CN105651968B - A kind of method using water potential meter on-line checking soil moisture content - Google Patents
A kind of method using water potential meter on-line checking soil moisture content Download PDFInfo
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- CN105651968B CN105651968B CN201610126221.2A CN201610126221A CN105651968B CN 105651968 B CN105651968 B CN 105651968B CN 201610126221 A CN201610126221 A CN 201610126221A CN 105651968 B CN105651968 B CN 105651968B
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Abstract
The invention discloses a kind of method using water potential meter on-line checking soil moisture content, belong to agriculture water and soil conservation and agricultural engineering field.The present invention is based on the Gibbs function of compounding substances chemical potential, before soil moisture content to be measured is surveyed, by the model soil water potential ψ for determining soil to be measuredSWith the water content P at corresponding moment, the model soil water potential ψ of soil to be measured is establishedSMathematical modeling between water content P, and the parameter in model is determined, produce the model soil water potential of soil to be measured and the relation table of water content；Then, the flow of water of the real time measure soil to be measured, water content corresponding to the flow of water is obtained by tabling look-up.The present invention can on-line checking rhizosphere soil water content, with water potential meter can simultaneously obtain soil water potential and water content information, provide facility for water-saving irrigation.
Description
Technical field
The invention belongs to agriculture water and soil conservation and agricultural engineering field, and in particular to utilize water potential meter on-line checking to one kind
The method of soil moisture content.
Background technology
The water regime of soil especially rhizosphere soil not only influences absorption of the crop to moisture, while can also influence crop
Utilization to nutrient, it is an important factor for influenceing plant growth.The dynamic change of soil moisture content is to reflect the moisture shape of soil
The important indicator of condition.A measure inherently cumbersome thing for soil moisture content.Need to take if being determined with weighting method after dried
Soil drying, so can neither be online, also relatively time-consuming.It is this aqueous as although TDR methods can quickly determine the water content of soil
Amount is volume moisture content, wants the accurate moisture information for obtaining soil, it is also necessary to fetches earth and surveys its unit weight, therefore does not also possess online
Function.Therefore, a kind of method of quickly and easily mass water content of soil is developed, the water management to farmland has important
Meaning.
Acting on the power of the soil water mainly has the penetration of solute contained by the suction and the soil water of gravity, soil particle, because
Total flow of water of this soil is typically expressed as the summation for point gesture that any of the above power is formed.Soil water potential is typically expressed as negative pressure
Power, therefore also referred to as soil moisture tension.The absolute value of soil water potential is small during soil saturation, soil water potential when soil moisture content is low
Absolute value it is big.Therefore the size of soil water potential absolute value reflects the difficulty or ease of soil water movement, can pass through soil water potential
Change understand water regime of soil.
The detecting instrument of soil water potential main tensioned meter, vacuum meter and dew point water potential meter etc..Tensometer is by three parts group
Into porous ceramic cup, pressure gauge and the connecting tube of ceramic cup and pressure gauge；Tensometer is the main method for measuring matric potential, native
The earth flow of water is by the coefficient result such as solute potential, matric potential, pressure potential, and matric potential is the numerous soil water potentials of soil into therefore
One, there is limitation, and tensometer measurement range very little；Gong Zhen equalitys (Gong Zhenping, Shao Xiaohou, Zhang Fucang, wait agrology with
Geoponics [M] Beijing:Chinese Water Conservancy water power publishing house, 2009：82-84.)《Agrology and geoponics》Point out to open in one book
The measurement range of power meter be usually -0.8~0Mpa, can neither on-line checking, can not determine soil moisture content it is low when soil
The flow of water；In addition, the method for embedding of tensometer can also have an impact to measurement result, so accuracy is relatively low.Vacuum meter
Principle and tensometer are identicals, so precision is also very low.
Dew point water potential meter is the instrument that the flow of water is specially measured by thermocouple sensor, is maintained automatically under dew-point temperature
Thermocouple junction constant temperature senses and control circuit, and accuracy is very high, and stably；In recent years, much on soil water potential
Research be all that observation instrument is used as using dew point water potential meter；Soil water potential is determined with it quickly and soil is not destroyed, Ke Yi
Line obtains the change of soil water potential；Other kinds of soil water potential instrument all has the work(of online quick obtaining soil water potential information
Energy.
The content of the invention
In view of the shortcomings of the prior art, the invention provides a kind of side using water potential meter on-line checking soil moisture content
Method, soil water potential and water content information, and the soil environment of not broken ring measure only can be obtained simultaneously with water potential meter；According to soil
The real time information of the flow of water and water content, technical support can be provided with Forecasting Soil Moisture variation tendency for Farmland Water management.
The present invention is to realize above-mentioned technical purpose by following technological means.
A kind of method using water potential meter on-line checking soil moisture content, including step：
Step 1), the model soil using the soil around the soil to be measured in field or field as soil to be measured, takes to be measured
The model pedotheque of soil is appropriate, is placed in clean smooth table top and makes thinner, removes impurity removing after air-drying, and sample is pulverized；
Step 2), the field capacity of the model pedotheque of soil to be measured is detected with core cutter method, is designated as C；
Step 3), take etc. quality it is above-mentioned pulverize after soil to be measured two parts of model pedotheque, and be labeled as soil
Sample A and B, water is added into pedotheque, its water content is reached the field capacity of the model soil of the soil to be measured, mixes and stirs
Uniformly, identical container is loaded；
Step 4), by pedotheque A and B, while it is placed under same environment, makes its continuous dehydration；
Step 5), different dehydration moment pedotheque A soil water potential and corresponding moment pedotheque B are determined respectively
Water content, 10~15 groups of data are continuously measured according to the situation of change of pedotheque A soil water potential；
Step 6), the model soil water potential ψ of soil to be measured is derived by the Gibbs function of compounding substances chemical potentialSWith containing
Water P mathematical modeling (1+P) ψS=y0+ kln (1+P), the data measured according to step 5) determine model parameter y0With k value；
Step 7), the model soil water potential ψ according to soil to be measuredSWith water content P mathematical modeling, soil to be measured is produced
Model soil water potential and water content relation table；
Step 8), the instant water potential value ψ of soil to be measured is obtained using water potential meterR；
Step 9), it is ψ to obtain soil water potential by the relation table of the model soil water potential and water content of looking into soil to be measuredRWhen
Soil moisture content, soil moisture content as to be measured.
Further, in the step 3) into pedotheque plus water, the mass ratio of soil and water is 1：C.
Further, y in the step 6)0Value with k is the model soil water potential ψ by soil to be measuredSWith water content P's
Mathematical modeling (1+P) ψS=y0+ kln (1+P) fittings determine.
Further, the model soil water potential of soil to be measured and the relation table of water content are produced in the step 7), wherein
The span of water content is 0-C, and water content is scale with 0.5%.
Further, it is by looking into the model soil water potential of soil to be measured and the relation table of water content in the step 9)
With ψRTwo neighbouring class values, it is ψ using interpolation calculation soil water potentialRWhen soil moisture content.
The beneficial effects of the invention are as follows：
1. the model soil water potential ψ for the soil to be measured that the present invention establishesSContain with water content P mathematical modeling available for soil
Water P and soil water potential ψSExchange, i.e. known moisture content P can obtain soil water potential ψS；If conversely, known soil water potential ψSThen
Water content can be finally inversed by, is provided convenience for simulating drought research.
2. the present invention obtains soil water potential and water content information simultaneously merely with water potential meter can.
3. the present invention does not disturb in continuous mode to soil, as a result online real-time；Can the real time measure rhizosphere online
The water content of soil, provided convenience for influence of the research overlying plant to water retention in soil.
4. the present invention can determine the dynamic change of soil moisture, provided for research soil property and water retention in soil
Facility.
5. soil water potential and the mathematical modeling of water content that the present invention is built are the gibbs according to compounding substances chemical potential
Derived based on function, be the model for having mechanism background, there is reliability.Larger water can be determined using the model
Divide content range (0-100%), determine simple and efficient.
Brief description of the drawings
The scatter diagram of Fig. 1 relations between the model soil water potential and water content of two kinds of soil to be measured.
In figure：The model soil measured data of ▼-soil sample 1, ● the model soil measured data of-soil sample 2.
Embodiment
Below in conjunction with the accompanying drawings and specific embodiment the present invention is further illustrated, but protection scope of the present invention is not
It is only limitted to this.
The present embodiment is the measure that two kinds of soil moisture contents to be measured change over time.Soil types is respectively loam and loamy texture
Clay, soil sample are designated as soil sample 1 and soil sample 2 respectively.
Step 1), respectively fetched earth model soil of the earth 20kg as each soil to be measured in two kinds of soil adjacents to be measured respectively,
All model soil is placed in into clean smooth table top to make thinner, removes impurity removing after air-drying, and pedotheque is pulverized.Wherein,
The model soil of soil to be measured is the similar soil to soil same type to be measured, is in soil adjacent to be measured, take out it is a small amount of this
Kind soil does not make a difference to soil to be measured.
Step 2), the field capacity of the model soil of soil sample 1 and the model soil of soil sample 2 is detected with core cutter method, respectively
For C1=23.8% and C2=35.4%.
Step 3), takes two parts of each 5kg of model soil of the soil sample after pulverizing 1, and is labeled as pedotheque A1, B1, respectively
1.19kg water is added into A1, B1, the field capacity of the model soil of soil sample 1 is reached, uniform mixing, loads identical
Container；The model soil of soil sample 2 is handled in the same way, and two parts of 5kg of model soil of soil sample 2 sample is labeled as soil
Earth sample A2, B2,1.77kg water is added into A2, B2 respectively, reach the field capacity of the model soil of soil sample 2.
Step 4), pedotheque A1, A2, B1, B2 are placed under same environment simultaneously, make its continuous dehydration.
Step 5), different dehydration moment pedotheque A1, A2 soil water potential and corresponding moment soil-like are determined respectively
Product B1, B2 water content, 15 groups of data are continuously measured according to the situation of change of pedotheque A1, A2 soil water potential；
The assay method of soil water potential is：By two soil water potentials of dew point water potential meter probe inserting step 3 respectively) in fill
Enter 8~10cm depths inside pedotheque A1, A2 of container to be measured；Soil moisture content P is by determining corresponding moment soil
Earth sample B1, B2 quality obtains.
Step 6), build the model soil water potential ψ of soil to be measuredSWith water content P mathematical modeling, specific building process
For：
By the Gibbs function u=△ G of material chemical potential0+ RTlnX, substance A, B chemical potential uA,uBRepresent respectively
For：
uA=GA+RT lnXA (1)
uB=GB+RT lnXB (2)
In above-mentioned (1), (2) formula, GA、GBIt is substance A, B standard Gibbs free energy respectively, XA、XBBe respectively substance A,
B molar concentration, R are gas constant, and T is environment temperature.
Therefore, the Gibbs free energy G of system can be expressed as with chemical potential after mixing：
G=uAXA+uBXB (3)
Namely the Gibbs free energy G of system is after mixing：
G=(GA+RT lnXA)XA+(GB+RT lnXB)XB (4)
Aqueous soil can regard the hybrid system of two kinds of materials of soil and water as, and soil water potential is the chemical potential of the system, soil
Earth regards substance A as, and water regards substance B as, and therefore (3) formula is represented by：
ψS=uSXS+uWXW (5)
In formula, ψSFor the model soil water potential of soil to be measured, uSFor the chemistry of the soil in the model soil of soil to be measured
Gesture, uWFor the chemical potential of the water in the model soil of soil to be measured, XSAnd XWSoil and water in the model soil of soil to be measured respectively
Concentration.
Because (5) u in formulaW=0, therefore (5) formula can be simplified to：
ψS=uSXS (6)
By the chemical potential u of the soil in the model soil of soil to be measuredS=dG0+RT·lnXSAnd the model clay of soil to be measured
The concentration of soil in earthExpression formula substitute into (6) formula, can obtain：
(7) formula can be transformed into：
(1+P)ψS=MdG0+MRTlnM-RTM ln(1+P) (8)
In formula, ψSFor the model soil water potential of soil to be measured, unit MPa；P is the model soil water-containing of soil to be measured
Amount, unit %, dG0For the standard free energy of the model soil of soil to be measured；M is molar concentration conversion coefficient.
Make y0=MdG0+ MRTlnM, k=-RTM, then (8) formula become：
(1+P)ψS=y0+kln(1+P) (9)
By (1+P) ψ in (9) formulaSReplaced with f (x), ln (1+P) represents that then (9) formula can be write as with x：
F (x)=y0+kx (10)
According to above-mentioned pedotheque A1, A2 measured soil water potential and corresponding moment pedotheque B1, B2 water content,
Model soil water potential ψ with Sigmaplot12.5 to two kinds of soil to be measuredSMapped with water content P relation, such as Fig. 1 institutes
Show；Pass through f (x) and x mathematical modeling f (x)=y0+ kx fittings determine y0With k value.
Step 7), the model soil water potential ψ according to soil to be measuredSWith water content P mathematical modeling, soil to be measured is produced
Model soil water potential and water content relation table.
Step 8), utilize the instant water potential value ψ of the water potential meter two kinds of soil to be measured of detection in continuous 10 daysR。
Step 9), pass through measured value ψR, the model soil water potential of soil to be measured and the relation table of water content are looked into, from soil to be measured
Found in the model soil water potential of earth and the relation table of water content and ψRTwo neighbouring class values, soil to be measured is obtained by interpolation method
The flow of water is ψRWhen soil moisture content, soil moisture content as to be measured.
A kind of method using water potential meter on-line checking soil moisture content provided by the present invention has been carried out in detail above
Introduce, apply specific case herein and the principle and embodiment of the present invention are set forth, be noted that above institute
Only presently preferred embodiments of the present invention is stated, is not intended to limit the invention.Institute within the spirit and principles of the invention
All any modification, equivalent and improvement of work etc., should be included in the scope of the protection.
Claims (5)
- A kind of 1. method using water potential meter on-line checking soil moisture content, it is characterised in that comprise the following steps：Step 1), the model soil using the soil around the soil to be measured in field or field as soil to be measured, takes soil to be measured Model pedotheque it is appropriate, be placed in clean smooth table top and make thinner, remove impurity removing after air-drying, and sample is pulverized；Step 2), the field capacity of the model pedotheque of soil to be measured is detected with core cutter method, is designated as C；Step 3), take etc. quality it is above-mentioned pulverize after soil to be measured two parts of model pedotheque, and be labeled as pedotheque A And B, into pedotheque plus water, its water content is reached the field capacity of the model soil of the soil to be measured, uniform mixing, Load identical container；Step 4), by pedotheque A and B, while it is placed under same environment, makes its continuous dehydration；Step 5), determine respectively different dehydration moment pedotheque A soil water potential and corresponding moment pedotheque B it is aqueous Amount, 10~15 groups of data are continuously measured according to the situation of change of pedotheque A soil water potential；Step 6), the model soil water potential ψ of soil to be measured is derived by the Gibbs function of compounding substances chemical potentialSWith water content P Mathematical modeling (1+P) ψS=y0+ kln (1+P), the data measured according to step 5) determine model parameter y0With k value；Step 7), the model soil water potential ψ according to soil to be measuredSWith water content P mathematical modeling, the mould of soil to be measured is produced The relation table of type soil water potential and water content；Step 8), the instant water potential value ψ of soil to be measured is obtained using water potential meterR；Step 9), it is ψ to obtain soil water potential to be measured by the relation table of the model soil water potential and water content of looking into soil to be measuredRWhen Soil moisture content, soil moisture content as to be measured.
- A kind of 2. method using water potential meter on-line checking soil moisture content as claimed in claim 1, it is characterised in that the step It is rapid 3) in into pedotheque plus water, the mass ratio of soil and water is 1：C.
- A kind of 3. method using water potential meter on-line checking soil moisture content as claimed in claim 1, it is characterised in that the step It is rapid 6) in y0Value with k is the model soil water potential ψ by soil to be measuredSWith water content P mathematical modeling (1+P) ψS=y0+ Kln (1+P) fittings determine.
- A kind of 4. method using water potential meter on-line checking soil moisture content as claimed in claim 1, it is characterised in that institute's step 7) the model soil water potential of soil to be measured and the relation table of water content are produced in, the wherein span of water content is 0-C, is contained Water is scale with 0.5%.
- A kind of 5. method using water potential meter on-line checking soil moisture content as claimed in claim 1, it is characterised in that the step It is rapid 9) in be by look into the model soil water potential of soil to be measured and the relation table of water content with ψRTwo neighbouring class values, using insert It is ψ that value method, which calculates soil water potential,RWhen soil moisture content.
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