WO2003081362A1

WO2003081362A1 - Agricultural irrigation schedules based on evapotranspiration

Info

Publication number: WO2003081362A1
Application number: PCT/US2002/008722
Authority: WO
Inventors: John Addink; Sylvan Addink
Original assignee: Aqua Conservation Systems Inc
Current assignee: Aqua Conservation Systems Inc
Priority date: 2002-03-21
Filing date: 2002-03-21
Publication date: 2003-10-02
Anticipated expiration: 2004-09-21
Also published as: AU2002255860A1

Abstract

The present invention provides systems and methods in which an agricultural irrigation controller (40) automatically derives an irrigation schedule that is at least partly based on an evapotranspiration (ET) value and automatically executes the irrigation schedule though a center pivot irrigation system (30-34). The ET value may be a potential ET value, estimated ET value, or historical ET value. The ET value maybe calculated by a microprocessor disposed in the agricultural irrigation controller.

Description

AGRICULTURAL IRRIGATION SCHEDULES BASED ON EVAPOTRANSPIRATION

Field of the Invention

The field of the invention is agricultural irrigation.

Background of the Invention

In arid areas of the world water is becoming one of the most precious natural resources. Meeting future water needs in these arid areas may require aggressive conservation measures. One useful aspect of conservation involves limiting the water applied to an agricultural field in an amount close to the actual water requirements of the plants being irrigated. However, very few agricultural irrigation systems marketed today execute an irrigation schedule that closely meets the actual water requirements of plants.

Many agricultural irrigation systems are set to irrigate the fields on a regular basis for a preset period of time with the frequency of irrigation varying based on the time of the year and the maturity of the crop. Generally, this results in under or over watering of the plants with the tendency for the producer to over water the crop so that crop yields are optimized. Over watering is costly, both in water cost and cost incurred in applying the excess water. Additionally, disease, poor root development and other crop problems may develop because of over watering. Furthermore, over watering may have a detrimental effect on the environment because of soil erosion and leaching of fertilizers and chemicals into the ground water.

Some agricultural producers vary the irrigation schedule based on a soil moisture 'feel test' . For a given field that is irrigated by one center pivot unit that covers approximately 130 acres, the 'feel test' is not very accurate because the soil moisture is only known at the site where the 'feel test' is made. Additionally, because of the many acres producers are farming today, if accurate representative 'feel tests' were made, it would be a very time consuming method to determine when irrigations should be made to a field.

Other agricultural producers use soil moisture sensing methods to schedule the irrigation of their fields. Agricultural irrigation controllers that derive all or part of the irrigation schedule from soil moisture sensing methods are discussed in US Patent No. 4,015,366 issued April, 1977 to Hall, III, US Patent No. 4,396,149 issued August, 1983 to Hirsch, US Patent No. 4,545,396 issued October, 1985 to Miller et. al., US Patent No. 4,662,563 issued May, 1987 to Wolfe, Jr., US Patent No. 5,740,038 issued April, 1998 and US Patent No. 6,108,590 issued August, 100 both to Hergert, US Patent No. 5,884,224 issued March, 1999 and US Patent 5,927,603 issued July, 1999 both to McNabb, et. al. The problem with soil moisture sensors is that they may interfere with normal tillage practices. Additionally, they only monitor the soil moisture in the immediate vicinity of the soil moisture sensor. Placement of the soil moisture sensors are critical for the correct determination of an efficient irrigation schedule for the entire field. For large agricultural fields, soil moisture sensors, used alone, are not a cost effective method for providing the necessary information to efficiently irrigate the field.

Two of the above listed patents, 5,740,038 and 6,108,590, use in addition to soil moisture sensors, satellite imaging techniques to derive irrigation schedules. However, inclement weather may affect the reliability of the information generated by the satellite's imaging devices. US Patent 4,755,942 issued July, 1988 to Gardner, et al. discusses the use of crop water stress measurements to derive irrigation schedules. As was mentioned above with soil sensors, it would also be difficult to obtain reliable data for a large agricultural field by measuring crop water stress in a few areas of the field. Crop water stress measurements are specific for the site where the measurements are obtained and may not apply to the remainder of the field. Soils are heterogeneous and topography varies, which will affect the water stress measurements obtained.

What was needed was some effective method that agricultural producers could use to assist them in the accurate application of water to their fields to meet the water requirements of the plants. This need was met when producers started to apply irrigations based on evapotranspiration (ET) data. ET values closely approximate the water requirements of plants. Evapotranspiration is the water removed from the soil by direct evaporation from the soil and plant and by transpiration from the plant surface. There are several closely related terms used herein with respect to ET. "Actual ET" is the amount of water actually removed from the soil by direct evaporation from the soil and plant and by transpiration from the plant surface. At present, actual ET must be measured using a lysimeter or equivalent device. "Potential ET" is a calculated approximation of actual ET, using one of the well accepted formulas, Penman, Penman-Monteith, Hargraeves, Blaney-Criddle, Thornthwaite, Jensen- Haise, Priestley-Taylor, Turc, FAO-24 Radiation, and so forth. "Historical ET" is determined for a given area from several prior years of potential or actual ET data collected from a given area. A "modified ET value" is a potential or historical ET value that has been modified by some factor. "Estimated ET" is an estimate of potential ET, such as that derived from a regression analysis (as for example that described in pending US patent application serial no. PCT/USOO/18705).

The agricultural producers or their consultants generally obtain the ET data from a government agency or university resource and then based, at least in part, on the ET data they derive irrigation schedules that are then applied to their agricultural fields. The derivation of the irrigation schedules is generally accomplished with microprocessors disposed in personal computers using simulation models, formulas, etc. However, the agricultural producers, consultants or employees of the agricultural producer have to personally execute the irrigation schedules that are derived from the ET data. The irrigation schedules are executed by various means, including personally inputting activation data into a central computer located distal to the irrigation site, activation through pagers or cell phones carried on the operators, by manual manipulation of buttons or knobs on a controller located at the irrigation site, through telephone connections, and so forth.

The problem is that with ET based irrigation applications the derivation of the irrigation schedules and/or the execution of the irrigation schedules require human intervention. Additionally, far too often producers do not rely on the ET data but rather on the appearance of the crop and the soil moisture "feel test", even though they have ET data available to them. Most producers, during their entire life, have relied on their own determinations of when to irrigate and the quantity of water to apply. It is not obvious to them to base their irrigation applications on ET values and especially not to have the controller automatically derive an irrigation schedule that is at least partly based on an ET value and then let the irrigation controller automatically execute the irrigation schedule.

However, very likely the most efficient use of water would occur, if the agricultural irrigation controller were permitted to automatically derive and execute the irrigation schedule.

What is needed is an agricultural irrigation controller that automatically derives an irrigation schedule that is at least partly based on an ET value and then automatically executes the irrigation schedule through an agricultural irrigation system. Summary of the Invention

The present invention provides systems and methods in which an agricultural irrigation controller automatically derives an irrigation schedule that is at least partly based on an evapotranspiration (ET) value, and automatically executes the irrigation schedule through a center pivot irrigation system.

All commercially acceptable variations are contemplated. For example, the agricultural irrigation controller can be a stand alone device, or it may comprise a personal computer. Similarly, although the agricultural irrigation controller is preferably located at the irrigation site, it may alternatively be located at a site distal to the irrigation site.

All versions of ET are contemplated, including potential ET, estimated ET, historical

ET and modified ET. ET values can be provided in any suitable manner, including being calculated by a microprocessor disposed in the agricultural irrigation controller, or being received from a distal source. Additionally, the irrigation schedule is at least partly derived from one or more of the following: a crop coefficient value, an irrigation efficiency value, rainfall data, water flow data, water pressure data, and electric load data.

In a preferred embodiment of the present invention, the agricultural irrigation controller sends information to the irrigation operator.

Various objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention, along with the accompanying drawings in which like numerals represent like components..

Brief Description of the Drawings

Figure 1 is a block diagram of an irrigation system controlled by agricultural irrigation controllers according to an aspect of the present invention.

Figure 2 is a block diagram of an alternative embodiment of an irrigation system controlled by an agricultural irrigation controller according to an aspect of the present invention.

Figure 3 is a schematic of an agricultural irrigation controller. Figure 4 is a flow chart of exemplary steps in deriving and executing an irrigation schedule by an agricultural irrigation controller according to an aspect of the present invention.

Figure 5 is a flow chart of exemplary steps in the determination of a regression model, which would be programmed in the agricultural irrigation controller.

Figure 6 is a flow chart of events during the execution of the irrigation schedule by the agricultural irrigation controller according to an aspect of the present invention.

Detailed Description

Figure 1 is a block diagram of an irrigation system 10 controlled by agricultural irrigation controllers 40 according to an aspect of the present invention. Although, the term agricultural as used herein refers to agricultural crops, it is contemplated the present inventive concept could apply to vegetables, fruits, and any other irrigated crops. The irrigation units 30-34 apply water and other substances, such as, fertilizer, weed control chemicals, etc. to the agricultural fields. The irrigation units 30-34 shown in Figure 1 are termed center pivots. However, it can be appreciated that the inventive concept, as discussed herein, could apply to part circle center pivots, linear moving lines, wheel lines and any other agricultural irrigation systems. Generally, with all of the agricultural irrigation systems there will be a water pump (not shown) that when activated transfers the water from the water source to the irrigation system that then applies the water to the agricultural field. Also, there will generally be some drive mechanism (not shown) to propel the irrigation system across the agricultural field.

Most irrigation water pumps and drive mechanisms are powered by electricity. However, either the water pump or drive mechanism or both of them may be powered by diesel or gas engines, water hydraulic mechanisms, oil hydraulic mechanisms or other means. The present invention would apply to any means used to power the water pumps and drive mechanisms of agricultural irrigation systems.

Most irrigation manufacturers install control units 20-24 that control the water pump and drive mechanisms of each of their irrigation units 30-34. These control units 20-24 can vary from very simple control units to very complex control units. Simple control units would involve the manual pressing of buttons and/or turning of knobs to activate the water pump and drive mechanism. Complex control units not only allow for manual activation of the water pump and drive mechanism at the irrigated site, but also allow for activation of the water pump from a central computer 50 that is located distal to the irrigation site. Additionally or alternatively, manufacturers may have the water pump and drive mechanism activated by mobile devices carried by the irrigation operator on their person, in their vehicle and so forth. These mobile devices may be pagers, cell phones and other remote control devices. Furthermore, many of the complex control units also control the adding of substances, such as, fertilizers, weed control chemicals, etc. to the irrigation water as it is applied through the irrigation system to the fields. Some of these complex control units also monitor the irrigation system and warn the irrigation operator, if problems with the irrigation system are detected.

hi a preferred embodiment of the present invention the agricultural irrigation controller 40 does not replace the manufacturer's control units 20-24, but instead is connected to the control units 20-24. Preferably the com ection is a hardwire connection but may be a wireless connection, such as, by radio, optical, hydraulic or ultrasonic connection. Alternatively, the agricultural irrigation controller may replace the control units 20-24 and may be directly connected to the water pump and drive mechanism. It is also contemplated that circumstances may exist when it would be advantageous to connect the agricultural irrigation controller 40 directly to the water pump and drive mechanism and bypass the control units 20-24. For example, if the agricultural irrigation controller 40 controlled or monitored functions relating to the irrigation application but not controlled by the control units 20-24, then it might be advantageous to directly connect the agricultural irrigation controller 40 to the water pump and drive mechanism and bypass the existing control units 20-24. Moreover, it is contemplated that the other functions the agricultural irrigation controller 40 may control or monitor include any or all of the following: rainfall (see 291, Figure 3), water flow 292, water pressure 293, soil moisture 294, alignment of the irrigation system (not shown), water application by individual irrigation heads (not shown), and operation of individual drive wheels (not shown).

The agricultural irrigation controllers 40 can advantageously be connected to a central computer 50 located at the farmstead, or at any other facility frequented by persomiel who have an interest in the operation of the irrigation system. This may include the farm owner, an employee of the farm owner, a consultant, and any other individuals responsible for or who have an interest in the crop production on the farm. The term 'irrigation operator', as used herein, will include any of the above listed individuals who have responsibility for or who have an interest in the crop production on the farm.

In a preferred embodiment, the connection between the agricultural irrigation controllers 40 and the central computer 40 would be bi-directional. Data contemplated to be transmitted from the central computer 50 to the agricultural irrigation controllers 40 most likely involves informational inputs by the irrigation operator that are used by the agricultural irrigation controller 40 to derive an irrigation schedule (See Figure 4). The information communicated from the agricultural irrigation controller 40 to the irrigation operator may include warning information when problems with the irrigation system exist as well as other general information related to the operation of the irrigation system (See Figure 6). Preferably, the information from the agricultural irrigation controller 40 will be communicated to the irrigation operator via the central computer 50 monitor or printed material generated by the central computer 50. Alternatively, the information from the agricultural irrigation controller 40 will be directly displayed to the irrigation operator on the display of the agricultural irrigation controller (see Figure 3, numeral 250). It is further contemplated that the agricultural irrigation controller 40 may communicate information to the irrigation operator via hand held devices or other portable devices the irrigation operator would carry on himself or herself or in their vehicles.

Figure 2 is an alternative embodiment of an irrigation system 12 controlled by an agricultural irrigation controller 40. The agricultural irrigation controller 40 is connected to the control units 25-29 and control the water applied to the producer's fields through the irrigation units 35-39. There is no central computer and the agricultural irrigation controller 40 derives and executes an irrigation schedule and also provides the functions of a central computer. It is contemplated that an agricultural irrigation controller 40 in this type of irrigation system 12 would comprise a personal computer with the microprocessor (see numeral 220, Figure 3) programmed to execute the functions of an agricultural irrigation controller 40 in addition to other personal computer functions. It is further contemplated that with this irrigation system 12 the agricultural irrigation controller 40 would be located at a site distal to the irrigation site. This could be at the house, office, or other location frequented by the irrigation operator. However, it can be appreciated that with this type of irrigation system 12 the agricultural irrigation controller 40 could be located at one of the irrigation sites. The irrigation system 10 of Figure 1, with the agricultural irrigation controller 40 located at the irrigation site, is preferred over the alternative irrigation system 12 of Figure 2 where the agricultural irrigation controller 40 is likely located at a site distal to the irrigated sites. If the agricultural irrigation controller 40 is located at the irrigation site, the agricultural irrigation controller 40 can advantageously directly receive data from the irrigated site that the agricultural irrigation controller 40 would use in deriving an irrigation schedule. This data may include any or all of the following: temperature, solar radiation, wind, relative humidity, water flow, water pressure, soil moisture, rainfall and so forth. If the agricultural irrigation controller 40 is located distal (for example, more than 1 km) to the irrigated site, all of the above information that is used by the agricultural irrigation controller 40 in deriving an irrigation schedule has to be transmitted from the irrigated site to the agricultural irrigation controller 40. It is contemplated that if the agricultural irrigation controller 40 is located distal to the irrigated site, that most, if not all, of the sensor signals or data would be transmitted to the agricultural irrigation controller 40 via radio, Internet, telephone line, pager, two-way pager, cable, TV carrier wave or any other suitable means. This would likely incur a greater cost to the irrigation operator than if the agricultural irrigation controller 40 was located at the site and some of the information could be received via direct wire connections between the agricultural irrigation controller 40 and the sensors 291-295, Figure 3. Alternatively, the agricultural irrigation controller 40 at the irrigated site may receive the signals or data from the sensors by any suitable wireless link, such as optical, radio, hydraulic or ultrasonic.

Figure 3 is a schematic of an agricultural irrigation controller 40 according to an aspect of the present invention that generally includes a microprocessor 220, an on-board memory 210, some manual input devices 230 through 232 (buttons and/or knobs), an input/output (I/O) circuitry 221 connected in a conventional manner, a display screen 250, a communications port 240, a serial, parallel or other communications connection 241 coupling the agricultural irrigation controller 40 to one or more communication sources, electrical connectors 260 which are connected to a water pump controller 271, a sprinkler line driver controller 272, a chemical pump controller 273 and a power supply 280, a rain detection device 291, a flow sensor 292, a pressure sensor 293, a temperature sensor 294 and a soil moisture sensor 295. Each of these components by itself is well known in the electronic industry, with the exception of the programming of the microprocessor in accordance with the functionality set forth herein. There are hundreds of suitable chips that can be used for this purpose. At present, experimental versions have been made using a generic Intel 80C54 chip, and it is contemplated that such a chip would be satisfactory for production models.

In a preferred embodiment, the controller has one or more common communication internal bus(es). The bus can use a common or custom protocol to communicate between devices. There are several suitable communication protocols, which can be used for this purpose. At present, experimental versions have been made using an I C serial data communication, and it is contemplated that this communication method would be satisfactory for production models. This bus is used for internal data transfer to and from the EEPROM memory, and is used for communication with personal computers, peripheral devices, and measurement equipment including but not limited to a rain detection device 291, a flow sensor 292, a pressure sensor 293, a temperature sensor 294 and a soil moisture sensor 295.

Preferably, the agricultural irrigation controller 40 will be a standalone device located at the irrigation site and the microprocessor 220 will be disposed in the agricultural irrigation controller 40. Alternatively, the microprocessor 220 may be disposed in another device that provides control of the agricultural irrigation system, such as a personal computer located at the farm office or other central facility on the farm, a hand held computer or any other device that could function as an agricultural irrigation controller.

Referring to Figure 4, when the agricultural irrigation controller is first installed the irrigation operator inputs information into the agricultural irrigation controller that may be used by the agricultural irrigation controller in the deriving of an irrigation schedule 400. Preferably the irrigation operator will interface directly with the agricultural irrigation controller to enter the information, through the manipulation of buttons, knobs, and displays such as those depicted in Figure 3. It should also be appreciated, however, that the irrigation operator may interface with the agricultural irrigation controller through other means such as a personal computer coupled to the agricultural irrigation controller, a telephone, a hand held computer, a two-way pager, a radio, or other suitable means for transmitting information to the agricultural irrigation controller. This inputted information may include some or all of the following: environmental data, irrigation efficiency values, crop coefficient values, crops that are planted at the irrigated site, crop planting dates, crop maturity dates, electric load data, soil data, geographic data, topographic data and any other data that may assist in the derivation of the most efficient irrigation schedules that will be applied to producer's fields. It can be appreciated that some of the above data could be entered in the agricultural irrigation controller at the factory rather than inputted into the agricultural irrigation controller by the irrigation operator.

Some of the data, inputted by the irrigation operator, would only have to be done at the time the agricultural irrigation controller was installed, such as, irrigation efficiency values and soil, geographic, topographic and other data from the irrigated site. Other values or data may have to be inputted more frequently but likely not on a daily basis.

Additionally, the agricultural irrigation controller may receive information from sensors located at the irrigated site 410. Information from sensors may include some or all of the following: temperature, wind, solar radiation, humidity, rainfall, soil moisture, sensors that detect irrigation system problems, and so forth. Preferably, the agricultural irrigation controller receives the information from the irrigated site on a minimum of a daily basis. However, it can be appreciated that it may be advantageous for the agricultural irrigation controller to receive some of the data less frequently or more frequently than on a daily basis.

It is further contemplated that some of the information the agricultural irrigation controller will use to derive the irrigation schedule will be received from distal locations 410. The information from a distal location may include any or all of the following: environmental data, ET values, electric load data, satellite imaging data, aerial photography data and any other data that may assist in the derivation of the most efficient irrigation schedules that will be applied to producer's fields. The information received by the agricultural irrigation controller from a distal location may be via one or more of the following sources, including radio, Internet, telephone line, pager, two-way pager, cable, TV carrier wave or any other suitable means.

It is contemplated that as the growing season progresses, additional crop information or other data may be received or inputted into the agricultural irrigation controller so that the irrigation applications will meet the needs of the irrigated plants.

In Step 420 the agricultural irrigation controller receives or calculates a current day's ET value. There are many government agencies and some private agencies that provide potential ET values for consumer's use. Government agencies include such agencies as, CrMIS (California Irrigation Management Information System, maintained by the California Department of Water Resources), CoAgMet maintained by Colorado State University- Atmospheric Sciences, AZMET maintained by University of Arizona-Soils, Water and Environmental Science Department, New Mexico State University- Agronomy and Horticulture, and Texas A&M University- Agricultural Engineering Department. Although variations in the methods used to determine the potential ET values do exist, most potential ET values are based on the Penman-Monteith formula or some variation of the Penman- Monteith formula, which generally utilizes the following environmental factors: temperature, solar radiation, wind speed, and relative humidity.

Alternative formulas used for determining potential ET include Hargraeves, Blaney- Criddle, Thornthwaite, Jensen-Haise, Priestley-Taylor, Turc, FAO-24 Radiation, and so forth. These formulas are explained in Evapotranspiration and Irrigation Water Requirements. ASCE Manuals and Reports on Engineering Practice No. 70, 1990 and Hargraeves, G.H.

1994. Defining and Using Reference Evapotranspiration. Journal of Irrigation and Drainage Engineering, Volume 120, No. 6:1132-1139.

The potential ET value is made available to the consumer in various forms, including dissemination through printed materials, radio, television, telephone, Internet, and so forth. Preferably, if the agricultural irrigation controller receives a potential ET value from a distal site it will automatically obtain the potential ET value for a given site via some communication means such as radio, telephone, Internet, or any other suitable communication means. It is contemplated that with an irrigation system, such as depicted in Figure 2, a potential ET value from a government or private agency would be received by the agricultural irrigation controller and used in the deriving of an irrigation schedule. However, if the location from which the weather data used in the determination of the potential ET value is not near the irrigated site then preferably the agricultural irrigation controller would calculate its' own potential ET value or determine an estimated ET value using weather data collected from the irrigated site.

There would have to be a weather station at the irrigated site that provided temperature, solar radiation, wind and relative humidity data, if the agricultural irrigation controller were to calculate its' own potential ET value using the Penman-Monteith equation. Due to the cost of a weather station that provided temperature, solar radiation, wind and relative humidity data, it is contemplated that the agricultural irrigation controller would determine an estimated ET value rather than to calculate a potential ET value. Temperature data is only required in the determination of an estimated ET value. Although, it can be appreciated that there may be certain circumstances where it would be advantageous for the agricultural irrigation controller to use a calculated potential ET value rather than to use an estimated ET value in the deriving of an irrigation schedule.

Figure 5 provides a flow chart of the steps involved in the determination of an estimated ET according to the present invention. Preferably, the steps in determining an estimated ET comprises: providing historical ET values 510; providing corresponding enviromnental values 520; performing a linear regression of the historical environmental values against the historical ET values 530; determining a regression model 540; obtaining a current local value for an environmental factor 550; and applying that value to the regression model to determine an estimated ET value 560 (For a more detailed explanation of the determination of an estimated ET value see pending US patent application serial no. PCT/USOO/18705).

It is contemplated that if the agricultural irrigation controller is not able to receive a potential ET value or obtain weather information to calculate a potential ET value or determine an estimated ET value then the agricultural irrigation controller will use a historical ET value, a modified ET value or soil moisture data (see below) in the deriving and executing of an irrigation schedule.

Referring again to Figure 4 and step 430 where the agricultural irrigation controller accumulates current ET values and past ET values that were not applied. It is contemplated the agricultural irrigation controller will generally not execute daily irrigation applications. Therefore, the current ET values received or calculated by the agricultural irrigation controller will be accumulated until an irrigation application is executed. Additionally, it is contemplated that unapplied ET values will be accumulated with the current ET values. For example, the total accumulated ET value is 1.12 inches of water that would be applied during the next scheduled irrigation. During the next scheduled irrigation application, it is determined the center pivot system applied 1 inch of water. It is contemplated that the agricultural irrigation controller will be programmed to automatically determine the irrigation amount applied by the irrigation system during any one irrigation application. The agricultural irrigation controller will use land area information that is inputted into the agricultural irrigation controller by the irrigation operator and water flow data that the agricultural irrigation controller receives from the water flow sensor (See Step 600, Figure 6) to arrive at an estimate of the actual water applied to the irrigated area. If 1.12 inches should have been applied but only 1 inch of water was applied there still remains 0.12 inches to be applied. This 0.12 inches will be carried over and accumulated with the current ET values 430 and applied during the next irrigation application.

Effective rainfall can replace some of the water that should have been applied by the irrigation system based on an ET value. Preferably the agricultural irrigation controller will receive rainfall data from a rain detector that measures the quantity of rain that has occurred 430 (as for example the rain detector described in pending US patent application serial no. PCT/US00/22821). Alternatively, rain information could be obtained from weather stations but this information may not always apply to the specific location where the irrigation system is located. Therefore, it is preferred that a rain detector that can quantify the rain be located at each irrigated site. The agricultural irrigation controller would receive, from the rain detector, the rainfall information that would then be used by the agricultural irrigation controller in the deriving of an irrigation schedule.

The agricultural irrigation controller will be programmed to use the accumulated ET values, rainfall data and other received and inputted data to automatically derive an irrigation schedule 450

In a preferred embodiment of the present invention, the agricultural irrigation controller receives soil moisture data from at least one soil moisture sensor 460. It is contemplated the soil moisture data may be used to override the automatic execution of an irrigation schedule by the agricultural irrigation controller. For example, if the soil moisture is above a set threshold level 461 then the irrigation schedule will not be executed.

Preferably the set threshold level would be inputted into the agricultural irrigation controller when the controller is installed. If the automatic execution of the irrigation schedule was prevented, the agricultural irrigation controller would automatically add the unapplied ET values to the future ET values received or calculated by the agricultural irrigation controller 430. If the soil moisture is below a set threshold level 462, then the execution of the irrigation schedule 490 by the agricultural irrigation controller will proceed as scheduled.

It is further contemplated that the soil moisture data may be at least part of the criteria used in determining when the irrigation schedule will be executed by the agricultural irrigation controller (step not shown). For example, if current ET values cannot be received or weather data to calculate the current ET value cannot be obtained by the agricultural irrigation controller then the agricultural irrigation controller may be programmed to use the soil moisture sensor data to determine when the irrigation schedule is executed. It can be appreciated that the data from the soil moisture sensor could also be used to initiate the execution of an irrigation schedule regardless of whether ET data was available or not. For example, if the soil moisture sensor indicated that the soil was extremely dry then the agricultural irrigation controller may be programmed to automatically execute an irrigation application although the ET value did not indicate that an irrigation schedule should be executed.

Wind is not merely a factor that may be used in the determination of the current potential ET value. It may also be a factor in whether an irrigation schedule should be executed. It is contemplated that the agricultural irrigation controller will receive wind data from a wind sensor 470 and if the wind exceeds a set threshold level then the agricultural irrigation controller may automatically prevent the execution of the irrigation schedule 471. Preferably, the set threshold level would be inputted into the agricultural irrigation controller when the controller is installed. If the automatic execution of the, irrigation schedule is prevented, the agricultural irrigation controller will add the unapplied ET values to future ET values, received or calculated by the agricultural irrigation controller 430. If the wind is below a set threshold level 472, then the execution of the irrigation schedule 490 by the agricultural irrigation controller will proceed as scheduled.

Electrically operated agricultural irrigation systems use extremely high amounts of electric power during the execution of an irrigation application. If several center pivots serviced by the same electric utility company were operating at the same time, the demand for electricity might exceed the capacity of the electric utility company to provide the electricity, or at least might result in an increased electricity rate fee imposed by the electric utility company. Frequently, the price the electric utility companies pay for electricity increases with increases in monthly or yearly peak usage of electricity by the electric utility company. Generally, electric utility companies do not directly regulate the use of electricity, but instead they use load management to reduce these high peak demands for electricity. Load management may involve charging a higher electric rate for electricity used during a certain time period. For example, if there is generally a high demand for electricity during the hours from 8:00 to 12:00 am the electric utility company may charge the electric users a higher rate for any electricity they use during those hours. In a preferred embodiment of the present invention the irrigation operator will program the agricultural irrigation controller to execute the irrigation schedule when the electricity rate is below a set threshold amount 482. If the electricity rate is above a set rate then the execution of the irrigation schedule will be prevented 481. If the automatic execution of the irrigation schedule is prevented, the agricultural irrigation controller will accumulate the unapplied ET values with future ET values received or calculated by the agricultural irrigation controller 430. It can be appreciated that the electric utility companies may use load management methods other than differential electric rate charges and it is anticipated that what ever load management methods are initiated by the electric utility companies the agricultural irrigation controller will be programmed to optimize the load management methods initiated.

It is contemplated that the agricultural irrigation controller will directly access the electric utility company's information to obtain electric load data on which to base the timing of the irrigation applications. The agricultural irrigation controller may receive the electric load data via radio, Internet, telephone line, pager, two-way pager, cable, TV carrier wave or other suitable means.

It is further contemplated that to reduce the potential for high peak electric use, the agricultural irrigation controller can be programmed to average the received or calculated ET values that are used in deriving an irrigation schedule. Preferably the received or calculated ET values will be averaged over a period of seven days. However, it can be appreciated that the ET values could be averaged over a period of less than or more than seven days or not averaged at all. By averaging the ET values it reduces the likelihood that there will be days when there will be extremely high irrigation amounts applied that would also result in high demands for electricity. For example, in one geographic area, if there were several irrigation systems that based there irrigations on the previous days ET values, then the day after an extremely hot, dry day all these systems would be irrigating and at relatively high irrigation rates. If all the irrigation systems were powered by electricity, this would result in an extremely high electricity demand on the day following an extremely hot, dry day. However, if the ET values were averaged over seven days then it is unlikely there would ever be extremely high demands for water for irrigation applications. By using a rolling average of ET values in determining the ET value to use in deriving an irrigation schedule this should reduce extremely high daily irrigation applications and therefore also reduce extremely high daily electricity demands (Rolling averages of ET values are described in greater detail in pending PCT patent application serial no. PCT/USOl/46728). Referring to Figure 6, it is contemplated that during the execution of the irrigation application, the agricultural irrigation controller will be receiving irrigation water flow data from a water flow sensor 600. Preferably, the water flow data will be used by the agricultural irrigation controller to automatically determine the irrigation application rate 610. The area of the irrigated field will be inputted into the agricultural irrigation controller by the irrigation operator. The total amount of water applied, during each irrigation application, is received by the agricultural irrigation controller from the water flow sensor. The irrigation application rate is determined by dividing the total amount of water applied to the irrigated area by the area of land that is irrigated. It is contemplated that this actual application irrigation rate will be communicated to the irrigation operator along with the rate that should have been applied based at least in part on received or calculated ET data 650. The irrigation operator, if necessary, can then make appropriate inputs into the agricultural irrigation controller so that future irrigation applications will more closely correlate with a desired rate of application based at least in part on received or calculated ET data.

Additionally, it is contemplated that the water flow data will be used to detect potential problems with the irrigation system 620. Water flow extremes can be an indicator of problems with the irrigation system. For example, if the water flow is below a minimum threshold level this could indicate there are irrigation system problems, such as, plugged irrigation heads, blockages in the irrigation line, or problems with the water pump. If the water flow is above a maximum threshold level this could indicate there are irrigation system problems, such as, broken irrigation heads or broken irrigation lines. Alternatively, water flow below a minimum threshold level or above a maximum threshold level could also indicate the water pressure is low or high, respectively. Therefore, water pressure data will be received by the agricultural irrigation controller 630 and taken into consideration in the determination of whether a potential irrigation system problem is or is not present 620.

The agricultural irrigation controller can advantageously be programmed to generate a warning that is transmitted to the irrigation operator 621 whenever the agricultural irrigation controller detects water flow that is below a minimum threshold level or above a maximum threshold level. The warning may be issued through any suitable means, including, for example, a flashing display on the central computer, a message via a telephone to a cell phone carried by the irrigation operator or a message sent via a two-way pager to a pager carried by the irrigation operator or any other suitable means that would communicate the warning to the irrigation operator. The irrigation operator could then check the irrigation system to determine, if an irrigation system problem actually exists and if there is a problem then correct the problem.

It is further contemplated that if the agricultural irrigation controller detects water flow that is a set amount or percent below the minimum threshold level or above the maximum threshold level that a warning will be sent to the irrigation operator and additionally the irrigation application will be stopped 622. The irrigation operator may not always receive the warning, when a potentially serious irrigation problem exists, or be able to timely correct the problem. Therefore, it may be advantageous to turn the irrigation system off to prevent the potential of additional damage occurring to the irrigation system or to the irrigated field were the irrigation system allowed to continue operating. After the irrigation system is checked and repaired, if needed, the irrigation system can be activated again.

If the water flow remains between a minimum and maximum threshold level then the irrigation application will proceed as scheduled 623.

Water pressure affects even water distribution. With low water pressure, field areas located between irrigation heads frequently will receive a lower amount of water than areas adjacent to irrigation heads. High water pressure, though not as significant a problem as low water pressure, may also affect water distribution. Therefore, it is contemplated that the water pressure will be monitored 630 and if the water pressure is below a minimum threshold level or above a maximum threshold level the agricultural irrigation controller will transmit a warning to the irrigation operator 631. The warning may be through any suitable means or similar to those mentioned above for irrigation problems detected by extremes in water flow. Again, as mentioned above, the irrigation operator could then check the irrigation system to determine, if an irrigation system problem actually exists and if there is a problem then correct the problem.

It is further contemplated that if the agricultural irrigation controller detects water pressure that is a set amount or percent below the minimum threshold level or above the maximum threshold level that a warning will be sent to the irrigation operator and additionally the irrigation application will be stopped 632. As was mentioned above with the extreme water flows, the irrigation operator may not always receive the warning, when a potentially serious irrigation problem exists, or be able to timely correct the problem. Therefore, it may be advantageous to turn the irrigation system off to prevent the potential of additional damage occurring to the irrigation system or to the irrigated field were the irrigation system allowed to continue operating. After the irrigation system is checked and repaired, if needed, the irrigation system can be activated again.

If the water pressure remains between a minimum and maximum threshold level then the irrigation application will proceed as scheduled 633.

Preferably, the center pivot system will complete at least one or more complete revolutions during the execution of an irrigation application 640. This would result in the entire field area, serviced by a center pivot system, receiving water. For various reasons, the center pivot may be prevented from making a complete revolution, including any of the following reasons: irrigation system problems, such as those listed above or other irrigation system problems including improper alignment of the irrigation line, drive wheel problems, and so forth; automatic termination of the irrigation application due to rainfall, automatic termination of the irrigation application due to wind, and for other reasons. It is contemplated the agricultural irrigation controller will be programmed to malce modifications to future irrigation schedules, when some of these irrigation system anomalies occur where the center pivot was not able to make a complete revolution.

As mentioned above, the agricultural irrigation controller can be programmed to receive water flow and water pressure data as well as other information and data from other sensors and other sources. The agricultural irrigation controller will be programmed to use this information to derive and execute efficient irrigation schedules, detect irrigation system problems, warn the irrigation operator if potential irrigation system problems are detected and stop the irrigation application, if potentially serious irrigation system problems are detected. It is contemplated that the information received by the agricultural irrigation controller, the irrigation schedules derived by the agricultural irrigation controller, and any other information generated by the agricultural irrigation controller will be stored in the memory (see numeral 210, Figure 3) of the agricultural irrigation controller for a minimum period of seven days. However, it is contemplated that the information could be stored in the memory of the agricultural irrigation controller for a period less than or more than seven days.

In a preferred embodiment of the present invention, some or all of the information stored in the memory of the agricultural irrigation controller will be communicated to the irrigation operator 650, Figure 6. The information may include, for example, any or all of the following information: water flow for given increments of time; total quantity of water applied during each irrigation application; actual irrigation application rates; desired irrigation application rates; water pressure at specific times during the irrigation application; daily ET data received or calculated by the agricultural irrigation controller; daily or other time periods of rainfall data, soil moisture data or other environmental data that the agricultural irrigation controller had obtained from sensors located at the irrigated site; infonnation on the imgation schedule derived by the agricultural irrigation controller; and any potential irrigation system problems the agricultural irrigation controller detected. It can be appreciated that current information from the agricultural irrigation controller will also be communicated to the irrigation operator including water flow rate, total water flow, and so forth. It is contemplated that all this information will be communicated to the irrigation operator via a liquid crystal display. (see numeral 250, Figure 3) disposed in the agricultural irrigation controller, on a monitor of the central computer, in printed format or any other suitable means that would communicate the information to the irrigation operator 650. This information could then be used by the irrigation operator to assist him/her to achieve the most efficient irrigation of their agricultural fields with the least waste of water.

Thus, specific embodiments and applications of agricultural irrigation controllers used to automatically derive an irrigation schedule that is at least partly based on an evapotranspiration (ET) value and automatically execute the irrigation schedule through a center pivot irrigation system have been disclosed. It should be apparent, however, to those skilled in the art that many more modifications besides those described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims.

Claims

CLAIMSWhat is claimed is:

1. An agricultural irrigation controller that automatically derives an irrigation schedule that is at least partly based on an evapotranspiration (ET) value, and automatically executes the irrigation schedule through a center pivot irrigation system.

2. The controller of claim 1 wherein the controller comprises a stand alone device.

3. The controller of claim 1 wherein the controller comprises a personal computer.

4. The controller of claim 1 wherein the controller is located at the irrigation site.

5. The controller of claim 1 wherein the controller is located distal to the irrigation site.

6. The controller of claim 1 wherein the ET value is a potential ET value.

7. The confroUer of claim 1 wherein the ET value is an estimated ET value.

8. The controller of claim 1 wherein the ET value is a historical ET value.

9. The controller of claim 1 wherein the ET value is a modified ET value.

10. The controller of claim 1 wherein the ET value is calculated by a microprocessor disposed in the controller.

11. The controller of claim 1 wherein the controller receives an ET value from a distal source.

12. The controller of claim 1, further comprising the controller using an irrigation efficiency value to at least partly affect the irrigation schedule.

13. The controller of claim 1, further comprising the controller using a crop coefficient value to at least partly affect the irrigation schedule.

14. The controller of claim 1, further comprising the controller using rainfall data to at least partly affect the irrigation schedule.

15. The controller of claim 1, further comprising the controller using water flow data to at least partly affect the irrigation schedule.

16. The controller of claim 1, further comprising the controller using water pressure data to at least partly affect the irrigation schedule.

17. The controller of claim 1, further comprising the controller using electric load data to at least partly affect the irrigation schedule.

18. The controller of claim 1 , further comprising the controller sending information to the irrigation operator.

19. A method of managing the irrigation of agricultural fields by an agricultural irrigation controller that automatically derives an irrigation schedule that is at least partly based on an evapotranspiration (ET) value and automatically executes the irrigation schedule through a center pivot irrigation system.