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CN-121970558-A - Cohesive soil improvement method

CN121970558ACN 121970558 ACN121970558 ACN 121970558ACN-121970558-A

Abstract

The invention relates to the technical field of soil improvement methods, and discloses a cohesive soil improvement method which comprises the following steps of S1-S4. Through a synergistic improvement mode, the organic matter content of the soil is improved, the heavy metal content of the soil is removed, the hardening rebound rate is reduced, meanwhile, the pH of the soil is adjusted to be in a proper range of 6.0-7.5, and the comprehensive improvement effect is obvious; meanwhile, the ecological materials such as bamboo fibers, earthworms and straws are adopted, so that the dosage of chemical reagents is greatly reduced, secondary pollution is avoided, the adverse effect of the residual leaching agent after water discharge and biodegradation is reduced, and an improved closed loop is formed through later measures such as rotation, periodic repair and permeability maintenance, so that rebound after short-term effect is avoided, and the improvement effect is effectively prolonged.

Inventors

  • WANG LI
  • BAI PING
  • ZHONG JIAN
  • DING ANG

Assignees

  • 四川省林业科学研究院（四川省林产工业研究设计所）

Dates

Publication Date
20260505
Application Date
20251208

Claims (9)

  1. 1. A method of improving a cohesive soil comprising the steps of: S1, pollution screening and pretreatment strengthening, namely detecting the pH value, the cosmid content, the organic matter content and the Cu, pb, ni, zn, cr heavy metal content of soil, classifying and judging according to detection results, adopting targeted leaching treatment if heavy metal exceeds standard plots in the stage, then removing stones and weed rhizomes in the soil, deep ploughing 25-30cm along contour lines, then sunning upturned or frozen upturned soil for 15-20 days, and fully irrigating the soil moisture after leaching or sunning upturned soil until the water content of the soil is 20-25%; S2, synergistic improvement, namely mixing 200-300kg of fine sand, 300-400kg of fine slag and 300-450kg of crushed straw uniformly by rotary tillage according to the dosage of each mu, realizing physical loosening and viscosity reduction, broadcasting chemical modifier to adjust pH according to the acid-base property of soil in the stage, constructing an ecological biological system of super absorbent bamboo fibers, earthworms and chicory, and supplementing organic matters by matching 1500-2000kg of decomposed farmyard manure; S3, cultivation adaptation, namely constructing high furrows with furrow height of 15-25cm along the contour lines, forming a multi-furrow drainage system by matching furrow furrows, waist furrows and surrounding furrows when the land length exceeds a certain threshold value, leveling and moderately compacting soil, and covering soil moisture after sowing or transplanting; S4, post-maintenance, namely adopting a three-year-round-of-crop-deep-root-gramineous-crop system of leguminous crops to perform rotation optimization, performing soil moisture and nutrient management, regularly punching holes to maintain permeability, and performing regular monitoring and repair.
  2. 2. The cohesive soil improvement method according to claim 1, wherein in the S1 stage, specific operations of targeted leaching comprise selecting 0.1mol/L ferric trichloride solution when Cu, ni and Pb exceed standard, selecting oxalic acid solution when Zn exceed standard, independently adapting leaching agent according to soil pH when Cr exceed standard, mixing the leaching agent with the ferric trichloride solution and the oxalic acid solution in proportion, spraying the leaching agent according to a water-soil ratio of 10:1 (w/w), shallow turning for 5cm, keeping wetting for 1 hour, repeatedly leaching at intervals of 7 days, accumulating leaching for 3 times, and ditching and draining after leaching.
  3. 3. A method for improving cohesive soil according to claim 1, wherein in the S2 stage, the ecological biological system is used in an amount of 24-30g/m2 of super absorbent bamboo fiber, 20-25 strips/m 2 of Eisenia foetida and 3g/m2 of chicory seeds, and the bamboo fiber is firstly turned into the soil shallowly when put in, then the earthworm is covered with thoroughly decomposed organic fertilizer, and then the chicory seeds are planted in a drill.
  4. 4. A method for improving a cohesive soil according to claim 1, wherein in the S2 stage, after the ecological biosystem is constructed, the use of a high concentration of agricultural chemical is avoided, and the soil humidity is maintained at 20-25% for 3 days after the earthworm is put in.
  5. 5. The method for improving cohesive soil according to claim 1, wherein in the S2 stage, the chemical modifier is applied in a mode that 50-80kg of quicklime or 150kg of plant ash, 50-80kg of ferrous sulfate are sprayed when the pH is less than 6.5, the ferrous sulfate dosage is increased to 100-150 kg/mu when Cr exceeds standard, 40-60kg of gypsum is sprayed when the pH is 6.5-7.5, 1000g of soil leavening agent is sprayed, 80-100 kg/mu of humic acid is additionally added when Cr exceeds standard, and 80-100kg of humic acid is sprayed when the pH is more than 7.5, 100kg of superphosphate and 120-150 kg/mu of humic acid are added when Cr exceeds standard.
  6. 6. A method for improving a cohesive soil according to claim 1, wherein in the S3 stage, the soil moisture preservation operation by covering the furrow surface with 5-8cm straw or straw curtain to prevent rain water from washing out surface soil and reduce water evaporation and inhibit weed growth is carried out, and in particular, a dry season can be covered with a mulching film and the edges are compacted, and the straw coverage is maintained in a rainy season.
  7. 7. A method for improving a cohesive soil according to claim 1, wherein in the S3 stage, the multi-ditch drainage system has the specifications that the width of the ditches is 30-40cm, the depth is 15-20cm, the waist ditches are arranged when the ground length exceeds 30m, the width of the waist ditches is 40cm and the depth is 30cm, the width of the surrounding ditches is 50cm and the depth is 40-50cm, and the multi-ditches are communicated and deepened step by step.
  8. 8. A method for improving a cohesive soil according to claim 1, wherein in the S4 stage, the operation of punching maintenance comprises punching holes with a hole diameter of 15-20mm at the end of summer with a distance of 20cm x 20cm and a depth of 25-35cm, and filling crushed straws after punching.
  9. 9. The method for improving cohesive soil according to claim 1, wherein the deep ploughing depth is adjusted to 20cm in the S1 stage, the straw covering thickness is increased to 8-10cm in the S3 stage, the lumbar ditch spacing is encrypted to 25m, the furrow height is increased to 25cm in the S3 stage, the organic fertilizer dosage is adjusted to 1000-1500 kg/mu in the S2 stage, and the gypsum dosage is increased to 80 kg/mu in the S3 stage for valley low-lying land blocks.

Description

Cohesive soil improvement method Technical Field The invention relates to the technical field of soil improvement methods, in particular to a cohesive soil improvement method. Background The cohesive soil has the problems of poor pore structure, poor air and water permeability, easy hardening and the like due to high clay ratio (generally more than 35 percent), and seriously limits the growth of crop root systems, so that the moisture infiltration is difficult and the nutrient migration is blocked. The viscous soil in southwest area is also faced with special challenges that mountains and hills are easy to cause water and soil loss, rain and high humidity environment causes modifier loss and soil erosion, and part of land parcels have the phenomenon of exceeding standard of Cu, pb, ni and other heavy metals due to industrial activities or agricultural pollution. The traditional cohesive soil improvement method has various limitations that the traditional physical improvement (such as pure sand doping) is short in effect and easy to rebound, the chemical modifier (such as single gypsum and quicklime) is large in use amount, the salinization or acid-base unbalance of the soil can be caused, the biological improvement mostly adopts single strain or organic fertilizer, no synergistic effect is formed, the leaching technology aiming at heavy metal pollution is not combined with the conventional improvement, and the technical scheme for adapting to southwest topography and climate is deficient. In addition, the existing method mostly omits the later maintenance and scene adaptation, so that the improvement effect is difficult to last, and the requirements of multiple scenes such as farmlands, orchards, lawns and the like cannot be met. Therefore, there is a need to develop a method for improving the cohesive soil, which combines ecology, pertinency, long-acting performance and scene suitability, and solves the problems of cohesive soil hardening, nutrient deficiency, heavy metal pollution and improvement brought by special environments in southwest areas through multi-technology cooperation. Disclosure of Invention The invention mainly provides a cohesive soil improvement method which solves the problems that the existing cohesive soil improvement method is short in effect, poor in adaptability, not compatible with heavy metal pollution treatment and the like. In order to solve the technical problems, the invention adopts the following technical scheme: a method of improving a cohesive soil comprising the steps of: S1, pollution screening and pretreatment strengthening, namely detecting the pH value, the cosmid content, the organic matter content and the Cu, pb, ni, zn, cr heavy metal content of soil, classifying and judging according to detection results, adopting targeted leaching treatment if heavy metal exceeds standard plots in the stage, then removing stones and weed rhizomes in the soil, deep ploughing 25-30cm along a contour line, sunning upturned soil or frozen upturned soil for 15-20 days, and fully irrigating soil moisture after leaching or upturned soil until the soil moisture content is 20-25%, wherein the stage S1 is carried out 2-3 months (after rainy season is finished) before sowing or transplanting, and laying a foundation for core improvement. Specifically, 0-20cm of plough layer soil is collected, and the pH value, the cosmid content, the organic matter content and the Cu, pb, ni, zn, cr heavy metal content are detected. Classified according to the detection result, the clay accounts for more than 40 percent and is high-viscosity soil, the pH value is acid soil and the pH value is 7.5 and is alkaline soil, and the soil with the heavy metal content higher than (GB 15618-2018) in table 1 and equal to or lower than that in table 3 and capable of taking control measures can be used for improving agricultural heavy metal out-of-standard soil. Heavy metal pollution of cohesive soil in southwest is mainly Cu, pb, ni, zn, cr, and Hg and As are concentrated in specific industrial pollution areas such As mercury mine periphery and gallium arsenide production area, which belongs to low-frequency pollution and is not considered. In the deep ploughing of clearing impurities, the severely hardened land is divided into 2 times of deep ploughing and 10 days apart, and the laminated layer is broken. The upturned soil is sunk 15-20 days after deep ploughing in summer, the high Wen Fenghua granules are utilized, the upturned soil is sunk 15-20 days after deep ploughing in winter, and the agglomeration of the cosmid grains is broken alternately through freeze thawing. The leaching agent is prevented from being used together with strong alkaline materials such as quicklime and the like, more than 7 days are needed, and deep ploughing and leaching are not performed in rainy seasons, namely about 5-9 months, so that soil scouring and modifier loss are avoided. S2, synergistic improvement, namely mixing 200-300kg of