A method for repairing and improving saline-alkali soil

Abstract

The application belongs to the technical field of soil improvement, and relates to a method for repairing and improving saline-alkali soil, which comprises the following steps: layering and stripping soil in a vertical direction; then, fresh straw is returned to the field and ploughed, biochar and iron ore slag are laid, and a straw-biochar-iron ore slag blocking layer is formed; then, the iron ore slag and non-surface soil are uniformly mixed and backfilled to form an iron ore slag salt and alkali reduction function reconstruction layer; finally, the surface soil is mixed with the iron ore slag, an improving agent and gypsum, and backfilled to form an improved layer. The application uses straw as a partition layer to isolate the upper layer of cultivated soil from the lower layer of saline-alkali soil, and cut off the water channel for the upward movement of soil salt, so as to achieve the effects of isolating salt and improving soil. The application mainly uses waste such as straw and iron ore slag as raw materials, and has low treatment cost; efficient salt isolation and reduction can be achieved through simple operation, and the application is suitable for large-area saline-alkali soil treatment.

Description

Technical Field

[0001] This invention belongs to the field of soil improvement technology and relates to a method for remediating and improving saline-alkali soil. Background Technology

[0002] Saline-alkali land is a general term for land that is salinized and alkalized to varying degrees. The main characteristic of saline-alkali land is that it contains a large amount of water-soluble salts or alkaline substances. Due to the high salt and alkalinity, soil humus is leached away, organic matter content is low, and soil structure is damaged. This results in soil that is sticky when wet and hard when dry, often with white salt deposits on the surface. Aeration and water permeability are poor, the soil is hard and compacted, and soil temperature rises slowly. Salts mixed in the compacted soil are difficult to separate, leading to gradual precipitation and increasingly higher salt content over the years. Essential mineral elements for crops are also difficult for crops to absorb and utilize due to the high soil pH, which causes precipitation.

[0003] Soil improvement methods mainly include biological methods, engineering methods, and chemical amendments. However, biological methods have a long improvement cycle and slow results; engineering methods have high costs and complex operations, making them difficult for farmers to implement independently; and chemical amendments only address the symptoms and not the root cause, hindering sustainable development. Therefore, it is essential to develop efficient, low-cost, environmentally friendly, and easy-to-operate soil remediation technologies. Summary of the Invention

[0004] In view of the current problems in the improvement of saline-alkali soil, this invention provides a method for improving saline-alkali soil, which has obvious effects, low cost and simple operation.

[0005] To achieve the above objectives, the present invention adopts the following technical solution.

[0006] A method for improving saline-alkali soil includes the following steps:

[0007] (1) The soil is stripped in layers in the vertical direction;

[0008] (2) In the plot where the soil has been stripped, fresh straw is returned to the field and plowed to a depth of 30-35cm. Then, a layer of biochar with a thickness of 20-40cm is laid, followed by a layer of iron slag with a thickness of 20-30cm, forming a straw-biochar-iron slag barrier layer with a thickness of 70-90cm.

[0009] (3) After uniformly mixing the iron slag and non-topsoil, backfill to form a 30-70cm thick iron slag desalination and alkali reduction functional reconstruction layer;

[0010] (4) Mix the topsoil with iron slag, amendment and gypsum and backfill to form an amendment layer 10-30cm thick.

[0011] The amount of straw returned to the field is 10-12 t / hm. 2 .

[0012] Topsoil is soil 0-20cm below the soil surface; non-topsoil is soil after the topsoil has been removed.

[0013] In step (3), the amount of iron slag used is 1.5%-2.5% of the soil weight.

[0014] The soil conditioner is composed of biochar, organic fertilizer, rice husks and topsoil, with a mass ratio of (0.5-3):(1-4):(0.2-1):(1-2).

[0015] The mass ratio of topsoil: iron slag: amendment: gypsum is (1-3):(0.5-2):(0.5-1):(0.2-0.6).

[0016] The mechanism / synergistic effect of this invention is as follows:

[0017] This invention proposes a three-tiered, long-lasting technology for controlling salinity and alkalinity: a bottom-layer layer of "straw-biochar-iron slag superimposed blocking," a middle-layer layer of "direct application of iron slag to reconstruct saline-alkali soil for treatment and control," and a surface-layer layer of "co-improvement using iron slag-straw-gypsum." The soil is layered and separated. The bottom layer consists of a base layer formed by deep tillage and natural fermentation of fresh straw. The middle layer contains a thick layer of biochar for adsorption, and the top layer is covered with iron slag to block the upward movement of saline water, forming a straw-biochar-iron slag superimposed blocking layer. The middle layer involves direct application of iron slag to dilute soil salinity, cut off capillary pathways, and reduce water evaporation. The iron slag and soil colloidal double electron layer form basic iron carbonate, inhibiting sodium chloride formation. + Cl - Diffusion, passivation of CO3 2- and HCO 3- This process creates a salinity-reducing and salinity-reconstructing layer from iron slag. The surface layer mixes iron slag, amendments, gypsum, and other substances with the surface soil to achieve synergistic effects, such as iron slag controlling water evaporation and salt diffusion, amendments improving soil structure and fertilizer efficiency, and gypsum passivating salt ions with sulfate ions, thus forming a synergistic improvement layer of iron slag, straw, and gypsum.

[0018] The present invention has the following advantages:

[0019] This invention uses materials such as straw as a separator to isolate the upper layer of cultivated soil from the lower layer of saline-alkali soil, cutting off the channels through which soil salt rises with water, thereby achieving the effects of salt isolation and soil improvement. This invention mainly utilizes waste materials such as straw and iron slag as raw materials, resulting in low treatment costs; it achieves efficient salt isolation and reduction through simple operation, making it suitable for large-scale saline-alkali land treatment. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the layered structure of the improved soil. Detailed Implementation

[0021] Example 1: Improvement of saline-alkali soil

[0022] The following two methods were used to improve the saline-alkali soil (with high sodium chloride content) in the Yellow River saline-alkali area of ​​Dongying, Shandong:

[0023] 1. Method 1

[0024] (1) The soil is stripped in layers in the vertical direction: topsoil 0-10cm from the soil surface, middle soil 10-30cm from the soil surface, and bottom soil 30-60cm from the soil surface.

[0025] (2) In the stripped soil plots, the soil return rate is 12 t / hm 2 Fresh corn stalks are crushed and returned to the field for plowing to a depth of 30cm. Then, a 20cm thick layer of biochar is laid, followed by a 30cm thick layer of iron slag, forming an 80cm thick straw-biochar-iron slag barrier layer.

[0026] (3) After uniformly mixing the bottom soil and 2% iron slag, backfill the mixture. Then, mix the middle soil and 1.5% iron slag and backfill the mixture to form an iron slag desalination and alkali reduction functional reconstruction layer with a thickness of about 70cm.

[0027] (4) Mix straw biochar, decomposed chicken manure, rice husk and topsoil in a mass ratio of 1:1:0.2:1 to obtain an amendment; then mix topsoil, iron slag, amendment and gypsum in a mass ratio of 1:0.5:1:0.2 and backfill to form an amendment layer about 30cm thick.

[0028] After improvement, the land was used as a fallow area and not cultivated. After three years, the pH of the topsoil (0-30cm) decreased by 1.5, while organic matter, available phosphorus, and available potassium increased by 22.7%, 23.2%, and 19.1%, respectively; surface biomass (fresh weight) increased 3.74 times; and soil Ca... 2+ The content increased by 15.3%, Na + and Cl - These figures decreased by 36.1% and 18.2% respectively.

[0029] 2. Method 2

[0030] (1) The soil is stripped in layers in the vertical direction: the topsoil is 0-10cm from the soil surface, and the middle soil is 10-40cm from the soil surface;

[0031] (2) In the stripped soil plots, the soil return rate is 12 t / hm 2 Fresh corn stalks are crushed and returned to the field for plowing, with a plowing depth of 30cm.

[0032] (3) Backfill with the middle layer of soil;

[0033] (4) Mix straw biochar, decomposed chicken manure, rice husk and topsoil in a mass ratio of 1:1:0.2:1 to obtain an amendment; mix topsoil, amendment and gypsum in a mass ratio of 1:1:0.2 and backfill.

[0034] After three years of rest following soil improvement, the pH of the topsoil decreased by 1.1 units, while organic matter, available phosphorus, and available potassium increased by 18.4%, 17.4%, and 15.0%, respectively; surface biomass (fresh weight) increased by 2.07 times; and soil Ca... 2+ The content increased by 8.4%, Na + and Cl - These figures decreased by 24.4% and 10.7% respectively.

[0035] For improving saline-alkali land with high sodium chloride content, such as riverbanks and estuaries, Method 1 is superior to Method 2 in lowering pH, reducing soil organic matter leaching, and increasing soil organic matter and calcium content. 2+ More effective in terms of content; and can effectively reduce Na + and Cl - Content; due to the decrease in pH and salinity, the soil is more suitable for plant growth, and the surface biomass increases significantly.

[0036] Example 2: Improvement of saline-alkali soil

[0037] The following two methods were used to improve the saline-alkali soil (with high carbonate content) in Zhenben, Jilin:

[0038] 1. Method 1

[0039] (1) The soil is stripped in layers in the vertical direction: topsoil 0-15cm from the soil surface, middle soil 15-30cm from the soil surface, and bottom soil 30-50cm from the soil surface.

[0040] (2) In the stripped soil plots, the soil return rate is 12 t / hm 2 Fresh wheat straw is crushed and returned to the field for plowing to a depth of 30cm. Then, a 40cm thick layer of biochar is laid, followed by a 20cm thick layer of iron slag, forming a 90cm thick straw-biochar-iron slag barrier layer.

[0041] (3) After uniformly mixing the bottom soil and middle soil with 2% iron slag, backfill them in sequence to finally form an iron slag desalination and alkali reduction functional reconstruction layer with a thickness of about 40cm.

[0042] (4) Mix straw biochar, decomposed pigpen bedding, rice husk and topsoil in a mass ratio of 1:2:0.5:0.5 to obtain an amendment; then mix topsoil, iron slag, amendment and gypsum in a mass ratio of 1:0.5:0.5:0.5 and backfill to form an amendment layer about 30cm thick.

[0043] After improvement, the pH of the saline soil decreased by 1.3 units, and the soil cation Ca... 2+ Mg 2+ The contents increased by 18.4%, 24.9%, and SO4, respectively. 2- CO3 2- These figures decreased by 22.6% and 20.9% respectively.

[0044] 2. Method 2

[0045] (1) The soil is stripped in layers in the vertical direction: the topsoil is 0-15cm from the soil surface, and the middle soil is 15-30cm from the soil surface;

[0046] (2) In the stripped soil plots, the soil return rate is 12 t / hm 2 Fresh corn stalks are crushed and returned to the field for plowing, with a plowing depth of 30cm.

[0047] (3) Backfill with the middle layer of soil;

[0048] (4) Mix straw biochar, decomposed pigpen bedding, rice husk and topsoil in a mass ratio of 1:2:0.5:0.5 to obtain an amendment; then mix topsoil, amendment and gypsum in a mass ratio of 1:0.5:0.5 and backfill.

[0049] After improvement, the pH of the saline soil decreased by 0.8 units, and the soil's cation Ca content increased. 2+ Mg 2+ The contents increased by 14.9%, 13.2%, and SO4, respectively. 2- CO3 2- These figures decreased by 17.4% and 16.5% respectively.

[0050] For improving inland saline-alkali land, method 1 is more effective than method 2 in lowering pH and increasing calcium content. 2+ Mg 2+ It is more effective in reducing the content of beneficial mineral cations in plants; and it is also more effective in reducing anions such as sulfates and carbonates.

Claims

1. A method for improving saline-alkali soil, characterized in that, Includes the following steps: (1) The soil is stripped in layers in the vertical direction; (2) In the plot where the soil has been stripped, fresh straw is returned to the field and plowed to a depth of 30-35cm. Then, a layer of biochar with a thickness of 20-40cm is laid, followed by a layer of iron slag with a thickness of 20-30cm, forming a straw-biochar-iron slag barrier layer with a thickness of 70-90cm. (3) After uniformly mixing the iron slag and non-topsoil, backfill to form a 30-70cm thick iron slag desalination and alkali reduction functional reconstruction layer; (4) Mix the topsoil with iron slag, amendment and gypsum and backfill to form an amendment layer 10-30cm thick.

2. The method according to claim 1, characterized in that, The amount of straw returned to the field is 10-12 t / hm. 2 .

3. The method according to claim 1, characterized in that, The topsoil is the soil layer 0-20cm below the soil surface.

4. The method according to claim 1, characterized in that, In step (3), the amount of iron slag used is 1.5%-2.5% of the soil weight.

5. The method according to claim 1, characterized in that, The soil conditioner is composed of biochar, organic fertilizer, rice husks and topsoil, with a mass ratio of (0.5-3):(1-4):(0.2-1):(1-2).

6. The method according to claim 1, characterized in that, The mass ratio of topsoil: iron slag: amendment: gypsum is (1-3):(0.5-2):(0.5-1):(0.2-0.6).

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