CN113642269A - Accurate irrigation method and irrigation system - Google Patents
Accurate irrigation method and irrigation system Download PDFInfo
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- 238000003973 irrigation Methods 0.000 title claims abstract description 65
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- 230000005068 transpiration Effects 0.000 claims description 11
- 230000004907 flux Effects 0.000 claims description 9
- 239000003621 irrigation water Substances 0.000 claims description 9
- 230000007246 mechanism Effects 0.000 claims description 9
- 230000008595 infiltration Effects 0.000 claims description 8
- 238000001764 infiltration Methods 0.000 claims description 8
- 239000002344 surface layer Substances 0.000 claims description 8
- 239000002352 surface water Substances 0.000 claims description 8
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- A—HUMAN NECESSITIES
- A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
- A01G—HORTICULTURE; CULTIVATION OF VEGETABLES, FLOWERS, RICE, FRUIT, VINES, HOPS OR SEAWEED; FORESTRY; WATERING
- A01G25/00—Watering gardens, fields, sports grounds or the like
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Abstract
The invention relates to the field of agricultural irrigation, in particular to an accurate irrigation method and an irrigation system based on an optimal control algorithm. Comprises collecting parameters related to crop production; a soil-plant-environment continuum oriented hydrodynamic equilibrium relation model is constructed based on an optimal control theory, and a research object, a state variable, a control variable and an external disturbance factor in the model are determined by combining collected parameters. On the premise of not influencing the normal production of crops, the soil moisture information and the crop stem moisture information of different depth profiles of a crop root zone are collected noninvasively; then, according to the water demand characteristics of the crops at different growth stages, the water migration rule of the soil-plant-environment system is comprehensively considered, the optimal irrigation index is obtained by utilizing the optimal control theory and comprehensive decision, and the irrigation system is utilized to realize the accurate irrigation of the crops.
Description
Technical Field
The invention relates to the field of agricultural irrigation, in particular to an accurate irrigation method and an irrigation system based on an optimal control algorithm.
Background
Water is an important basic resource for guaranteeing national economy and social development. However, in recent years, the problem of water resource safety has become serious. Especially, as a big agricultural country, China is currently in the key stage of industrial adjustment, and the contradiction between agriculture and industrial water competition is inevitable. And as agricultural irrigation with the most consumption of fresh water, the irrigation efficiency is less than 40%. Therefore, it is necessary to find a method for effectively improving agricultural water efficiency and realizing accurate irrigation.
When the soil is in an unsaturated water state, the dominance of soil and plants on water migration is established on the mutual competition relationship of soil water suction and plant root suction. The water migration is always in the dynamic balance of the two suction forces. Therefore, irrigation decision making by comprehensively considering the moisture information of the soil-plant system is more scientific. At present, most of researches on accurate irrigation methods of crops at home and abroad are based on selecting reasonable irrigation indexes, and the indexes are generally limited to moisture information of soil or single plant objects and have great limitations. If soil moisture at a certain depth is measured or multiple soil sensors are placed at different depths in soil to obtain soil moisture at multiple points, obviously, the conventional soil sensing technology will inevitably cause disturbance to the in-situ soil environment of crops, and the consistency of the sensor probes is difficult to ensure; the common method for acquiring the plant moisture information is to measure the leaf water potential, the stem flow rate and the like. However, such methods generally have a certain influence on the normal growth of plants, and the obtained moisture information is not representative. Therefore, the method has the advantages that the soil-plant and environment moisture information of the crops are obtained noninvasively, the characteristics of the growth stage of the crops are combined, and the reasonable irrigation indexes are selected as the basic premise for realizing accurate irrigation.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, provides an accurate irrigation method and an irrigation system, and noninvasively acquires the soil moisture information and the crop stem moisture information of different depth profiles of a crop root zone on the premise of not influencing the normal production of crops; then, according to the water demand characteristics of the crops at different growth stages, the water migration rule of the soil-plant-environment system is comprehensively considered, the optimal irrigation index is obtained by utilizing the optimal control theory and comprehensive decision, and the irrigation system is utilized to realize the accurate irrigation of the crops.
The technical scheme of the invention is as follows: a method of precision irrigation comprising the steps of:
s1, collecting parameters related to crop production, including microclimate information of farmlands, soil environment information, key moisture information of crops, surface water evaporation and infiltration information and irrigation water quantity;
s2, constructing a soil-plant-environment continuum oriented hydrodynamic balance relation model based on an optimal control theory, and determining a research object, state variables, control variables and external disturbance factors in the model by combining the parameters collected in the step S1, wherein the state variables comprise surface water evaporation, infiltration, root region soil water storage, crop stem flow, crop stem moisture and leaf transpiration, the control variables comprise irrigation water quantity, and the external disturbance factors comprise temperature, illumination, wind speed and rainfall values;
s3, establishing a relation between the model and the parameters, determining an objective function for optimal irrigation decision and control, and in a farmland with vegetation coverage and in a non-saturated soil water state, determining a hydrodynamic equilibrium relation model of the soil-plant-environment continuum as follows
The method comprises the following steps of (1) determining the water content of soil, wherein theta (t) is the water content of the soil, q (t) is the three-dimensional water flux of the soil water in the directions of x, y and z, S (t) is a source and sink term, the source and sink term depends on the absorption of the plant root system to the soil water or the transpiration of leaf water and the water evaporation of the surface layer of the soil, wherein the absorption of the plant root system to the soil water or the transpiration of the leaf water is embodied by a stem flow parameter, the stem flow parameter is detected by a stem flow sensor, the water evaporation of the surface layer of the soil is detected by a lysimeter, and the source and sink term is the sum of the two;
respectively selecting points outside the root zone of the plant, wherein the coordinate of the point in the root zone is (x)1,y1,z1) The coordinates of the points outside the root zone are (x)1,y1,z2) Respectively placing soil moisture sensors at the two points to obtain one-dimensional soil water equation sets at two different depths
Wherein, θ z1、θz2For the soil water content, q, measured by two soil moisture sensorsz1、qz2Is the z-direction water flux, S (z)1T) is a source and sink item;
irrigation valve switch decision function of
Among them, threshold1And threshold2For z-direction water flow flux value q determined according to specific constraint conditionszThe corresponding soil water content value is theta z detected by the soil water sensor in real time1Value and threshold1Comparison, θ z2And threshold2Comparing, and accurately controlling the on-off of the irrigation valve according to the formula (3);
s4, selecting different objective functions or multi-objective functions according to actual requirements, namely threshold in formula (3)1And threshold2The joint solution of the post-system equation is determined depending on equation (2), the objective function and the specific constraints.
In the present invention, the limiting constraint conditions of the state variables and the control variables are: valve flow Q has an upper bound; (ii) the change of the soil water takes the water content of the soil with plant growth retardation or the water content of plant wilting as the lower bound of the variable; (iii) the change of the soil water takes the water content of saturated soil or the maximum field water capacity as an upper bound;
wherein the critical point of the water content of the soil with plant growth retardation or the water content of plant wilting in (ii) is derived from the plant stem water information.
In step S4, the objective function is an objective function for reducing water leakage of soil below the root zone
Q when the soil water leakage is ensured to be minimum is obtained by solving according to the formula (4)z2Value of q isz2Substituting into equation (1) to obtain the corresponding threshold2Value of θ z to be actually detected2And threshold2And (4) controlling whether to start or stop the irrigation valve according to the formula (3).
The invention also comprises an accurate irrigation system which comprises a water pipe, wherein a water inlet of the water pipe is provided with an electromagnetic valve, a flowmeter is arranged at the electromagnetic valve, the accurate irrigation system also comprises a stem moisture sensor, a stem flow sensor, a three-depth moisture sensor, an electromagnetic valve, an lysimeter, a microclimate station and a main control box, the stem moisture sensor and the stem flow sensor are fixed at a crop stem, the three-depth moisture sensor is positioned in soil of a crop root zone, the lysimeter is positioned below the soil of the crop root zone, and the stem moisture sensor, the stem flow sensor, the three-depth moisture sensor, the electromagnetic valve, the flowmeter at the electromagnetic valve, the lysimeter and the microclimate station are respectively connected with the main control box;
the stem moisture sensor comprises a signal conditioning circuit board and a sensor probe supporting mechanism, the signal conditioning circuit board is electrically connected with the sensor probe supporting mechanism, the sensor probe supporting mechanism comprises a crop stem fixing sliding block, a sliding block sliding supporting rod, a sensor probe supporting block and a sensor probe, the crop stem fixing sliding block and the sensor probe supporting block are oppositely arranged, the crop stem fixing sliding block and the sensor probe supporting block are in sliding connection through the sliding block sliding supporting rod, one end of the sliding supporting rod is fixedly connected with the sensor probe supporting block, and the crop stem fixing sliding block is sleeved on the outer side of the sliding block sliding supporting rod in a sliding mode;
a crop stem inserting hole for fixing a crop stem is formed in the crop stem fixing sliding block, a sensor probe is arranged on one side, facing the crop stem fixing sliding block, of the sensor probe supporting block, the sensor probe is arranged in the sensor probe supporting block in a sliding mode, the sensor probe is electrically connected with the signal conditioning circuit board, the sensor probe is in contact with the crop stem, a sensor supporting rod inserting hole is further formed in the sensor probe supporting block, and an inserting rod for fixing the sensor probe supporting block is arranged in the sensor supporting rod inserting hole;
the three-depth soil moisture sensor comprises a PVC connecting rod, the head of the PVC connecting rod is provided with a PVC conical head, three groups of soil moisture sensor electrodes with different depths are arranged at intervals along the height direction of the PVC connecting rod, and the soil moisture sensor electrodes are respectively connected with a signal processing circuit through coaxial cables.
The crop stem is positioned in the crop stem inserting hole, a stem fastening screw is arranged at the crop stem inserting hole, and the crop stem is fixed in the crop stem inserting hole by screwing the stem fastening screw;
the crop stem fixing sliding block is also provided with a supporting rod fastening screw, the supporting rod fastening screw is positioned at a through hole in the crop stem fixing sliding block, so that the sliding supporting rod of the sliding block slides, the supporting rod fastening screw is screwed, and the fixed connection of the sliding supporting rod of the sliding block and the crop stem fixing sliding block is realized.
The signal conditioning circuit board is connected with the main controller through a data cable.
The outer side of the sensor probe is provided with a probe guide rod, the sensor probe is arranged in the probe guide rod in a sliding mode, and the probe guide rod is fixed in the insertion hole of the sensor probe supporting block.
The invention has the beneficial effects that:
(1) compared with the existing irrigation decision making depending on an empirical value or a single index, the accurate irrigation method and the irrigation system comprehensively consider the water migration rule of a soil-plant-environment system, and utilize an optimal control theory to comprehensively make a decision to obtain an optimal irrigation index, so that the accurate irrigation of crops is realized;
(2) on the premise of not influencing the normal production of crops, the stem moisture sensor is used for collecting the moisture information of the crop stem without wound, and the three-depth moisture sensor is used for collecting the moisture of the soil of the sections of different depths of the soil without wound;
(3) the stem moisture sensor, the stem flow sensor and the three-depth moisture sensor in the irrigation system are simple to mount and dismount, high in precision and relatively low in cost, irrigation precision can be improved, water is saved, high quality and high yield of crops can be guaranteed, and the method has very important significance for reducing agricultural energy consumption, improving economic benefits and promoting agricultural sustainable and high-quality efficient development.
Drawings
Fig. 1 is a schematic view of the installation of a precision irrigation system.
FIG. 2 is a schematic diagram of a stem moisture sensor configuration;
FIG. 3 is a schematic diagram of a three depth soil moisture sensor configuration;
in the figure: 1. a water pipe;
2. a stem moisture sensor; 201. a data cable; 202. a crop stem fixing slide block; 203. the slide block slides the support rod; 204. crop stem insertion holes; 205. a stalk fastening screw; 206. a support rod fastening screw; 207. a sensor probe; 209. a sensor probe supporting block; 210. a sensor support rod jack; 211. a signal conditioning circuit board;
3. a stem flow sensor;
4. a three depth soil moisture sensor; 401. a sensor circuit board mounting hole; 402. a coaxial cable; 403. a first deep soil moisture sensor electrode; 404. II, a deep soil moisture sensor electrode; 405. III deep soil moisture sensor electrode; 406. PVC conical heads; 407. a PVC connecting rod;
5. an electromagnetic valve; 6. a lysimeter; 7. a microclimate station; 8. and a main control box.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
In the following description, specific details are set forth in order to provide a thorough understanding of the present invention. The invention can be implemented in a number of ways different from those described herein and similar generalizations can be made by those skilled in the art without departing from the spirit of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.
The invention comprises a precise irrigation method based on an optimal control theory, which comprises the following steps.
The method comprises the steps of firstly, collecting relevant parameters of crop production, including microclimate information of farmlands, soil environment information, key moisture information of crops, surface water evaporation and infiltration information and irrigation water quantity.
As shown in FIG. 1, microclimate information of the farmland can be collected by the microclimate station 7, including the temperature, illumination, wind speed, rainfall and the like of the environment of the farmland. The diameter of the crop stem is collected in real time by the stem moisture sensor 2, thereby obtaining moisture information, such as moisture content, of the crop stem. The information such as crop stem flow, leaf transpiration and the like is collected in real time through the stem flow sensor 3. Surface water evaporation and infiltration parameter information is collected through the lysimeter 6. The irrigation water quantity is collected through the electromagnetic valve 5 and a flow meter at the electromagnetic valve.
Secondly, constructing a soil-plant-environment continuum oriented hydrodynamic equilibrium relation model based on an optimal control theory, and determining a research object, a state variable, a control variable and an external disturbance factor in the model by combining the data acquired in the first step; wherein the state variables comprise surface water evaporation, infiltration, root zone soil water storage, crop stem flow, crop stem moisture and leaf transpiration; the control variable comprises irrigation water amount; the external disturbance factors comprise specific numerical values such as temperature, illumination, wind speed, rainfall and the like.
The defined constraints of the state variables and the control variables are as follows: valve flow Q has an upper bound; (ii) the change of the soil water takes the water content of the soil with plant growth retardation or the water content of plant wilting as the lower bound of the variable; (iii) the soil water change is bounded above by the saturated soil water content or the maximum field water capacity.
Wherein the critical point of the water content of the soil with plant growth retardation or the water content of plant wilting in (ii) is derived from the plant stem water information.
And thirdly, establishing a relation between the model and the sensor data, and determining an optimal irrigation decision and control objective function. In a farmland with vegetation coverage and in a state of unsaturated soil water, the hydrodynamic equilibrium relation model of the soil-plant-environment continuum is
The method comprises the following steps of measuring the water content of soil, measuring the water content of soil on the surface layer of soil, and obtaining the water evaporation of the soil surface layer, wherein theta (t) is the water content of the soil, q (t) is the three-dimensional water flux of the soil water in the directions of x, y and z, S (t) is a source-sink item, the source-sink item mainly depends on the absorption of the plant root system to the soil water or the water transpiration of leaves and the water evaporation of the soil surface layer, the absorption of the plant root system to the soil water or the water transpiration of the leaves is embodied by a stem flow parameter, the stem flow parameter is obtained by the detection of a stem flow sensor, the water evaporation of the soil surface layer is obtained by the detection of a lysimeter, and the source-sink item is the sum of the two.
Further, selecting points in a root zone and outside the root zone of a plant at a certain position in the field respectively, and setting the root zone point as an A point and the coordinate as (x)1,y1,z1) Outside the root zone is point B with coordinates of (x)1,y1,z2) The point B may be located above or below the point a. A soil moisture sensor is respectively arranged at the two points, and meanwhile, the influence space of the moisture sensor is limited, so that one-dimensional soil water equation sets at two different depths can be approximately obtained, namely, the z-direction soil water equation set
Wherein, θ z1、θz2For the soil water content, q, measured by two soil moisture sensorsz1、qz2Is the z-direction water flux, S (z)1T) is a source and sink term, θ z1、θz2And S (z)1And t) are all observable variables.
Known from the classical optimal control theory, no matter the energy consumption is optimal, the time is optimal, or the energy consumption and the time are both optimal, a generalized optimal solution of an actual engineering problem is usually a switching decision function to be determined, namely:
among them, threshold1And threshold2For z-direction water flow flux value q determined according to specific constraint conditionszThe corresponding soil water content value is theta z detected by the soil water sensor in real time1Value and threshold1Comparison, θ z2And threshold2And comparing, determining whether to finally start and stop the irrigation valve according to the comparison condition, namely determining the optimal irrigation time point of the switch electromagnetic valve, so as to realize accurate irrigation of the electromagnetic valve.
Fourthly, according to actual requirements, different objective functions or multi-objective functions can be selected, and the threshold in the formula (3)1And threshold2The joint solution of the post-system equation is determined depending on equation (2), the objective function and the specific constraints.
The invention also comprises a precision irrigation system. As shown in fig. 1 to 3, accurate irrigation system includes water pipe 1, stem moisture sensor 2, stem flow sensor 3, three degree of depth moisture sensor 4, solenoid valve 5, lysimeter 6, little weather station 7 and main control box 8, the stem department of the plant that awaits measuring all is equipped with stem moisture sensor 2 and stem flow sensor 3, in this embodiment, stem moisture sensor 2 is located the top that stem flow sensor 3, stem moisture sensor 2 is used for gathering crop stem moisture information, stem flow sensor 3 is used for gathering crop stem flow information, it is odd to pass through stem moisture sensor and stem flow, can acquire crop stem moisture, key moisture information such as crop stem flow and blade transpiration. Be equipped with three degree of depth moisture sensor 4 in the root zone soil of the plant that awaits measuring, three degree of depth moisture sensor 4 are used for gathering the soil water content of the different degree of depth in the soil that crop root zone was located. The soil top of the plant that awaits measuring is equipped with several water pipes 1, and the water inlet department of water pipe 1 is equipped with solenoid valve 5, and 5 departments of solenoid valve are equipped with the flowmeter, and solenoid valve 5 is used for the switching in the automatic control water pipe 1, can detect the flow of irrigation water in the water pipe 1 through the flowmeter simultaneously, through the switching time of control flow and solenoid valve 5, the automatic control irrigation water yield. And an lysimeter 6 is arranged below the root of the plant to be detected and is used for collecting the evaporation and infiltration amount of surface water. The microclimate station 7 is used for collecting microclimate information of a farmland, including temperature, illumination, wind speed, rainfall and the like. The stem moisture sensor 2, the stem flow sensor 3, the three-depth moisture sensor 4, the electromagnetic valve 5, the flowmeter at the electromagnetic valve, the lysimeter 6 and the microclimate station 7 are respectively connected with the main control box 8.
The stem moisture sensor collects crop stem moisture information by measuring the diameter of the crop stem. As shown in fig. 2, the stem moisture sensor 2 includes a signal conditioning circuit board 211 and a sensor probe supporting mechanism, the signal conditioning circuit board 211 is connected to the main controller 8 through a data cable 201, and the signal conditioning circuit board 211 is electrically connected to the sensor probe supporting mechanism. The sensor probe supporting mechanism comprises a crop stem fixing sliding block 202, a sliding block sliding supporting rod 203, a sensor probe supporting block 209 and a sensor probe 207, the crop stem fixing sliding block 202 and the sensor probe supporting block 209 are arranged oppositely, the crop stem fixing sliding block 202 is in sliding connection with the sensor probe supporting block 209 through a sliding block sliding supporting rod 203, one end of the sliding supporting rod 203 is fixedly connected with the sensor probe supporting block 209, and the crop stem fixing sliding block 202 is sleeved on the outer side of the sliding block sliding supporting rod 203 in a sliding mode. In the sliding process of the sliding block sliding support rod 203, the adjustable distance between the sensor probe supporting block 209 and the crop stem fixing sliding block 202 is realized, so that the sensor probe 207 is driven to move towards or away from the direction of the crop stem to be detected.
A crop stem inserting hole 204 is formed in the crop stem fixing slider 202, the crop stem is positioned in the crop stem inserting hole 204, a stem fastening screw 205 is disposed at the crop stem inserting hole 204, and the crop stem can be fixed in the crop stem inserting hole 204 by screwing the stem fastening screw 205. Meanwhile, a support rod fastening screw 206 is further provided on the crop stem fixing slider 202, the support rod fastening screw 206 is located at a through hole in the crop stem fixing slider 202 for allowing the slider sliding support rod 203 to slide, and the slider sliding support rod 203 and the crop stem fixing slider 202 are fixedly connected by screwing the support rod fastening screw 206.
The sensor probe 207 is arranged on one side, facing the crop stem fixing sliding block 202, of the sensor probe supporting block 209, the sensor probe 207 is arranged in the sensor probe supporting block 209 in a sliding mode, in the embodiment, a probe guide rod is arranged outside the sensor probe 207, the sensor probe 207 is arranged in the probe guide rod in a sliding mode, and the probe guide rod is fixed in a jack of the sensor probe supporting block 209. The sensor probe is electrically connected with the signal conditioning circuit board 211, when the sensor probe 207 is propped against the crop stem, the diameter parameter of the crop stem is collected and transmitted to the signal conditioning circuit board 211, and finally the crop stem is conveyed to the main control box 8, and the moisture information of the crop stem can be obtained according to the diameter of the crop stem. A sensor support rod jack 210 is further arranged in the sensor probe support block 209, an insert rod is arranged in the sensor support rod jack 210, the insert rod is fixed in the sensor support rod jack 210 by screwing a bolt, and the sensor probe support block 209 is fixed in soil by the insert rod.
When the stem moisture sensor 2 works, firstly, the sliding block sliding support rod 203 slides to drive the sensor probe support block 209 to move towards the direction of the crop stem, and after the sensor probe support block 209 approximately slides in place, the support rod fastening screw 206 is screwed to fix the sliding block sliding support rod 203 in the crop stem fixing slide block 202; then, the position of the sensor probe 207 is adjusted, so that the sensor probe 207 is in contact with the stalks of the crops to be detected, the sensor probe 207 is used for monitoring the diameter parameters of the stalks of the crops to be detected in real time, the diameter parameters are transmitted to the main controller 8 through the signal conditioning circuit board 211, and the moisture information of the stalks with the diameters to be detected can be monitored in real time through the diameter parameters.
As shown in fig. 3, the three-depth soil moisture sensor 4 includes a PVC connecting rod 407, and a PVC cone 406 is provided at a head of the PVC connecting rod 407 so that the PVC connecting rod 407 is inserted into soil. Set up three soil moisture sensor electrodes of group along PVC connecting rod 407's direction of height interval, from top to bottom be I degree of depth soil moisture sensor electrode 403, II degree of depth soil moisture sensor electrode 404, III degree of depth soil moisture sensor electrode 405 respectively, the soil water content of the different degree of depth that above-mentioned three electrode is used for monitoring, and above-mentioned soil moisture sensor electrode is connected with signal processing circuit through coaxial cable 402 respectively. During installation, the sensor circuit board mounting hole 401 is drilled at the mounting point of the soil moisture sensor electrode, and the soil moisture sensor electrode is inserted into the mounting hole, so that the soil moisture sensor electrode is ensured to be in reliable and close contact with soil, and the in-situ soil is hardly disturbed. In order to reduce power consumption, the signal processing circuit can supply power through solar energy, and soil moisture sensor electrodes and the signal processing circuit thereof at different depths are electrified in a time-sharing mode to acquire soil moisture parameters. In this embodiment, the data collected by the soil moisture sensor electrode may be sent to the main control box 8 in a wireless manner.
The stem flow sensor 3 in the present application can adopt a probe-type stem flow sensor and a package-type stem flow sensor, which are all the prior art, and therefore the structure thereof is not repeated.
Example 1
In the embodiment, an objective function for water-saving irrigation is provided as
J1The physical meaning of (a) is to minimize soil water seepage below the root zone.
Q when the soil water leakage is ensured to be minimum is obtained by solving according to the formula (4)z2Value of q isz2Substituting into equation (1) to obtain the corresponding θ z2And then determining whether to finally turn on or off the irrigation valve according to the formula (3).
The above detailed description of the precise irrigation method and irrigation system provided by the present invention is provided. The principles and embodiments of the present invention are explained herein using specific examples, which are presented only to assist in understanding the method and its core concepts. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention. The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (7)
1. A method of precision irrigation comprising the steps of:
s1, collecting parameters related to crop production, including microclimate information of farmlands, soil environment information, key moisture information of crops, surface water evaporation and infiltration information and irrigation water quantity;
s2, constructing a soil-plant-environment continuum oriented hydrodynamic balance relation model based on an optimal control theory, and determining a research object, state variables, control variables and external disturbance factors in the model by combining the parameters collected in the step S1, wherein the state variables comprise surface water evaporation, infiltration, root region soil water storage, crop stem flow, crop stem moisture and leaf transpiration, the control variables comprise irrigation water quantity, and the external disturbance factors comprise temperature, illumination, wind speed and rainfall values;
s3, establishing a relation between a model and parameters, determining an objective function of optimal irrigation decision and control, and in a farmland with a plant covering and in a non-saturated soil water state, determining a hydrodynamic balance relation model of the soil-plant-environment continuum as
The method comprises the following steps of (1) determining the water content of soil, wherein theta (t) is the water content of the soil, q (t) is the three-dimensional water flux of the soil water in the directions of x, y and z, S (t) is a source and sink term, the source and sink term depends on the absorption of the plant root system to the soil water or the transpiration of leaf water and the water evaporation of the surface layer of the soil, wherein the absorption of the plant root system to the soil water or the transpiration of the leaf water is embodied by a stem flow parameter, the stem flow parameter is detected by a stem flow sensor, the water evaporation of the surface layer of the soil is detected by a lysimeter, and the source and sink term is the sum of the two;
selecting points in the root zone and outside the root zone, and setting the coordinate of the root zone as (x)1,y1,z1) The coordinates of the points outside the root zone are (x)1,y1,z2) Respectively placing soil moisture sensors at the two points to obtain one-dimensional soil water equation sets at two different depths
Wherein,
for the soil water content, q, measured by two soil moisture sensorsz1、qz2Is the z-direction water flux, S (z)1T) is a source and sink item;
irrigation valve switch decision function of
Among them, threshold1And threshold2For z-direction water flow flux value q determined according to specific constraint conditionszThe corresponding soil water content value is detected by the soil water sensor in real time
Value and threshold1In comparison, the method has the advantages that,
and threshold2Comparing, and controlling the opening and the closing of the irrigation valve according to a formula (3);
s4, selecting different objective functions or multi-objective functions according to actual requirements, namely threshold in formula (3)1And threshold2The joint solution of the post-system equation is determined depending on equation (2), the objective function and the specific constraints.
2. A method of precision irrigation according to claim 1, characterized in that the defined constraints of state variables and control variables are: valve flow Q has an upper bound; (ii) the change of the soil water takes the water content of the soil with plant growth retardation or the water content of plant wilting as the lower bound of the variable; (iii) the change of the soil water takes the water content of saturated soil or the maximum field water capacity as an upper bound;
wherein the critical point of the water content of the soil with plant growth retardation or the water content of plant wilting in (ii) is derived from the plant stem water information.
3. The method for precision irrigation according to claim 1, wherein the objective function is an objective function for reducing soil water leakage under the root zone in step S4
Q when the soil water leakage is ensured to be minimum is obtained by solving according to the formula (4)z2Value of q isz2Substituting into equation (1) to obtain the corresponding threshold2Value to be actually detected
And threshold2And (4) controlling whether to start or stop the irrigation valve according to the formula (3).
4. A precision irrigation system using the precision irrigation method according to any one of claims 1 to 3, comprising a water pipe (1), wherein an electromagnetic valve (5) is arranged at the water inlet of the water pipe (1), a flowmeter is arranged at the electromagnetic valve (5), the precision irrigation system is characterized by further comprising a stem water sensor (2), a stem flow sensor (3), a three-depth water sensor (4), an electromagnetic valve (5), an lysimeter (6), a microclimate station (7) and a main control box (8), wherein the stem water sensor (2) and the stem flow sensor (3) are fixed at a crop stem, the three-depth water sensor (4) is positioned in soil of a crop root zone, the lysimeter (6) is positioned below the soil of the crop root zone, the stem water sensor (2), the stem flow sensor (3), the three-depth water sensor (4), the electromagnetic valve (5), the flowmeter at the electromagnetic valve, a water level sensor (3), The lysimeter (6) and the microclimate station (7) are respectively connected with a main control box (8);
the stem moisture sensor (2) comprises a signal conditioning circuit board (211) and a sensor probe supporting mechanism, the signal conditioning circuit board (211) is electrically connected with the sensor probe supporting mechanism, the sensor probe supporting mechanism comprises a crop stem fixing sliding block (202), a sliding block sliding supporting rod (203), a sensor probe supporting block (209) and a sensor probe (207), the crop stem fixing sliding block (202) and the sensor probe supporting block (209) are oppositely arranged, the crop stem fixing sliding block (202) is in sliding connection with the sensor probe supporting block (209) through the sliding block sliding supporting rod (203), one end of the sliding supporting rod (203) is fixedly connected with the sensor probe supporting block (209), and the crop stem fixing sliding block (202) is slidably sleeved on the outer side of the sliding block sliding supporting rod (203);
a crop stem jack (204) for fixing a crop stem is arranged in the crop stem fixing sliding block (202), a sensor probe (207) is arranged on one side, facing the crop stem fixing sliding block (202), of a sensor probe supporting block (209), the sensor probe (207) is arranged in the sensor probe supporting block (209) in a sliding manner, the sensor probe is electrically connected with a signal conditioning circuit board (211), the sensor probe (207) is in contact with the crop stem, a sensor supporting rod jack (210) is further arranged in the sensor probe supporting block (209), and an inserting rod for fixing the sensor probe supporting block is arranged in the sensor supporting rod jack (210);
three degree of depth soil moisture sensor (4) include PVC connecting rod (407), and the head of PVC connecting rod (407) is equipped with PVC conical head (406), sets up the soil moisture sensor electrode of the different degree of depth of three groups along the direction of height interval of PVC connecting rod (407), and soil moisture sensor electrode is connected with signal processing circuit through coaxial cable (402) respectively.
5. The precision irrigation system of claim 4, wherein the crop stem is positioned in a crop stem receptacle (204), a stem fastening screw (205) is provided at the crop stem receptacle (204), and the crop stem is fixed in the crop stem receptacle (204) by tightening the stem fastening screw (205);
the crop stem fixing sliding block (202) is further provided with a supporting rod fastening screw (206), the supporting rod fastening screw (206) is located at a through hole in the crop stem fixing sliding block (202) for enabling the sliding block sliding supporting rod (203) to slide, the supporting rod fastening screw (206) is screwed, and the sliding block sliding supporting rod (203) is fixedly connected with the crop stem fixing sliding block (202).
6. Precision irrigation system according to claim 4, characterized in that the signal conditioning circuit board (211) is connected to the main controller (8) by a data cable (201).
7. The precision irrigation system as claimed in claim 4, wherein a probe guide rod is arranged on the outer side of the sensor probe (207), the sensor probe (207) is slidably arranged in the probe guide rod, and the probe guide rod is fixed in a jack of the sensor probe support block (209).
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