, and then vibrate it through an aggregate automatic sieving instrument (amplitude 3 cm, frequency 25 times / min) to collect soil particles > 2 mm remaining on the sieve. Continue to pass the remaining solution through a 0.25 mm sieve with the same vibration method to obtain 0.25 - 2 mm fraction aggregates. Repeat the above operation, continue to pass the remaining soil sample solution through a 0.53 mm sieve to collect 0.25 - 0.53 mm fraction aggregates. The remaining soil sample solution is centrifuged at 1250×g for 30 min to obtain < 0.053 mm fraction aggregates. Place them in an oven at 60 °C for drying and weighing.

[0069] Soil pore structure method: The undisturbed soil is scanned using an X-CT system (GE, phoenix v|tome x m) to analyze the characteristics of the soil pore structure. The instrument parameters are voltage, 100 kV; current, 100 μA; resolution, 30 μm; a total of 1600 32-bit tiff format grayscale images. Image J software is used for image processing.

[0070] Crop yield measurement method: Measure the row spacing and plant spacing in the demonstration plot. For each experimental treatment, select three representative sample points, measure 10 row spacings to calculate the average row spacing, select a representative 20 meters among 10 rows, count the number of plants, and calculate the number of plants per mu; Continuously pick 10 sunflower heads (double rows) at each sample point, thresh and weigh them. After measuring the moisture content using a grain moisture meter, calculate the final grain yield.

[0071] Comparative Example 1: Method for improving saline-alkali land through an organic interlayer

[0072] The method for improving saline-alkali land through an organic interlayer in this Comparative Example 1 includes the following steps:

[0073] (1) Land leveling: Plow, harrow, and roll the land to be improved to form a finely leveled land with a surface elevation difference ≤ 5 cm.

[0074] (2) Construction of the organic interlayer:

[0075] On the finely leveled land in the above step (1), apply 250 kg / mu of cow dung, and use a subsoiler to turn it over and press it into the 40-cm soil layer in 3 times, with a 7-day interval each time. The total operation depth error ≤ 5 cm.

[0076] (3) Surface straw mulching: When plowing in autumn or preparing the land before sowing, crush the crop straw (such as corn straw) to a length of 5 - 10 cm, evenly spread it on the ground surface (coverage rate ≥ 90%), with an annual mulching amount of 2.5 tons / mu, and implement it continuously for several years.

[0077] (4) Flushing and desalting with water: The irrigation volume is 1500 m³ / hm² 2 ~1800 m³ / hm² 2 .

[0078] (5) Cover the land with plastic film and apply fertilizer to plant sunflowers after rotary tillage and leveling. Apply 450 kg / hm² of urea 2 , 375 kg / hm² of diammonium phosphate 2 , 180 kg / hm² of potassium sulfate 2 , and the planting density is 49,000 plants / hm² 2 .

[0079] Effect: Measure the soil salt content, organic matter, and yield. The measurement method is the same as that in Example 1.

[0080] Comparative Example 2: Method for improving saline-alkali land through an inorganic interlayer

[0081] The method for improving saline-alkali land through an inorganic interlayer in this Comparative Example 2 includes the following steps:

[0082] (1) Modification of bentonite: Take 100 kg of calcium-based bentonite (montmorillonite content ≥ 85%) and add it to an aqueous sodium silicate solution with a mass percentage concentration of 6%. Stir for 30 minutes, let it stand for dissociation, then add an aqueous sodium aluminate solution with a mass percentage concentration of 4%. Adjust the pH to 7 and let it stand for 24 hours to form silica-alumina gel-modified bentonite. The calcium-based bentonite modified with silica-alumina gel forms a Si-O-Al network structure.

[0083] (2) Land leveling: Plow, harrow, and roll the land to be improved to form a finely leveled land with a surface elevation difference ≤ 5 cm.

[0084] (3) On the finely leveled land in step (2) above, apply 150 kg / mu of the silica-alumina gel-modified bentonite and 150 kg / mu of attapulgite prepared in step (1). Use a subsoiler to turn and press it 3 times to a depth of 40 cm, with a 7-day interval each time, and the total operation depth error ≤ 5 cm.

[0085] (4) Surface straw mulching: When plowing in autumn or preparing the land before sowing, crush crop straw (such as corn straw) to a length of 5 - 10 cm and evenly spread it on the ground surface (coverage rate ≥ 90%), with an annual mulching amount of 2.5 tons / mu, and implement it year after year.

[0086] (5) Flushing and desalting: The flushing water volume is 1500 m³ / hm 2 ~1800 m³ / hm 2 .

[0087] (6) On the land leveled by rotary tillage, cover with plastic film and apply fertilizers to plant sunflowers, with 450 kg / hm of urea 2 , 375 kg / hm of diammonium phosphate 2 , 180 kg / hm of potassium sulfate 2 , and a planting density of 49,000 plants / hm 2 .

[0088] Effect: Measure the soil salt content, organic matter, and yield, and the measurement method is the same as in Example 1.

[0089] Control group, method for improving saline-alkali land without interlayer

[0090] The method for improving saline-alkali land without interlayer in this control group includes the following steps:

[0091] (1) Surface straw mulching: When plowing in autumn or preparing the land before sowing, crush crop straw (such as corn straw) to a length of 5 - 10 cm and evenly spread it on the ground surface (coverage rate ≥ 90%), with an annual mulching amount of 2.5 tons / mu, and implement it year after year.

[0092] (2) Flushing and desalting: The flushing water volume is 1500 m³ / hm 2 ~1800 m³ / hm 2 .

[0093] (3) Apply plastic film and fertilize to plant sunflowers on the rotary tillage and leveled land, with 450 kg / hm of urea 2 , 375 kg / hm of diammonium phosphate 2 , 180 kg / hm of potassium sulfate 2 , and the planting density is 49,000 plants / hm 2 .

[0094] Effect: Measure the soil salt content, organic matter, and yield. The measurement method is the same as that in Example 1.

[0095] Statistically analyze the soil salt resistance and fertility improvement effects of different treatments (Example 1, Comparative Example 1, Comparative Example 2, and the control group). The results are as follows:

[0096] The influence results of different treatments on the soil organic carbon content are shown in Table 1 and Figure 2 as follows. As can be seen from Table 1 and Figure 2 , in Example 1 of the present invention, the method of synergistically improving saline-alkali land through organic and inorganic interlayers significantly reduces the soil salt content. During the 5-year period of Example 1, compared with the control example, Comparative Example 1, and Comparative Example 2, the organic carbon content increased by 23.26%-32.60%, 14.53%-19.45%, 8.63%-28.22%, 13.27%-16.66%, and 3.50%-20.77% respectively.

[0097] Table 1 Influence of different treatments on soil organic carbon content

[0098]

[0099] Table 2 shows the influence results of different treatments on the aggregate stability. As can be seen from Table 2, compared with the control example, in Example 1 of the present invention, the method of synergistically improving saline-alkali land through organic and inorganic interlayers significantly improves the soil aggregate stability. Among them, the increase rate of the mean weight diameter is 24.50%, the increase rate of the geometric mean diameter is 24.53%, and the increase rate of the proportion of large aggregates is 8.98% (P<0.05).

[0100] Table 2 Influence of different treatments on aggregate stability

[0101]

[0102] Figure 3 shows the influence results of different treatments on the change of soil salt content. As can be seen from Figure 3 , in Example 1 of the present invention, the method of synergistically improving saline-alkali land through organic and inorganic interlayers significantly reduces the soil salt content. During the 3-year period of Example 1, compared with the control example, Comparative Example 1, and Comparative Example 2, the salt content decreased by 11.44%-27.52%, 5.88%-22.61%, and 1.58%-17.24% respectively.

[0103] Figure 4 The results of the effects of different treatments on the change in soil water content. From Figure 4 It can be seen that the method for synergistically improving saline-alkali land by organic and inorganic interlayers in Example 1 of the present invention significantly increased the soil salt content. During the 3-year period of Example, compared with the control example, Comparative Example 1 and Comparative Example 2, the water contents increased by 5.33%-8.65%, 4.16%-6.32% and 3.46%-6.15% respectively.

[0104] Figure 5 The results of the effects of different treatments on the change in soil total nitrogen content. From Figure 5 It can be seen that the method for synergistically improving saline-alkali land by organic and inorganic interlayers in Example 1 of the present invention significantly increased the soil total nitrogen content. During the 3-year period of Example, compared with the control example, Comparative Example 1 and Comparative Example 2, the total nitrogen contents increased by 26.96%-30.10%, 11.36%-21.43% and 9.16%-16.97% respectively.

[0105] Figure 6 The results of the effects of different treatments on crop yield. From Figure 6 It can be seen that the method for synergistically improving saline-alkali land by organic and inorganic interlayers in Example 1 of the present invention significantly increased the crop yield. During the 3-year period of Example, compared with the control example, Comparative Example 1 and Comparative Example 2, the yields increased by 6.32%-33.43%, 2.44%-9.30% and 2.40%-4.31% respectively.

[0106] Figure 7 And Table 3 shows the results of the effects of different treatments on the porosity of different soil layers. From Figure 7 and Table 3, it can be seen that the examples significantly increased the porosity of soil layers greater than 50 microns. In the 0-20 cm soil layer, compared with the control example, Comparative Example 1 and Comparative Example 2, the porosity of 50 microns increased by 132.35%, 27.98% and 18.07% respectively; in the 20-40 cm soil layer, compared with the control example, Comparative Example 1 and Comparative Example 2, the porosity of 50 microns increased by 97.76%, 13.95% and 18.23% respectively; in the 20-40 cm soil layer, compared with the control example, Comparative Example 1 and Comparative Example 2, the porosity of 50 microns increased by 242.50%, 112.40% and 48.11% respectively.

[0107] Table 3 Effects of different treatments on soil porosity >50 microns

[0108]

[0109] The above specific embodiments do not constitute a limitation on the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can occur depending on design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for improving saline-alkali land, comprising the following steps: The calcium-based bentonite which can replace the sodium ions in the saline-alkali soil is dissociated by sodium silicate and cross-linked with sodium aluminate to obtain silica-alumina modified bentonite; Spreading organic fertilizer, silica-alumina modified bentonite and attapulgite in layers on the land to be improved to construct an organic-inorganic interlayer; Straw mulch is implemented year after year.

2. The method for improving saline-alkali land according to claim 1, characterized in that: The calcium-based bentonite is dissociated with sodium silicate and cross-linked with sodium aluminate by immersing the calcium-based bentonite in a sodium silicate aqueous solution, adding a sodium aluminate aqueous solution after dissociation, adjusting the pH value to 7.0-7.5, and standing to form alumina-silica modified bentonite.

3. The method for improving saline-alkali land according to claim 1 or 2, characterized in that: The silica-alumina gel-modified bentonite forms a Si-O-Al network structure.

4. The method for improving saline-alkali land according to claim 2, characterized in that: The mass percentage concentration of the sodium silicate aqueous solution is 5% to 8%; the mass percentage concentration of the sodium aluminate aqueous solution is 2% to 5%; the molar ratio of the sodium aluminate to the sodium silicate is 1:(1.2 to 1.5).

5. The method for improving saline-alkali land according to claim 2, characterized in that: The calcium-based bentonite is immersed in the sodium silicate solution and stirred for 30 minutes to 60 minutes; the standing time is 18 hours to 24 hours.

6. The method for improving saline-alkali land according to claim 1, characterized in that: Before constructing the organic-inorganic barrier, the method also includes plowing, raking and compacting the land to be improved to form finely leveled land with a surface elevation difference of ≤5 cm.

7. The method for improving saline-alkali land according to claim 1, characterized in that: The dosage of the organic fertilizer is 200-300 kg / mu; the dosage of the silica-alumina modified bentonite is 100-200 kg / mu; and the dosage of the attapulgite is 100-200 kg / mu.

8. The method for improving saline-alkali land according to claim 1, characterized in that: After the layered paving, the step also includes using a deep tiller to compact the soil to a 35 cm to 50 cm layer 2 to 4 times; each compaction is performed at an interval of 3 to 5 days.

9. The method for improving saline-alkali land according to claim 1, characterized in that: The continuous implementation of straw covering the ground surface is that during autumn plowing or land preparation before sowing, corn straw is crushed into 5-10 cm length and evenly spread on the ground surface, with a coverage rate of ≥90% and an annual coverage amount of 0.8-2.5 tons / mu, which is implemented continuously.

10. The method for improving saline-alkali land according to claim 1, characterized in that: After the straw covering is carried out for many years, the step of watering and washing salt is also included, and the watering amount is 1500 cubic meters / hm each time. 2 ~1800m3 / hm 2 .

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