A fertilization method for rapidly reducing the salinity of polder coastal sandy soil

Abstract

The application discloses a fertilization method for quickly reducing the salinity of reclamation coastal sandy soil. The method comprises the following steps: S1, performing structure treatment on the reclamation coastal sandy soil to improve the physical permeability, and excavating a planting ditch; S2, embedding a water infiltration pipeline in the planting ditch; S3, applying granular biological organic fertilizer to the reclamation coastal sandy soil twice before and after the plant planting construction; and S4, planting plants in the planting ditch, providing nutrients by the granular biological organic fertilizer, exchanging the nutrient ions in the fertilizer with the soil base ions, and combining irrigation or natural precipitation to perform leaching, so that the salt-containing water is collected into the water infiltration pipeline and discharged. The method solves the problems of easy salt return, difficult fertilizer preservation and low survival rate of shallow-rooted plants of the sandy soil by ion exchange and directional drainage, and realizes quick desalination and long-acting fertilization.

Description

Technical Field

[0001] This invention relates to the field of soil improvement technology, and more specifically, to a fertilization method for rapidly reducing the salinity of reclaimed coastal sandy soils. Background Technology

[0002] my country's coastal areas possess abundant reclaimed tidal flat resources, providing an important means to alleviate arable land shortages and expand agricultural development space. However, the coastal sandy soils formed by reclamation generally suffer from high salinity, lack of organic matter, loose soil structure, and poor water and fertilizer retention capacity. In particular, sandy soils have well-developed capillary pores, resulting in rapid water transport and making them highly susceptible to salt accumulation under intense evaporation. This leads to severe salt return in spring, making conventional improvement measures ineffective and easily causing secondary salinization.

[0003] Currently, the main improvement technologies for coastal saline-alkali land include physical improvement, hydraulic improvement, and chemical improvement. Physical improvement typically involves soil replacement or high-volume water pressure to remove salt, which is labor-intensive, costly, and consumes a great deal of freshwater. Hydraulic improvement mainly relies on open ditches or wells for drainage, but for sandy soils with high permeability, traditional flooding for salt leaching often results in incomplete leaching and severe deep seepage, with salt easily seeping down to the root zone and then rising back up with capillary water. Chemical improvement often uses chemical amendments such as gypsum and desulfurized gypsum to replace sodium ions in soil colloids, but chemical improvement alone often neglects the restoration of soil biological activity, and the amendments have poor fixation in sandy soils, making them easily leached away, resulting in short-lived improvement effects.

[0004] In terms of fertilization techniques, existing methods for fertilizing saline-alkali land mostly involve single-application as basal fertilizer or simple topdressing. However, in coastal sandy soil environments, this extensive fertilization approach has significant drawbacks: firstly, ordinary chemical fertilizers are easily washed away by water during leaching, resulting in low utilization rates and potential groundwater pollution; secondly, it lacks targeted nutrient molecules (such as Ca). 2+ NH4 + (etc.) and harmful basic ions in the soil (Na+, etc.) + Cl - The design of the exchange mechanism is flawed; thirdly, the timing of fertilization does not match the salt return pattern under the coastal climate. For example, organic matter and beneficial bacteria are not replenished in time before the arrival of the hot and rainy season in summer, which causes plants to suffer from salt stress during the critical growth period.

[0005] Furthermore, existing technologies rarely address the specific nutrient requirements of landscaping plants (such as garden trees and ground cover plants like Liriope muscari) on coastal sandy soils. For instance, shallow-rooted ground cover plants like Liriope muscari are extremely sensitive to surface soil salinity, while conventional improvement measures often focus on deeper soil layers, neglecting the rapid desalination and fertilization of the shallow topsoil.

[0006] Therefore, developing a fertilization method that integrates physical structure improvement, precise water and salt regulation, phased application of biological organic fertilizer at specific times, and efficient drainage, tailored to the characteristics of reclaimed coastal sandy soil, to achieve rapid salt leaching, effective nutrient retention, and healthy plant growth, is a technical problem that urgently needs to be solved in the field of saline-alkali land ecological management. Summary of the Invention

[0007] To overcome the shortcomings of the existing technologies, this invention provides a fertilization method for rapidly reducing the salinity of sandy soils in reclaimed coastal areas. It aims to simultaneously address the industry pain points in the improvement of existing sandy saline-alkali lands, such as low leaching efficiency, poor water-fertilizer coupling, salt return and death of shallow-rooted plants, and easy nutrient loss with water. This method meets the practical needs of rapid desalination, long-term fertilization, and high seedling survival rate in the process of landscaping and ecological vegetation construction in reclaimed areas.

[0008] The first aspect of this invention provides a fertilization method for rapidly reducing the salinity of sandy soils in reclaimed coastal areas, comprising the following steps: S1. Structural treatment of the reclaimed coastal sandy soil to improve physical permeability and excavation of planting trenches; S2. Install a seepage pipe in the planting trench; S3. Apply granular bio-organic fertilizer to the reclaimed coastal sandy soil twice, before and after planting. S4. Plants are planted in the planting trench, and nutrients are provided by the granular bio-organic fertilizer, which allows nutrient ions in the fertilizer to exchange with soil base ions. Combined with irrigation or natural rainfall, the salt water is collected and discharged into the seepage pipe.

[0009] Compared with existing technologies, this invention breaks through the technical barriers of "poor salt suppression effect of irrigation and easy nutrient leakage" in traditional coastal sandy soil improvement by constructing a full-process collaborative system of "physical soil improvement - underground pipe salt removal - phased nutrient supply - plant utilization". This method utilizes the exchangeable cations in fertilizers to undergo a displacement reaction with sodium salts adsorbed by soil colloids, promoting the removal of salts from the root zone. Combined with underground pipe technology, it directionally extracts salt-rich water, achieving rapid soil desalination while simultaneously completing long-term fertilization and structural improvement of the plant rhizosphere microenvironment. This fundamentally solves the contradiction between the weak water and fertilizer retention capacity and the easy return of salts in reclaimed sandy soil.

[0010] In one possible implementation, step S1 specifically includes: using mechanical tillage to make the soil particle structure uniform and removing stones from the soil.

[0011] Compared with existing technologies, this invention, through deep mechanical structural treatment of reclaimed land, not only effectively removes stone obstacles that affect pipeline laying and root growth, but more importantly, reshapes the aggregate structure and pore distribution of sandy soil. This pretreatment significantly reduces soil bulk density, eliminates vertical infiltration obstruction caused by soil compaction, and greatly improves the uniformity and permeability of leachate migration downwards, providing a loose, homogeneous, and stable growth substrate for subsequent rapid desalination and deep root development.

[0012] In one possible implementation, in step S2, the seepage pipe is buried at a depth of 15cm in the planting trench and the seepage pipe is arranged in a grid pattern. The drainage pipe is a mesh PVC pipe or a bamboo fiber spiral pipe, and the diameter of the drainage pipe is 2-3cm.

[0013] Compared with existing technologies, this invention buries highly permeable specialized drainage pipes at a specific depth in the planting ditch, constructing an efficient underground salt interception and discharge channel. This design cleverly utilizes gravitational potential difference to promptly remove the high-concentration saline solution collected at the bottom of the root zone after leaching, effectively blocking the path of salt back to the surface in sandy soil caused by capillary action. This powerfully suppresses salt return during the dry season, ensuring the long-term survival of plant roots.

[0014] In one possible implementation, the specific steps of applying granular bio-organic fertilizer to the reclaimed coastal sandy soil in two stages in step S3 are as follows: First application of fertilizer: Apply as base fertilizer before planting construction, using trench application method, with a trench depth of 0-20cm, and the fertilization time is from March to April; The second fertilization should be carried out within 3 days after 1 month of planting, using the method of spreading the fertilizer in strip trenches. The fertilization time is from July to August.

[0015] Compared with existing technologies, this invention creatively adopts a phased fertilization strategy of "laying the foundation in spring and promoting growth in summer" based on the unique climatic rhythms and plant physiological cycles of coastal areas. During the rising ground temperature period from March to April, root development and soil improvement are promoted; and during the abundant natural rainfall of the flood season from July to August, the salt leaching effect is enhanced. Simultaneously, nutrient replenishment is closely coupled with the hydrological processes of the rainy season, thus avoiding the risk of salt damage during the seedling stage and fully utilizing the energy of natural rainfall, achieving low-cost and high-efficiency dynamic water and salt regulation.

[0016] In one possible implementation, the total application rate of the granular bio-organic fertilizer during the two fertilization processes is 215.00-280.00 kg / 667 m³. 2 .

[0017] Compared with existing technologies, this invention precisely balances the relationship between soil improvement needs and plant salt tolerance thresholds by scientifically limiting the total amount of fertilizer applied. This dosage setting ensures that the organic fertilizer forms sufficient exchange sites in the soil to replace sodium ions, while avoiding additional osmotic pressure stress or seedling burn risks caused by excessive fertilizer concentration. It achieves the best marginal benefit between improvement effect, plant survival rate and input cost, and avoids resource waste and environmental burden caused by blindly increasing application.

[0018] In one possible implementation, when applying the granular bio-organic fertilizer, the granular bio-organic fertilizer must be avoided around the roots of the plants, and the soil should be covered and compacted in a timely manner after fertilization.

[0019] Compared with existing technologies, this invention constructs a safe rhizosphere nutrient slow-release microzone by strictly regulating the fertilization location and soil covering and compaction process. The operation of avoiding the root system when applying fertilizer eliminates the heat damage and high-concentration burns caused by localized fertilizer fermentation, while timely soil covering and compaction effectively reduce the risks of fertilizer volatilization, wind erosion, and surface runoff. This ensures the effective accumulation and slow release of nutrients around the roots, significantly improving fertilizer utilization and the localized soil improvement effect in the root zone.

[0020] In one possible implementation, in step S3, EM microbial fertilizer is also applied simultaneously with the application of the granular bio-organic fertilizer.

[0021] Compared with existing technologies, this invention introduces EM (Effective Microorganisms) fertilizer as a bio-enhancing agent, which greatly activates the activity of indigenous microorganisms and ecosystem service functions in reclaimed soil. The colonization of beneficial bacteria not only accelerates the mineralization and decomposition of organic materials and the release of nutrients, but also inhibits the growth of soil-borne pathogens through biological antagonism. At the same time, it promotes the formation of soil aggregates, enhances the water and fertilizer retention capacity and buffering capacity of sandy soil, and realizes a qualitative change from simple "chemical desalination" to "biological salt stabilization" and "ecological improvement".

[0022] In one possible implementation, the physicochemical properties of the granular bio-organic fertilizer meet the following requirements: The pH value is 5.5-5.6; The total nitrogen content is 3.2-3.3 g / kg; The alkaline nitrogen content is 87-88 mg / kg; The organic matter content is 9.6-9.7 g / kg; The available phosphorus content is 23.00-23.10 mg / kg; Electrical conductivity is 245-246 / (ms·m) -1 ); The chloride ion content is 59-60 mg / kg.

[0023] Compared with existing technologies, this invention eliminates the risk of secondary pollution from the "adding salt while improving soil" process by strictly limiting the key physicochemical indicators of granular bio-organic fertilizer. The low pH value and suitable acidity / alkalinity help neutralize the alkaline environment of coastal soils, while the low chlorine content avoids the toxicity of chloride ions to salt-sensitive plants. The high organic matter and total nitrogen content provide ample carbon and nitrogen sources for soil microorganisms, ensuring the simultaneous optimization of the soil's chemical and biological environments during the salinization process.

[0024] In one possible implementation, before treatment, the reclaimed coastal sandy soil is a chloride-type saline soil with NaCl and MgCl2 as the main soluble salts, with a total salt content of 0.082-0.134 wt% and a pH value of 6.23-8.45.

[0025] Compared with existing technologies, this invention provides a highly targeted improvement solution for chloride-type saline soil, the most difficult soil type to manage in coastal reclamation areas. By utilizing calcium ions to replace sodium ions on soil colloids and combining this with leaching to remove chloride salts, the vicious cycle of sodium chloride crystallization and repeated migration in sandy soil is effectively broken. This allows moderately to severely saline-alkali land, which was previously unusable due to excessive salinity, to quickly reach the planting standards for garden plants in a short period of time, thus expanding the sources of green space.

[0026] In one possible implementation, in step S4, the plant includes garden trees or ground cover plants, wherein the ground cover plants include Liriope muscari.

[0027] Compared with existing technologies, this invention is specifically designed to address the physiological characteristics of shallow-rooted, highly sensitive ground cover plants such as Liriope muscari. By optimizing the microenvironment of the planting trench and precisely combining it with low-chlorine fertilizer, it overcomes the fatal threats to the survival of ground cover plants posed by the easy accumulation of salt and drought in shallow soil. It also solves the shortcomings of traditional soil improvement methods that neglect the needs of shallow-layer plants when treating deep soil, thus achieving high-quality, high-density, rapid establishment and long-term maintenance of landscape green spaces on coastal sandy soil. Detailed Implementation

[0028] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter range described in the present invention. Reasonable variations derived therefrom are still within the protection scope of the claims of the present invention.

[0029] It should be noted that the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0030] Unless otherwise defined, all terms, symbols, and other scientific terms used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In some instances, terms having a conventional meaning are defined herein for clarification or ease of reference, and such definitions should not be construed as indicating a significant difference from conventional understanding in the art. The technical methods described or referenced herein are generally well understood by those skilled in the art and employed by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents, and instruments shall be performed according to the manufacturer's instructions and parameters.

[0031] It is worth mentioning that the determination of total soluble salt content was performed using a gravimetric method. 100 g of air-dried, ground soil sample (accurate to 0.1 g) was weighed and placed in a 1000 ml wide-mouth plastic bottle. 500 ml of carbon dioxide-distilled water was added, and the mixture was shaken for 8 min at a frequency of 200 times / min for 30 min. After standing, the solid and liquid phases were separated using a centrifuge at 4000 r / min. The mixture was then filtered under vacuum, and 100 ml of the supernatant was transferred to a pre-weighed porcelain evaporating dish. The dish was evaporated to dryness in a water bath, then dried in a 105℃ oven for 4 h. Afterward, it was transferred to a desiccator and cooled for 30 min. The sample was then weighed using an analytical balance. The deviation between two parallel samples was ≤5%, and the criterion for constant weight after drying was ≤0.01 g.

[0032] Example 1 This example is a basic implementation of soil improvement for the green space south of Shitang, Hangzhou Bay, Cixi, Ningbo. The soil type in the test area is coastal saline soil, with sandy and silty textures as the main components. Before improvement, the soil salinity was 0.113-0.124%, and the pH value was 7.95-8.10, which is classified as slightly saline soil.

[0033] Step 1: Soil pretreatment. The soil in the test area was prepared by mechanical rotary tillage to a depth of 25-30cm to remove stones, weeds and other debris from the soil, so as to make the soil particle structure uniform and improve soil permeability.

[0034] Step 2: Installation of the drainage network. At a depth of 15cm in the planting trench, PVC drainage mesh pipes with a diameter of 2.5cm are buried in a grid pattern. The pipe walls are evenly distributed with drainage holes of 3-5mm in diameter, spaced 5-8cm apart. The pipes are arranged in an east-west and north-south crisscross pattern to form a grid, with a grid spacing of 3m. The ends of the pipes are connected to the drainage ditch to ensure that dissolved salts can be smoothly discharged.

[0035] Step 3: First Fertilization. The first fertilization should be carried out in late March, before planting the greenery. Use trench fertilization, with trenches 15cm deep, 20cm wide, and spaced 40cm apart. Apply granular bio-organic fertilizer at a rate of 240kg / 667m². 2 Spread the fertilizer evenly into the furrow as base fertilizer. Immediately after fertilization, cover with soil and compact it to ensure full contact between the fertilizer and the soil.

[0036] Step 4: Planting. 3-5 days after the first fertilization, plant *Liriope muscari* ground cover in the improved area. The planting density is 64 plants per square meter, with a planting depth of 5-8 cm. Water thoroughly immediately after planting, using approximately 30-40 L / m². 2 .

[0037] Step 5: Second Fertilization. The second fertilization should be carried out 30 days after planting, i.e., in late April. Use a trenching method, digging trenches 8-10 cm deep and 15 cm wide between the plant rows. Apply granular bio-organic fertilizer at a rate of 240 kg / 667 m². 2 Spread the fertilizer evenly into the furrow. When fertilizing, avoid the area above 15 cm of the plant roots to prevent direct contact with the roots and potential root burn. Cover with soil and compact it promptly after fertilizing.

[0038] Step 6: Regular irrigation. After fertilization, irrigate 1-2 times per week, with each irrigation amount being 20-30 L / m². 2 Irrigation water seeps into the drainage network through the soil, dissolving soluble salts in the soil, and is then discharged through the network. Sprinkler or drip irrigation is used to avoid soil compaction caused by flooding.

[0039] Step 7: Fertilize in the second year. Fertilize twice in late March and mid-July of the second year, using the same method and amount as in the first year.

[0040] Improvement Effects: After two fertilizations over one year, soil samples were taken from the 0-25cm soil layer in late December for testing. Results showed that soil pH decreased from 7.95-8.10 before improvement to 7.45-7.72, a reduction of 2.89-8.02%. Soil salinity decreased from 0.113-0.124% before improvement to 0.086-0.077%, a reduction of 23.89-37.9%. After four fertilizations over two consecutive years, soil pH decreased by 6.75-9.35%, and salinity decreased by 27.56-39.34%. The *Liriope muscari* ground cover plants grew well, achieving a coverage of over 85%, with dark green leaves and vigorous growth.

[0041] Example 2 This example focuses on improving soils with higher salinity. The soil salinity in the test area was 0.15-0.18%, and the pH value was 8.20-8.45, classifying it as moderately saline soil.

[0042] The improved method is basically the same as that in Example 1, the main difference being that the application rate of granular bio-organic fertilizer is increased to 280 kg / 667 m³. 2 The first fertilization was carried out in mid-March, with the trench depth increased to 20 cm to provide deeper nutrient supply and stronger base exchange capacity. The second fertilization was carried out at the end of July, using the same method and procedure as in Example 1.

[0043] Improvement effects: After two applications of fertilizer per year, the soil pH decreased from 8.20-8.45 to 7.45-7.68, a reduction of 9.2%. Soil salinity decreased from 0.15-0.18% to 0.086-0.103%, a reduction of 42.5%. Higher fertilization levels provided stronger base exchange capacity, increasing Ca... 2+ Mg 2+ Isotrophic ions can more fully interact with Na in the soil. + The exchange process accelerated the desalination process.

[0044] Example 3 This embodiment uses bamboo fiber spiral wound pipe instead of PVC pipe to improve the environmental friendliness of the improvement scheme. The soil salinity in the test area was 0.113-0.124%, and the pH value was 7.95-8.10.

[0045] The improved method is basically the same as in Example 1, with the main difference being that the drainage network uses bamboo fiber spiral wound pipes with a diameter of 3cm. These pipes are woven from natural bamboo fibers and possess excellent permeability and biodegradability. The pipes are buried at a depth of 15cm with a grid spacing of 3m. The permeability of bamboo fiber spiral wound pipes is superior to that of PVC pipes, allowing for faster drainage of dissolved salts. Furthermore, they can naturally degrade after 3-5 years of use, preventing soil pollution.

[0046] Improvement effects: After two fertilizations a year, the soil pH value decreased by 7.85%, and the salt content decreased by 35.2%. The permeability of bamboo fiber spiral pipes makes salt leaching efficiency slightly higher than that of PVC pipes, while also being more environmentally friendly, making them suitable for ecological green space projects with higher environmental protection requirements.

[0047] As can be seen from the above results, the advantages of the method of the present invention are mainly reflected in the following aspects: First, by using the deep application technology of granular bio-organic fertilizer, the Ca in the organic fertilizer is utilized. 2+ Mg 2+ Isotrophic ions and Na in soil + First, the exchange of basic ions enables biological desalination of the soil, achieving a higher desalination efficiency than simple irrigation leaching. Second, the installation of a grid-like infiltration pipe network promotes the leaching and removal of exchanged salts by irrigation water or rainfall, significantly improving salt leaching efficiency. Third, the use of multiple fertilization and stratified fertilization methods ensures both basic soil improvement before planting and continuous improvement after planting, avoiding soil structure fragmentation caused by repeated tilling. The construction process is simple and the improvement cycle is short.

[0048] While the disclosure is as stated above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the protection scope of this invention.

Claims

1. A fertilization method for rapidly reducing salinity in reclaimed coastal sandy soils, characterized in that, Includes the following steps: S1. Structural treatment of the reclaimed coastal sandy soil to improve physical permeability and excavation of planting trenches; S2. Install a seepage pipe in the planting trench; S3. Apply granular bio-organic fertilizer to the reclaimed coastal sandy soil twice, before and after planting. S4. Plants are planted in the planting trench, and nutrients are provided by the granular bio-organic fertilizer, which allows nutrient ions in the fertilizer to exchange with soil base ions. Combined with irrigation or natural rainfall, the salt water is collected and discharged into the seepage pipe.

2. The fertilization method according to claim 1, characterized in that, In step S1, the structural treatment specifically includes: using mechanical land preparation to make the soil particle structure uniform and removing stones from the soil.

3. The fertilization method according to claim 1, characterized in that, In step S2, the seepage pipes are buried at a depth of 15cm in the planting trench and the seepage pipes are arranged in a grid pattern. The drainage pipe is a mesh PVC pipe or a bamboo fiber spiral pipe, and the diameter of the drainage pipe is 2-3cm.

4. The fertilization method according to claim 1, characterized in that, In step S3, the specific steps for applying granular bio-organic fertilizer to the reclaimed coastal sandy soil in two stages are as follows: First application of fertilizer: Apply as base fertilizer before planting construction, using trench application method, with a trench depth of 0-20 cm, and the fertilization time is from March to April; The second fertilization should be carried out within 3 days after 1 month of planting, by spreading the fertilizer in trenches. The fertilization time is from July to August.

5. The fertilization method according to claim 4, characterized in that, During the two fertilization processes, the total application rate of the granular bio-organic fertilizer was 215.00-280.00 kg / 667 m³. 2 .

6. The fertilization method according to claim 1, characterized in that, When applying the granular bio-organic fertilizer, the fertilizer must be avoided around the roots of the plants, and the soil should be covered and compacted promptly after application.

7. The fertilization method according to claim 1, characterized in that, In step S3, EM microbial fertilizer is also applied simultaneously with the granular bio-organic fertilizer.

8. The fertilization method according to claim 1, characterized in that, The physicochemical properties of the granular bio-organic fertilizer meet the following requirements: The pH value is 5.5-5.6; The total nitrogen content is 3.2-3.3 g / kg; The alkaline nitrogen content is 87-88 mg / kg; The organic matter content is 9.6-9.7 g / kg; The available phosphorus content is 23.00-23.10 mg / kg; Electrical conductivity is 245-246 / (ms·m) -1 ); The chloride ion content is 59-60 mg / kg.

9. The fertilization method according to claim 1, characterized in that, Before treatment, the reclaimed coastal sandy soil was a chloride-type saline soil with NaCl and MgCl2 as the main soluble salts, with a total salt content of 0.082-0.134 wt% and a pH value of 6.23-8.

45.

10. The fertilization method according to claim 1, characterized in that, In step S4, the plants include garden trees or ground cover plants, wherein the ground cover plants include Liriope muscari.