CN107330805B - Method for determining irrigation frequency and intensity - Google Patents
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- 238000003973 irrigation Methods 0.000 title claims abstract description 133
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Abstract
The invention discloses a method for determining irrigation frequency and intensity, and belongs to the field of irrigation. The method comprises the steps of receiving a plurality of irrigation intensity sets input by a user, then calculating the water utilization rate corresponding to each irrigation intensity set, wherein the irrigation intensity set with higher water utilization rate causes higher water resource utilization rate, and the irrigation intensity set with lower water utilization rate causes lower water resource utilization rate. In the embodiment, each irrigation intensity included in the irrigation intensity set with the highest water utilization rate, and the irrigation duration and irrigation start time corresponding to each irrigation intensity are output for the user to irrigate crops, so that the utilization efficiency of water resources is improved.
Description
Technical Field
The invention relates to the field of irrigation, in particular to a method for determining irrigation frequency and irrigation intensity.
Background
The farmland irrigation frequency refers to the duration of irrigation intervals, the farmland irrigation intensity refers to the water quantity of irrigation at each time, and the farmland irrigation frequency and the irrigation intensity are important contents to be determined for planning a farmland irrigation plan.
In a few conditional areas, farmland irrigation test methods are usually adopted to determine irrigation frequency and irrigation intensity, and other areas can only be determined by the past irrigation experience. However, the determination of irrigation frequency and irrigation intensity by the test method is a time-consuming and labor-consuming work, and the irrigation frequency and irrigation intensity of different regions cannot be used universally, so that at present, most regions draw up farmland irrigation plans only by experience, and the utilization efficiency of water resources is low.
Disclosure of Invention
In order to improve the utilization efficiency of water resources, the invention provides a method for determining irrigation frequency and intensity. The technical scheme is as follows:
the invention provides a method for determining irrigation frequency and intensity, which comprises the following steps:
receiving a plurality of irrigation intensity sets, equation names of lower boundary condition equations, theoretical transpiration intensity of each unit time interval in T unit time intervals, lower boundary moisture flux of each unit time interval and soil moisture content of each Z position point in soil to be tested in the 0 th unit time interval, wherein the Z position points are positioned on the same straight line, the straight line is perpendicular to the surface of the soil to be tested, the interval between two adjacent position points in the Z position points is a preset distance, and any one of the plurality of irrigation intensity sets comprises a plurality of irrigation intensities and irrigation duration and irrigation starting time corresponding to each irrigation intensity in the plurality of irrigation intensities;
establishing a lower boundary condition equation corresponding to the equation name;
determining whether the target irrigation intensity set defines irrigation within the ith unit time interval according to the irrigation starting time corresponding to each irrigation intensity in the target irrigation intensity set, wherein the target irrigation intensity set is any one of the multiple irrigation intensity sets, i is 1, 2 and 3 … … T, and T is an integer greater than 0;
if the water filling in the ith unit time interval is not defined, calculating the average volume water content of the surface layer of the soil to be tested in the ith unit time interval according to the soil water content of each position point in the (i-1) th unit time interval
According to the average volume water content of the surface layer
Constructing an upper boundary equation, wherein the upper boundary equation is a target upper boundary equation of the ith unit time interval shown in the following formula (1):
in the formula (1), ES(i) Is the soil evaporation intensity in the ith unit time period; theta1And theta2Respectively is a preset average volume water content of surface soil, ES0Presetting the water surface evaporation intensity, wherein a and b are preset values;
if the water filling in the ith unit time interval is defined, establishing a target upper boundary equation of the ith unit time interval according to the soil moisture content of each position point in the (i-1) unit time interval;
calculating the soil moisture content of each position point in the ith unit period according to the lower bound condition equation, the target upper bound equation and a preset soil moisture content distribution change model;
according to the soil moisture content of each position point in the ith unit time interval, calculating the actual transpiration amount of the crop in the ith unit time interval according to the following formula (2)
In the formula (2), the first and second groups,
is the soil moisture content of the z-th position point in the i-th unit time interval, L (i) is the growth length of the root system of the crop in the i-th unit time interval, EC(i) Is the theoretical transpiration intensity of the unit time interval, deltaz is the distance between two adjacent position points, deltat is the time length of the unit time interval, A and thetaminAnd thetamaxRespectively are preset values;
according to the actual transpiration amount of the crops in each unit time interval of the T unit time intervals
And calculating the water utilization rate f corresponding to the target irrigation intensity set according to the following formula (3)m；
In formula (3), i (i) is the irrigation intensity in the i-th unit period defined in the target irrigation intensity set, and t (i) is the irrigation duration in the i-th unit period;
selecting an irrigation intensity set corresponding to the maximum water utilization rate from the irrigation intensity sets;
outputting each irrigation intensity included in the selected irrigation intensity set and the irrigation duration and irrigation start time corresponding to each irrigation intensity.
Optionally, the establishing of the lower boundary condition equation corresponding to the equation name includes:
when the equation name is the constant head boundary, establishing a first lower boundary condition equation shown in the following formula (4) as follows:
in the formula (4), hzFor the lower boundary water head, which is a preset value,
the soil negative pressure water head of the Z-th position point in the i-th unit time interval;
and establishing a second lower boundary condition equation shown in the following formula (5) when the equation name is the flux boundary:
in the formula (5), h is a soil negative pressure water head, α is an included angle between the soil to be tested and a horizontal plane, K is a soil water conductivity, and sigma (i) is a lower boundary water flux in the unit time interval of the ith,
Ksthe saturated hydraulic conductivity of the soil is a preset value, and h is a soil negative pressure water head; thetas、θrRespectively setting the saturated water content and the residual water content to preset values; a. n is a preset parameter;
and when the equation name is the free drainage boundary, establishing a third lower boundary condition equation shown in the following formula (6) as follows:
optionally, the average surface volume water content of the soil to be tested in the ith unit period is calculated according to the soil water content of each position point in the (i-1) unit period
According to the average volume water content of the surface layer
Constructing an upper bound equation, wherein the upper bound equation is a target upper bound equation of the ith unit time interval shown in the following formula (1), and the target upper bound equation comprises the following components:
calculating the surface average volume water content of the soil to be tested in the ith unit period according to the soil water content of the 1 st position point in the (i-1) th unit period, the soil water content of the 2 nd position point in the (i-1) th unit period and the soil water content of the 3 rd position point in the (i-1) th unit period
Establishing a first upper boundary condition equation shown as a formula (1), wherein the 1 st position point is positioned on the surface of the soil to be tested;
calculating the middle soil moisture content of each position point in the ith unit period according to the lower boundary condition equation, the first upper boundary condition equation shown in the formula (1) and the preset soil moisture content distribution change model shown in the formula (7)
According to the middle soil moisture content of the 1 st position point in the ith unit period, the middle soil moisture content of the 2 nd position point in the ith unit period and the middle soil moisture content of the 3 rd position point in the ith unit period, the surface average volume moisture content of the soil to be tested in the ith unit period is recalculated
According to the recalculated average volume water content of the surface layer
The upper boundary equation of the object as shown in equation (1) is reconstructed.
Optionally, if it is defined that irrigation is performed in the ith unit time interval, establishing a target upper boundary equation of the ith unit time interval according to the soil moisture content of each position point in the (i-1) unit time interval, where the target upper boundary equation includes:
establishing a second upper boundary condition equation as described in the following equation (8),
calculating the middle soil moisture content of each position point in the ith unit period according to the lower boundary condition equation, a second upper boundary condition equation shown in a formula (8) and a preset soil moisture content distribution change model shown in a formula (7)
If the 1 st position point is at the middle soil moisture content of the i unit time period
Less than a predetermined value thetasIf the water content of the earth surface soil is determined not to reach saturation, the second upper boundary condition equation of the formula (8) is determined asConditional equations above the target.
Optionally, the method further includes:
if the water content of the surface soil is saturated, the constructed target upper boundary condition equation is a third upper boundary equation shown in the following formula (9):
in the formula (I), the compound is shown in the specification,
the head for the 1 st position point in the (i +1) th unit period; k is a radical of1、k2The starting time and the ending time of surface water accumulation; zxjl (i +1) and zxjl (i) are the water accumulation depths of the earth surface in the unit time interval of the (i +1) th unit time interval and the (i) th unit time interval respectively; ZXNL is the energy storage capacity of the earth surface vegetation, and is a preset value; RS (i +1) is the infiltration intensity in the unit time interval of the (i +1) th unit time interval,
dt (i +1) is a time step of the (i +1) th unit period; when the surface accumulated water depth zxjl (i +1) is smaller than the surface vegetation stagnation energy storage force ZXNL, the super-seepage produced flow newly generated under the vegetation stagnation effect is stagnated on the surface to form a hydrostatic head which is equal to the accumulated water depth in numerical value; when the surface water depth zxjl (i +1) is larger than the surface vegetation stagnant energy storage force ZXNL, the accumulated water exceeding the surface stagnant energy storage capacity forms runoff and flows away, and the surface water depth reaches the maximum at the moment and is equal to the surface vegetation stagnant energy storage force in numerical value.
Optionally, the calculating the soil moisture content of each position point in the ith unit time period according to the lower bound condition equation, the target upper bound equation and a preset soil moisture content distribution change model includes:
the first step is as follows: taking the soil moisture content of each position point in the ith-1 unit time interval as the first soil moisture content of each position point in the ith unit time intervalRate of change
The second step is that: calculating the soil moisture content of each position point in the ith unit period according to the lower bound condition equation, the target upper bound equation and a preset soil moisture content distribution change model
The soil moisture content of each position point in the ith unit time interval
As the second soil moisture content
The third step: determining a first soil moisture content for each of said location points during the ith unit time period
And second soil moisture content
The condition shown in the following formula (10) is met, and epsilon is an allowable relative error and is a preset numerical value;
if the condition shown in the formula (10) is met, determining the soil moisture content of each position point in the ith unit time interval
Equal to the second water content
Namely, it is
If the condition shown in the formula (10) is not satisfied, the second water content of each position point in the ith unit period is determined
Respectively as the first water content in the ith unit period
Namely, it is
And then returns to performing the second step.
The technical scheme provided by the invention has the beneficial effects that:
in the embodiment of the invention, a plurality of irrigation intensity sets input by a user are received, then the water utilization rate corresponding to each irrigation intensity set is calculated, the higher the water utilization rate is, the higher the water resource utilization rate is, and the lower the water utilization rate is, the lower the water resource utilization rate is. In the embodiment, each irrigation intensity included in the irrigation intensity set with the highest water utilization rate, and the irrigation duration and irrigation start time corresponding to each irrigation intensity are output for the user to irrigate crops, so that the utilization efficiency of water resources is improved.
Drawings
FIG. 1 is a flow chart of a method for determining frequency and intensity of irrigation water according to an embodiment of the present invention;
FIG. 2 is a profile of water content of a soil section according to an embodiment of the present invention;
fig. 3 is a soil profile negative pressure water head distribution diagram provided by the embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
Examples
Referring to fig. 1, the embodiment of the present invention provides a method for determining irrigation frequency and intensity, the method comprising:
step 101: receiving a plurality of irrigation intensity sets, an equation name of a lower boundary condition equation, theoretical transpiration intensity of each unit time interval in T unit time intervals, lower boundary moisture flux of each unit time interval and soil moisture content of each Z position point in soil to be tested in the 0 th unit time interval, wherein the Z position points are positioned on the same straight line and the straight line is perpendicular to the surface of the soil to be tested, the interval between two adjacent position points in the Z position points is a preset distance, and any one of the plurality of irrigation intensity sets comprises irrigation duration time and irrigation starting time corresponding to each of the plurality of irrigation intensities.
The execution subject of the embodiment may be a computer, and a user may input a plurality of irrigation intensity sets and initial conditions to the computer through input and output devices such as a keyboard of the computer.
Besides the above parameters, the user can also input other parameters such as evaporation parameters, space step length and the like. For example, referring to table 1, the parameters that the user may enter may be.
TABLE 1
Step 102: and establishing a lower boundary condition equation corresponding to the equation name.
The lower boundary condition equation comprises a first lower boundary condition equation, a second lower boundary condition equation and a third lower boundary condition equation, and a user selects one lower boundary condition equation according to the actual situation and inputs the equation name of the lower boundary condition equation into the computer.
The step can be realized by the following three steps:
1021: when the equation name is the constant head boundary, a first lower boundary condition equation shown in the following formula (4) is established as follows:
in the formula (4), hzFor the lower boundary water head, which is a preset value,
the soil negative pressure water head of the Z-th position point in the i-th unit time interval;
1022: in the case where the equation name is a flux boundary, a second lower boundary condition equation shown in the following equation (5) is established as:
in the formula (5), h is a soil negative pressure water head, α is an included angle between the soil to be tested and the horizontal direction, K is a soil water conductivity, sigma (i) is a lower boundary moisture flux in the ith unit period, and the lower boundary moisture energy sigma (i) in the ith unit period is input in advance by a user, wherein,
Ksthe saturated hydraulic conductivity of the soil is a preset value, and h is a soil negative pressure water head; thetas、θrRespectively setting the saturated water content and the residual water content to preset values; a. n is a preset parameter;
1023: in the case where the equation name is a free drainage boundary, a third lower boundary condition equation shown in the following formula (6) is established as follows:
step 103: and determining whether the target irrigation intensity set defines irrigation within the ith unit time interval according to the irrigation starting time corresponding to each irrigation intensity in the target irrigation intensity set, wherein the target irrigation intensity set is any one of a plurality of irrigation intensity sets, i is 1, 2 and 3 … … T, and T is an integer greater than 0.
Step 104: if the water filling in the ith unit time interval is not defined, calculating the average volume water content of the surface layer of the soil to be tested in the ith unit time interval according to the soil water content of each position point in the (i-1) th unit time interval
According to the average volume water content of the surface layer
An upper bound equation is constructed, and the upper bound equation is a target upper bound equation of the i-th unit period as shown in the following formula (1).
In the formula (1), ES(i) Is the soil evaporation intensity in the ith unit time period; theta1And theta2Respectively is a preset average volume water content of surface soil, ES0The evaporation intensity of the water surface is preset, and a and b are preset values.
①, firstly, calculating the average volume water content of the surface layer of the soil to be tested in the ith unit period according to the soil water content of the 1 st position point in the (i-1) th unit period, the soil water content of the 2 nd position point in the (i-1) th unit period and the soil water content of the 3 rd position point in the (i-1) th unit period
And according to the average volume water content of the surface layer
First, a first upper boundary condition equation shown in formula (1) is preliminarily established, wherein the 1 st position point is located on the surface of the soil to be tested.
It should be noted that: at this time, the water content is reduced due to the average volume of the surface layer
Is calculated according to the soil moisture content in the (i-1) th unit time interval, and the average volume moisture content of the surface layer calculated according to the calculation result
It may not be the true value in the ith unit period, so that the preliminarily established first upper boundary condition equation shown in equation (1) may be erroneous. For this purpose, this step also needs to be corrected in the following way, and the correction process is as follows:
②, calculating the middle soil moisture content of each position point in the ith unit period according to the lower boundary condition equation, the first upper boundary condition equation shown in formula (1) and the preset soil moisture content distribution change model shown in formula (7)
A is a preset value.
For example, assuming that the lower boundary condition equation established in step 102 is the second lower boundary condition equation as shown in equation (5), the intermediate soil moisture content of each location point in the i-th unit period is calculated according to equations (1), (5) and (7)
③, finally, according to the middle soil moisture content of the 1 st position point in the ith unit period, the middle soil moisture content of the 2 nd position point in the ith unit period and the middle soil moisture content of the 3 rd position point in the ith unit period, recalculating the surface average volume moisture content of the soil to be tested in the ith unit period
According to the recalculated average volume water content of the surface layer
The first upper boundary condition equation shown in equation (1) is reconstructed and used as the target upper boundary equation.
Step 105: and if the water is poured in the ith unit time interval, establishing a target upper boundary equation of the ith unit time interval according to the soil moisture content of each position point in the (i-1) unit time interval.
In the ith unit time interval, irrigation comprises two conditions of saturated soil moisture content and unsaturated soil moisture content of the soil surface layer, the established equations of the target upper boundary conditions in each condition are different, and the detailed establishment process is as follows:
1051: firstly, assuming that the soil moisture content of the soil surface layer is not saturated, namely the 1 st position point is not saturated, establishing a second upper boundary condition equation described in the following formula (8) under the unsaturated condition,
1052: according to the lower boundary condition equation, a second upper boundary condition equation shown in a formula (8) and a preset soil moisture content distribution change model shown in a formula (7), calculating the middle soil moisture content of each position point in the ith unit period
For example, assuming that the lower boundary condition equation established in step 102 is the second lower boundary condition equation as shown in equation (5), the intermediate soil moisture content of each location point in the i-th unit period is calculated according to equations (5), (8) and (7)
1053: if the 1 st position point is at the middle soil moisture content of the i unit time period
Less than a predetermined value thetasAnd if the water content of the earth surface soil is determined not to reach saturation, determining the second upper boundary condition equation described in the formula (8) as a target upper boundary condition equation.
1054: if the water content of the surface soil is saturated, the constructed target upper boundary condition equation is a third upper boundary equation shown in the following formula (9):
in the formula (I), the compound is shown in the specification,
the head for the 1 st position point in the (i +1) th unit period; k is a radical of1、k2The starting time and the ending time of surface water accumulation; zxjl (i +1) and zxjl (i) are the water accumulation depths of the earth surface in the unit time interval of the (i +1) th unit time interval and the (i) th unit time interval respectively; ZXNL is the energy storage capacity of the earth surface vegetation, and is a preset value; RS (i +1) is the infiltration intensity in the unit time interval of the (i +1) th unit time interval,
dt (i +1) is a time step of the (i +1) th unit period; when the surface accumulated water depth zxjl (i +1) is smaller than the surface vegetation stagnation energy storage force ZXNL, the super-seepage produced flow newly generated under the vegetation stagnation effect is stagnated on the surface to form a hydrostatic head which is equal to the accumulated water depth in numerical value; when the surface water depth zxjl (i +1) is larger than the surface vegetation stagnant energy storage force ZXNL, the accumulated water exceeding the surface stagnant energy storage capacity forms runoff and flows away, and the surface water depth reaches the maximum at the moment and is equal to the surface vegetation stagnant energy storage force in numerical value.
Step 106: and (3) calculating the soil moisture content of each position point in the ith unit period according to the lower bound condition equation, the target upper bound equation and a preset soil moisture content distribution change model shown in the formula (7).
The method comprises the following steps:
the first step is as follows: taking the soil moisture content of each position point in the ith-1 unit time interval as the first soil moisture content of each position point in the ith unit time interval
The second step is that: calculating the soil moisture content of each position point in the ith unit period according to the lower bound condition equation, the target upper bound equation and a preset soil moisture content distribution change model shown in the formula (7)
The soil moisture content of each position point in the ith unit time interval
As the second soil moisture content
For example, assuming that the lower boundary condition equation established in step 102 is the second lower boundary condition equation as shown in equation (5) and the target upper boundary condition equation established in step 105 is the second upper boundary condition equation as shown in equation (8), the soil moisture content of each location point in the i-th unit period is calculated according to equations (5), (8) and (7)
As the second soil moisture content
The third step: determining a first soil moisture content for each location point within an ith unit time period
And second soil moisture content
The condition shown in the following formula (10) is met, and epsilon is an allowable relative error and is a preset numerical value;
if the condition shown in the formula (10) is met, determining the soil moisture content of each position point in the ith unit time interval
Equal to the second water content
Namely, it is
Ending and returning;
if the condition shown in the formula (10) is not satisfied, the second water content of each position point in the ith unit period is determined
Respectively as the first water content in the ith unit period
Namely, it is
And then returns to performing the second step.
Step 107: according to the soil moisture content of each position point in the ith unit time interval, calculating the actual transpiration amount of the crop in the ith unit time interval according to the following formula (2)
In the formula (2), the first and second groups,
is the soil moisture content of the z-th position point in the i-th unit time interval, L (i) is the growth length of the crop root system in the i-th unit time interval, EC(i) Is the theoretical transpiration intensity of the ith unit time interval, Δ z is the distance between two adjacent position points, Δ t is the time length of the unit time interval, and θminAnd thetamaxRespectively, preset values. Wherein, l (i) ═ 4.4013+0.7744i +0.00036i2。
The steps of the above steps 103 to 107 are repeatedly performed to calculate the actual transpiration amount for the 1 st unit period
Actual transpiration amount of 2 nd unit time period
Until the actual transpiration amount of the Tth unit time interval is calculated
Until then.
Step 108: according to the actual transpiration amount of the crops in each unit time interval of the T unit time intervals
And calculating the water utilization rate f corresponding to the target irrigation intensity set according to the following formula (3)m；
In formula (3), i (i) is the irrigation intensity in the i-th unit period defined in the target irrigation intensity set, and t (i) is the irrigation duration in the i-th unit period.
For each of the other sets of intensity values, each of the other sets of intensity values is calculated as described above in connection with the steps 103 to 108, as described above for the target set of intensity valuesCorresponding water utilization factor fm。
Step 109: an irrigation intensity set corresponding to the maximum water use ratio is selected from the plurality of irrigation intensity sets.
Step 110: and outputting each irrigation intensity included by the selected irrigation intensity set, and the irrigation duration and irrigation starting time corresponding to each irrigation intensity.
In the embodiment of the invention, a plurality of irrigation intensity sets input by a user are received, then the water utilization rate corresponding to each irrigation intensity set is calculated, the higher the water utilization rate is, the higher the water resource utilization rate is, and the lower the water utilization rate is, the lower the water resource utilization rate is. In the embodiment, each irrigation intensity included in the irrigation intensity set with the highest water utilization rate, and the irrigation duration and irrigation start time corresponding to each irrigation intensity are output for the user to irrigate crops, so that the utilization efficiency of water resources is improved.
The following examples of the present invention are provided.
In the application example, taking a certain wheat test field in north China as an example, the maximum water content and the minimum water content are allowed to be 0.296 and 0.08 respectively, and the soil hydrodynamic parameters are shown in the following table 2.
TABLE 2
Considering the time-space distribution of the water absorption rate of the root system, the water absorption rate and the water absorption depth of the root system are linearly changed, and the calculation formula is as follows:
in the formula, EC(t) plant transpiration strength under sufficient water supply conditions; a is an economic coefficient, and is taken as 0.597;t is the number of days from the winter wheat sowing date until the counting start time. When t is smaller, zr(t)<0, not matching reality, take zr(t)＝0。
The influence of the average water content of the soil within 5cm of the surface soil on evaporation is considered for the inter-crop evaporation strength, and the following relation is obtained by a field test of winter wheat:
in the formula (I), the compound is shown in the specification,
the average volume water content of a surface soil layer within 5 cm; eS0The water surface evaporation intensity.
The basic data of the theoretical transpiration strength of winter wheat under the condition of sufficient water supply are shown in the following table 3:
TABLE 3
| Growth period | Sowing-overwintering | Overwintering-turning green | Turning green-plucking joint | Node-ear plucking | Heading-ripening |
| Days/d | 78 | 114 | 153 | 185 | 230 |
| ES0/mm/d | 0.53 | 0.28 | 0.53 | 0.27 | 0.23 |
| EC/mm/d | 0.37 | 0.57 | 1.23 | 3.52 | 3.78 |
The space step length is 4cm, the simulated soil layer depth is 200cm, the lower boundary condition is a free drainage boundary, the simulation duration is 230d for the whole wheat growth, the time step length is 0.01d, the maximum surface water accumulation depth is 1cm, the surface gradient is 0, and the maximum allowable error is 0.0001.
Receiving the input irrigation frequency and intensity to obtain the irrigation intensity set shown in the following table 4:
TABLE 4
The following table 5 shows the calculated water utilization rate of each combination, from which the combination with the irrigation frequency of 30d and the irrigation strength of 4.4cm is the best.
TABLE 5
| Irrigation waterIntensity assembly | Water utilization rate |
| Set 1 | 0.6514 |
| Set 2 | 0.6596 |
| Set 3 | 0.6935 |
| Set 4 | 0.8216 |
Fig. 2 and 3 show the water content distribution and the soil negative pressure water head distribution of the soil section at the 114 th day, 153 th day and 230 th day under the optimal irrigation frequency and intensity.
It will be understood by those skilled in the art that all or part of the steps for implementing the above embodiments may be implemented by hardware, or may be implemented by a program instructing relevant hardware, where the program may be stored in a computer-readable storage medium, and the above-mentioned storage medium may be a read-only memory, a magnetic disk or an optical disk, etc.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (6)
1. A method for determining frequency and intensity of irrigation, the method comprising:
receiving a plurality of irrigation intensity sets, equation names of lower boundary condition equations, theoretical transpiration intensity of each unit time interval in T unit time intervals, lower boundary moisture flux of each unit time interval and soil moisture content of each Z position point in soil to be tested in the 0 th unit time interval, wherein the Z position points are positioned on the same straight line, the straight line is perpendicular to the surface of the soil to be tested, the interval between two adjacent position points in the Z position points is a preset distance, and any one of the plurality of irrigation intensity sets comprises a plurality of irrigation intensities and irrigation duration and irrigation starting time corresponding to each irrigation intensity in the plurality of irrigation intensities;
establishing a lower boundary condition equation corresponding to the equation name;
determining whether the target irrigation intensity set defines irrigation within the ith unit time interval according to the irrigation starting time corresponding to each irrigation intensity in the target irrigation intensity set, wherein the target irrigation intensity set is any one of the multiple irrigation intensity sets, i is 1, 2 and 3 … … T, and T is an integer greater than 0;
if the water filling in the ith unit time interval is not defined, calculating the average volume water content of the surface layer of the soil to be tested in the ith unit time interval according to the soil water content of each position point in the (i-1) th unit time interval
According to the average volume water content of the surface layer
Constructing an upper boundary equation, wherein the upper boundary equation is a target upper boundary equation of the ith unit time interval shown in the following formula (1):
in the formula (1), ES(i) Is the soil evaporation intensity in the ith unit time period; theta1And theta2Respectively is a preset average volume water content of surface soil, ES0Presetting the water surface evaporation intensity, wherein a and b are preset values;
if the water filling in the ith unit time interval is defined, establishing a target upper boundary equation of the ith unit time interval according to the soil moisture content of each position point in the (i-1) unit time interval;
calculating the soil moisture content of each position point in the ith unit period according to the lower bound condition equation, the target upper bound equation and a preset soil moisture content distribution change model;
according to the soil moisture content of each position point in the ith unit time interval, calculating the actual transpiration amount of the crop in the ith unit time interval according to the following formula (2)
In the formula (2), the first and second groups,
is the soil moisture content of the z-th position point in the i-th unit time interval, L (i) is the growth length of the root system of the crop in the i-th unit time interval, EC(i) Is the theoretical transpiration intensity of the unit time interval, deltaz is the distance between two adjacent position points, deltat is the time length of the unit time interval, A and thetaminAnd thetamaxRespectively are preset values;
according to the actual transpiration amount of the crops in each unit time interval of the T unit time intervals
And calculating the water utilization rate f corresponding to the target irrigation intensity set according to the following formula (3)m；
In formula (3), i (i) is the irrigation intensity in the i-th unit period defined in the target irrigation intensity set, and t (i) is the irrigation duration in the i-th unit period;
selecting an irrigation intensity set corresponding to the maximum water utilization rate from the irrigation intensity sets;
outputting each irrigation intensity included in the selected irrigation intensity set and the irrigation duration and irrigation start time corresponding to each irrigation intensity.
2. The method of claim 1, wherein establishing the lower boundary condition equation corresponding to the equation name comprises:
when the equation name is the constant head boundary, establishing a first lower boundary condition equation shown in the following formula (4) as follows:
in the formula (4), hzFor the lower boundary water head, which is a preset value,
the soil negative pressure water head of the Z-th position point in the i-th unit time interval;
and establishing a second lower boundary condition equation shown in the following formula (5) when the equation name is the flux boundary:
in the formula (5), h is a soil negative pressure water head, α is an included angle between the soil to be tested and a horizontal plane, K is a soil water conductivity, and sigma (i) is a lower boundary water flux in the unit time interval of the ith,
Ksthe saturated hydraulic conductivity of the soil is a preset value, and h is a soil negative pressure water head; thetas、θrRespectively saturated water contentAnd the residual water content are preset values; a. n is a preset parameter;
and when the equation name is the free drainage boundary, establishing a third lower boundary condition equation shown in the following formula (6) as follows:
3. the method as claimed in claim 2, wherein the average surface volume water content of the soil to be tested in the ith unit time period is calculated according to the soil water content of each position point in the (i-1) unit time period
According to the average volume water content of the surface layer
Constructing an upper bound equation, wherein the upper bound equation is a target upper bound equation of the ith unit time interval shown in the following formula (1), and the target upper bound equation comprises the following components:
calculating the surface average volume water content of the soil to be tested in the ith unit period according to the soil water content of the 1 st position point in the (i-1) th unit period, the soil water content of the 2 nd position point in the (i-1) th unit period and the soil water content of the 3 rd position point in the (i-1) th unit period
Establishing a first upper boundary condition equation shown as a formula (1), wherein the 1 st position point is positioned on the surface of the soil to be tested;
calculating the middle soil moisture content of each position point in the ith unit period according to the lower boundary condition equation, the first upper boundary condition equation shown in the formula (1) and the preset soil moisture content distribution change model shown in the formula (7)
According to the middle soil moisture content of the 1 st position point in the ith unit period, the middle soil moisture content of the 2 nd position point in the ith unit period and the middle soil moisture content of the 3 rd position point in the ith unit period, the surface average volume moisture content of the soil to be tested in the ith unit period is recalculated
According to the recalculated average volume water content of the surface layer
The upper boundary equation of the object as shown in equation (1) is reconstructed.
4. The method of claim 3, wherein establishing a target upper bound equation for an ith unit time period based on the soil moisture content of each location point for an (i-1) th unit time period if irrigation is defined within the ith unit time period comprises:
establishing a second upper boundary condition equation as described in the following equation (8),
calculating the middle soil moisture content of each position point in the ith unit period according to the lower boundary condition equation, a second upper boundary condition equation shown in a formula (8) and a preset soil moisture content distribution change model shown in a formula (7)
If the 1 st position point is at the middle soil moisture content of the i unit time period
Less than a predetermined value thetasAnd if the water content of the earth surface soil is determined not to reach saturation, determining the second upper boundary condition equation in the formula (8) as a target upper boundary condition equation.
5. The method of claim 4, wherein the method further comprises:
if the water content of the surface soil is saturated, the constructed target upper boundary condition equation is a third upper boundary equation shown in the following formula (9):
in the formula (I), the compound is shown in the specification,
the head for the 1 st position point in the (i +1) th unit period; k is a radical of1、k2The starting time and the ending time of surface water accumulation; zxjl (i +1) and zxjl (i) are the water accumulation depths of the earth surface in the unit time interval of the (i +1) th unit time interval and the (i) th unit time interval respectively; ZXNL is the energy storage capacity of the earth surface vegetation, and is a preset value; RS (i +1) is the infiltration intensity in the unit time interval of the (i +1) th unit time interval,
dt (i +1) is a time step of the (i +1) th unit period; when the surface accumulated water depth zxjl (i +1) is smaller than the surface vegetation stagnation energy storage force ZXNL, the super-seepage produced flow newly generated under the vegetation stagnation effect is stagnated on the surface to form a hydrostatic head which is equal to the accumulated water depth in numerical value; when the surface water depth zxjl (i +1) is larger than the surface vegetation stagnant energy storage force ZXNL, the accumulated water exceeding the surface stagnant energy storage capacity forms runoff and flows away, and the surface water depth reaches the maximum at the moment and is equal to the surface vegetation stagnant energy storage force in numerical value.
6. The method of claim 1, wherein the calculating the soil moisture content of each of the location points in the ith unit time period according to the lower bound condition equation, the target upper bound equation and a preset soil moisture content distribution change model comprises:
the first step is as follows: taking the soil moisture content of each position point in the ith-1 unit time interval as the first soil moisture content of each position point in the ith unit time interval
The second step is that: calculating the soil moisture content of each position point in the ith unit period according to the lower bound condition equation, the target upper bound equation and a preset soil moisture content distribution change model
The soil moisture content of each position point in the ith unit time interval
As the second soil moisture content
The third step: determining a first soil moisture content for each of said location points during the ith unit time period
And second soil moisture content
The condition shown in the following formula (10) is met, and epsilon is an allowable relative error and is a preset numerical value;
if the condition shown in the formula (10) is met, determining the soil moisture content of each position point in the ith unit time interval
Equal to the second water content
Namely, it is
If the condition shown in the formula (10) is not satisfied, the second water content of each position point in the ith unit period is determined
Respectively as the first water content in the ith unit period
Namely, it is
And then returns to performing the second step.
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| CN102726273A (en) * | 2012-06-15 | 2012-10-17 | 中农先飞（北京）农业工程技术有限公司 | Decision-making method for soil moisture monitoring and intelligent irrigation of root zone of crop |
| CN104620945A (en) * | 2014-12-31 | 2015-05-20 | 石河子大学 | Land irrigation quota determining method |
| CN105210801A (en) * | 2015-10-30 | 2016-01-06 | 张凡 | Irrigation opportunity and irrigate method for determination of amount and device |
| CN106613783A (en) * | 2016-10-20 | 2017-05-10 | 河北农业大学 | Universal intelligent irrigation system and control method thereof |
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| CN102726273A (en) * | 2012-06-15 | 2012-10-17 | 中农先飞（北京）农业工程技术有限公司 | Decision-making method for soil moisture monitoring and intelligent irrigation of root zone of crop |
| CN104620945A (en) * | 2014-12-31 | 2015-05-20 | 石河子大学 | Land irrigation quota determining method |
| CN105210801A (en) * | 2015-10-30 | 2016-01-06 | 张凡 | Irrigation opportunity and irrigate method for determination of amount and device |
| CN106613783A (en) * | 2016-10-20 | 2017-05-10 | 河北农业大学 | Universal intelligent irrigation system and control method thereof |
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