Method for improving plough pan of sandy farmland by using iron tailings

Abstract

The application aims at the problem that aeolian sandy soil is not suitable for plowing without plow subsoil, and provides a method for improving aeolian sandy soil plow subsoil by using iron tailings. The method comprises the following steps: 1) renovating the aeolian sandy soil farmland to be improved; 2) constructing the plow subsoil of the aeolian sandy soil farmland in the form of interval strip; 3) preparing the plow subsoil by using silicate cement and iron tailings; and 4) backfilling the farmland soil of the plowing layer on the plow subsoil. The application uses iron tailings as the material, and the iron tailings are by-products produced during the production of iron concentrate in iron mines, and are a kind of multipurpose siliceous material. Through experimental research, the iron tailings are used to improve the aeolian sandy soil plow subsoil by mixing with silicate cement and adding water in a proper proportion, and the method has the advantages of low cost, simple method, easy-to-obtain raw materials, good effect, durability and the like.

Description

Technical Field

[0001] This invention belongs to the field of land improvement technology, and specifically relates to a method for improving the plow pan of sandy farmland using iron tailings. Background Technology

[0002] Aeolian sandy soil refers to soil developed from aeolian sandy parent material. Its main characteristics include a mineral composition almost entirely of fine sand particles, indistinct stratification in the soil profile, inability to form a plow pan through cultivation, small particle size, high compactness, poor water absorption, poor water tolerance, and low fertility. To address these characteristics, a series of improvement measures are needed to better utilize this type of soil.

[0003] The plow pan is a relatively firm layer of soil located below the topsoil. It is formed by repeated plowing and the deposition of clay particles with rainfall over long periods of cultivation. It is generally 12 to 18 centimeters below the surface, about 5 to 7 centimeters thick, but can reach up to 20 centimeters in some cases. The plow pan is very beneficial for soil nutrient retention and moisture conservation. The permeability coefficient of the plow pan in paddy fields is generally about 5 mm / day, while in dry fields it is about 20 mm / day. Sandy soils lack clay particles and cannot form a plow pan through cultivation, resulting in fertilizer and water loss and hindering effective crop cultivation. Because the permeability coefficient of sandy soils exceeds 20 mm / day, current methods for cultivating crops in sandy soils rely mainly on traditional methods, such as regular irrigation using wells and river water. This is water-intensive, time-consuming, and labor-intensive, resulting in low crop yields and low economic benefits. It is a typical low-yield field, dependent on rainfall, and unable to achieve effective irrigation and utilization. To address the issue of sandy soil lacking a plow pan, a water-retaining layer needs to be constructed below the topsoil at the plow pan location. This layer will retain fertilizer and water, achieving the goal of water conservation, fertilizer conservation, high yield, and high efficiency in normal soil conditions.

[0004] According to the search, the following patents exist for improving the soil's water and fertilizer retention capacity by modifying the plow pan:

[0005] The application for "A Method for Constructing a Rapid and Effective Plow Subbase" (application number 201711026895.6) includes the following steps: leveling the land and removing topsoil and debris; removing the topsoil layer; tilling, breaking up, and leveling the subsoil used to construct the plow subbase, and removing impurities; adjusting the moisture content of the soil to be compacted; mechanical compaction; after compaction, and after sampling and measuring the soil density or determining the soil hardness on-site to confirm that the expected target has been achieved, uniformly backfilling and leveling the topsoil layer.

[0006] "An Aluminum Ash Material for Farmland Transformation and Its Application Method", application number 202010169881.5, application publication number CN111303892 A. This invention makes full use of the physical and chemical properties of raw materials, uses locally available materials and aluminum ash, a waste product from the aluminum industry, as raw materials, and applies the material construction technology to agricultural activities in a targeted manner.

[0007] The application, "A Slurry for Farmland Improvement and its Preparation Method", with application number 202011069759.7, describes a slurry for farmland improvement made of a material consisting of 50-85 parts by weight of calcium carbonate material and 15-50 parts by weight of a gelling powder material, which is homogenized and mixed with water as a mediator. The gelling powder material is two or more of the following: silica fume, aluminum ash, phosphogypsum, clay powder, and denitrification gypsum.

[0008] "A Magnesium Slag Powder Material for Farmland Improvement", application number 202210500886.0, this invention uses water as a medium to inject waste magnesium slag and locally sourced loess fine powder into the soil layer beneath the farmland using a non-excavation grouting method. The magnesium slag slurry constructs a capillary network structure in the soil layer below the cultivated soil layer to maintain the soil moisture of the upper soil layer.

[0009] "A gypsum slurry for flue gas denitrification and its preparation method for farmland improvement", application number 202011069545.X. The slurry is a farmland improvement slurry made by homogenizing and mixing a material consisting of 50-85 parts by weight of calcium carbonate material and 15-50 parts by weight of cementing material with water as a mediator.

[0010] The methods used in the above-mentioned patents for farmland improvement each have their own characteristics. They all aim to improve the water retention capacity of farmland and increase yields, but they are costly or have poor water and fertilizer retention effects, making them unsuitable for large-scale promotion. Summary of the Invention

[0011] The purpose of this invention is to address the problem of sandy soil lacking a plow pan, making it unsuitable for cultivation, and to provide a method for modifying the plow pan of sandy farmland using iron tailings. This method uses iron tailings as the material. Iron tailings are a byproduct of iron ore concentrate beneficiation in iron mines and are a versatile siliceous material. Through experimental research, a plow pan mixture made from iron tailings, silicate cement, and an appropriate proportion of water has been developed to modify the plow pan of sandy soil. This method has advantages such as low cost, simple method, readily available raw materials, and good and durable results.

[0012] The technical solution of the present invention is as follows:

[0013] A method for modifying the plow pan of sandy farmland using iron tailings includes the following steps:

[0014] 1) Repair sandy soil farmland with a plow pan.

[0015] The fields are divided into plots according to the planting plan and the natural height of the field surface. Fields with similar heights are grouped into the same plot, which helps to save on the amount of field leveling work. Field ridges are built between the plots, with a height of 40-50 cm, a top width of 30-40 cm, and a slope of 1:0.8-1.2.

[0016] Preferably, the height of the field surface is measured to determine the relative average elevation of 30 cm below the field surface, and the benchmark height for constructing the plow layer of the field is determined. After the topsoil is cleared according to the determined elevation, debris is cleared and leveled. After leveling, the height difference of the construction surface is less than 2 cm.

[0017] 2) The plow pan of sandy soil farmland is constructed in a spaced-out strip pattern.

[0018] The field is divided into several plowing and subsurface construction zones, each 8-10 meters wide, with a digging depth of 25-35 centimeters from the field surface; then the field bottom is compacted 2-3 times using construction equipment.

[0019] Preferably, agricultural non-woven fabric is used as the isolation cloth between the plow pan mixture and the wind-blown sand and soil in the field. The quality requirement for the non-woven fabric is 30-50 g / m². 2 The overlap width of the non-woven fabric should be 15-20 cm.

[0020] 3) Use silicate cement and iron tailings to prepare the plowshare layer.

[0021] Prepare the plow pan mixture by mixing solid materials at a mass ratio of 17%-30% silicate cement and 83%-70% iron tailings, and add water at a mass ratio of 6%-8% of the mass of the solid anhydrous dry material. If the iron tailings contain moisture, the mass of the water should be deducted. The permeability coefficient of the plow pan mixture should be less than 10 mm / day. Then spread the plow pan mixture on the compacted field bottom and build a plow pan with a thickness of 4-6 cm.

[0022] Preferably, the iron tailings are magnetically separated iron tailings with a silica content greater than 65% and a particle size ≤ 1 mm. Among them, the content of particles with a particle size > 0.05 mm and ≤ 1 mm is < 70%, the content of particles with a particle size > 0.002 mm and ≤ 0.05 mm is > 30%, and the content of particles with a particle size ≤ 0.002 mm is ≤ 5%. The moisture content of the iron tailings is less than 5%. The content of cadmium (Cd), mercury (Hg), arsenic (As), lead (Pb), chromium (Cr), and thallium (Tl) in the iron tailings meets the limit requirements of mercury, arsenic, cadmium, lead, and chromium in water-soluble fertilizers in NY 1110-2010 issued by the Ministry of Agriculture and Rural Affairs of the People's Republic of China. The content of cadmium (Cd) and mercury (Hg) in the iron tailings also meets the requirements of the pollution risk screening value standard in GB15618. The leaching toxicity and terrestrial plant growth test of the iron tailings also meet the requirements of GB 38400.

[0023] The preferred method for spreading the plow layer mixture is as follows: transport the plow layer mixture to the site, divide the plow layer mixture into small piles according to the amount required, spread and level it, with a spreading thickness of 5-7 cm, and compact it to a thickness of 4-6 cm.

[0024] Preferably, after the plow layer mixture is spread and leveled, the top surface is covered with agricultural non-woven fabric for protection. The non-woven fabric should have a quality requirement of 30-50 g / m². 2 The overlap width of the non-woven fabric should be 15-20 cm.

[0025] 4) Backfill the topsoil layer above the plow pan:

[0026] The excavated topsoil is evenly backfilled onto the plow pan, and then leveled until the surface of the field is 2-4 cm higher than the ground.

[0027] The preferred method for leveling the field surface is to first use a bulldozer for rough leveling, and then use a grader for leveling.

[0028] Preferably, the plow pan should be watered and maintained within 7 days, requiring 100-120 kg of water per square meter.

[0029] Compared with the prior art, the advantages of the present invention are:

[0030] 1. By using silicate cement and iron tailings in a certain proportion to construct a plow pan beneath the topsoil, the problem of water retention and fertilizer loss in sandy soil without a plow pan was solved.

[0031] 2. Save irrigation water, improve irrigation and fertilization efficiency and yield, and transform low-yield fields into high-yield fields.

[0032] 3. One-time investment yields long-term benefits, continuously increasing planting income and creating conditions for the continuous and efficient use of arable land.

[0033] 4. Iron tailings were utilized, which reduced tailings accumulation and land occupation. Detailed Implementation

[0034] The present invention will be further described below through specific embodiments.

[0035] Example 1

[0036] In a certain area of ​​Hebei Province, a project was undertaken to transform sandy soil farmland by constructing a plow pan, covering an area of ​​approximately 70 mu (about 4.7 hectares). A project team was formed based on the actual conditions to carry out the construction of the plow pan for the sandy soil.

[0037] The results of harmful element and particle size tests on iron tailings samples used in the plowing of this farmland are listed in Tables 1 and 2 below, and the samples meet the quality requirements for using iron tailings. The moisture content of the iron tailings samples was determined to be 3.6%, which meets the requirements for use.

[0038] Table 1. Results of determination of harmful elements in iron tailings

[0039] Cadmium (Cd) 0.02 Mercury (Hg) 0.01 Arsenic (As) 1.3 Lead (Pb) 6.1 Chromium (Cr) 12.6 Thallium (Tl) 0.01

[0040] Table 2 Results of Particle Size Distribution Detection of Iron Tailings

[0041] content(%) 0 61 35 4

[0042] Ordinary Portland cement was used. The permeability coefficients of the five mix proportions were determined in the laboratory and are listed in Table 3. In the following examples, the cement and iron tailings mix proportion selected for the plowing layer construction is Scheme 2, where 250 kg of ordinary Portland cement and 750 kg of iron tailings are added to 1000 kg of water-retaining layer mixture.

[0043] Table 3. Permeability coefficients of plow pan mixtures with different proportions under specific conditions.

[0044]

[0045] According to technical requirements, the site was surveyed and planned. The plot is 360 meters long from north to south and 132 meters wide from east to west. A central irrigation canal divides the plot into two strips, each strip into two sub-squabs. Each strip is further divided into seven work zones along its length, with five work zones each 10-12 meters wide and the edge work zones 5-6 meters wide. Excavators with a digging power of 200 horsepower were deployed to excavate and clear the topsoil above the planned elevation of the plow layer, according to the design elevation. The average excavation depth was 28 centimeters. The excavated and cleared plow layer construction surface passed inspection.

[0046] After clearing away the debris, a local Dongfanghong T120N-3 tracked bulldozer was used for leveling and compaction. The bulldozer weighs 13 tons, has a power of 93 kilowatts, a track width of 50 centimeters, a bulldozer blade width of 3.1 meters, and operates at a speed of 2.4 kilometers per hour in first gear. It compacts twice, with a track overlap width of 10-15 centimeters.

[0047] Agricultural non-woven fabric with a weight of 30g / m² is laid on the plow pan surface. 2 Non-woven fabric, 1.6 meters wide, with an overlap width of 15 centimeters, fixed with L-shaped iron sticks made of No. 8 iron wire, with a spacing of 3-4 meters between the iron sticks, an iron stick length of 12 centimeters, and a horizontal hook length of 3 centimeters.

[0048] The plowshare base mixture was mixed on-site using a JS500 forced concrete mixer with a feed capacity of 800 liters and a discharge capacity of 500 liters. The mixing time was ≤72 seconds, the mixing shaft speed was 31 rpm, and each mixing cycle consisted of approximately 600 kg, with two mixing cycles totaling about 150 seconds. A 200 kg platform scale was used for weighing. Iron tailings and cement were manually loaded into the mixer using a wheelbarrow, with a weighing error of less than 0.5 kg per loading. The finished plowshare base mixture was directly loaded into dump trucks and transported to the construction site for use.

[0049] On-site plowing and leveling of the plow base mixture is carried out. Dump trucks transport the plow base mixture to a special material trough placed on site. The material trough is made of 5 mm thick iron plate, 4 meters long, 3 meters wide, and 0.5 meters deep. An excavator is used to transport the plow base mixture to the construction surface according to the estimated amount and spread it. Manual labor is used to spread and level it with rakes. The spread thickness is 5-6 cm. Manual labor is used to compact it simply with a flat shovel. The thickness after compaction is about 5.5 cm.

[0050] After the plow pan mixture has passed quality inspection, the top surface is covered with agricultural non-woven fabric for protection. The non-woven fabric weighs 30g / m. 2 The fabric is 1.6 meters wide. The non-woven fabric is laid with an overlap of 15 centimeters, and the fabric is compacted and fixed using on-site sand.

[0051] For the backfilling of the topsoil layer above the plow layer, an excavator is used to evenly backfill the topsoil layer from the stockpile strip onto the non-woven fabric of the plow layer. At the same time, the soil layer of the stockpile strip is excavated and cleaned. The excavation depth meets the elevation requirements for the construction of the plow layer of the field. The remaining soil is piled on the area where the plow layer has been completed. The plow layer is constructed in accordance with the construction requirements of the plow layer. The construction of the plow layer and the backfilling of the topsoil layer of the entire field are completed in accordance with the requirements.

[0052] After completing the plow layer construction work for the entire field grid, a tracked bulldozer was used to perform rough leveling of the field surface. After rough leveling, the difference in height of the field surface was measured to be less than 5 centimeters, which met the conditions for fine leveling.

[0053] For the fine leveling of the field surface, a satellite laser leveler, model 1JP3.5, was used. It was paired with a tractor with a power of 120-140 kilowatts. After leveling, the difference in height of the field surface was found to be less than 2 centimeters, which met the quality requirements.

[0054] After the plowing and construction of the ground layer were completed, watering was carried out on the third day, with a water volume of about 60 cubic meters.

[0055] Actual irrigation verification showed that after constructing the plow pan, when the irrigation depth on the field surface was 9 cm, the infiltration rate was 3.1 mm / day, which met the needs of planting rice and other crops and achieved the quality target.

[0056] Example 2

[0057] In a certain area of ​​Hebei Province, a project was undertaken to transform sandy soil farmland by constructing a plow pan, covering an area of ​​approximately 132 mu (about 8.8 hectares). A project team was formed based on the actual conditions to carry out the plow pan transformation construction.

[0058] The results of harmful element and particle size tests on iron tailings samples taken from the plow layer used in this farmland renovation project are listed in Tables 4 and 5 below, and the samples meet the quality requirements for using iron tailings. The moisture content of the iron tailings samples was determined to be 3.6%, which meets the usage requirements.

[0059] Table 4. Results of determination of harmful elements in iron tailings

[0060] Cadmium (Cd) 0.03 Mercury (Hg) 0.02 Arsenic (As) 1.5 Lead (Pb) 8.2 Chromium (Cr) 9.7 Thallium (Tl) 0.01

[0061] Table 5 Results of Particle Size Distribution Detection for Iron Tailings

[0062] content(%) 0 62.5 34.7 2.8

[0063] The cement used is silicate cement. The permeability coefficients of the five mix proportions were determined in the laboratory and are listed in Table 6. The cement and iron tailings mix proportion selected for the plowing bottom construction is Scheme 1, with 300 kg of ordinary silicate cement and 700 kg of iron tailings added to every 1000 kg of plowing bottom mixture.

[0064] Table 6. Permeability coefficients of plow pan mixtures with different proportions under specific conditions.

[0065]

[0066] According to technical requirements, the site was surveyed and planned. The plot measures 178 meters north-south and 495 meters east-west. Two irrigation canals were constructed in the middle, dividing the plot into three strips. Each strip was further divided into three sections, and each strip was divided into seven work zones along its length. Five of these work zones were 10-12 meters wide, while the work zones along the edges were 5-6 meters wide. Excavators were deployed to the site, using a digging power of 220 horsepower. The plowing layer was excavated and cleared of sand and topsoil above the planned elevation, with an average excavation depth of 32 centimeters. The excavated plowing layer was inspected and approved.

[0067] After clearing the debris, the tracked bulldozer used was a Shantui SD16, with a power of 131 kilowatts, a track width of 56 centimeters, a weight of 17 tons, a bulldozer blade width of 3.4 meters, a working speed of 3 kilometers per hour in first gear, and two passes of compaction. The track overlap width was 10-15 centimeters.

[0068] Agricultural non-woven fabric with a weight of 30g / m² is laid on the plow pan surface. 2 Non-woven fabric, 1.6 meters wide, with an overlap width of 15 centimeters, fixed with L-shaped iron sticks made of No. 8 iron wire, with a spacing of 3-4 meters between the iron sticks, an iron stick length of 12 centimeters, and a horizontal hook length of 3 centimeters.

[0069] The plowshare base mixture was mixed on-site using a JS500 forced concrete mixer with a feed capacity of 800 liters and a discharge capacity of 500 liters. The mixing time was ≤72 seconds, the mixing shaft speed was 31 rpm, and each mixing cycle consisted of approximately 600 kg, with two mixing cycles totaling about 150 seconds. A 200 kg platform scale was used for weighing. Iron tailings and cement were manually loaded into the mixer using a wheelbarrow, with a weighing error of less than 0.5 kg per loading. The finished plowshare base mixture was directly loaded into dump trucks and transported to the construction site for use.

[0070] On-site plowing and leveling of the plow base mixture is carried out. Dump trucks transport the plow base mixture to a special material trough placed on site. The material trough is made of 5 mm thick iron plate and is 4.8 meters long, 3.5 meters wide, and 0.4 meters deep. An excavator is used to transport the plow base mixture to the construction surface according to the estimated amount and spread it. Manual labor is used to spread and level it with rakes. The spread thickness is 5-6 cm. Manual labor is used to compact it simply with a flat shovel. The thickness after compaction is about 5.3 cm.

[0071] After the plow layer mixture is laid on top and the non-woven fabric is laid, and the quality of the water-retaining layer mixture is inspected and accepted, the top surface is covered with agricultural non-woven fabric for protection. The non-woven fabric has a weight of 30g / m. 2 The fabric is 1.6 meters wide. The non-woven fabric is laid with an overlap of 15 centimeters, and the fabric is compacted and fixed using on-site sand.

[0072] For the backfilling of the topsoil layer above the plow layer, an excavator is used to evenly backfill the topsoil layer from the stockpile strip onto the non-woven fabric of the plow layer. At the same time, the soil layer of the stockpile strip is excavated and cleaned. The excavation depth meets the elevation requirements for the construction of the water-retaining layer of the field grid. The remaining soil is piled on the area where the plow layer has been constructed. The plow layer is constructed in accordance with the construction requirements of the plow layer. The plow layer transformation and topsoil backfilling of the entire field are completed in accordance with the requirements.

[0073] After completing the construction of the water-retaining layer for the entire field grid, the field surface was roughly leveled using a tracked bulldozer. After the rough leveling, the difference in the height of the field surface was measured to be less than 5 centimeters, which met the conditions for fine leveling.

[0074] For the fine leveling of the field surface, a satellite laser leveler, model 1JP3.5, was used. It was paired with a tractor with a power of 120-140 kilowatts. After leveling, the difference in height of the field surface was found to be less than 2 centimeters, which met the quality requirements.

[0075] After the plowing and burial of the plot were completed, watering was carried out on the 5th day, with a water volume of 62 cubic meters.

[0076] Actual irrigation verification showed that after constructing the plow pan, when the irrigation depth on the field surface was 7 cm, the infiltration rate was 2.7 mm / day, which met the needs of planting rice and other crops and achieved the quality target.

[0077] Example 3

[0078] In a certain area of ​​Hebei Province, a project was undertaken to transform sandy soil into farmland, involving the construction of a plow pan for paddy fields, covering an area of ​​approximately 97 mu (about 6.5 hectares). A project team was formed based on the actual conditions to carry out the construction of the plow pan for the sandy soil.

[0079] The results of harmful element and particle size tests on iron tailings samples used in the plowing of this farmland are listed in Tables 7 and 8 below, and the samples meet the quality requirements for using iron tailings. The moisture content of the iron tailings samples was determined to be 3.6%, which meets the requirements for use.

[0080] Table 7 Results of determination of harmful elements in iron tailings

[0081] Cadmium (Cd) 0.02 Mercury (Hg) 0.02 Arsenic (As) 1.7 Lead (Pb) 8.5 Chromium (Cr) 9.1 Thallium (Tl) 0.01

[0082] Table 8 Results of Particle Size Distribution Detection for Iron Tailings

[0083] content(%) 0 62.8 33.6 3.6

[0084] The cement used is silicate cement. The permeability coefficients of the five mix proportions were determined in the laboratory and are listed in Table 6. The cement and iron tailings mix proportion selected for the plowing bottom construction is Scheme 1, with 250 kg of ordinary silicate cement and 750 kg of iron tailings added for every 1000 kg of plowing bottom mixture.

[0085] Table 9. Permeability coefficients of plow pan mixtures with different proportions under specific conditions.

[0086]

[0087] As required, the site was measured and planned. The plot is 397 meters long from east to west and 163 meters wide from north to south. A water diversion canal was built in the middle, dividing the plot into two strips. Each strip was divided into three sections. Each strip was further divided into nine work zones along its length, with seven work zones having a width of 10-12 meters and the work zone along the edge having a width of 5-6 meters.

[0088] An excavator with a digging power of 220 horsepower was deployed to excavate and clear the topsoil above the planned elevation of the plow layer, according to the design elevation. The average excavation depth was 31 centimeters. The excavated and plowed layer construction surface passed inspection.

[0089] After clearing the debris, the tracked bulldozer used was a Shantui SD16, with a power of 131 kilowatts, a track width of 56 centimeters, a weight of 17 tons, a bulldozer blade width of 3.4 meters, a working speed of 3 kilometers per hour in first gear, and two passes of compaction. The track overlap width was 10-15 centimeters.

[0090] Agricultural non-woven fabric with a weight of 30g / m² is laid on the plow pan surface. 2 Non-woven fabric, 1.6 meters wide, with an overlap width of 15 centimeters, fixed with L-shaped iron sticks made of No. 8 iron wire, with a spacing of 3-4 meters between the iron sticks, an iron stick length of 12 centimeters, and a horizontal hook length of 3 centimeters.

[0091] The plowshare base mixture was mixed on-site using a JS500 forced concrete mixer with a feed capacity of 800 liters and a discharge capacity of 500 liters. The mixing time was ≤72 seconds, the mixing shaft speed was 31 rpm, and each mixing cycle consisted of approximately 600 kg, with two mixing cycles totaling about 150 seconds. A 200 kg platform scale was used for weighing. Iron tailings and cement were manually loaded into the mixer using a wheelbarrow, with a weighing error of less than 0.5 kg per loading. The finished plowshare base mixture was directly loaded into dump trucks and transported to the construction site for use.

[0092] On-site plowing and leveling of the plow base mixture is carried out. Dump trucks transport the plow base mixture to a special material trough placed on site. The material trough is made of 5 mm thick iron plate, 5 meters long, 3.2 meters wide, and 0.5 meters deep. An excavator is used to transport the plow base mixture to the construction surface according to the estimated amount and spread it. Manual labor is used to spread and level it with rakes. The spread thickness is 5-6 cm. Manual labor is used to compact it simply with a flat shovel. The thickness after compaction is about 5.3 cm.

[0093] After the plow pan mixture has passed quality inspection, the top surface is covered with agricultural non-woven fabric for protection. The non-woven fabric weighs 30g / m. 2 The fabric is 1.6 meters wide. The non-woven fabric is laid with an overlap of 15 centimeters, and the fabric is compacted and fixed using on-site sand.

[0094] For the backfilling of the topsoil layer above the plow layer, an excavator is used to evenly backfill the topsoil layer from the stockpile strip onto the non-woven fabric of the plow layer. At the same time, the soil layer of the stockpile strip is excavated and cleaned. The excavation depth meets the elevation requirements for the construction of the plow layer of the field. The remaining soil is piled on the area where the plow layer has been completed. The plow layer is constructed in accordance with the construction requirements of the plow layer. The construction of the plow layer and the backfilling of the topsoil layer of the entire field are completed in accordance with the requirements.

[0095] After completing the plow layer construction work for the entire field grid, a tracked bulldozer was used to perform rough leveling of the field surface. After rough leveling, the difference in height of the field surface was measured to be less than 5 centimeters, which met the conditions for fine leveling.

[0096] For the fine leveling of the field surface, a satellite laser leveler, model 1JP3.5, was used. It was paired with a tractor with a power of 120-140 kilowatts. After leveling, the difference in height of the field surface was found to be less than 2 centimeters, which met the quality requirements.

[0097] After the plowing and burial of the plot were completed, watering was carried out on the fourth day, with a water volume of 61 cubic meters.

[0098] Actual irrigation verification showed that after constructing the plow pan, when the irrigation depth on the field surface was 10 cm, the infiltration rate was 4.1 mm / day, which met the needs of planting rice and other crops and achieved the quality target.

Claims

1. A method for modifying the plow pan of sandy farmland using iron tailings, characterized in that, Includes the following steps: 1) Repair sandy soil farmland that needs to be transformed into a plow pan. The fields are divided into plots according to the planting plan and the natural height of the field surface. Fields with similar surface heights are placed in the same plot. Field ridges are built between the plots, with a height of 40-50 cm, a top width of 30-40 cm, and a slope of 1:0.8-1.

2. 2) The plow pan of sandy soil farmland is constructed in a spaced-out strip pattern. The field is divided into several plowing and subsurface construction zones, each 8-10 meters wide, with a digging depth of 25-35 centimeters from the field surface; then the field bottom is compacted 2-3 times using construction equipment. 3) Use silicate cement and iron tailings to prepare the plowshare layer. Prepare the plow pan mixture by mixing solid materials in a mass ratio of 17%-30% silicate cement and 83%-70% iron tailings, and add water at a mass ratio of 6%-8% of the mass of the solid anhydrous dry materials. The permeability coefficient of the plow pan mixture should be less than 10 mm / day. Then spread the plow pan mixture on the compacted field bottom and build a plow pan with a thickness of 4-6 cm. Agricultural non-woven fabric is used as a barrier between the plow pan mixture and the wind-blown sand and soil in the field. The quality requirement for the non-woven fabric is 30-50 g / m². 2 The overlap width of the non-woven fabric should be 15-20 cm. The method for spreading the plow layer mixture is as follows: transport the plow layer mixture to the site, divide the plow layer mixture into small piles according to the amount to be used on the construction surface, then spread and level it, with a spreading thickness of 5-7 cm, and compact it to a thickness of 4-6 cm; After the plow layer mixture is spread and leveled, the top surface is covered with agricultural non-woven fabric for protection. The non-woven fabric should have a quality requirement of 30-50 g / m². 2 The overlap width of the non-woven fabric should be 15-20 cm. 4) Backfill the topsoil layer above the plow pan. The excavated topsoil is evenly backfilled onto the plow pan, and then leveled until the surface is 2-4 cm higher than the ground. After step 4) is completed, water the plow layer again within 7 days, watering 100-120 kg per square meter.

2. The method for modifying the plow pan of sandy farmland using iron tailings according to claim 1, characterized in that, In step 1), after dividing the field and building the field ridges, the height of the field surface is measured to determine the average elevation 30 cm below the field surface, and the benchmark height for building the plow layer of the field is determined. After clearing the topsoil according to the determined elevation, debris is cleared and leveled. After leveling, the height difference of the construction surface is less than 2 cm.

3. The method for modifying the plow pan of sandy farmland using iron tailings according to claim 1, characterized in that, The iron tailings have a silica content greater than 65% and a particle size ≤ 1 mm. Among them, the content of particles with a particle size > 0.05 mm and ≤ 1 mm is < 70%, the content of particles with a particle size > 0.002 mm and ≤ 0.05 mm is > 30%, and the content of particles with a particle size ≤ 0.002 mm is ≤ 5%. The moisture content of the iron tailings is less than 5%.

4. The method for modifying the plow pan of sandy farmland using iron tailings according to claim 1, characterized in that, In step 4), the method for leveling the field surface is as follows: first, use a bulldozer to perform rough leveling, and then use a grader to level it.

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