Method for improving heavy salinized soil of facility farmland by deep ploughing and rotation

Abstract

The application relates to the technical field of soil improvement, and particularly discloses a deep-returning improvement method for heavy salinization soil of facility agricultural land through crop rotation, which comprises the following steps: S1, deep-rooting crops and shallow-rooting crops are planted through crop rotation on the facility agricultural land to be improved, so as to obtain a soil tillage layer pretreated through crop rotation; S2, a plurality of grooves are excavated on the soil tillage layer; S3, straw is crushed, and the crushed straw material is laid in the grooves; a microbial preparation is simultaneously applied, so as to obtain a groove structure; S4, chemical fertilizer is applied to the groove structure; S5, soil is covered on the fertilizer-straw composite layer, so as to form a covered soil layer; S6, ridging is performed to form a ridge structure, and water irrigation treatment is performed; and S7, topdressing treatment is performed on crops growing on the ridge structure. The improvement method can be used for rapid repair of secondary salinization soil in facility agriculture, and has the advantages of improving the physical and chemical properties of the soil and realizing spatial redistribution of salt.

Description

Technical Field

[0001] This application relates to the field of soil improvement technology, and more specifically, to a method for deep restoration and improvement of severely salinized soil in facility agricultural land through crop rotation. Background Technology

[0002] When dealing with severely salinized soils, water conservancy projects are used to quickly leach and remove excess surface salts, creating initial site conditions for crops. Following this, chemical amendments are employed, such as applying calcium-rich substances like gypsum and phosphogypsum to replace harmful sodium ions, or using novel polymeric soil conditioners to improve soil aggregate structure, fundamentally curbing salt return. Simultaneously, salt-tolerant pioneer plants are selected for bio-salt uptake, and specific microbial agents or organic materials are used to increase soil organic matter and activate microbial communities, thereby enhancing the soil's buffering and self-repairing capabilities. The advantage lies in the fact that this systematic improvement not only rapidly and effectively reduces soil salinity below the crop's tolerance threshold, increasing seed germination rate and crop yield, but also improves the soil's physical structure, chemical properties, and biological activity.

[0003] Severely saline soils can be improved through measures such as water leaching, surface application of soil conditioners, or planting salt-tolerant plants. However, these measures often only reduce salt content in the short term and lack the ability to repair the deep soil structure. Furthermore, the improved layer is shallow and easily affected by evaporation, causing salt to quickly return to the surface. This results in an unstable salinity environment in the crop root zone and makes it difficult to sustain the improvement effect. Summary of the Invention

[0004] To address the problem that measures such as water leaching, surface application of soil conditioners, or monoculture of salt-tolerant plants can lead to unstable salinity in the crop root zone and difficulty in sustaining the improvement effect in severely saline soils, this application provides a method for deep soil remediation through crop rotation in facility agriculture.

[0005] This application provides a method for improving severely salinized soil in facility-based agricultural land through crop rotation and deep restoration, employing the following technical solution: A method for improving severely salinized soil in facility-farmed land through crop rotation and deep restoration includes the following steps: S1. On the facility agricultural land to be improved, rotate deep-rooted crops with shallow-rooted crops, or rotate vegetable crops with grain crops, to obtain a soil tillage layer that has been pretreated by crop rotation. S2. On the topsoil layer obtained in S1, dig multiple trenches; S3. Crush the straw to obtain crushed straw material, and lay the crushed straw material in the trench obtained in S2 in stages; after each laying of the crushed straw material, apply the microbial preparation and compact it to obtain a trench structure with a straw layer containing the mixed microbial preparation. S4. Apply chemical fertilizer containing nitrogen and phosphorus fertilizer to the trench structure obtained in S3 to obtain a fertilizer-straw composite layer. S5. Cover the fertilizer-straw composite layer obtained in S4 with soil to form a cover soil layer; S6. Ridging is carried out on the soil layer obtained in S5 to form a ridge structure, and the ridge structure is irrigated at the same time. S7. During the crop growth period, apply topdressing fertilizer to the crops growing on the ridge structure obtained in S6.

[0006] By adopting the above technical solution, this method first breaks up soil compaction through crop rotation pretreatment and initially improves the structure of the tillage layer by utilizing the different nutrient absorption of different root crops. Subsequently, trenches are excavated and a deep improvement layer composed of crushed straw, microbial agents, and chemical fertilizers is constructed within them. This composite layer forms a stable biochemical reaction zone after being covered with soil. In this process, straw decomposition consumes oxygen and releases organic acids, while microbial agents accelerate this process and produce metabolites. The synergistic effect of the two can effectively reduce the local redox potential and promote the transformation and migration of insoluble salts in the soil. The covering soil layer and subsequent ridging and irrigation operations provide a suitable environment for water and salt movement, guiding salts to accumulate at the bottom of the furrows between the rows, thereby forming a relatively low-salt, fertile growth microzone in the main distribution area of ​​the crop roots. The topdressing step provides necessary nutrient supplementation for the middle and late stages of crop growth, ensuring that the improvement effect and crop yield are synergistically improved.

[0007] Preferably, in step S2, the trench is 28-32cm deep and 28-32cm wide.

[0008] By adopting the above technical solution, the depth setting precisely places the amendment material in the soil subsoil or above the subsoil layer, which is an obstacle zone where salt easily accumulates and roots extend downwards. This depth ensures that the amendment material affects the salinized subsurface layer while avoiding excessive engineering work and excessive disturbance of the topsoil caused by excessive excavation. The width setting provides sufficient space for filling with enough straw and fertilizer, ensuring the effective volume of the amendment zone. This is conducive to forming a continuous and stable physical isolation and biochemical amendment layer, laying the foundation for subsequent decomposition, salt reduction, and nutrient slow release processes.

[0009] Preferably, in step S3, the particle size of the crushed straw material is 4-6 cm, and the total amount of crushed straw material used is 45-60 t / hm².

[0010] By adopting the above technical solution, straw is crushed to a particle size of 4-6 cm, which enables it to form a filling layer with a suitable pore structure in the trench. This particle size range avoids poor air permeability and excessive anaerobic environment caused by excessively fine material, and also prevents incomplete filling and rapid loss of water and nutrients caused by excessively coarse material. It is conducive to maintaining the appropriate aeration conditions required by decomposing microorganisms. With the total amount of material used, sufficient organic carbon source can be introduced into the soil per unit area. During the decomposition process, this amount of organic material can consume a large number of free salt ions in the soil as accompanying ions for microbial metabolism, and reduce the salt concentration and alkalinity of the soil solution by complexing and passivating salts through the production of organic acids such as humic acid, while continuously improving the soil's aggregate structure and water and fertilizer retention capacity.

[0011] Preferably, in step S3, the microbial preparation is premixed with the topsoil or organic carrier before application.

[0012] By adopting the above-mentioned technical solution, the microbial agent is premixed with the topsoil or organic carrier before application. The main purpose is to improve the inoculation efficiency and activity of the microbial agent. This operation allows the functional microbial community to come into full and uniform contact with the carrier material, avoiding uneven distribution caused by wind dispersion or water clumping during application. Using the topsoil or organic carrier as a dilution medium can provide a temporary protective environment and initial nutrients for the microorganisms, buffering the environmental stress they may face when entering the straw layer, and helping to maintain and prolong the activity of the microorganisms in the microbial agent. The premixed microbial agent is evenly applied to the straw layer, which can more quickly colonize and initiate the decomposition process of the straw, thereby accelerating the biochemical activation of the entire improved layer and ensuring the timely and efficient salt passivation and nutrient release process.

[0013] Preferably, in step S4, the chemical fertilizer comprises diammonium phosphate and urea, wherein the application rate of diammonium phosphate is 33-37 kg / mu and the application rate of urea is 8-12 kg / mu.

[0014] By employing the above-mentioned technical solution, applying diammonium phosphate and urea to the straw layer in the trench aims to provide initial nutrients for the subsequent large-scale straw decomposition process driven by microorganisms. Diammonium phosphate, as a nitrogen-phosphorus compound fertilizer, contains ammonium nitrogen and available phosphorus, elements required for microbial reproduction and metabolism. Sufficient application of diammonium phosphate provides phosphorus to activate and maintain the activity of the microbial community, while also supplying some nitrogen. Urea, as a high-concentration nitrogen fertilizer supplement, is used to balance the high carbon-to-nitrogen ratio of the straw material, preventing microorganisms from competing for available nitrogen in the soil due to nitrogen shortage in the early stages of decomposition, thus avoiding nitrogen starvation in crops. This fertilizer combination and dosage provide nutritional conditions for rapid straw decomposition and, through microbial assimilation, convert inorganic nitrogen and phosphorus into organic forms, achieving initial nutrient fixation and slow release.

[0015] Preferably, in step S5, the thickness of the covering soil layer is 18-22 cm.

[0016] By adopting the above technical solution, controlling the thickness of the cover soil layer is to construct a functional isolation and buffer zone above the improved layer in the trench. This thickness is sufficient to physically isolate the straw fertilizer composite layer from the surface soil cultivation environment, preventing disturbance to the improved layer by subsequent cultivation or irrigation, and providing sufficient soil space for crop roots to grow downwards and penetrate the cover soil layer. At the same time, this cover soil thickness provides a suitable temperature and humidity gradient, which is conducive to the slow release of organic nutrients and active substances produced by decomposition from the lower improved layer upwards. In addition, the cover soil layer also plays a certain role in heat preservation and moisture retention for the fermentation process of microorganisms below, allowing it to take place in a relatively stable environment, and gradually spreading the improvement effect upwards to the main root zone of the crop.

[0017] Preferably, in step S6, the ridge width of the ridge structure is 30-50cm, the ridge height is 10-20cm, and the distance between adjacent ridges is 80-100cm.

[0018] By adopting the above technical solutions, the ridge width design ensures that the ridge body has a sufficient cross-sectional area to accommodate the crop root system and provides stable support for the improved layer under the cover soil. The ridge height limitation can effectively raise the relative position of the crop root zone. Combined with the control of the ridge spacing, it forms a spatial differentiation between the ridge platform and the furrow in the field. This structure changes the water and salt transport path on the surface. When irrigated or rained, water carrying salt mainly converges in the furrow. Due to the weakening of capillary action, salt accumulates on the sides of the ridge body and at the bottom of the furrow. The top area of ​​the ridge platform, i.e. the crop planting zone, can maintain a relatively low salt concentration, providing a local low-salt safety zone for crop seed germination and seedling growth.

[0019] Preferably, in step S6, the soil moisture content of the irrigation treatment is maintained at 70% to 80% of field capacity.

[0020] By adopting the above technical solution, this moisture content range ensures the full dissolution of salts, allowing soluble salts in the soil solution to move towards the pre-set furrows with the water. Secondly, this humidity condition is conducive to the straw decomposition process in the furrows, providing a moisture environment for decomposing microorganisms. It avoids decomposition stagnation caused by insufficient water and prevents severe anaerobic digestion and accumulation of harmful substances caused by water saturation. At the same time, this humidity range is also suitable for the growth and absorption activities of crop roots, achieving a balance between promoting desalination, ensuring biological decomposition, and meeting the crop's water requirements, so that the improvement process and the crop growth process proceed in synergy.

[0021] Preferably, in step S7, the topdressing treatment is carried out 1 to 2 times, and the fertilizer applied each time includes diammonium phosphate and potassium sulfate.

[0022] By adopting the above technical solution, one to two topdressings are applied during the crop's growth period to supplement the nutrient requirements of the crop in the middle and later stages of growth, achieving full-process nutrient management. Since this method applies a large amount of phosphorus and some nitrogen as starter fertilizer deep into the straw layer in the early stage, its main function is to promote decomposition and provide basic fertilizer. However, the crop has a greater demand for nutrients during the vigorous growth period. At this time, by applying diammonium phosphate, which contains both nitrogen and phosphorus, and potassium sulfate, which provides potassium, the crop's continuous demand for macronutrients can be met. As a physiologically acidic fertilizer, potassium sulfate provides potassium nutrition, and its by-product sulfate ions help to replace exchangeable sodium on soil colloids, further assisting in soil desalination. The multiple topdressings also conform to the crop's nutrient requirements and improve fertilizer utilization.

[0023] Preferably, the application rate of diammonium phosphate is 18-22 kg / mu per application, and the application rate of potassium sulfate is 8-12 kg / mu per application.

[0024] By adopting the above technical solution, the amount of diammonium phosphate and potassium sulfate used in each topdressing is controlled. Diammonium phosphate can supplement nitrogen while continuing to supply phosphorus to prevent nutrient deficiency in the later stage, and promote crop flowering, fruiting and yield formation. Potassium sulfate can meet the crop's demand for potassium, enhance crop resistance and improve product quality. This ratio and amount avoids premature aging and yield reduction caused by insufficient topdressing, and also prevents salt reaccumulation and nutrient loss caused by excessive topdressing, ensuring stable crop yield and economic benefits while improving the soil.

[0025] In summary, this application has the following beneficial effects: 1. This application improves soil structure by rotating different root crops in the topsoil layer, and then excavates trenches to construct a straw-microbial agent-fertilizer composite improvement layer. The loose topsoil layer produced by crop rotation provides a working basis for subsequent trench excavation. The straw buried deep in the topsoil decomposes in a directional manner under the action of microbial agents to produce organic acid substances. Together with the chemical fertilizers added at the same time, it reduces the local soil pH value and promotes the conversion of insoluble salts. At the same time, the ridging and irrigation operation utilizes the water-salt movement law to guide the dissolved salts to the furrows, so that a low-salt micro-zone is formed in the crop root zone. Therefore, it achieves the effect of improving the physical and chemical properties of the soil and realizing the spatial redistribution of salts.

[0026] 2. In this application, a trench structure is preferably used in conjunction with straw. The depth and width of the trench are controlled to ensure that the improved layer can reach the plow pan where salt accumulates, while providing filling space for crushed straw. The straw material within this particle size range can maintain a suitable pore structure to ensure aerobic fermentation by microorganisms, while avoiding excessive crushing that affects air permeability. With a certain amount, sufficient carbon source supply is formed, allowing the microbial agent to quickly colonize and start the decomposition process under the protection of the premixed carrier. Therefore, a continuous and stable biological improvement zone construction effect is obtained, providing a long-term basis for salt passivation and slow release of nutrients.

[0027] 3. The method of this application combines ridging operations with water and fertilizer management. By using furrows to provide space for water and salt diversion, and with irrigation standards of 70%-80% field water holding capacity to maintain the microbial activity environment, and by applying diammonium phosphate and potassium sulfate during the crop growth period, the ridge structure blocks the rise of salt. The potassium sulfate in the top dressing not only supplements potassium nutrition, but also replaces the exchangeable sodium in the soil through sulfate ions. Therefore, the crop growth needs and the soil desalination process are promoted in a coordinated manner during the improvement process, so as to achieve the effect of improving saline soil and producing high-yield and high-quality crops. Attached Figure Description

[0028] Figure 1 This is a flowchart illustrating the method for deep restoration and crop rotation to improve severely salinized soils in facility agricultural land, as proposed in this application. Detailed Implementation

[0029] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0030] Technical concept: Severely saline soils can be improved through measures such as water leaching, surface application of soil conditioners, or planting salt-tolerant plants. However, these measures often only reduce salt content in the short term and lack the ability to repair the deep soil structure. Furthermore, the improved layer is shallow and easily affected by evaporation, causing salt to quickly return to the surface. This results in an unstable salinity environment in the crop root zone and makes it difficult to sustain the improvement effect.

[0031] This application discloses a method for deep restoration and crop rotation to improve severely salinized soil in facility agricultural land. The method includes the following steps: S1, on the facility agricultural land to be improved, crop rotation is performed between deep-rooted and shallow-rooted crops to obtain a pre-treated soil tillage layer; S2, multiple trenches are dug in the soil tillage layer; S3, straw is shredded and the shredded straw material is laid in the trenches; simultaneously, a microbial agent is applied to obtain the trench structure; S4, chemical fertilizer is applied to the trench structure; S5, soil is covered on the fertilizer-straw composite layer to form a cover soil layer; S6, ridges are formed to create a ridge structure, and irrigation is performed; S7, topdressing is applied to the crops growing on the ridge structure.

[0032] This application improves soil structure by rotating different root crops in the topsoil layer, and then excavates trenches to construct a straw-microbial agent-fertilizer composite improvement layer. The loose topsoil layer produced by crop rotation provides a working foundation for subsequent trench excavation, while the deeply buried straw decomposes in a directed manner under the action of microbial agents to produce organic acids. These, together with the added chemical fertilizers, reduce the local soil pH and promote the conversion of insoluble salts. At the same time, the ridging and irrigation operation utilizes the water-salt movement law to guide dissolved salts to the furrows, resulting in the formation of low-salt micro-zones in the crop root zone. Therefore, it achieves the effect of both improving soil physicochemical properties and realizing the spatial redistribution of salts.

[0033] Example 1: This example provides a method for deep restoration and crop rotation to improve severely salinized soil in facility agriculture, comprising the following steps: S1. On the facility agricultural land to be improved, rotate deep-rooted crops with shallow-rooted crops, or rotate vegetable crops with grain crops, to obtain a soil tillage layer that has been pretreated by crop rotation.

[0034] S2. On the topsoil layer obtained in S1, dig multiple trenches.

[0035] The trench is 28cm deep and 28cm wide.

[0036] S3. Crush the straw to obtain crushed straw material, and lay the crushed straw material in the trench obtained in S2 in stages; after each laying of the crushed straw material, apply the microbial agent and compact it to obtain a trench structure with a straw layer containing the mixed microbial agent.

[0037] The particle size of the crushed straw material is 4 cm, and the total amount of crushed straw material used is 45 t / hm²; the microbial preparation is premixed with the topsoil or organic carrier before application.

[0038] S4. Apply chemical fertilizer containing nitrogen and phosphorus fertilizer to the trench structure obtained in S3 to obtain a fertilizer-straw composite layer.

[0039] The chemical fertilizer includes diammonium phosphate and urea, with the application rate of diammonium phosphate being 33 kg / mu and the application rate of urea being 8 kg / mu.

[0040] S5. Cover the fertilizer-straw composite layer obtained in S4 with soil to form a cover soil layer.

[0041] The thickness of the covering soil layer is 18cm.

[0042] S6. Ridging is carried out on the soil layer obtained in S5 to form a ridge structure, and the ridge structure is irrigated at the same time.

[0043] The ridge structure has a ridge width of 30cm, a ridge height of 10cm, and a spacing of 80cm between adjacent ridges; the soil moisture content of the irrigation treatment is maintained at 70% of field capacity.

[0044] S7. During the crop growth period, apply topdressing fertilizer to the crops growing on the ridge structure obtained in S6.

[0045] The topdressing treatment is carried out in one application, and the fertilizers applied each time include diammonium phosphate and potassium sulfate. The application rate of diammonium phosphate is 18 kg / mu each time, and the application rate of potassium sulfate is 8 kg / mu each time.

[0046] Example 2: This example provides a method for deep restoration and crop rotation to improve severely salinized soil in facility agriculture, comprising the following steps: S1. On the facility agricultural land to be improved, rotate deep-rooted crops with shallow-rooted crops, or rotate vegetable crops with grain crops, to obtain a soil tillage layer that has been pretreated by crop rotation.

[0047] S2. On the topsoil layer obtained in S1, dig multiple trenches.

[0048] The trench is 30cm deep and 30cm wide.

[0049] S3. Crush the straw to obtain crushed straw material, and lay the crushed straw material in the trench obtained in S2 in stages; after each laying of the crushed straw material, apply the microbial agent and compact it to obtain a trench structure with a straw layer containing the mixed microbial agent.

[0050] The particle size of the crushed straw material is 5 cm, and the total amount of crushed straw material used is 52.5 t / hm². The microbial preparation is premixed with the topsoil or organic carrier before application.

[0051] S4. Apply chemical fertilizer containing nitrogen and phosphorus fertilizer to the trench structure obtained in S3 to obtain a fertilizer-straw composite layer.

[0052] The chemical fertilizer includes diammonium phosphate and urea, with the application rate of diammonium phosphate being 35 kg / mu and the application rate of urea being 10 kg / mu.

[0053] S5. Cover the fertilizer-straw composite layer obtained in S4 with soil to form a cover soil layer.

[0054] The thickness of the covering soil layer is 20cm.

[0055] S6. Ridging is carried out on the soil layer obtained in S5 to form a ridge structure, and the ridge structure is irrigated at the same time.

[0056] The ridge structure has a ridge width of 40cm, a ridge height of 15cm, and a spacing of 90cm between adjacent ridges; the soil moisture content of the irrigation treatment is maintained at 75% of field capacity.

[0057] S7. During the crop growth period, apply topdressing fertilizer to the crops growing on the ridge structure obtained in S6.

[0058] The topdressing treatment is carried out in two applications, each application of which includes diammonium phosphate and potassium sulfate. The application rate of diammonium phosphate is 20 kg / mu, and the application rate of potassium sulfate is 10 kg / mu.

[0059] Example 3: This example provides a method for deep restoration and crop rotation to improve severely salinized soil in facility agriculture, comprising the following steps: S1. On the facility agricultural land to be improved, rotate deep-rooted crops with shallow-rooted crops, or rotate vegetable crops with grain crops, to obtain a soil tillage layer that has been pretreated by crop rotation.

[0060] S2. On the topsoil layer obtained in S1, dig multiple trenches.

[0061] The trench is 32cm deep and 32cm wide.

[0062] S3. Crush the straw to obtain crushed straw material, and lay the crushed straw material in the trench obtained in S2 in stages; after each laying of the crushed straw material, apply the microbial agent and compact it to obtain a trench structure with a straw layer containing the mixed microbial agent.

[0063] The particle size of the crushed straw material is 6 cm, and the total amount of the crushed straw material is 60 t / hm². The microbial preparation is premixed with the topsoil or organic carrier before application.

[0064] S4. Apply chemical fertilizer containing nitrogen and phosphorus fertilizer to the trench structure obtained in S3 to obtain a fertilizer-straw composite layer.

[0065] The chemical fertilizer includes diammonium phosphate and urea, with the application rate of diammonium phosphate being 37 kg / mu and the application rate of urea being 12 kg / mu.

[0066] S5. Cover the fertilizer-straw composite layer obtained in S4 with soil to form a cover soil layer.

[0067] The thickness of the covering soil layer is 22cm.

[0068] S6. Ridging is carried out on the soil layer obtained in S5 to form a ridge structure, and the ridge structure is irrigated at the same time.

[0069] The ridge structure has a ridge width of 50cm, a ridge height of 20cm, and a spacing of 100cm between adjacent ridges; the soil moisture content of the irrigation treatment is maintained at 80% of field capacity.

[0070] S7. During the crop growth period, apply topdressing fertilizer to the crops growing on the ridge structure obtained in S6.

[0071] The topdressing treatment is carried out in two applications, each time with diammonium phosphate and potassium sulfate. The amount of diammonium phosphate applied each time is 22 kg / mu, and the amount of potassium sulfate applied each time is 12 kg / mu.

[0072] Comparative Example 1: This comparative example refers to the content of Example 1, except that the trench excavated in step S2 is 20cm deep and 20cm wide, and the rest is the same as Example 1.

[0073] Comparative Example 2: This comparative example refers to the content of Example 1, except that the particle size of the crushed straw material in step S3 is 2cm, and the total amount of crushed straw material used is 30t / hm². The rest of the content is the same as that of Example 1.

[0074] Comparative Example 3: This comparative example refers to the content of Example 1, except that the chemical fertilizer mentioned in step S4 includes diammonium phosphate and urea, wherein the application rate of diammonium phosphate is 25 kg / mu and the application rate of urea is 5 kg / mu, and the rest of the content is the same as that of Example 1.

[0075] Comparative Example 4: This comparative example refers to the content of Example 1, except that the thickness of the soil covering layer in step S5 is 12cm, and the rest is the same as Example 1.

[0076] Comparative Example 5: This comparative example refers to the content of Example 1, except that the ridge width of the ridge structure in step S6 is 20cm, the ridge height is 5cm, and the distance between adjacent ridges is 60cm. The rest of the content is the same as that in Example 1.

[0077] Comparative Example 6: This comparative example refers to the content of Example 1, except that the soil moisture content of the irrigation treatment in step S6 is maintained at 50% of the field capacity, and the rest is the same as Example 1.

[0078] Performance testing Sample preparation: This experiment selected representative severely salinized soil from facility-farmed agricultural land as experimental plots. Soil improvement treatments were carried out according to the methods described in Examples 1-3 and Comparative Examples 1-6, and a blank control was set up with a plot of original salinized soil without any improvement treatment. Three replicate plots were set up for each treatment. After completing a full crop growth cycle, at the crop harvest period, soil samples from the 0-20 cm topsoil layer of each plot were collected using a soil auger. The soil samples from multiple points in the same replicate plot were mixed evenly, air-dried, and sieved for use in the determination of various physicochemical indicators. At the same time, the final yield of crops in each plot was recorded.

[0079] Soil soluble salt total and electrical conductivity detection: This test aims to quantify the effect of soil amendment methods on leaching and removal of soil salts; a certain mass of air-dried soil sample was weighed and added to carbon dioxide-free distilled water at a water-to-soil mass ratio of 5:1. The sample was placed on a shaker and shaken at a frequency of 180 times per minute for five minutes, followed by standing for 30 minutes of extraction; the extract was filtered with slow quantitative filter paper and the clear filtrate was collected; the electrical conductivity of the filtrate was measured using a calibrated electrical conductivity meter, and the total soluble salt content of the soil extract was determined; Test standard: NY / T1121.16-2006 Soil Testing Part 16: Determination of Total Soil Water-Soluble Salts.

[0080] Soil sodium adsorption ratio and exchangeable sodium percentage detection: Using the above-mentioned soil salt extract, the concentrations of calcium, magnesium, and sodium ions in the extract were determined using an atomic absorption spectrophotometer; the sodium adsorption ratio was obtained based on the measured ion concentration values; simultaneously, the soil cation exchange capacity was determined using the ammonium acetate exchange method, and combined with the sodium ion content of the extract, the exchangeable sodium percentage of the soil was further determined; Test standards: NY / T1121.18-2006 Soil Testing Part 18: Determination of Soil Sulfate Ion Content; LY / T1245-1999 Determination of Exchangeable Calcium and Magnesium in Forest Soils.

[0081] Soil organic matter content detection: The potassium dichromate dilution thermal method is used. A small amount of prepared soil sample is weighed, and a certain concentration of potassium dichromate standard solution and concentrated sulfuric acid are added. The mixture is heated to boiling in an oil bath, so that the soil organic carbon is oxidized by potassium dichromate under strong acid conditions. After cooling, the remaining potassium dichromate is titrated with ferrous sulfate standard solution using o-phenanthroline as an indicator. The soil organic matter content is obtained by measuring the amount of ferrous sulfate consumed. Test standard: NY / T1121.6-2006 Soil Testing Part 6: Determination of Soil Organic Matter.

[0082] Crop biological yield and economic yield detection: At the crop maturity stage, all plants in each plot are harvested and their total fresh weight is measured as biological yield; after threshing, the grains or fruits are dried to constant weight and weighed and recorded as economic yield; at the same time, some morphological indicators of the crop root system can be measured; crop yield reflects the degree of favorable environment created for crop growth by soil improvement methods.

[0083] Table 1: Comparison Table of Soil Physicochemical Properties

[0084] Table 2: Crop Yield Comparison Table

[0085] Example Conclusion: Based on Examples 1-3 and Comparative Example 1, and referring to Table 1, it can be seen that the depth and width of the trench are factors affecting the effectiveness of salt leaching and deep straw burial. A larger trench volume creates space for sufficient straw burial, forming a deep salt barrier and nutrient slow-release zone, while also facilitating vertical infiltration of irrigation water, pushing surface salts deeper. In contrast, a smaller trench volume has limited capacity, resulting in insufficient straw burial and a thinner barrier zone. This weakens the ability to block upward salt movement and regulate vertical water and salt transport, leading to reduced soil desalination efficiency and increased risk of salt accumulation on the surface. Therefore, optimizing trench dimensions is fundamental to achieving deep and long-term soil improvement.

[0086] Based on Examples 1-3 and Comparative Example 2, and in conjunction with Table 1, it can be seen that the physical specifications and total amount of straw material affect the stability of the soil amendment layer structure and the sustainability of organic matter enhancement. Appropriate straw particle size and a larger application rate can form a loose, porous, and well-aerated stable framework within the trench, both slowing down decomposition to provide a long-term source of organic matter and continuously improving soil physical structure. Conversely, excessively small particle size and insufficient application rate result in overly compacted material that decomposes too quickly, failing to form a durable physical amendment layer and weakening its long-term effects on soil structure improvement and salinity regulation. This indicates that sufficient straw with suitable physical morphology is essential for constructing a durable and efficient biological amendment layer.

[0087] Based on Examples 1-3 and Comparative Example 3, and in conjunction with Table 1, it can be seen that the nitrogen and phosphorus chemical fertilizers applied during deep straw return not only supplement crop nutrients but also act as initiators for regulating the carbon-nitrogen ratio and stimulating microbial activity during straw decomposition. Appropriate fertilizer provides balanced nutrition for microbial straw decomposition, accelerating straw humification and reducing the concentration of free base ions in the soil through microbial fixation. Conversely, lower fertilizer application leads to an imbalance in the carbon-nitrogen ratio, restricting microbial activity and slowing straw decomposition. This results in low organic matter conversion efficiency and weakens the synergistic removal of salts through biological processes. Therefore, combining appropriate amounts of chemical fertilizers with deep straw return can produce a synergistic benefit in promoting organic matter conversion and assisting in salt regulation.

[0088] Based on Examples 1-3 and Comparative Example 4, and in conjunction with Table 1, it can be seen that the thickness of the cover soil layer affects the stability of the straw decomposition environment and the redistribution of salts in the soil profile. A sufficient cover soil thickness provides a stable environment of humidity, temperature, and alternating anaerobic and aerobic conditions for the underlying straw layer, which is conducive to its steady decomposition. At the same time, a sufficiently thick soil layer can block the harmful substances produced in the early stages of straw decomposition from affecting the root system of surface crops and stably control salt levels below the plow pan. Conversely, an excessively thin cover soil layer places the straw layer too close to the surface, making it susceptible to drastic fluctuations in surface temperature and humidity, resulting in unstable decomposition. Furthermore, it causes salts to more easily return to the root zone with the evaporation of water, weakening the salt-suppressing effect of deep burial. This indicates that an appropriate cover soil thickness is a crucial barrier to ensure the stable effectiveness of biological improvement measures and prevent salt rebound.

[0089] Based on Examples 1-3 and Comparative Example 5, and in conjunction with Table 1, it can be seen that the size of the ridge structure is an agronomic measure to optimize the spatial distribution of water and salt in the root zone and create a suitable microenvironment for crop growth. Larger ridges expand the concentrated growth space of crop roots and relatively concentrate salt in the inter-ridge furrow area, achieving desalination in the root zone. At the same time, larger structures are conducive to the uniform infiltration of irrigation water and the lateral leaching of salt. In Comparative Example 5, smaller ridges restrict the space for root expansion, resulting in poor redistribution of water and salt in a narrow space, failing to effectively form a low-salt root zone microenvironment, and crop growth is still subject to salt stress. Therefore, reasonable ridge specifications are a means to connect deep soil improvement with surface crop growth and transform soil improvement benefits into crop production benefits.

[0090] Based on Examples 1-3 and Comparative Example 6, and in conjunction with Table 1, it can be seen that sufficient irrigation ensures the moisture of the straw layer in the furrows to promote microbial activity and simultaneously forms a stable water infiltration flow, driving salts to migrate from the crop root zone to deeper layers or between rows. Higher soil moisture content maintains the continuity of this salt leaching process. However, lower soil moisture content cannot form an effective water gradient, and water movement is mainly through evaporation, causing salts to accumulate on the surface with capillary water. This not only fails to leach salts but also exacerbates topsoil salinization, preventing the effects of improvement measures such as deep burial of straw from being realized through water and salt transport.

[0091] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for improving severely salinized soil in facility-based agricultural land through crop rotation and deep restoration, characterized in that, Includes the following steps: S1. On the facility agricultural land to be improved, rotate deep-rooted crops with shallow-rooted crops, or rotate vegetable crops with grain crops, to obtain a soil tillage layer that has been pretreated by crop rotation. S2. On the topsoil layer obtained in S1, dig multiple trenches; S3. Crush the straw to obtain crushed straw material, and lay the crushed straw material in the trench obtained in S2 in stages; after each laying of the crushed straw material, apply the microbial preparation and compact it to obtain a trench structure with a straw layer containing the mixed microbial preparation. S4. Apply chemical fertilizer containing nitrogen and phosphorus fertilizer to the trench structure obtained in S3 to obtain a fertilizer-straw composite layer. S5. Cover the fertilizer-straw composite layer obtained in S4 with soil to form a cover soil layer; S6. Ridging is carried out on the soil layer obtained in S5 to form a ridge structure, and the ridge structure is irrigated at the same time. S7. During the crop growth period, apply topdressing fertilizer to the crops growing on the ridge structure obtained in S6.

2. The method for deep restoration and crop rotation improvement of severely salinized soil in facility-based agricultural land according to claim 1, characterized in that, In step S2, the trench is 28-32cm deep and 28-32cm wide.

3. The method for deep restoration and crop rotation improvement of severely salinized soil in facility-based agricultural land according to claim 1, characterized in that, In step S3, the particle size of the crushed straw material is 4-6 cm, and the total amount of crushed straw material used is 45-60 t / hm².

4. The method for deep restoration and crop rotation improvement of severely salinized soil in facility-based agricultural land according to claim 1, characterized in that, In step S3, the microbial preparation is premixed with the topsoil or organic carrier before application.

5. The method for deep restoration and crop rotation improvement of severely salinized soil in facility-based agricultural land according to claim 1, characterized in that, In step S4, the chemical fertilizer comprises diammonium phosphate and urea, wherein the application rate of diammonium phosphate is 33-37 kg / mu and the application rate of urea is 8-12 kg / mu.

6. The method for deep restoration and crop rotation improvement of severely salinized soil in facility-based agricultural land according to claim 1, characterized in that, In step S5, the thickness of the covering soil layer is 18-22 cm.

7. The method for deep restoration and crop rotation improvement of severely salinized soil in facility-based agricultural land according to claim 1, characterized in that, In step S6, the ridge width of the ridge structure is 30-50cm, the ridge height is 10-20cm, and the distance between adjacent ridges is 80-100cm.

8. The method for deep restoration and crop rotation improvement of severely salinized soil in facility-based agricultural land according to claim 1, characterized in that, In step S6, the soil moisture content of the irrigation treatment is maintained at 70% to 80% of field capacity.

9. The method for deep restoration and crop rotation improvement of severely salinized soil in facility-based agricultural land according to claim 8, characterized in that, In step S7, the topdressing treatment is carried out 1 to 2 times, and the fertilizer applied each time includes diammonium phosphate and potassium sulfate.

10. The method for deep restoration and crop rotation improvement of severely salinized soil in facility-based agricultural land according to claim 1, characterized in that, The application rate of diammonium phosphate is 18-22 kg / mu per application, and the application rate of potassium sulfate is 8-12 kg / mu per application.

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