阅读说明：本技术 一种暗管排盐与结冰灌溉相结合的盐碱地治理方法 (Saline-alkali soil treatment method combining concealed pipe salt elimination and icing irrigation ) 是由 张美� 刘金铜 付同刚 高会 齐菲 王丰 高玥 李彦鑫 赵亮 于 2021-09-28 设计创作，主要内容包括：本发明公开了一种暗管排盐与结冰灌溉相结合的盐碱地治理方法。包括：土壤及地下水等环境要素调查及测定,“暗管排水排盐系统”设计、铺设,进行咸水/微咸水结冰灌溉,冰融淡化梯次入渗土壤,土壤盐分淋洗,暗管排水排盐等步骤。本方法是在冬季进行咸水/微咸水灌溉,形成一种土壤上层结冰、下层铺有暗管的特殊结构,利用春季咸水冰融淡化梯次入渗的规律淋洗土壤盐分,通过土壤下层铺设的“暗管排水排盐系统”将盐分排除土壤外,从而降低盐碱地的含盐量。本发明为缺少淡水资源、降雨量稀少、咸水/微咸水等非淡水资源丰富地区的盐碱地治理与生态建设提供了一种方法选择。(The invention discloses a saline-alkali soil treatment method combining concealed pipe salt elimination and icing irrigation. The method comprises the following steps: investigating and measuring environmental elements such as soil, underground water and the like, designing and laying a 'hidden pipe drainage and salt discharge system', freezing and irrigating saline water/brackish water, performing ice melting desalination and echelon infiltration of soil, leaching soil salt, draining and discharging salt through a hidden pipe and the like. The method is characterized in that saline water/brackish water irrigation is carried out in winter to form a special structure with frozen soil upper layer and laid hidden pipes on the lower layer, soil salinity is leached by utilizing the law of gradient infiltration of saline water ice melting desalination in spring, and the salt is removed from the soil through a hidden pipe drainage and salt discharge system laid on the soil lower layer, so that the salt content of the saline-alkali soil is reduced. The invention provides a method selection for saline-alkali soil treatment and ecological construction in areas which are short of fresh water resources, have rare rainfall, and are rich in non-fresh water resources such as saline water/brackish water.)

1. A saline-alkali soil treatment method combining concealed pipe salt elimination and icing irrigation is characterized by comprising the following steps:

(1) investigation and determination of environmental factors such as soil and groundwater

Comprises the investigation of soil, underground water, terrain, weather, water resource and water conservancy facility environmental elements,

investigating soil texture, soil salt content, permeability coefficient and plough layer depth; investigating the buried depth, the flow direction and the corresponding seasonal change condition of the underground water; surveying on the spot, collecting data, and acquiring information of topographic factors such as slope direction, elevation and the like; collecting air temperature, precipitation and evaporation capacity and seasonal distribution; surveying peripheral rivers, reservoirs and wetlands, which can use agricultural irrigation or soil salinity to rinse away guest water resources, pump stations and electric power facilities;

(2) design of concealed pipe drainage and salt discharge system

The concealed pipe drainage and salt elimination system consists of a concealed pipe network, a water collecting well, a water collecting pool and a pump station, and is designed according to investigation and determination results of saline-alkali soil and underground water environment elements;

hidden pipe network design: the concealed pipe network comprises a water suction pipe and a water collection pipe, the wall of the water suction pipe is provided with water permeable holes, one end of the water suction pipe is closed, the other end of the water suction pipe is connected with the water collection pipe, and the laying interval of the water suction pipe is 30-60 m; the laying distance of the water collecting pipes is designed by comprehensively considering the water collection amount and the crop planting arrangement, and the slope-to-fall ratio of the water suction pipe laying pipes is 0.5-0.7 per mill; the gradient ratio of the water collecting pipe laying is 0.8-1.2 per mill;

sand and stones are laid around the water suction pipe to serve as filter materials so as to prevent soil from blocking water permeable holes in the pipe wall of the water suction pipe;

designing a water collecting well: a water collecting well is arranged at the joint of the water suction pipe and the water collecting pipe, the water collecting well is provided with pipe holes and is connected with the water suction pipe and the water collecting pipe, the depth of the water collecting well is 0.5-1m, the water collecting well is buried below a plough layer by 20cm and is not less than 50cm away from the ground surface;

designing a water collecting tank: determining the volume of the water collecting pool according to the laying range of the concealed pipes and the water collection amount; determining the heights of the water collecting tank structure and the water collecting tank according to the soil structure and the underground water depth of the area;

pump station design: the method comprises the steps of designing the pump station lift, the pump station flow, the pump station running time and the power supply mode; the lift of the pump station is determined according to the distance between the drainage bearing area and the pump station, and the flow of the pump station and the running time of the pump station are designed by combining the volume of the water collecting pool and the emptying time of the water collecting pool; the power supply mode of the pump station is designed according to the power supply capacity or the power supply type of the location;

(3) constructing a concealed pipe drainage and salt discharge system;

the laying of the concealed conduit drainage and salt discharge system mainly comprises the following steps:

the hidden pipe laying construction comprises water suction pipe and water collecting pipe construction, and the water suction pipe construction comprises four steps of ditching, pipe burying, sand wrapping and soil covering;

the water collecting well construction comprises the steps of earth excavation, pipe burying, well body burying, soil covering and the like;

the water collecting pool construction comprises earth excavation, structure construction, pump station installation and earth covering reduction field;

(4) carrying out salt water/brackish water icing irrigation

In winter, when the temperature is reduced to below-5 ℃ for 5 days continuously, saline water/brackish water irrigation is started, the irrigation water is selected from saline water/brackish water non-fresh water resources, reasonable irrigation water quantity is set according to early-stage investigation to meet the purpose of salt washing by ice melting, the irrigation depth is 30-50cm, and the thickness of an ice layer after icing is 30-50 cm;

(5) ice melting desalination echelon infiltration soil

In spring, the temperature is above 0 ℃, the ice layer begins to melt, and the ice layer infiltrates into the soil in a gradient manner according to the rule that the bottom concentrated saline water melts first and the upper brackish water/fresh water melts later;

(6) soil salinity leaching

After the ice is melted, the brackish water/fresh water on the upper layer of the soil leaches the concentrated saline water at the bottom to the lower layer of the soil;

(7) drainage and salt discharge of concealed pipe

Soil water containing leached salt permeates into the water suction pipe, is collected into the water collecting pipe and the water collecting well through the water suction pipe, is discharged into the water collecting tank, and is discharged out of the soil body through the water collecting pump station, so that the salt content of the soil is reduced.

2. The saline-alkali soil treatment method according to claim 1, wherein in the step (2), the laying depth of the concealed conduit is 1.2-1.8m below the ground surface, wherein the suction pipes are arranged at equal intervals, and the intervals are 30-60 m.

Technical Field

The invention relates to a saline-alkali soil treatment method, in particular to a saline-alkali soil treatment method combining concealed pipe salt elimination and icing irrigation, and belongs to the technical field of ecological restoration.

Background

Due to the reasons of drought, less rain, shortage of surface water resources, shallow groundwater salt water level, unreasonable human agricultural planting system and the like, more and more farmlands are subjected to secondary salinization, and particularly in northern and northwest China, the area of secondary saline-alkali soil is continuously increased.

The hidden pipe water draining and salt eliminating technology is one important measure for preventing flood disaster and treating soil salinization in arid area and semi-arid area, and includes water sucking pipe and water collecting pipe, which has water permeating holes spread to certain depth underground and salt water entering the pipeline via the water permeating holes in the pipe wall. The technology of hidden pipe drainage and salt elimination is generally suitable for areas with large rainfall and rich surface fresh water resources, and the salt content of soil is reduced by adopting a large water flood irrigation salt pressing mode. However, in areas with rare fresh water resources, rare rainfall, abundant salt water resources and thick surface ice in winter, the use efficiency of underground pipe drainage and salt discharge is low, so that a special 'supply and demand' contradiction that water resources cannot be effectively utilized is caused, and agricultural production is influenced. In addition, secondary salinization can be exacerbated if irrigation with salt water is used during the non-icing period.

The research shows that when the salt water is used for irrigation, the concentrated salt water with high salinity content sinks to the bottom layer, the brackish water or the fresh water with low salinity content is arranged on the upper layer, and when the brackish water or the fresh water is frozen, the salinity of the ice layer on the bottom layer is high, and the salinity of the ice layer on the upper layer is low. When the salt water ice layer melts in spring, the bottom concentrated salt water melts firstly, the upper brackish water or fresh water melts later, the phenomenon of water gradient infiltration with different salinity can occur, the upper brackish water or fresh water melts later, the concentrated salt water which melts firstly at the bottom has a good leaching effect, the salt content of the soil surface layer, especially the plough layer can be reduced, and the ice layer is beneficial to keeping the soil moisture content. How to utilize the hidden pipe drainage and salt discharge technology and the law of gradient infiltration of melting of the ice layer of the salt water, solve the contradiction of 'supply and demand' that the salt water resource is abundant but can not be utilized, reduce the content of soil salt, improve the soil quality of saline-alkali soil, become the problem of the attack of the arid area with little rain and the area lacking surface fresh water resources.

Disclosure of Invention

The invention aims to provide a saline-alkali soil treatment method combining concealed pipe salt elimination and icing irrigation,

the problems of cold in winter, drought and raininess, shortage of surface fresh water resources, and water unavailability in regions with abundant saline water resources are solved.

Specifically, the saline-alkali soil treatment method combining concealed pipe salt elimination and icing irrigation provided by the invention comprises the following steps:

(1) investigation and determination of environmental factors such as soil and groundwater

Including the investigation of environmental elements such as soil, underground water, terrain, weather, water resources, water conservancy facilities and the like,

investigating soil texture, soil salt content, permeability coefficient and plough layer depth; investigating the buried depth, the flow direction and the corresponding seasonal change condition of the underground water; surveying on the spot, collecting data, and acquiring information of topographic factors such as slope direction, elevation and the like; collecting air temperature, precipitation and evaporation capacity and seasonal distribution; the investigation of peripheral rivers, reservoirs, wetlands and the like can refer to agricultural irrigation or soil salinity to rinse away the water resources, pump stations and electric facilities.

(2) Design of concealed pipe drainage and salt discharge system

The concealed pipe drainage and salt elimination system mainly comprises a concealed pipe network, a water collecting well, a water collecting pool, a pump station and the like, and is designed according to the investigation and measurement results of environmental factors such as saline-alkali soil, underground water and the like;

hidden pipe network design: the hidden pipe network comprises a water suction pipe and a water collection pipe, wherein the pipe wall of the water suction pipe is provided with water permeable holes, one end of the water suction pipe is closed, the other end of the water suction pipe is connected with the water collection pipe and is used for collecting downward-permeated salt-containing water, the water collection pipe is used for collecting the salt-containing water of the water suction pipe, the water suction pipe is laid in a horizontal row underground, the laying interval is 30-60m, the laying interval of the water collection pipe is designed by comprehensively considering water collection amount, crop planting arrangement and the like, and the slope-to-fall ratio of the laid water suction pipe is generally 0.5-0.7 per thousand; the slope-to-fall ratio of the water collecting pipe laying is generally 0.8-1.2 per mill;

the water suction pipe and the water collection pipe are laid at approximately the same depth underground and are generally vertically crossed, and a water collection well which is vertically upward is arranged at the crossed position;

sand and stones are laid around the water suction pipe to serve as filter materials so as to prevent soil from blocking water permeable holes in the pipe wall of the water suction pipe;

designing a water collecting well: the joint of the water suction pipe and the water collecting pipe is provided with a water collecting well, the water collecting well is provided with pipe holes and is connected with the water suction pipe and the water collecting pipe, the water collecting well is mainly used for collecting water in the water suction pipe, the depth of the water collecting well is generally set to be 0.5-1m, the distance between the well mouth of the water collecting well and the ground surface is not less than 50cm, and the farmland mechanized operation is facilitated;

designing a water collecting tank: determining the volume of the water collecting pool according to the laying range of the concealed pipes and the water collection amount; determining the heights of the water collecting tank structure and the water collecting tank according to the soil structure and the underground water depth of the area;

pump station design: the method comprises the steps of designing the pump station lift, the pump station flow, the pump station running time and the power supply mode; the lift of the pump station is determined according to the distance between the drainage bearing area and the pump station, and the flow of the pump station and the running time of the pump station are designed by combining the volume of the water collecting pool and the emptying time of the water collecting pool; the power supply mode of the pump station is designed according to the power supply capacity or the power supply type of the location;

(3) construction of concealed pipe drainage salt-removing system

The method comprises the following steps:

the hidden pipe laying construction comprises water suction pipe and water collecting pipe construction, and the water suction pipe construction comprises four steps of ditching, pipe burying, sand wrapping and soil covering;

the water collecting well construction comprises the steps of earth excavation, pipe burying, well body burying, soil covering and the like;

the water collecting tank and the pump station can be built and installed simultaneously, and the construction comprises earthwork excavation, structure construction, pump station installation, earth covering reduction field and the like;

the construction period of the closed-conduit drainage and salt-removal system is preferably selected in the season of the non-flood season with lower underground water level, the design and construction of the closed-conduit drainage and salt-removal system can be carried out at one time and repeatedly used for many years, and the closed-conduit drainage and salt-removal system is flushed every 15-20 years;

(4) carrying out salt water/brackish water icing irrigation

In winter, when the temperature is reduced to below-5 ℃ for 5 days continuously, saline water/brackish water irrigation is started, non-fresh water resources such as saline water/brackish water are selected as irrigation water, a reasonable irrigation water quantity is set according to early-stage investigation to meet the purpose of salt melting and washing, the irrigation depth is 30-50cm, the thickness of an ice layer after icing is 30-50cm, and a special structure of 'upper and lower pipes' is formed, namely the structure that the surface layer of soil is iced and the lower layer of soil contains a hidden pipe;

(5) ice melting desalination echelon infiltration soil

In spring, the ice layer begins to melt at the temperature of more than 0 ℃, and the ice layer infiltrates into the soil in a gradient manner according to the rule that the bottom concentrated saline water melts first and the upper brackish water/fresh water melts later;

(6) soil salinity leaching

After the ice is melted, the brackish water/fresh water on the upper layer of the soil leaches the concentrated saline water at the bottom to the lower part of the soil;

(7) drainage and salt discharge of concealed pipe

Soil water containing leached salt permeates into the water suction pipe, is converged into the water collecting pipe and the water collecting well through the water suction pipe, is discharged into the water collecting tank, and is discharged out of the soil body through the water collecting pump station, so that the salt content of the soil is reduced.

Preferably, in the step (2), the laying depth of the concealed conduits is 1.2-1.8m below the ground surface, wherein the water suction pipes are arranged at equal intervals, and the intervals are 30-60 m;

when the pipeline is long, a water collecting well is arranged at the position of 200-300 m. The water collecting well is generally buried below 20cm of a plough layer, and the distance from the water collecting well to the ground surface is not less than 50cm, so that the mechanized operation of the farmland is facilitated.

The method is characterized in that the freezing and irrigating time of the saline water is winter, and the time for leaching the soil salt by utilizing the law of gradient infiltration of saline water freezing and desalting is spring.

The method is suitable for areas with thick ice layers, rare rainfall and surface fresh water resources, but rich non-fresh water resources such as salt water/brackish water and the like in winter. Can realize the special hydrological cycle of the echelon infiltration of the ice-melt desalination in spring for many years in the winter irrigation of the salt water.

The invention has the following beneficial effects:

the method disclosed by the invention is used for carrying out freezing irrigation in winter, and by utilizing the echelon infiltration rule that concentrated saline water in a saline water ice layer is melted before brackish water/fresh water is melted when the saline water ice layer is melted in spring, salt in saline soil is leached, so that the salt content of the soil is reduced, the soil moisture content can be kept, and the planting and growth of crops in spring of the next year are facilitated. The method is suitable for arid regions with little rain, surface fresh water resource shortage, rich non-fresh water resources such as salt water/brackish water and the like and cold regions in winter, and can realize effective utilization of various non-fresh water sources such as return water, running water, trench water, pond water, underground salt water/brackish water and the like.

Drawings

FIG. 1 is a flow chart of the present invention.

FIG. 2 is a schematic view of the structure of the "ice-on-ice-down tube".

In the figure, 1, a soil planting layer, 2, a laid concealed conduit, 3 and an icing layer.

Detailed Description

The present invention is further illustrated by the following specific examples.

Example 1

The test area is located in five primary counties of an autonomous region of Mongolia autonomous region in China, is one of main planting areas in a river-sleeve irrigation area, and soil is not suitable for normal growth of crops due to shortage of water resources and large soil salinity of the irrigation area, so that the method is used for treatment. The specific steps are carried out according to the process flow shown in figure 1.

Firstly, environmental factors including soil investigation, underground water investigation, terrain investigation, meteorological investigation, water resource investigation and the like are investigated in a test area. Investigation shows that the annual precipitation of the area is about 200mm, the annual evaporation capacity is about 2500mm, the rainfall is less, and the evaporation is strong. The test land has flat terrain, the average buried depth of the underground water level is 1.8-2m, the soil is cohesive soil, the salt content of the soil is 0.8% -1.2%, and the thickness of the planting soil layer is about 1.8 m. Except yellow river water, other water resources in the test area surrounding the test area are saline water or brackish water. The test field is surrounded by the Wulan drain passage, and the electric facilities are lacked.

And (3) designing a hidden pipe drainage and salt discharge system according to the investigation result, wherein 13 water suction pipes are paved in the test area, the length of the water suction pipes is 2600m in total, the water suction pipes are PVC pipes with the pipe diameters of 8cm, and the pipe walls of the water suction pipes are provided with water permeable holes with the diameters of 3 mm. The slope-drop ratio of the water suction pipe embedded is 0.5 per mill, the pipe spacing is 30m, and the embedding depth is 1.6 m. A water collecting pipe vertical to the water suction pipe is laid in the test area, and the water collecting pipe is a PE pipe with the pipe diameter of 15 cm. The slope-drop ratio of the embedded water collecting pipe is 1 per thousand, the average embedded depth is 1.65m, and the length is about 500 m. And the intersection of the water suction pipe and the water collecting pipe is provided with 13 water collecting wells, and the total number of the collected water is 13. The distance between the wellhead of the water collecting well and the ground surface is 0.6m, the depth of the water collecting well is 1.1m, the water collecting well is sealed by a concrete pipe and a cast iron well cover, and the upper part of the water collecting well is covered with soil.

According to the drainage capacity of the water collecting pipe, a water collecting pond and a pump station 1 seat are arranged at the tail end of the water collecting pipe, the volume of the water collecting pond is 2m x 3m x 4m, and the water collecting pond is of a reinforced concrete structure and is subjected to waterproof treatment. The pumping station adopts an automatic control start-stop mode and is unattended. And carrying out water discharge amount calculation according to the calculated water collecting well pump station at 24.67 m/h. Selecting a water pump type: and (4) carrying out submerged pump cultivation at a lift of 15m and a flow rate of 25 m/h. The pump station is powered by solar energy.

According to the design scheme, the test area begins to be constructed in the middle ten days of 4 months in 2020, the water suction pipe construction is firstly carried out, the ditching and pipe burying integrated machine is adopted for construction, and the four steps of ditching, pipe burying, sand wrapping and soil covering are completed at one time; secondly, constructing a water collecting pipe and a water collecting well, wherein the water collecting pipe and the water collecting well are simultaneously and gradually constructed, and the construction steps sequentially comprise earth excavation, pipe burying, well body embedding and earth covering; thirdly, constructing a water collecting tank and a pump station, simultaneously constructing and installing the water collecting tank and the pump station, wherein the construction comprises earthwork excavation, then constructing a reinforced concrete structure, installing the pump station after the structural construction is finished, and finally covering soil and reducing a field; and finally, performing trial operation on the constructed 'hidden pipe drainage and salt discharge system', and finding out problems to overhaul and maintain in time.

According to the experimental setting, the temperature of a test area reaches-5 ℃ after 11 months and 5 days in 2020, the test area is continuously irrigated with salt water (the salt content is about 1.1%) by using the water removed from the Dracocephalum moldavica drainage, the irrigation mode adopts flood irrigation, the irrigation water is about 50cm, the icing thickness is about 56cm, and the structure of the iced soil is shown in figure 2.

In the early 3 months of 2021, the air temperature gradually warms up, the ice layer begins to melt, and the ice layer infiltrates into the soil in a gradient manner according to the rule that the bottom concentrated saline water melts first and the upper brackish water/fresh water melts later. And brackish water/fresh water is formed after ice melting to carry out leaching on the concentrated saline water at the bottom, so that the salt content of the soil is reduced.

The ice layer was completely melted at 4 months and 10 days in 2021. According to soil sampling detection, the salt content of the iced soil is 0.5% -0.8%, and the salt content of the soil is reduced by 27% -37%.

According to local planting requirements, crops mainly comprising millet, corn, sorghum and sunflower are planted in the test area and the peripheral control area within 22 days in 6 months. And (3) comparing the test area with the control area which is not subjected to the method of 'cooling the ice and dropping the tube' at the periphery by 5 days after 7 months, and finding that the crops in the test area have fast germination, high germination rate and good seedling growth vigor.

Experimental results show that the method utilizes the salt water/brackish water to carry out icing irrigation, fully utilizes other water resources except non-fresh water, and utilizes the salt-water freezing and thawing water salt motion law and the effects of salt discharge and alkali discharge of a concealed pipe to reduce the salt content in the saline-alkali soil. Meanwhile, the frozen irrigation in winter contributes to the effects of soil moisture preservation and soil moisture preservation, and the germination rate and the seedling growth vigor of the planted crops are obviously better than those of a control area.

Therefore, the saline-alkali soil treatment method is beneficial to reducing the salinity of the saline-alkali soil in the river-crossing region, and plays a good role in promoting agricultural production and ecological construction in the irrigation area.