In-situ determination and monitoring method of soil water supply rate

Abstract

The present invention discloses an in-situ measurement and monitoring method based on soil water supply rate, wherein the in-situ measurement method adopts a water pumping system mainly composed of a water pump, a pressure regulating device, an air extraction device and a water collection bottle, and then combines it with a soil tensiometer for measurement, so as to determine the relationship curve or relationship model between the soil matrix potential and the water supply rate at the corresponding soil. Then, based on the relationship curve or relationship model, the soil matrix potential is monitored in real time through the soil tensiometer, and the changes in the soil water supply rate are monitored, thereby providing new soil moisture management technology and irrigation decision-making basis for agricultural production.

Description

Technical Field

[0001] The present invention relates to soil detection technology, and in particular to an in-situ measurement and monitoring method for soil water supply rate. Background Art

[0002] The amount and effectiveness of soil moisture not only determines agricultural yields but also influences soil nutrient migration and transformation, agricultural product quality, and the incidence of plant diseases, insect pests, and weeds. Therefore, accurately and timely assessing soil moisture conditions and rationally managing soil moisture are crucial for agricultural production. Currently, soil moisture monitoring methods in production fall into two main categories: quantitative and energetic methods. Quantitative methods measure soil moisture content, with TDR and FDR, based on drying methods and measuring soil dielectric properties, being the most widely used. Energetic methods measure soil matric potential, with soil tensiometers being the most common. Although the quantity method can know the amount of water in the soil, due to the different water absorption capacity of soils of different textures, the effectiveness of the same water content in soils of different textures varies greatly. For example, when the volumetric water content in clay is 15%, plants are already severely affected by drought stress, while when the volumetric water content in sandy soil is 15%, the effectiveness of water is still very high. Therefore, the soil moisture control index established based on soil moisture content has poor versatility. The energy method directly measures the matrix potential of soil water to indicate the effectiveness of soil moisture. Water with the same matrix potential has the same effectiveness in different textures. Therefore, the soil moisture control index established based on soil matrix potential has better versatility.

[0003] However, in production practice, it has been found that when plants begin to experience drought stress, the soil matric potential remains above -100 kPa. Most literature reports indicate that the soil matric potential that begins to affect crop yield is above -60 kPa, while the average root water potential is around -1500 kPa. This indicates that when plants experience water stress, the soil matric potential is far from decreasing to the root water potential. In other words, as long as water reaches the root surface, the roots have no problem absorbing water. In-depth analysis reveals that the cause of drought stress in plants is not that the soil matric potential is so low that the plants cannot absorb water, but rather that the rate at which soil water from the non-root zone reaches the root surface is too slow, that is, water movement is too slow, resulting in insufficient water for plant transpiration. Although a decrease in soil matric potential also reduces soil hydraulic conductivity, the relationship between soil matric potential and soil hydraulic conductivity varies across different soils. This suggests that monitoring soil hydraulic conductivity is a more accurate indicator of the rate of soil water supply to plants than monitoring soil matric potential.

[0004] Current methods for measuring unsaturated hydraulic conductivity of soil, whether indoor or in situ, only consider the one-dimensional flow of water—vertically downward or upward—during irrigation, rainfall, and evaporation. Furthermore, both outdoor in situ and laboratory measurements require lengthy time, complex measurement equipment, and computational processes. Some parameters are calculated using theoretical formulas, and some calculations employ assumptions. This significantly disturbs the soil, leading to discrepancies between measured results and actual results. These methods fail to capture the three-dimensional water movement from the soil surrounding the roots to the roots. Root water uptake is a three-dimensional water movement process, and current methods for measuring unsaturated hydraulic conductivity in one dimension cannot capture the rate at which soil water is supplied from the surrounding areas to the root surface. Summary of the Invention

[0005] The present invention aims to overcome the shortcomings of the above-mentioned existing technologies and provides a method for in-situ measurement and monitoring of soil water supply rate. This method can rapidly detect soil water supply rate with high accuracy, providing new soil moisture management technology and a basis for irrigation decision-making in agricultural production.

[0006] The object of the present invention is achieved by the following technical solution: The in-situ determination and monitoring method of soil water supply rate comprises the following steps:

[0007] S1. Install a soil tensiometer and a water pump at the depth of the soil layer to be measured, then irrigate the soil to the field capacity. After the soil tensiometer reading stabilizes, record the soil tensiometer reading at this time.

[0008] S2, the water pump is connected to the pressure regulating device, the air pumping device and the water collecting bottle in sequence through the water pumping pipe to form a water pumping system;

[0009] S3. Turn on the air extraction device and adjust the pressure through the pressure regulating device to -80 kPa. At the same time, start timing and observe the soil tensiometer reading every 0.5 to 1 hour.

[0010] S4. When the soil tensiometer reading reaches -5 kPa, temporarily close it and suck out the water in the water collection bottle to determine the volume of this water as V, and calculate the soil water supply rate:

[0011]

[0012] Where q is the water supply rate under unit water potential gradient conditions, V is the volume of water pumped, S is the water-influent surface area of ​​the pump, t is the time from opening the air pump to closing the air pump, Δψ is the pressure difference between the pump and the ceramic head of the tensiometer, that is, the difference between the tensiometer reading and the pressure of the pumping system, and L is the distance between the pump and the ceramic head of the tensiometer.

[0013] S5. Repeat steps S3 and S4, and each time the soil tensiometer reading in step S4 is decreased by a certain arithmetic interval until the water supply rate q is less than 0.01 cm / d; thereby recording a corresponding data set of the soil tensiometer reading and the water supply rate, and establishing a relationship curve or relationship model between the two based on the data set;

[0014] S6. Then, through the soil tensiometer reading, based on the relationship curve or relationship model, the real-time soil water supply rate is indirectly monitored.

[0015] Preferably, the water pump includes a ceramic head and a sealing joint, the sealing joint is installed at the open end of the ceramic head to form a sealed cavity, and one end of the water pumping pipe passes through the sealing joint and extends into the bottom of the sealed cavity.

[0016] Preferably, one end of the water pumping pipe is wedge-shaped.

[0017] Preferably, the sealing joint includes a joint base, a locking cap and a locking rubber ring. The joint base includes a sealing part, a limiting part and a threaded part connected in sequence. The sealing part is inserted into the opening of the ceramic head and sealed with the opening. The side of the limiting part is in contact with the end face of the opening of the ceramic head. One end of the locking rubber ring is inserted into the threaded part and locked by the locking cap.

[0018] Preferably, the pressure regulating device is a pressure regulating valve with a pressure display.

[0019] Preferably, the air extraction device is a DC-powered micro peristaltic pump.

[0020] Preferably, the water collecting bottle is a cylindrical glass bottle of equal diameter, and the body of the cylindrical glass bottle of equal diameter has a scale showing the volume.

[0021] The present invention has the following advantages over the prior art:

[0022] The present invention utilizes a soil tensiometer in combination with a pumping system to establish a relationship curve or relationship model, thereby enabling the rapid determination of the soil water supply rate based on the soil tensiometer. This method is highly accurate and efficient, and is an innovative approach to irrigation decision-making, providing a reliable basis for subsequent irrigation to ensure timely irrigation of plants.

[0023] The in-situ measurement method of the present invention adopts a water pumping system mainly composed of a water pump, a pressure regulating device, an air pumping device and a water collecting bottle, and then combines it with a soil tensiometer for measurement. This method uses simple equipment, is easy to operate, and ensures the accuracy of the measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of a water pump in the in-situ measurement and monitoring method of soil water supply rate of the present invention.

[0025] Figure 2 It is a structural schematic diagram of the pumping system in the in-situ measurement and monitoring method of soil water supply rate of the present invention.

[0026] Figure 3 This is a relationship curve established by the in-situ measurement and monitoring method of soil water supply rate in clay loam.

[0027] Figure 4 The present invention is a relationship curve established by the in-situ measurement and monitoring method of soil water supply rate in sandy loam.

[0028] Among them, 1 is a ceramic head, 2 is a sealing joint, 21 is a joint base, 22 is a locking rubber ring, 23 is a locking cap, 3 is a water pumping pipe, 4 is a pressure regulating device, 5 is an air extraction device, and 6 is a water collecting bottle. DETAILED DESCRIPTION

[0029] The present invention will be further described below with reference to the accompanying drawings and examples.

[0030] The in-situ determination and monitoring method of soil water supply rate comprises the following steps:

[0031] S1. Install a soil tensiometer and a water pump at the depth of the soil layer to be measured, then irrigate the soil to the field water holding capacity. After the soil tensiometer reading stabilizes, record the soil tensiometer reading at this time; specifically, the soil tensiometer reading is the soil matrix potential of the soil at this location.

[0032] S2. The water pump is connected to the pressure regulating device, the air pumping device and the water collecting bottle in sequence through the water pumping pipe to form a water pumping system. Figure 1 and Figure 2 Specifically, the water pump includes a ceramic head and a sealing joint. The sealing joint is installed at the open end of the ceramic head to form a sealed cavity. One end of the water pump is wedge-shaped and extends through the sealing joint into the bottom of the sealed cavity, ensuring that all water in the water pump is pumped out and the water pump is not blocked. Moisture in the soil passes through the ceramic head and enters the sealed cavity, collecting the moisture in the corresponding soil. At the same time, the water collected over a certain period of time is sent to a water collection bottle, and the water volume in the water collection bottle during this period is recorded.

[0033] S3. Turn on the vacuum device and adjust the pressure through the pressure regulating device to make the pressure of the pumping system -80kPa; at the same time, start timing and observe the soil tensiometer reading every 0.5 to 1 hour; specifically, directly adjust the pressure regulating valve with pressure display to ensure that the pressure of the sealed cavity in the pumping pipe and the ceramic head is stable at -80kPa.

[0034] S4. When the soil tensiometer reading reaches -5 kPa, temporarily close it and suck out the water in the water collection bottle to determine the volume of this water as V, and calculate the soil water supply rate:

[0035]

[0036] Where q is the water supply rate (cm·d) under unit water potential gradient (kPa / cm) -1 ), V is the volume of water pumped out (cm 3 ), S is the water inlet surface area of ​​the pump (cm 2 ), t is the time from opening the air extraction device to closing the air extraction device (d), Δψ is the pressure difference between the water extractor and the ceramic head of the tensiometer (kPa), that is, the difference between the tensiometer reading and the pressure of the water extraction system, and L is the distance between the water extractor and the ceramic head of the tensiometer (cm);

[0037] S5, repeat steps S3 and S4, and each time it is repeated, the reading of the soil tensiometer in step S4 is gradually reduced by a certain arithmetic difference. In the present embodiment, -5kPa is used as an equivalent value, that is, the reading of the soil tensiometer in step S4 reaches -5kPa, -10kPa, -15kPa, -20kPa ... in sequence each time water is pumped, until the value of the water supply speed q is less than 0.01cm / d; the corresponding data group of the soil tensiometer reading (i.e., soil matrix potential) and the water supply rate is recorded in this way, and a relationship curve or relationship model of the two is established based on this data group; specifically, the relationship curve is a curve connected by the points made by the measured data, and the relationship model is a mathematical relationship simulation relationship curve. For example, the point of the approximate straight line can be described by a linear equation. When the degree of fit between the soil tensiometer reading and the water supply rate is high, a relationship model can be established, thereby quickly determining the soil water supply rate at the measurement location according to the counting of the soil tensiometer.

[0038] S6. Based on the relationship curve or relationship model, the soil water supply rate is monitored by a soil tensiometer.

[0039] In the present invention, the soil water supply rate in the corresponding area is determined by a soil tensiometer and a pumping system, so that a relationship curve or relationship model can be established. The soil matrix potential of the soil in this area can be measured by the soil tensiometer to indirectly obtain the water supply rate, so as to achieve the goal of monitoring the soil water supply rate at any time, providing a feasible basis for plant irrigation, ensuring that plants grow in a good soil environment, and improving crop yield and quality.

[0040] like Figure 1 and Figure 2As shown, the water pump includes a ceramic head and a sealing joint. The sealing joint is installed at the open end of the ceramic head to form a sealed cavity. One end of the water pump pipe extends into the sealed cavity after passing through the sealing joint. Specifically, the ceramic head can be made of ceramic or other hydrophilic porous materials. The ceramic head has a hollow structure, is tubular, and has a closed bottom end in a spherical shape. The upper end opening of the ceramic head is connected to the sealing joint with glue to form a sealed cavity. This simple structure ensures the sealing effect of the sealed cavity to ensure the effective execution of the work.

[0041] The sealing joint includes a joint base, a locking cap, and a locking rubber ring. The joint base includes a sealing portion, a limiting portion, and a threaded portion connected in sequence. The sealing portion is inserted into the opening of the ceramic head and sealed therewith. The side surface of the limiting portion abuts against the end surface of the opening of the ceramic head. One end of the locking rubber ring is inserted into the threaded portion and locked by the locking cap. Specifically, the water pump is made of a silicone tube. When the locking cap is tightened to the base, the locking rubber ring is squeezed by the chamfered structure inside the locking cap, thereby clamping the water pump to achieve a sealing effect.

[0042] The pressure regulating device is a pressure regulating valve with a pressure display. Specifically, in this embodiment, the pressure regulating range of the pressure regulating valve is 0 to 95 kPa to ensure effective measurement.

[0043] The air extraction device is a DC-powered micro peristaltic pump, which is easy to control and has high precision, further ensuring the accuracy of the measurement results.

[0044] Based on the application of the above-mentioned in-situ measurement and monitoring method of soil water supply rate, in general, when the soil water supply rate is less than 0.01 cm / d, the plant's water needs are not met and irrigation is required. If the water consumption rate of a certain plant at different growth stages is known, the soil water supply rate can be determined based on the soil tensiometer reading, combined with a relationship curve or relationship model. The water supply rate can then be compared with the plant's water consumption rate to more accurately determine whether irrigation is needed:

[0045] When the rate of water supply from the soil is greater than the rate of water consumption by the plants, irrigation is not required;

[0046] Irrigation is required when the rate at which the soil supplies water is less than the rate at which the plants consume it.

[0047] For example, when the method of the present invention is used to measure the water supply rate of a certain clay loam, the measured data are shown in Table 1 below:

[0048]

[0049] Table 1

[0050] Based on the data in Table 1, a relationship curve is established, such as Figure 3As shown in the figure. In clay loam soil, when the soil matric potential drops to -60 kPa, the soil water supply rate drops to 0.01 cm / day, meaning the soil water moves only 0.1 mm per day. At this point, the soil water supply rate is insufficient for most plants to maintain normal growth, necessitating irrigation. Therefore, in this type of soil, during crop growth, the soil matric potential is monitored using a soil tensiometer. Irrigation can be initiated when the soil matric potential drops to -60 kPa, i.e., when the soil tensiometer reading drops to -60 kPa. If the crop water consumption rate at different growth stages is known, the critical water requirement period can be more accurately determined based on the water consumption rate and the soil water supply rate, thereby ensuring optimal soil moisture conditions for the crop.

[0051] For another example, when the method of the present invention is used to measure the water supply rate of a certain sandy loam, the measured data are shown in Table 2 below:

[0052]

[0053] Table 2

[0054] Based on the data in Table 2, a relationship curve is established as follows: Figure 4 As shown in the figure, when the matric potential of sandy loam soil drops to -40 kPa, the soil water supply rate has dropped to 0.01 cm / day, meaning that the soil water moves only 0.1 mm per day. At this point, the soil water supply rate is no longer sufficient for most plants to grow normally, and irrigation is required. Therefore, in this type of soil, during crop growth, the soil matric potential is monitored using a soil tensiometer. Irrigation can be initiated when the matric potential reaches -40 kPa, i.e., when the soil tensiometer reading is -40 kPa. If the water consumption rate of crops at each growth stage is known, the critical water requirement period can be more accurately determined based on the water consumption rate and the soil water supply rate, thereby ensuring that soil moisture conditions are optimal for crops.

[0055] From the data measured on the two soils above, it can be seen that when the soil matrix potential is the same at -40 kPa, the water supply rate of clay loam is 0.1229 cm / d, and the soil can still fully supply water to plants, while the water supply rate of sandy loam is 0.01 cm / d, which can no longer fully supply water to plants. Therefore, this method can essentially solve the problem of soil moisture status monitoring and provide more reliable technical support for soil moisture management decisions in agricultural production.

[0056] The above specific implementation manner is a preferred embodiment of the present invention and does not limit the present invention. Any other changes or other equivalent replacement methods that do not deviate from the technical solution of the present invention are included in the protection scope of the present invention.

Claims

1. A method for in-situ determination and monitoring of soil water supply rate, characterized in that: The following steps are involved: S1. Install a soil tensiometer and a water pump at the depth of the soil layer to be measured, then irrigate the soil to the field capacity. After the soil tensiometer reading stabilizes, record the soil tensiometer reading at this time. S2, the water pump is connected to the pressure regulating device, the air pumping device and the water collecting bottle in sequence through the water pumping pipe to form a water pumping system; S3. Turn on the air extraction device and adjust the pressure through the pressure regulating device to -80 kPa. At the same time, start timing and observe the soil tensiometer reading every 0.5 to 1 hour. S4. When the soil tensiometer reading reaches -5 kPa, temporarily close it and suck out the water in the water collection bottle to determine the volume of this water as V, and calculate the soil water supply rate: Where q is the water supply rate under unit water potential gradient conditions, V is the volume of water pumped, S is the water-influent surface area of ​​the pump, t is the time from opening the air pump to closing the air pump, Δψ is the pressure difference between the pump and the ceramic head of the tensiometer, that is, the difference between the tensiometer reading and the pressure of the pumping system, and L is the distance between the pump and the ceramic head of the tensiometer. S5. Repeat steps S3 and S4, and each time the soil tensiometer reading in step S4 is decreased by a certain arithmetic interval until the water supply rate q is less than 0.01 cm / d; thereby recording a corresponding data set of the soil tensiometer reading and the water supply rate, and establishing a relationship curve or relationship model between the two based on the data set; S6. Then, through the soil tensiometer reading, based on the relationship curve or relationship model, the real-time soil water supply rate is indirectly monitored.

2. The method for in-situ measurement and monitoring of soil water supply rate according to claim 1, characterized in that: The water pump comprises a ceramic head and a sealing joint, wherein the sealing joint is installed at the open end of the ceramic head to form a sealing cavity, and one end of the water pumping pipe passes through the sealing joint and extends into the bottom of the sealing cavity.

3. The in-situ measurement and monitoring method of soil water supply rate according to claim 2, characterized in that: One end of the water pumping pipe is wedge-shaped.

4. The in-situ measurement and monitoring method of soil water supply rate according to claim 2, characterized in that: The sealing joint includes a joint base, a locking cap and a locking rubber ring. The joint base includes a sealing part, a limiting part and a threaded part connected in sequence. The sealing part is inserted into the opening of the ceramic head and sealed with the opening. The side surface of the limiting part is in contact with the end face of the opening of the ceramic head. One end of the locking rubber ring is inserted into the threaded part and locked by the locking cap.

5. The in-situ measurement and monitoring method of soil water supply rate according to claim 1, characterized in that: The pressure regulating device is a pressure regulating valve with a pressure display.

6. The in-situ measurement and monitoring method of soil water supply rate according to claim 1, characterized in that: The air pumping device is a DC-powered micro peristaltic pump.

7. The in-situ measurement and monitoring method of soil water supply rate according to claim 1, characterized in that: The water collecting bottle is a cylindrical glass bottle of equal diameter, and the bottle body of the cylindrical glass bottle of equal diameter is provided with a scale showing the volume.

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