CN201163918Y - A device for automatically controlling constant soil water potential - Google Patents

Abstract

The utility model discloses a device for automatically controlling constant soil water potential. The device mainly uses semi-permeable materials and a solution with a constant water potential to control the soil water potential within a certain range to be constant at a specific value. The device includes a constant water pressure water supply device, an automatic control water inlet device, a semi-permeable material water control device and a microporous container; the constant water pressure water supply device can supply water at a constant water pressure, and the automatic control water inlet device can automatically control The amount of water delivered to the constant water potential solution ensures that its water potential is constant; the semi-permeable material water control device is a device with semi-permeable material as the main functional component, which realizes the water exchange between the constant water potential solution and the closed water body, micro The surface of the porous container has many micro-sized holes, which can permeate water, but the air intake value is low, so as to realize the water exchange between the closed water body and the soil. The utility model can effectively control the soil water potential to be constant, and is widely applicable to the fields of agriculture and scientific research.

Description

A device for automatically controlling constant soil water potential

technical field

The utility model relates to a device for automatically controlling constant soil water potential. It belongs to the field of agricultural science and technology.

Background technique

The world's population is increasing day by day, and the earth can provide us with limited resources, coupled with global warming and frequent droughts, it has brought problems to agricultural production in many countries around the world. Agricultural research workers are facing a new challenge: how to use limited agricultural resources to continue to develop agricultural production and meet the needs of social production and people's lives. Among the contradictions between agricultural production and agricultural resources, the contradiction between agricultural production and water resources is quite prominent. In modern society, the development level of agricultural production largely depends on the water supply and supply time in agricultural production. Agronomists need to study the water demand of different crops, determine the rational layout of crops, irrigation amount and irrigation time according to the law of water demand, coordinate regional agricultural water use plans, etc., in order to better use the natural resources of each region and play the role of each region. Advantages of natural resources, good social and ecological benefits.

Most of the water needed for crop growth comes from the soil. Most indicators about the effectiveness of soil moisture to crops are expressed by soil water content. The percentage of dry soil weight can reflect the availability of soil moisture to crops to a certain extent. But soil is a mixture of many substances, especially on saline-alkali soil. Although the absolute water content is high, it is difficult for crops to absorb and use the water in the soil for growth. This is because the salt content in the soil is too high and the water potential is very high. Low, the crops can not absorb the sake. At this time, it is not very reasonable to use soil water content to represent the availability of water to crops; under the same soil water content, soil with different salinization degrees has different availability of soil water to crop growth. Soil water potential adopts the unit of energy, which is uniform and versatile, suitable for use on any type of soil, and can also be compared with the water potential changes in plants, so the soil water potential is used to express and study soil moisture The effectiveness of crops is more reasonable, and it can overcome the shortage of using soil water content to express the availability of soil moisture to crops.

In the current method for soil water potential control, the soil water potential is mainly measured and studied by a soil water potential tensiometer, and the soil water potential is controlled by watering. This research method is to embed a soil tensiometer in the soil. Due to various reasons, the soil water is lost in the atmosphere or seeps down, which makes the soil water potential lower. By observing the changes in the tensiometer readings, the soil is watered, so that The soil water potential rises to a preset range or a specific value, and this method is used to study the impact of soil water potential on crops or other indicators. This method is generally used under field conditions, and it is reasonable, but it also has disadvantages: ①Under field conditions, the soil water potential varies in a large range, and it is not possible to determine well under which soil water potential conditions, the test index will occur. ②It is difficult to control the soil water potential. Using this method to study the soil water potential will inevitably require a lot of work. It will take more time to observe when the soil water potential is adjusted by irrigation water. If the soil water conductivity is poor , the soil water potential tensiometer changes slowly; it will take more time; ③The control of soil water potential requires other facilities to be invested. In order to prevent the influence of water flow between test areas, it is necessary to prevent the flow of groundwater or the entry of external water test area. ④ This test method cannot automatically and constantly control the soil water potential.

At present, there are almost no research reports on the constant control device of soil water potential.

Utility model content

The utility model overcomes the shortcomings in the prior art and provides a device capable of automatically controlling the constant soil water potential. The device mainly uses semi-permeable materials and a constant water potential solution to control the constant soil water potential.

The technical scheme of the utility model is summarized as follows:

A device for automatically controlling constant soil water potential, characterized in that the device includes a constant water pressure water supply device, an automatic water inlet device, a semi-permeable material water control device and a microporous container; a constant water pressure water supply device, which automatically controls the water inlet The water device and the semi-permeable material water control device are all provided with a water inlet and a water outlet, and the microporous container is provided with a water inlet; the water outlet of the constant water pressure water supply device is connected to the water inlet of the automatic control water inlet device, and the automatic control water inlet device The water outlet of the semipermeable material water control device is connected to the water inlet of the semipermeable material water control device, and the water outlet of the semipermeable material water control device is connected to the water inlet of the microporous container, wherein:

The constant water pressure water supply device is a water container, and the device can supply water with constant water pressure, such as a mariot bottle.

The automatic control water inlet device is a container containing a constant water potential solution. The solution does not fill the entire container, and the part other than the solution is filled with air. This part of the air is in a closed state and the air pressure is constant; the device can automatically control the amount of water entering the constant water potential solution. , to ensure the constant volume and concentration;

The semi-permeable material water control device is a container containing liquid. The container is divided into two cavities by the semi-permeable material near the middle of the container, with a water inlet and a water outlet respectively. The cavity connected to the water inlet is equipped with There is a constant water potential solution, and the cavity connected with the water outlet is filled with water. Semipermeable materials refer to those materials that allow the solvent molecules in the solution to pass through freely, but the solute cannot pass through, such as animal bladders, intestinal casings, cell membranes, and membranes that use external pressure to purify water. The semipermeable material of the utility model is preferably a reverse osmosis membrane or a semipermeable membrane.

The microporous container is a water container, and there are many tiny holes on the wall of the container, which can be used to permeate water, but cannot penetrate air and soil. The device is in direct contact with the soil, and the water lost by the soil is replenished through this microporous container. The microporous container of the utility model is preferably a microporous ceramic container. The micropore diameter is in the range of 250-800 microns, and the microporous ceramic container cannot pass through air when the container wall is saturated with water, and its air intake value is relatively low, in the range of 0.3-0.6MPa. Intake value: When the air pressure is increased to a certain value on one side of the water-saturated porous ceramic plate, the ceramic plate starts to drain, but the air cannot pass through the ceramic plate. Corresponding to the difference) is defined as the intake value.

Water located between the walls of the microporous container and the semipermeable material is enclosed. form a closed body of water.

Further, the above-mentioned constant water pressure water supply device is provided with an air inlet near the water outlet. The air inlet is located below the water surface and is in an open state when the entire device is in operation; the water inlet is in a closed state when the entire device is in operation. When filling water, first close the water outlet and air inlet at the lower end, then open the water inlet at the upper end to inject water; after reaching a certain amount, first close the water inlet at the upper end, and then use a rubber tube to connect the water outlet of the constant water pressure water supply device and the automatic control The water inlet of the water inlet device is finally opened to realize constant water pressure water supply. When water needs to be injected during the working period, the water outlet and the air inlet are first closed, and then the water inlet is opened to inject water. After the water injection is completed, the water inlet is first closed, then the water outlet is opened, and finally the air inlet is opened. The working principle of the device is briefly described as follows: In the calculation formula of water pressure P=ρ×g×h, ρ is the density of water 1000kg/m ³ , g is the acceleration of gravity about 9.8m/s ² , and h is the air intake of the device The vertical height (m) between the mouth and the drip pipe outlet of the automatic water inlet device. Therefore, during the use of the device, as long as the size of h is kept constant, that is, the relative position between the device and the automatic water inlet device is kept fixed, the device can supply water to the automatic water inlet device with constant water pressure.

The water inlet of the above-mentioned automatic control water inlet device extends into the inner cavity of the device for a section to form a drip tube suspended in the inner cavity of the device for forming water droplets. The working principle of the device is briefly described as follows: when the device supplies water to the semi-permeable material water control device, the constant water potential solution in the device decreases, and the liquid level drops, so that the volume of the enclosed air above the liquid surface increases and the pressure decreases , so the drip pipe starts to drip water, and the liquid level gradually rises until the air pressure returns to the initial level. At this time, the liquid level rises to the initial height, and the air volume returns to the initial volume. constant.

水势(bar)，T：温度(℃)，C_PEG：聚乙二醇浓度(g/g)，水势误差在5％以内。根据上述公式可以计算欲控制土壤水势的水平，上述公式适宜的PEG浓度范围为0-0.8g/g。恒定水势溶液也可以通过某些强电解质盐配置。The above-mentioned constant water potential solution is prepared with chemically stable substances, and the water potential and concentration of the solution have a one-to-one correspondence, which can be calculated or measured. Such as polyethylene glycol (PEG), the water potential is calculated by the following formula,

Water potential (bar), T: temperature (°C), C _PEG : polyethylene glycol concentration (g/g), water potential error within 5%. The level of soil water potential to be controlled can be calculated according to the above formula, and the suitable PEG concentration range of the above formula is 0-0.8g/g. Constant water potential solutions can also be formulated with certain strong electrolyte salts.

The connection methods between the above-mentioned devices are all connected by rubber tubes.

Furthermore, as a simplification of the device of the present invention, the above-mentioned automatic control water inlet device and the semi-permeable material water control device share the same container for the cavity containing the constant water potential solution. In other words, the automatic control water inlet device simultaneously serves as a cavity for containing a constant water potential solution as a semipermeable material water control device.

In order to be able to constantly control the soil water potential in a wider range, the semi-permeable material water control device may include multiple water outlets, which are respectively connected to multiple microporous containers.

Compared with prior art, the advantage of the utility model device is:

1. This device can automatically control the constant soil water potential, minimizing the adverse effects caused by changes in soil water potential;

2. As long as there is enough water in the constant water pressure water supply device, the device can work continuously;

3. The device can precisely control the soil water potential, save manpower, material and financial resources, and can effectively improve work efficiency.

Description of drawings

Fig. 1 is the connection diagram of each functional part of the utility model embodiment

Fig. 2 is a schematic diagram of the constant water pressure water supply device of the utility model embodiment

Fig. 3 is a schematic diagram of the automatic control water inlet device of the utility model embodiment

Fig. 4 (a) is the three-dimensional structure diagram of the semi-permeable material water control device of the embodiment of the present invention

(b) is a side view structure diagram of the semipermeable material water control device according to the embodiment of the utility model

Fig. 5 is a schematic diagram of the simplified structure of the automatic control water inlet device and the semipermeable material water control device of the embodiment of the present invention

Fig. 6 is a perspective view of the simplified structure of the automatic control water inlet device and the semipermeable material water control device of the embodiment of the utility model

Fig. 7 is a schematic structural diagram of the actual use state of the utility model embodiment

Fig. 8 is a schematic diagram of the work of connecting a plurality of microporous ceramic containers with a semipermeable material water control device according to an embodiment of the present invention

in:

1-Constant water pressure water supply device

2- Automatic control water inlet device

3-Semi-permeable material water control device

4- Microporous ceramic container

5- soil container

11-water inlet 12-water surface 13-air inlet

14-Water outlet 21-Water inlet 22-Drip pipe

23-liquid level 24-water outlet 31-splint

32-Screw hole 33-Screw 34-Reverse osmosis membrane

35-Water inlet 36-Water outlet

Detailed ways

Below in conjunction with accompanying drawing and specific embodiment, this device is described in further detail:

As shown in Figure 1, the device consists of a constant water pressure water supply device 1, an automatic water inlet control device 2, a semipermeable material water control device 3 and a microporous ceramic container 4.

As shown in Figure 2, the constant water pressure water supply device 1 is a cylindrical water container, the upper end is provided with a water inlet 11, the water inlet 11 is connected to the water source, the lower end is provided with a water outlet 14, and the water outlet 14 is connected to the automatic valve through a rubber tube. The water inlet 21 of the water inlet device 2 is controlled, and an air inlet 13 is arranged near the water outlet 14. The air inlet 13 is located below the water surface 12. During normal use, the water inlet 11 is closed, and the air inlet 13 is opened. The device can supply water with constant water pressure. When filling water, first close the water outlet 14 and the air inlet 13 at the lower end, then open the water inlet 11 at the upper end to inject water; after reaching the required amount, first close the water inlet 11 at the upper end, then open the water outlet 14, and finally open the air inlet Port 13 can realize constant water pressure water supply. When needing water injection during work, first water outlet 14 and air inlet 13 are closed, then open water inlet 11 water injection, after water injection finishes, close water inlet 11 earlier, then open water outlet 14, open air inlet 13 at last. The working principle of the device is briefly described as follows: In the calculation formula of water pressure P=ρ×g×h, ρ is the density of water 1000kg/m ³ , g is the acceleration of gravity about 9.8m/s ² , and h is the air intake of the device The vertical height (m) between the mouth and the drip pipe outlet of the automatic water inlet device. Therefore, during the use of the device, as long as the size of h is kept constant, that is, the relative position between the device and the automatic control water inlet device 2 is kept fixed, the device can supply water to the automatic control water inlet device 2 with a constant water pressure. .

As shown in Figure 3, the automatic control water inlet device 2 is a cylindrical container for holding a constant water potential solution, the upper end is provided with a water inlet 21, and the water inlet 21 is connected to the water outlet 14 of the constant water pressure water supply device through a rubber tube. The water port 21 extends into the inner cavity of the device for a section to form a drip pipe 22 for forming water droplets. The liquid surface 23 is located up and down in the middle of the container; the upper area A is equipped with closed air, and the air pressure is constant. The lower end is provided with a water outlet 24, and the water outlet 24 Connect to the water inlet 35 of the semi-permeable material water control device 3 through a rubber tube. The device can automatically control the amount of water entering the constant water potential solution to ensure constant volume and concentration, thereby ensuring constant water potential of the constant water potential solution. The working principle of the device is briefly described as follows: when the device supplies water, the amount of water in the device decreases, and the liquid level drops, so that the volume of the enclosed air above the liquid surface increases, and the air pressure decreases, so the dripping pipe starts to drip water, and the liquid level gradually decreases. Increase until the air pressure returns to the initial level, at this time the liquid level rises to the initial height, the air volume returns to the initial volume, and the volume, concentration, and water potential of the constant water potential solution remain unchanged.

水势(bar)，T：温度(℃)，C_PEG：聚乙二醇浓度(g/g)，水势误差在5％以内。根据上述公式可以设计欲控制土壤水势的水平，上述公式适宜的PEG溶液的浓度范围是0-0.8g/g。The above-mentioned constant water potential solution is prepared from chemically stable substances, and the water potential of the solution has a one-to-one correspondence with the concentration of the solution, which can be obtained by calculation or measurement. Taking polyethylene glycol (PEG) as an example, the water potential can be calculated by the following formula,

Water potential (bar), T: temperature (°C), C _PEG : polyethylene glycol concentration (g/g), water potential error within 5%. The level of soil water potential to be controlled can be designed according to the above formula, and the concentration range of the PEG solution suitable for the above formula is 0-0.8g/g.

As shown in Figure 4, the semi-permeable material water control device 3 is a nearly spherical container for containing liquid, and the middle part of the container is provided with a reverse osmosis membrane 34, and the reverse osmosis membrane 34 is clamped and fixed by the support plate 31 and connected with the entire container For sealing, the middle of the support plate 31 is dug out to form a cavity for the solution to pass through, and the support plates 31 are fixed by screws 33 . The reverse osmosis membrane 34 divides the whole device into two independent chambers C and D. C cavity is provided with water inlet 35, is connected with the water outlet 24 of automatic control water inlet device 2, and constant water potential solution is housed in this cavity, and D cavity is provided with water outlet 36, is connected with the water inlet of microporous ceramic container 4 , water is housed in this area, and this part of water body between the reverse osmosis membrane 34 and the microporous ceramic container 4 is in a closed state. The reverse osmosis membrane 34 separates the closed water body and the constant water potential solution, and becomes a medium for water exchange between the two. Water molecules can pass freely, but solute molecules in the constant water potential solution cannot pass freely. The model of the reverse osmosis membrane used in this embodiment is PA1-4040. Under the pressure condition of about 1 Pa, the water permeability of the reverse osmosis membrane 34 is 1.2255 m ³ /m ² /h.

The microporous ceramic container 4 is a cylindrical water container, the container wall is saturated with water, and there are many micropores with a diameter in the range of 250-800 microns on the container wall, and the air intake value is low, in the range of 0.3-0.6MPa , in the case of a small pressure difference, the water in the wall of the microporous ceramic container can be discharged. The device is in direct contact with the soil, and the water lost by the soil is replenished through the device.

When using the utility model device, at first the microporous ceramic container 4 and the semipermeable material water control device 3 are connected, and water is filled in the water filling cavity of the microporous ceramic container 4 and the semipermeable material water control device 3 . In order to make the device work better, the air in the closed water body should be removed as much as possible when filling the water, and it is best to complete the installation underwater. This section of closed water body needs to bear a certain negative pressure, so the sealing work should be done well. After filling the water, connect the water outlet 24 of the automatic control water inlet device 2 and the water inlet 35 of the semipermeable material water control device 3 with a rubber tube. Fill the constant water potential solution from the water inlet 21 of the automatic control water inlet device 2 until the liquid level 23 rises to about the middle part of the automatic control water inlet device 2 . Then fill water in the constant water pressure water supply device 1, close the water inlet 11 and the air inlet 13 after completion, the water outlet 14 is connected with the water inlet 21 of the automatic control water inlet device 2 with a rubber tube, and then open the air inlet 13 , thus completing the connection of the main functional components. Preferably the position of the liquid level 23 is marked as the initial height record of the liquid level. Now the microporous ceramic container 4 is installed in the soil container 5, and the soil is filled with a certain bulk density, and the constant control of the soil water potential can be realized after a period of balance, as shown in Figure 7.

The working driving force of the device of the utility model comes from the change of soil water potential. During use, the loss or infiltration of soil moisture causes the water potential of the soil to decline, and at this time a water potential difference is generated between the soil water potential and the water potential of the constant water potential solution, so that the water in the microporous ceramic container 4 tends to pass through the microporous ceramic container 4. The pores flow to the soil, so the water in the closed water body decreases, and the resulting negative pressure makes the water in the constant water potential solution on the other side of the reverse osmosis membrane 34 pass through the reverse osmosis membrane 34 and enter the water chamber, that is, the closed water body, Supplement the water lost in the closed water body, until the soil water potential and the solution water potential are equal, and the movement of water stops temporarily. The closed water body plays the role of transferring water between the constant water potential solution and the soil in the whole process, and also plays the role of transferring the change of soil water potential to the constant water potential solution.

When the water in the constant water potential solution enters the closed water body through the reverse osmosis membrane 34, the volume of the constant water potential solution decreases and the concentration increases, and this small volume change is reflected in the automatic control water inlet device 2. The drop of liquid level 23 makes the volume of air at the upper end of liquid level 23 increase, and the air pressure decreases, so the drip pipe 22 at the upper end of the water inlet device 2 automatically controls to drip water, the liquid level 23 rises, the volume of air decreases, and the pressure increases. until it returns to its original level. At this time, the concentration and volume of the constant water potential solution remain constant, and the water potential of the solution therefore remains constant.

Under normal circumstances, the water potential of the soil is equal to or less than the water potential of the constant water potential solution, which ensures that the above-mentioned device can operate normally, that is, water flows from the constant water potential solution to the closed water body through the reverse osmosis membrane 34 and then flows to the soil through the microporous ceramic container 4. When the soil water potential suddenly rises higher than the constant water potential solution due to some reasons, such as rainfall or excessive irrigation in the area where the soil is located, a counterflow phenomenon will occur, that is, the moisture in the soil enters the microporous ceramic container 4, and the water body is closed The moisture in the water enters the automatic control water inlet device 2. If backflow occurs, the rubber tube connecting the constant water pressure water supply device 1 and the automatic water inlet device 2 should be disconnected, and the rubber tube should be connected again when the liquid level 23 of the constant water potential solution returns to the initial height record. It is worth noting that The whole process must ensure that the relative position between the constant water pressure water supply device 1 and the automatic control water inlet device 2 remains unchanged, and the amount of solute in the constant water potential solution remains unchanged.

As a simplification of the device of the present invention, the connection between the cavity of the automatic control water inlet device 2 and the semipermeable material water control device 3 for containing the constant water potential solution can be omitted, and the two share the same container. In other words, the automatic control water inlet device 2 also serves as a cavity for the semipermeable material water control device 3 to hold a constant water potential solution, as shown in Figures 5 and 6 .

At the same time, in order to be able to constantly control the soil water potential in a wider range, the semipermeable material water control device 3 can include a plurality of water outlets 36, which are respectively connected with a plurality of microporous ceramic containers 4 to form a shared constant water pressure water supply device 1, which is automatically The array of microporous ceramic containers 4 that control the water inlet device 2 and the semipermeable material water control device 3, as shown in Figure 8, not only saves equipment costs, but also facilitates the unification of soil water potential within a specific area.

Claims (9)

1. A constant device for automatic control of soil water potential is characterized in that the device comprises a constant water pressure water supply device, an automatic control water inlet device, a semipermeable material water control device and a microporous container; a constant water pressure water supply device, automatically Control the water inlet device, the semi-permeable material water control device is equipped with a water inlet and outlet, and the microporous container is equipped with a water inlet; the water outlet of the constant water pressure water supply device is connected to the water inlet of the automatic control water inlet device, and the automatic control of the water inlet The water outlet of the water device is connected to the water inlet of the semipermeable material water control device, and the water outlet of the semipermeable material water control device is connected to the water inlet of the microporous container, wherein: The constant water pressure water supply device is a water container, which can supply water with constant water pressure; The automatic control water inlet device is a container containing a constant water potential solution. The solution does not fill the entire container, and the part except the solution is filled with air. The air in this part is in a closed state and the air pressure is constant; The semi-permeable material water control device is a container containing liquid. The container is divided into two cavities by the semi-permeable material near the middle of the container, with a water inlet and a water outlet respectively. The cavity connected to the water inlet is equipped with There is a constant water potential solution, and the cavity connected to the water outlet is filled with water; The microporous container is a water container, and there are many small holes on the wall of the container, which can be used to permeate water, but cannot penetrate air and soil; Water located between the walls of the microporous container and the semipermeable material is enclosed. 2. The device for automatically controlling the constant soil water potential as claimed in claim 1, wherein the constant water pressure water supply device is provided with an air inlet near the water outlet, and the air inlet is located below the water surface, and works in the whole device. It is in the open state; the water inlet is in the closed state when the whole device is working. 3. The device for automatically controlling the constant soil water potential as claimed in claim 1, wherein the water inlet of the automatic control water inlet device extends into the inner cavity of the device for a section to form a dripping water suspended in the inner cavity of the device. Tubes that can form water droplets. 4. The constant device for automatically controlling soil water potential as claimed in claim 1, wherein the semipermeable material in the semipermeable material water control device is a reverse osmosis membrane or a semipermeable membrane. 5. The device for automatically controlling constant soil water potential as claimed in claim 1, wherein said microporous container is a microporous ceramic container. 6. The device for automatically controlling constant soil water potential as claimed in claim 6, characterized in that, the micropore diameter of the microporous container is between 250-800 microns, and the air intake value is within the range of 0.3-0.6 MPa. 7. The device for automatically controlling the constant soil water potential as claimed in claim 1, characterized in that, the connection modes between the devices are all connected by rubber tubes. 8. The device for automatically controlling constant soil water potential as claimed in claim 1, wherein the cavity for holding the constant water potential solution in the automatic control water inlet device and the semipermeable material water control device share the same container. 9. The device for automatically controlling the constant soil water potential as claimed in claim 1, wherein the semipermeable material water control device comprises a plurality of water outlets, which are respectively connected with a plurality of microporous containers.

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