Ecological improvement method for reserved cultivated land of severe saline-alkali soil

Abstract

The invention relates to the technical field of saline-alkali soil treatment, in particular to a severe saline-alkali soil reserve cultivated land ecological improvement method. Comprising the following steps: taking corresponding physical desalting measures on soil according to the condition of the saline-alkali soil to be improved; a halophyte community is constructed, and the soil is improved; a salt-tolerant plant community is constructed, and the soil is improved; salt-tolerant crops are planted, and soil conservation is achieved. The problems of high salinity and poor texture of saline-alkali soil can be gradually improved, and the soil quality of severe saline-alkali soil is improved.

Description

Technical Field

[0001] The invention relates to the technical field of saline-alkali soil treatment, in particular to an ecological improvement method for converting heavy saline-alkali land into reserve arable land. Background Art

[0002] Saline-alkali land is an important reserve arable land resource in China. The total area of ​​saline-alkali land of varying degrees in the world exceeds 830 million hectares. "Saline-alkali land management and use" is a global problem. The salinity and alkali content of saline-alkali land is significantly higher than normal, making it difficult for crops to grow. When the soil salt content exceeds 6‰, the crop emergence rate will be less than 50% and the yield will be reduced by 90%.

[0003] Commonly used saline-alkali land improvement technologies in my country include chemical improvement technology and engineering improvement measures. At present, large-scale saline-alkali land improvement projects for severely saline-alkali land, especially saline-alkali wasteland and bare land, often adopt measures of imported soil, which requires large investment and low effect; and after the construction, the soil quality often does not meet the crop planting standards or the crop yield is low, the soil salt is not fully removed, the soil organic matter content is low, the structure is poor, and the soil quality continues to deteriorate, resulting in a serious waste of natural resources and social resources. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned defects of the prior art and propose an ecological improvement method for severely saline-alkali land reserve arable land, which can gradually improve the problems of high salinity and poor texture of saline-alkali land soil and improve the soil quality of severely saline-alkali land.

[0005] The technical solution of the present invention is: a method for ecological improvement of severely saline-alkali land into reserve arable land, comprising the following steps:

[0006] S1. Take appropriate physical desalination measures for the soil according to the conditions of the saline-alkali land to be improved;

[0007] S2. Construct halophyte communities to improve soil;

[0008] S3. Build salt-tolerant plant communities to improve the soil;

[0009] S4. Plant salt-tolerant crops to achieve soil conservation.

[0010] In step S1 of the present invention, when the severely saline-alkali land to be improved has no surface vegetation coverage and has obvious ground salt crystals, or the surface soil has a salt crust and the degree of soil salinization is very serious, enhanced physical desalination measures are adopted for the saline-alkali land:

[0011] S1.1.1. In the spring when the soil surface salt accumulation is the most serious, remove the soil surface layer with a thickness of 3-5cm and the salt crystals connected to the soil and move them out of the site to be improved;

[0012] S1.1.2. Deeply till and loosen the surface soil to a depth of more than 60 cm;

[0013] S1.1.3. Divert water to flood the salt washing area to a depth of more than 30 cm, maintain the flooding time for at least seven days, and drain the accumulated water from the salt washing area;

[0014] S1.1.4. After the surface soil is dry, deep loosen the soil again to a depth of more than 60 cm and apply organic amendments to the soil surface;

[0015] S1.1.5. Till the soil several times to break up soil clods and keep the soil loose. No additional treatment is required in summer, and natural precipitation is used to wash the salt from the surface soil. Till the soil at least twice in late October, with each tillage operation at a depth of 25 cm to keep the surface soil loose.

[0016] When the surface of the heavily saline-alkali land to be improved is covered with halophytes such as weeds, reeds, and saltwort, and although there is some salt return on the surface in spring, no salt accumulation has formed, and there is alternating dry and wet conditions on the ground during the day and night, general physical desalination measures are adopted:

[0017] S1.2.1. Use summer precipitation to naturally reduce the salinity of the surface soil of saline-alkali soil;

[0018] S1.2.2. In September, deep tillage and loosening of the surface soil were carried out and organic amendments were applied to the surface of the soil;

[0019] S1.2.3. Till the soil several times to break up soil clods until the soil remains loose.

[0020] The application of 5 tons of organic amendment per acre of soil;

[0021] Organic amendments include straw, fungus residue, and herbivorous animal manure.

[0022] In step S2, the halophytes may be selected from Suaeda salsa and Malva sylvestris, and the construction of the halophyte community is achieved through the following specific steps:

[0023] S2.1. Keep the soil loose and porous;

[0024] S2.2. In the first year, in the middle and early November, when the maximum temperature stabilizes below 10℃, sow halophyte seeds in the site to be improved, with a sowing rate of 2-2.5kg per mu, and carry out 1-2 rounds of sowing; no treatment is done in winter;

[0025] S2.3. In the spring of the second year, under the action of natural precipitation, the seeds sown in winter will germinate naturally, and the surface of the site to be improved will be planted; after the crops emerge, spread 20kg / mu of coated slow-release urea;

[0026] S2.4. The halophyte vegetation continues to expand and the surface coverage gradually increases. One week after the halophytes have completely covered the surface, the halophytes are mowed for the first time, with a stubble height of 30 cm. The mowed crops are collected and removed from the site to be improved, and 5 kg / mu of granular urea is applied;

[0027] S2.5, as the halophytes continue to grow, one week after they complete the second surface coverage, the halophytes are mowed for the second time, the same as step S2.4;

[0028] S2.6. Halophytes continue to grow until the late autumn of the second year. When they mature, they are mowed close to the ground and the remaining plants are used to cover the soil surface, keeping the ground covered throughout the winter.

[0029] In step S3, the salt-tolerant plants may be selected from sesbania, kenaf, tamarind, amaranth, sorghum, and cassia seed, and the construction of the salt-tolerant plant community is achieved through the following specific steps:

[0030] S3.1. In the spring of the third year, when the minimum temperature is stable above 15°C, the soil is rotary tilled to a depth of more than 25 cm to restore the soil to a loose state. Seeds of salt-tolerant plants are sown on the site to be improved, with a sowing rate of 6-7 kg per mu, and 1-2 times of sowing;

[0031] S3.2. Under the influence of natural precipitation, salt-tolerant plants grow naturally. When the salt-tolerant plants have completed the surface coverage, 5 kg / mu of granular urea is applied;

[0032] S3.3. In the autumn of the third year, when the salt-tolerant plants are not fully mature, use a field return machine to kill the stubble of the salt-tolerant plants. After returning all the plants to the field, rotary till the soil at a depth of more than 25 cm.

[0033] In step S4, the salt-tolerant crops may be selected from salt-tolerant winter rapeseed, camelina, mustard, cabbage, radish, and carrot, and the planting of salt-tolerant crops is achieved through the following specific steps:

[0034] S4.1. In mid-September of the third year, before effective precipitation occurs, use drones to sow salt-tolerant crop seeds on the site to be improved, with a sowing rate of 0.6-0.8 kg per mu, and carry out 1-2 sowing operations. After sowing, spread 30 kg / mu of coated slow-release urea and harrow it with a toothed harrow;

[0035] S4.2. Allow salt-tolerant crops to grow naturally in autumn. If they grow too vigorously, carry out chemical growth control treatment. If irrigation conditions are available, carry out winter irrigation before the soil freezes in winter. Keep the ground covered with salt-tolerant crops in winter.

[0036] S4.3. In the spring of the fourth year, salt-tolerant crops grow naturally, and irrigation is carried out if irrigation conditions permit. After turning over, strip-forming or thinning the salt-tolerant crops, wait for the salt-tolerant plants to mature.

[0037] The beneficial effects of the present invention are:

[0038] (1) In the process of soil engineering physical desalination, differentiated engineering measures are adopted according to the salinization characteristics of the severely saline-alkali land to be improved, which can ensure the soil desalination efficiency while ensuring the improvement effect;

[0039] (2) Adopting the agricultural improvement strategy of hierarchical planting of halophytes, salt-tolerant plants, and salt-tolerant crops, combined with seasonal natural precipitation processes, targeted improvement of heavily saline-alkali soils can be carried out. Soil ecological improvement can be carried out while irrigation facilities are being constructed;

[0040] (3) Avoid the increase in improvement costs caused by large-scale soil imports. After implementing ecological improvement, the soil quality can be gradually improved and the risk of secondary salinization can be reduced under the stable farming and planting mode;

[0041] (4) The use of drone seeding and fertilization can reduce costs by more than 50% compared to mechanical seeding and manual spreading, and also avoid the compaction of saline-alkali soil by large machinery.

[0042] To summarize, this application takes the development and utilization of severely saline-alkali land as its main goal, in order to solve the problem of agricultural development and utilization of severely saline-alkali land, especially saline-alkali wasteland and saline-alkali bare land; combined with small-scale engineering improvement, soil tillage improvement and salt-tolerant plant planting and other improvement technical measures, it will take 2-3 years to complete the target salt-tolerant crop establishment and ecological utilization of saline-alkali land; for severely salt-accumulating bare land and severely saline-alkali wasteland, differentiated engineering improvement strategies are adopted, regional halophyte tiered improvement technology is utilized, natural precipitation is fully utilized, and under the condition of limited irrigation facilities, a new strip improvement machinery, drone aerial seeding and other practical technologies are adopted to complete the agricultural improvement strategy of halophytes-salt-tolerant plants-salt-tolerant crops, achieve full coverage of vegetation throughout the year for severely saline-alkali land, enhance the ecological effect of severely saline-alkali land during the improvement period, and form a certain agricultural productivity after the improvement period. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of the improved method of the present invention. DETAILED DESCRIPTION

[0044] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0045] In the following description, specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in a variety of other ways than those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0046] Example 1

[0047] In this embodiment, the method for ecological improvement of severely saline-alkali land as reserve arable land comprises the following steps: Figure 1 shown.

[0048] The first step is to carry out physical desalination engineering operations on the soil. In this application, it is necessary to take corresponding physical desalination engineering measures according to the conditions of the saline-alkali land to be improved.

[0049] When the severely saline-alkali land to be improved has no surface vegetation cover, has obvious surface salt crystallization, or has a salt crust on the surface soil, and the degree of soil salinization is very serious, it is necessary to take enhanced physical desalination measures for the saline-alkali land.

[0050] In this embodiment, the enhanced physical desalination measures are as follows: in the spring when the surface salt is the heaviest, bulldozers, loaders, shovelers and other engineering machinery are used to remove the soil with a thickness of 3-5 cm together with the salt crystals on the surface layer, and move them out of the repair site. Use excavators, reversing plows and other machinery to deep-plow the surface soil to a working depth of more than 60 cm. Immediately thereafter, water is diverted and flooded to wash the salt, with a flooding depth of more than 30 cm, and the flooding time is maintained for at least seven days to discharge the accumulated water from the salt washing. After the surface soil is dry, the soil is deep-plowed again to a working depth of more than 60 cm. After deep-plowing, an organic amendment made from waste organic matter such as straw, fungus residue, and herbivorous animal feces is applied to the soil surface.

[0051] In this embodiment, 5 tons of the above organic improver is applied per mu of soil. The organic improver is made from agricultural waste such as straw, fungus residue, and herbivorous animal feces, and is made through aerobic composting and fermentation for 25-30 days.

[0052] In this embodiment, the organic improver is specifically mixed by the following substances: grain straw, with a mass ratio of 1; vegetable waste, with a mass ratio of 0.8-1; mushroom residue, with a mass ratio of 1-1.2; herbivorous animal feces, with a mass ratio of 1-1.2; omnivorous animal feces, with a mass ratio of 0.5-0.6.

[0053] Add biochar at a ratio of 3%-5% of the total mass of the above mixed materials. Use loaders, mixers and other machines to mix the above materials, adjust the moisture content to 60%-65%, and pile them into strip piles or put them into fermentation tanks for fermentation. Use normal organic fertilizer production processes for aeration or turning to maintain sufficient oxygen supply inside the pile. After 25-30 days of pile making, the temperature of the pile drops to below 35°C and remains relatively constant, completing the preparation of the organic improver.

[0054] The soil is subjected to multiple rotary tillage treatments using a rotary tillage machine to break up soil clods until the soil remains loose. In this embodiment, the soil is subjected to 2-4 rotary tillage treatments, and the rotary tillage treatment is performed in a continuous operation mode. No additional treatments such as rotary tillage are performed in the summer, and the surface soil salt is washed away by natural precipitation. In late autumn, that is, in late October, the soil is subjected to rotary tillage operations, which are repeated at least twice, and the rotary tillage operation depth is 25 cm each time, so that the surface soil remains loose.

[0055] When the surface of the heavily saline-alkali land to be improved is covered with halophytes such as weeds, reeds, and saltwort, and although there is some salt return on the surface in spring, no salt accumulation is formed, and the ground has alternating dry and wet conditions during the day and night, general physical desalination measures are adopted.

[0056] In this embodiment, the general physical desalination measures are: using the abundant rainfall in summer to naturally reduce the salinity of the surface soil of saline-alkali soil; in the early autumn season, usually in September, using excavators, reversing plows and other machinery to deep-plow and loosen the surface soil, with an operating depth of more than 60 cm. Apply organic amendments made from waste organic matter such as straw, fungus residue, and herbivorous animal feces to the surface, and apply 5 tons of organic amendments per mu of soil. The specific formula and composting process of the organic amendment are as described above, so they will not be repeated here. Use a rotary tillage machine to perform multiple rotary tillage treatments on the soil to break up the soil clods until the soil remains loose.

[0057] The second step is to build a halophyte community to improve the soil.

[0058] After completing the physical desalination engineering operation steps, the soil is kept loose and porous. If there is heavy rainfall in autumn, it is necessary to re-till the soil to break up the soil clods until the soil remains loose.

[0059] In the early winter of the first year, generally in mid-to-early November, when the maximum temperature stabilizes below 10°C, use drones to sow salsa seeds in the site to be improved, with a sowing rate of 2-2.5kg per mu, to ensure uniform sowing without missing any seeds. If conditions permit, two rounds of salsa sowing can be carried out. No treatment is done in winter. In the spring of the second year, under the action of natural precipitation, the seeds sown in winter will germinate naturally, completing the establishment of halophytes on the surface of the improved site. After the crops emerge, drones or manual application of coated slow-release urea 20kg / mu.

[0060] With the change of seasons, the Suaeda salsa vegetation continues to expand and the surface coverage gradually increases. One week after the Suaeda salsa has completely covered the surface, the first mowing is carried out, leaving a stubble height of 30 cm. The cut crops are collected and moved out of the improved site, and then 5 kg / mu of granular urea is applied.

[0061] Wait for the Suaeda to grow, and one week after the second surface covering is completed, mow the Suaeda for the second time, following the same steps as the first mowing.

[0062] After that, no further treatment is carried out and the Suaeda salsa is allowed to grow naturally. In the late autumn of the second year, when the Suaeda salsa seeds are mature, they are mowed close to the ground and the remaining plants are used to cover the soil surface, keeping the surface covered throughout the winter.

[0063] The third step is to build a salt-tolerant plant community to improve the soil.

[0064] In the spring of the third year, when the minimum temperature is stable above 15℃, the soil is directly rotary tilled to a depth of more than 25cm to restore the soil to a loose state. Drones are used to sow sesbania seeds in the site to be improved, with a sowing rate of 6-7kg per mu, to ensure uniform sowing without missing any seeds. If conditions permit, two rounds of sesbania sowing can be carried out.

[0065] Under the influence of natural precipitation, the Sesbania was allowed to grow naturally. When the Sesbania completed the surface coverage, 5 kg / mu of granular urea was applied, and no additional treatment was generally done afterwards.

[0066] In the autumn of the third year, around early September, when the sesbania has formed pods but is not fully mature, use a field return machine to kill the stubble of the sesbania. After returning all the pods to the field, the soil is rotary tilled with an operating depth of more than 25 cm.

[0067] The fourth step is to plant salt-tolerant crops to achieve soil conservation.

[0068] In mid-September of the third year, depending on the weather conditions and before effective precipitation occurs, use drones to sow salt-tolerant winter rapeseed seeds in the site to be improved, with a sowing rate of 0.6-0.8kg per mu, to ensure uniform sowing without missing any seeds. If conditions permit, sow the winter rapeseed seeds twice. After sowing the rapeseed, apply 30kg / mu of coated slow-release urea and rake it flat with a toothed harrow. Allow the rapeseed to grow naturally in autumn. If it grows too vigorously, carry out chemical control treatment in time to avoid bolting before winter. If there are irrigation conditions, carry out winter irrigation before the soil freezes in winter. Keep the surface rapeseed covered in winter without additional treatment.

[0069] In the spring of the fourth year, rapeseed grows naturally, and irrigation is carried out if there are irrigation conditions. According to the physical and chemical properties and nutrient content of the soil, it is possible to choose to turn over rapeseed to plant spring crops, plant crops after strip improvement, or wait for rapeseed to mature and harvest rapeseed after thinning.

[0070] In the subsequent planting process, keep the soil in a cultivated state, reduce the input of chloride ions and sulfate ions, increase the use of organic fertilizers and slow-release fertilizers in the soil, return straw to the fields, and keep crops or green manure covering the surface in winter.

[0071] The improved method described in the present application is further described below based on the technical effects that can be achieved in this embodiment and the principles of each step.

[0072] The vertical distribution of salinity in saline-alkali soil has significant seasonal characteristics. Before the spring and summer rainy seasons, the soil surface salt content reaches the highest level of the year. The salt content of heavily saline-alkali soil continues to accumulate. According to indoor simulation experiments, the accumulated salt content of the 20cm saline-alkali soil surface can reach more than 10 times the average content of the soil. Therefore, in this embodiment, the use of differentiated soil physical desalination measures can improve the soil desalination efficiency while controlling costs.

[0073] In Table 1, after the original heavy saline-alkali soil was subjected to different salt washing treatments, the saline-alkali soil in different layers was compared after the soil dried. According to the comparison, the efficiency of direct flooding and water desalination is relatively low. In the physical desalination stage of heavy saline-alkali land, water washing and water washing need to be supplemented with certain soil cultivation measures.

[0074] Table 1 Salt content of heavy saline-alkali soil after different desalination treatments (g / kg)

[0075]

[0076] From the comparison in Table 2, it can be seen that compared with the currently commonly used desalination measures of "laying concealed pipes + flooding to wash salt + adding soil", the physical desalination method of this application has outstanding advantages in economy and desalination effect.

[0077] Table 2 Input and effectiveness of different desalination engineering measures

[0078]

[0079] Maintaining surface vegetation coverage and improving the productivity of salt-tolerant plants are key factors in the ecological restoration of saline-alkali land. Indoor experiments have shown that when the surface is covered with straw or moisturizing mulch, the amount of water evaporation and salt accumulation in the soil surface are significantly reduced. Plant coverage can effectively alleviate the accumulation of surface salt. At the same time, the salt in the soil can be enriched in the plant body and removed by mowing. According to the calculation of 300kg of dry biomass per mu and 25% plant salt content, the soil salt removed by plant harvesting each growing season is equivalent to reducing the total salt content of the 0-20cm soil layer by about 0.5g / kg, which has a certain desalination effect. In addition, plant coverage can reduce the evaporation rate of water on the soil surface, thereby reducing the phenomenon of salt accumulation on the surface.

[0080] Therefore, this application utilizes the improvement strategy of halophytes-salt-tolerant plants-salt-tolerant crops, which can ensure the ecological improvement effect of saline-alkali land and avoid the impact of improved plant planting on the next step of farming and utilization. The specific principles are as follows: the planting of Suaeda salsa in the first season can complete the vegetation coverage of the surface under soil conditions with high salinity, increase the dry matter yield of Suaeda salsa by "mowing + topdressing", improve the efficiency of salt removal and maintain winter surface coverage; in the second season, Sesbania salsa is planted, and its high coverage, high biomass and high plant height are used to remove the Suaeda salsa seeds that germinate in the soil in the first season through shading. At the same time, the Sesbania salsa seeds are returned to the field when they are not yet mature, so as to avoid the damage to crops caused by the germination of Sesbania salsa seeds in the next season; salt-tolerant rapeseed is selected to maintain winter surface coverage, further reduce the accumulation of salt on the surface, and at the same time, the soil is continuously fertilized by returning organic matter to the field.

[0081] In the severely saline-alkali land in Dongying, the improvement scheme described in the application was verified in the field. Since the experimental site was already covered with halophytes, the soil fertilization measure of "mechanical deep loosening + organic matter application" was adopted, and field sesbania was planted in summer and returned to the field in full in autumn to further improve the soil structure, and slow-release fertilizer and organic matter were applied. After the severely saline-alkali land in the experimental area was improved by the improvement method described in this embodiment, the changes in its soil physical and chemical properties and soil nutrient indexes are shown in Table 3. According to the table, the soil quality of the saline-alkali land gradually improves with the improvement process.

[0082] Table 3 Soil improvement indexes of field effect test of comprehensive improvement and utilization of severe saline-alkali land in Dongying

[0083]

[0084] Example 2

[0085] The organic improver used in this embodiment is prepared from the following materials: medicinal residues and coffee residues. The specific process of preparing the organic improver using the above materials can adopt the preparation process of the organic improver disclosed in Example 1.

[0086] The rest is the same as in Example 1.

[0087] Example 3

[0088] In this embodiment, halophytes such as seashore mallow can be used to replace the Suaeda salsa in embodiment 1. The specific planting method is the same as the planting method of Suaeda salsa.

[0089] The rest is the same as in Example 1.

[0090] Example 4

[0091] In this embodiment, kenaf can be used to replace the sesbania in Example 1, and the specific planting method is the same as the planting method of sesbania.

[0092] In the present application, salt-tolerant plants such as Tamarind, Amaranthus chinensis, Sorghum sorghum, and Cassia seed may be used to replace the Sesbania sessica in Example 1.

[0093] The rest is the same as in Example 1.

[0094] Example 5

[0095] In this embodiment, camelina can be used to replace the salt-tolerant winter rapeseed in Example 1.

[0096] In the present application, salt-tolerant plants such as mustard, cabbage, radish, carrot, etc. may also be used to replace the salt-tolerant winter rapeseed in Example 1.

[0097] The rest is the same as in Example 1.

[0098] The above is a detailed introduction to the ecological improvement method for the reserve cultivated land of heavy saline-alkali land provided by the present invention. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The above description of the disclosed embodiments enables professionals and technicians in this field to implement or use the present invention. Various modifications to these embodiments will be obvious to professionals and technicians in this field, and the general principles defined in this article can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown in this article, but will conform to the widest range consistent with the principles and novel features disclosed herein.

Claims

1. A method for ecological improvement of severely saline-alkali land reserve arable land, characterized in that: The following steps are involved: S1. Take appropriate physical desalination measures for the soil according to the conditions of the saline-alkali land to be improved; S2. Construct halophyte communities to improve soil; S3. Build salt-tolerant plant communities to improve the soil; S4. Plant salt-tolerant crops to achieve soil conservation.

2. The method for ecological improvement of severely saline-alkali land as reserve arable land according to claim 1, characterized in that: In step S1, when the severely saline-alkali land to be improved has no surface vegetation cover and has obvious ground salt crystals, or the surface soil has salt crust and the degree of soil salinization is very serious, enhanced physical desalination measures are adopted for the saline-alkali land: S1.1.

1. In the spring when the soil surface salt accumulation is the most serious, remove the soil surface layer with a thickness of 3-5cm and the salt crystals connected to the soil and move them out of the site to be improved; S1.1.

2. Deeply till and loosen the surface soil to a depth of more than 60 cm; S1.1.

3. Divert water to flood the salt washing area to a depth of more than 30 cm, maintain the flooding time for at least seven days, and drain the accumulated water from the salt washing area; S1.1.

4. After the surface soil is dry, deep loosen the soil again to a depth of more than 60 cm and apply organic amendments to the soil surface; S1.1.

5. Till the soil several times to break up soil clods and keep the soil loose. No additional treatment is required in summer, and natural precipitation is used to wash the salt from the surface soil. Till the soil at least twice in late October, with each tillage operation at a depth of 25 cm to keep the surface soil loose.

3. The ecological improvement method for severely saline-alkali land reserve arable land according to claim 1, characterized in that: When the surface of the heavily saline-alkali land to be improved is covered with halophytes such as weeds, reeds, and saltwort, and although there is some salt return on the surface in spring, no salt accumulation has formed, and there is alternating dry and wet conditions on the ground during the day and night, general physical desalination measures are adopted: S1.2.

1. Use summer precipitation to naturally reduce the salinity of the surface soil of saline-alkali soil; S1.2.

2. In September, deep tillage and loosening of the surface soil were carried out and organic amendments were applied to the surface of the soil; S1.2.

3. Till the soil several times to break up soil clods until the soil remains loose.

4. The ecological improvement method for severely saline-alkali land reserve arable land according to claim 2 or 3, characterized in that: The application of 5 tons of organic amendment per acre of soil; Organic amendments include straw, fungus residue, and herbivorous animal manure.

5. The method for ecological improvement of severely saline-alkali land as reserve arable land according to claim 1, characterized in that: In step S2, the halophytes may be selected from Suaeda salsa and Malva sylvestris, and the construction of the halophyte community is achieved through the following specific steps: S2.

1. Keep the soil loose and porous; S2.

2. In the first year, in the middle and early November, when the maximum temperature stabilizes below 10℃, sow halophyte seeds in the site to be improved, with a sowing rate of 2-2.5kg per mu, and carry out 1-2 rounds of sowing; no treatment is done in winter; S2.

3. In the spring of the second year, under the action of natural precipitation, the seeds sown in winter will germinate naturally, and the surface of the site to be improved will be planted; after the crops emerge, spread 20kg / mu of coated slow-release urea; S2.

4. The halophyte vegetation continues to expand and the surface coverage gradually increases. One week after the halophytes have completely covered the surface, the halophytes are mowed for the first time, with a stubble height of 30 cm. The mowed crops are collected and removed from the site to be improved, and 5 kg / mu of granular urea is applied; S2.5, as the halophytes continue to grow, one week after they complete the second surface coverage, the halophytes are mowed for the second time, the same as step S2.4; S2.

6. Halophytes continue to grow until the late autumn of the second year. When they mature, they are mowed close to the ground and the remaining plants are used to cover the soil surface, keeping the ground covered throughout the winter.

6. The ecological improvement method for severely saline-alkali land reserve arable land according to claim 1, characterized in that: In step S3, the salt-tolerant plants may be selected from sesbania, kenaf, tamarind, amaranth, sorghum, and cassia seed, and the construction of the salt-tolerant plant community is achieved through the following specific steps: S3.

1. In the spring of the third year, when the minimum temperature is stable above 15°C, the soil is rotary tilled to a depth of more than 25 cm to restore the soil to a loose state. Seeds of salt-tolerant plants are sown on the site to be improved, with a sowing rate of 6-7 kg per mu, and 1-2 times of sowing; S3.

2. Under the influence of natural precipitation, salt-tolerant plants grow naturally. When the salt-tolerant plants have completed the surface coverage, 5 kg / mu of granular urea is applied; S3.

3. In the autumn of the third year, when the salt-tolerant plants are not fully mature, use a field return machine to kill the stubble of the salt-tolerant plants. After returning all the plants to the field, rotary till the soil at a depth of more than 25 cm.

7. The ecological improvement method for severely saline-alkali land reserve arable land according to claim 1, characterized in that: In step S4, the salt-tolerant crops may be selected from salt-tolerant winter rapeseed, camelina, mustard, cabbage, radish, and carrot, and the planting of salt-tolerant crops is achieved through the following specific steps: S4.

1. In mid-September of the third year, before effective precipitation occurs, use drones to sow salt-tolerant crop seeds on the site to be improved, with a sowing rate of 0.6-0.8 kg per mu, and carry out 1-2 sowing operations. After sowing, spread 30 kg / mu of coated slow-release urea and harrow it with a toothed harrow; S4.

2. Allow salt-tolerant crops to grow naturally in autumn. If they grow too vigorously, carry out chemical growth control treatment. If irrigation conditions are available, carry out winter irrigation before the soil freezes in winter. Keep the ground covered with salt-tolerant crops in winter. S4.

3. In the spring of the fourth year, salt-tolerant crops grow naturally, and irrigation is carried out if irrigation conditions permit. After turning over, strip-forming or thinning the salt-tolerant crops, wait for the salt-tolerant plants to mature.

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