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Android version of Arkansas Soil Moisture Sensor Calculator result for the example.
The app does all of the calculations except adjusting for rainfall.
The app can be downloaded at the Google Play Store.
Printed by University of Arkansas Cooperative Extension Service Printing Services.
Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S.
Department of Agriculture, Director, Cooperative Extension Service, University of Arkansas.
The University of Arkansas System Division of Agriculture offers all its Extension and Research programs and services without regard to race, color, sex, gender identity, sexual orientation, national origin, religion, age, disability, marital or veteran status, genetic information, or any other legally protected status, and is an Affirmative Action/Equal Opportunity Employer.
A REVIEW OF MECHANICAL MOVE SPRINKLER IRRIGATION CONTROL AND AUTOMATION TECHNOLOGIES
ABSTRACT.
Electronic sensors, equipment controls, and communication protocols have been developed to meet the growing interest in using center pivot and lateral move irrigation systems to deliver different irrigation depths to management zones based on previous production levels, soil texture, or topography.
Onboard and field-distributed sensors can collect data necessary for real-time irrigation management decisions and transmit the information directly or through wireless networks to the main control panel or base computer.
Equipment controls necessary to alter water application depth to meet the management criteria for relatively small management zones are now commercially available from irrigation system manufacturers and after-market suppliers.
Communication systems such as cell phones, satellite radios, and internet-based systems are also available and allow the operator to query the main control panel or base computer from any location at any time.
Selection of the communications system for remote access depends on local and regional topography and cost relative to other methods.
Recent developments in the center pivot sprinkler industry have led to contractual relationships between after-market suppliers and irrigation system manufacturers that should support further development of technologies necessary to improve the management of water, nutrient and pesticide applications.
Although the primary focus of this article is center pivot sprinkler irrigation, much of the discussion could also apply to lateral move sprinkler irrigation systems.
Keywords.
Center pivot sprinkler, Distributed sensor networks, Site-specific irrigation, Variable rate irrigation, Wireless communication.
A gricultural fields are variable in terms of crop production for many reasons, including topographic relief, changes in soil texture, tillage and compaction, fertility differences, and localized pest distributions.
The effects of different sources of variability on management can be additive and interrelated.
Fortunately, recent advances in communications and microprocessors have enabled the general implementation of site-specific water applications by self-propelled center pivot and lateral move sprinkler irrigation systems.
The design of an irrigation system suitable for varying water application spatially based on a series of data inputs
Submitted for review in August 2011 as manuscript number SW 9313; approved for publication by the Soil & Water Division of ASABE in March 2012.
Presented at the 5th Decennial Irrigation Symposium as Paper No.
9632-IRR10.
can be complex because of the need to address and integrate constraints imposed by the field site, irrigation system capabilities, and producer management.
The field site constraints may be the most difficult to address because they may be numerous and may be exhibited in varying extents from year-to-year.
Often, the underlying cause of crop performance variation is not fully understood.
Extreme fieldto-field variability further compounds selection of appropriate irrigation system capabilities required to achieve the desired objective.
The general management philosophy and operational preferences of the owner/operator must also be addressed through the use of decision support systems.
These issues are discussed in detail by Buchleiter et al.
, Evans et al.
, Sadler et al.
, Perry et al.
, Sadler et al.
, and McCarthy et al..
McCarthy et al.
developed a predictiveadaptive control model for site-specific irrigation water application of cotton using a center pivot sprinkler, concluding that although the framework accommodated a range of system control strategies, further work was necessary for using data with a range of spatial and temporal scales.
Decision support systems should provide a holistic and robust approach to irrigated crop management.
After the irrigator defines the decision criteria and management
guidelines to be used within the field, DSS must implement the approach through software and microprocessor-based control systems.
Results of geo-referenced grid sampling of soils, yield maps, and other precision agriculture tools can be major components in defining rules for these management systems.
These "rules" are used as the basis for analysis and interpreting data from real-time data networks, remote sensing, irrigation monitoring systems, agronomic, and other information used to provide direction and implement basic commands.
Decision support systems can also include instructions for chemigation and provide alerts to the grower based on output from established models using real-time environmental data.
In essence, DSS provide more management flexibility by implementing near term, routine commands to direct irrigation schedules and other basic operations, which frees the irrigator to concentrate on other management activities.
Successful DSS will require the integration of various sensor systems , irrigation system hardware and controllers to manage sprinkler application and hydraulics, accurate determination of field position , and ample computer processing speed and power.
The maximum benefits will be derived when DSS respond to actual crop conditions.
Crop conditions can be estimated from field-based or remotelysensed plant measurements , or inferred from soil water measurements or crop evapotranspiration estimates.
Ideally, the most robust monitoring system will be an integration of multiple approaches.
General, broad-based, and easily modified software for managing these DSS for a multitude of crops, climatic conditions, topography, and soil textures are not currently available from manufacturers, government agencies, or consultants.
Development and updating of management maps for these irrigation systems based on soils, soil water sensors, yield, or water availability is a highly specialized process that is currently done only once a year or less.
However, widespread implementation will require userfriendly data input capabilities that allow management maps to be adjusted much more frequently.
The objectives of this article are to provide a general discussion of the progression of sprinkler control and monitoring technologies to include: wireless sensor networks and communication protocols; available sensors and data management schemes; remote access for irrigation systems; their network and communication requirements; available sensors and data management schemes; and the current status of commercially available monitoring and control systems.
Mechanically-moved sprinkler irrigation systems, such as center pivot sprinklers and lateral move sprinklers, in current usage have a wide range of drive technologies.
These irrigation systems often operate on fields having both variable topography and soil textures.
In-field soil variability issues such
as low water holding capacity or low infiltration rates present significant challenges to managers in decisions about how much water to apply to various areas of the field.
Each of these factors represents a reason for using some sort of monitor/controller to manage water applications based upon need.
Precision application, variable rate irrigation, and site-specific irrigation are terms developed to describe water application devices with the goal of maximizing the economic and/or environmental value of the water applied via a moving irrigation system.
Probably, the earliest center pivot sprinkler control was the methodology to alter the water application depth by mechanical adjustment of the speed of lateral travel.
Additional early developments provided a very limited set of controls to turn end guns on and off and to stop the center pivot sprinkler operation based on field position or completion of the irrigation cycle.
The development of programmable control panels allowed the speed of sprinkler travel to be adjusted multiple times during an irrigation event.
This approach was often used by producers when portions of the field were planted to a different crop, but these control panels generally lacked the flexibility necessary to supply water at rates required to meet the management objectives of relatively small field areas with irregular-shaped boundaries.
In the past few years, some companies have begun marketing control panels with an option to change irrigation system pivot travel speed in very small increments ranging from <1 to 10 as the lateral rotates around the field.
This tactic effectively changes application depths in each defined radial sector of the field, and generally no additional hardware is needed.
This technique is commonly referred to as speed or sector control, but could also be referred to as variable depth irrigation.
Nevertheless, field variability seldom occurs in long, narrow pie-slice shaped parcels and because the sprinkler packages apply the same depth along the entire lateral length, adjusting speed of rotation may not provide a sufficient level of water application control.
A number of methods have been under development to address varying application depths along the moving lateral.
A variable flow sprinkler was developed for controlling irrigation water application by King and Kincaid at Kimberly, Idaho.
The variable flow sprinkler uses a mechanically-activated pin to alter the nozzle orifice area which adjusts the sprinkler flow rate over the range of 35% to 100% of its design flow rate based on operating pressure.
The pin was controlled using either electric or hydraulic actuators.
The main concern with this approach is that the wetted pattern and water droplet size distribution of the sprinkler changed with flow rate which created water application uniformity issues due to a change in sprinkler pattern overlap.
Changes in water application depth can also be accomplished by using a series of on-off time cycles or "pulsing" individual or groups of sprinklers.
Management of the on-off of sprinklers can be used to manage the time-averaged water application rate.
Later efforts in Washington State involved equipping a center
Figure 1.
Schematic diagram showing a soil survey map overlain by center pivot speed of travel settings changed every 12 or in 30 locations during a single revolution.
pivot sprinkler with a custom-built electronic controller to activate water operated solenoid valves in groups or banks of 2 to 4 sprinkler nozzles.
The use of normally-open solenoids protected the irrigation system from damage and ensured irrigation water was applied even if the control system failed.
Precise and accurate control of irrigation using a series of in-field and onboard wireless monitoring spread spectrum radios/sensors networks that pulsed individual sprinkler solenoid valves according to prescription maps was reported by Chvez et al..
In this research with two different lateral move systems, deviations related to positioning of sprinklers when irrigating were on average 2.5 H 1.5 m due mainly to the accuracy of the digital global positioning systems.
This level of accuracy is a vast improvement over systems not equipped with a GPS of any kind.
Controlling irrigation water application depth has also been accomplished through the use of multiple manifolds, each with different sized sprinkler nozzles to vary water and nitrogen application.
These systems often included two to three manifolds where simultaneous activation of one or more solenoid valves controlling individual manifolds adjusted the water application rate and depth.
When individual or groups of sprinkler nozzles are managed by on-off cycles or use the multiple manifolds, an irrigation system is termed to use zone control for sprinkler applications.
Zone control involves spatially defining irregularly-shaped management zones following specific guidelines , and differentially applying water to each management zone.
Most zone control systems vary water application depths by various forms of pulse modulation for a given irrigation system speed, but zone control systems could potentially be combined with aspects of speed control to
better balance water flow rates provided to the irrigation system.
Although the previously discussed speed control techniques are the most common site-specific sprinkler irrigation systems in use today, zone control systems probably have the largest potential for achieving the most efficient and economically viable management of water and energy.
Current uses of site specific, variable rate irrigation on agricultural fields are generally on a fairly coarse scale.
Probably the most common use is limited to site-specific treatment of complex shaped, non-cropped areas such as waterways, ponds, roads, drainage ways, or rocky outcrops where some sprinkler nozzles are turned off.
However, SS-VRI also has application for animal production systems that wish to use the center pivot to apply liquid animal waste to field areas where there are legally required setbacks from wells, surface water impoundments, or other areas.
Similarly, setbacks may be required to meet water quality protection goals such as minimizing nitrate leaching or contamination of wildlife areas.
In these situations, normal cost recovery based on crop yield may be of secondary importance due to the potential for savings in product application cost.
Two main approaches to SS-VRI sprinkler controls can have advantages and disadvantages depending on the desire to match infield management zones.
For example, the map presented in figure 2a is based strictly upon the soil mapping units presented in figure 1.
If the water management zones were defined strictly based on soil mapping units, grouping three to five sprinklers together in blocks along the lateral might fit the contour at Position A quite precisely.
At Position B, since the grouping of sprinklers is fixed by the original installation, the same three to five sprinklers may need to irrigate more than one management zone.
Thus, the attempt to match water application depths to contour-shaped management zones using blocks of sprinklers may limit the number of effective management zones within a field.
The second approach is to control each individual sprinkler along the lateral independently.

Android version of Arkansas Soil Moisture Sensor Calculator result for the example.

The app does all of the calculations except adjusting for rainfall.

The app can be downloaded at the Google Play Store.

Printed by University of Arkansas Cooperative Extension Service Printing Services.

Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S.

Department of Agriculture, Director, Cooperative Extension Service, University of Arkansas.

The University of Arkansas System Division of Agriculture offers all its Extension and Research programs and services without regard to race, color, sex, gender identity, sexual orientation, national origin, religion, age, disability, marital or veteran status, genetic information, or any other legally protected status, and is an Affirmative Action/Equal Opportunity Employer.

A REVIEW OF MECHANICAL MOVE SPRINKLER IRRIGATION CONTROL AND AUTOMATION TECHNOLOGIES

ABSTRACT.

Electronic sensors, equipment controls, and communication protocols have been developed to meet the growing interest in using center pivot and lateral move irrigation systems to deliver different irrigation depths to management zones based on previous production levels, soil texture, or topography.

Onboard and field-distributed sensors can collect data necessary for real-time irrigation management decisions and transmit the information directly or through wireless networks to the main control panel or base computer.

Equipment controls necessary to alter water application depth to meet the management criteria for relatively small management zones are now commercially available from irrigation system manufacturers and after-market suppliers.

Communication systems such as cell phones, satellite radios, and internet-based systems are also available and allow the operator to query the main control panel or base computer from any location at any time.

Selection of the communications system for remote access depends on local and regional topography and cost relative to other methods.

Recent developments in the center pivot sprinkler industry have led to contractual relationships between after-market suppliers and irrigation system manufacturers that should support further development of technologies necessary to improve the management of water, nutrient and pesticide applications.

Although the primary focus of this article is center pivot sprinkler irrigation, much of the discussion could also apply to lateral move sprinkler irrigation systems.

Keywords.

Center pivot sprinkler, Distributed sensor networks, Site-specific irrigation, Variable rate irrigation, Wireless communication.

A gricultural fields are variable in terms of crop production for many reasons, including topographic relief, changes in soil texture, tillage and compaction, fertility differences, and localized pest distributions.

The effects of different sources of variability on management can be additive and interrelated.

Fortunately, recent advances in communications and microprocessors have enabled the general implementation of site-specific water applications by self-propelled center pivot and lateral move sprinkler irrigation systems.

The design of an irrigation system suitable for varying water application spatially based on a series of data inputs

Submitted for review in August 2011 as manuscript number SW 9313; approved for publication by the Soil & Water Division of ASABE in March 2012.

Presented at the 5th Decennial Irrigation Symposium as Paper No.

9632-IRR10.

can be complex because of the need to address and integrate constraints imposed by the field site, irrigation system capabilities, and producer management.

The field site constraints may be the most difficult to address because they may be numerous and may be exhibited in varying extents from year-to-year.

Often, the underlying cause of crop performance variation is not fully understood.

Extreme fieldto-field variability further compounds selection of appropriate irrigation system capabilities required to achieve the desired objective.

The general management philosophy and operational preferences of the owner/operator must also be addressed through the use of decision support systems.

These issues are discussed in detail by Buchleiter et al.

, Evans et al.

, Sadler et al.

, Perry et al.

, Sadler et al.

, and McCarthy et al..

McCarthy et al.

developed a predictiveadaptive control model for site-specific irrigation water application of cotton using a center pivot sprinkler, concluding that although the framework accommodated a range of system control strategies, further work was necessary for using data with a range of spatial and temporal scales.

Decision support systems should provide a holistic and robust approach to irrigated crop management.

After the irrigator defines the decision criteria and management

guidelines to be used within the field, DSS must implement the approach through software and microprocessor-based control systems.

Results of geo-referenced grid sampling of soils, yield maps, and other precision agriculture tools can be major components in defining rules for these management systems.

These "rules" are used as the basis for analysis and interpreting data from real-time data networks, remote sensing, irrigation monitoring systems, agronomic, and other information used to provide direction and implement basic commands.

Decision support systems can also include instructions for chemigation and provide alerts to the grower based on output from established models using real-time environmental data.

In essence, DSS provide more management flexibility by implementing near term, routine commands to direct irrigation schedules and other basic operations, which frees the irrigator to concentrate on other management activities.

Successful DSS will require the integration of various sensor systems , irrigation system hardware and controllers to manage sprinkler application and hydraulics, accurate determination of field position , and ample computer processing speed and power.

The maximum benefits will be derived when DSS respond to actual crop conditions.

Crop conditions can be estimated from field-based or remotelysensed plant measurements , or inferred from soil water measurements or crop evapotranspiration estimates.

Ideally, the most robust monitoring system will be an integration of multiple approaches.

General, broad-based, and easily modified software for managing these DSS for a multitude of crops, climatic conditions, topography, and soil textures are not currently available from manufacturers, government agencies, or consultants.

Development and updating of management maps for these irrigation systems based on soils, soil water sensors, yield, or water availability is a highly specialized process that is currently done only once a year or less.

However, widespread implementation will require userfriendly data input capabilities that allow management maps to be adjusted much more frequently.

The objectives of this article are to provide a general discussion of the progression of sprinkler control and monitoring technologies to include: wireless sensor networks and communication protocols; available sensors and data management schemes; remote access for irrigation systems; their network and communication requirements; available sensors and data management schemes; and the current status of commercially available monitoring and control systems.

Mechanically-moved sprinkler irrigation systems, such as center pivot sprinklers and lateral move sprinklers, in current usage have a wide range of drive technologies.

These irrigation systems often operate on fields having both variable topography and soil textures.

In-field soil variability issues such

as low water holding capacity or low infiltration rates present significant challenges to managers in decisions about how much water to apply to various areas of the field.

Each of these factors represents a reason for using some sort of monitor/controller to manage water applications based upon need.

Precision application, variable rate irrigation, and site-specific irrigation are terms developed to describe water application devices with the goal of maximizing the economic and/or environmental value of the water applied via a moving irrigation system.

Probably, the earliest center pivot sprinkler control was the methodology to alter the water application depth by mechanical adjustment of the speed of lateral travel.

Additional early developments provided a very limited set of controls to turn end guns on and off and to stop the center pivot sprinkler operation based on field position or completion of the irrigation cycle.

The development of programmable control panels allowed the speed of sprinkler travel to be adjusted multiple times during an irrigation event.

This approach was often used by producers when portions of the field were planted to a different crop, but these control panels generally lacked the flexibility necessary to supply water at rates required to meet the management objectives of relatively small field areas with irregular-shaped boundaries.

In the past few years, some companies have begun marketing control panels with an option to change irrigation system pivot travel speed in very small increments ranging from <1 to 10 as the lateral rotates around the field.

This tactic effectively changes application depths in each defined radial sector of the field, and generally no additional hardware is needed.

This technique is commonly referred to as speed or sector control, but could also be referred to as variable depth irrigation.

Nevertheless, field variability seldom occurs in long, narrow pie-slice shaped parcels and because the sprinkler packages apply the same depth along the entire lateral length, adjusting speed of rotation may not provide a sufficient level of water application control.

A number of methods have been under development to address varying application depths along the moving lateral.

A variable flow sprinkler was developed for controlling irrigation water application by King and Kincaid at Kimberly, Idaho.

The variable flow sprinkler uses a mechanically-activated pin to alter the nozzle orifice area which adjusts the sprinkler flow rate over the range of 35% to 100% of its design flow rate based on operating pressure.

The pin was controlled using either electric or hydraulic actuators.

The main concern with this approach is that the wetted pattern and water droplet size distribution of the sprinkler changed with flow rate which created water application uniformity issues due to a change in sprinkler pattern overlap.

Changes in water application depth can also be accomplished by using a series of on-off time cycles or "pulsing" individual or groups of sprinklers.

Management of the on-off of sprinklers can be used to manage the time-averaged water application rate.

Later efforts in Washington State involved equipping a center

Figure 1.

Schematic diagram showing a soil survey map overlain by center pivot speed of travel settings changed every 12 or in 30 locations during a single revolution.

pivot sprinkler with a custom-built electronic controller to activate water operated solenoid valves in groups or banks of 2 to 4 sprinkler nozzles.

The use of normally-open solenoids protected the irrigation system from damage and ensured irrigation water was applied even if the control system failed.

Precise and accurate control of irrigation using a series of in-field and onboard wireless monitoring spread spectrum radios/sensors networks that pulsed individual sprinkler solenoid valves according to prescription maps was reported by Chvez et al..

In this research with two different lateral move systems, deviations related to positioning of sprinklers when irrigating were on average 2.5 H 1.5 m due mainly to the accuracy of the digital global positioning systems.

This level of accuracy is a vast improvement over systems not equipped with a GPS of any kind.

Controlling irrigation water application depth has also been accomplished through the use of multiple manifolds, each with different sized sprinkler nozzles to vary water and nitrogen application.

These systems often included two to three manifolds where simultaneous activation of one or more solenoid valves controlling individual manifolds adjusted the water application rate and depth.

When individual or groups of sprinkler nozzles are managed by on-off cycles or use the multiple manifolds, an irrigation system is termed to use zone control for sprinkler applications.

Zone control involves spatially defining irregularly-shaped management zones following specific guidelines , and differentially applying water to each management zone.

Most zone control systems vary water application depths by various forms of pulse modulation for a given irrigation system speed, but zone control systems could potentially be combined with aspects of speed control to

better balance water flow rates provided to the irrigation system.

Although the previously discussed speed control techniques are the most common site-specific sprinkler irrigation systems in use today, zone control systems probably have the largest potential for achieving the most efficient and economically viable management of water and energy.

Current uses of site specific, variable rate irrigation on agricultural fields are generally on a fairly coarse scale.

Probably the most common use is limited to site-specific treatment of complex shaped, non-cropped areas such as waterways, ponds, roads, drainage ways, or rocky outcrops where some sprinkler nozzles are turned off.

However, SS-VRI also has application for animal production systems that wish to use the center pivot to apply liquid animal waste to field areas where there are legally required setbacks from wells, surface water impoundments, or other areas.

Similarly, setbacks may be required to meet water quality protection goals such as minimizing nitrate leaching or contamination of wildlife areas.

In these situations, normal cost recovery based on crop yield may be of secondary importance due to the potential for savings in product application cost.

Two main approaches to SS-VRI sprinkler controls can have advantages and disadvantages depending on the desire to match infield management zones.

For example, the map presented in figure 2a is based strictly upon the soil mapping units presented in figure 1.

If the water management zones were defined strictly based on soil mapping units, grouping three to five sprinklers together in blocks along the lateral might fit the contour at Position A quite precisely.

At Position B, since the grouping of sprinklers is fixed by the original installation, the same three to five sprinklers may need to irrigate more than one management zone.

Thus, the attempt to match water application depths to contour-shaped management zones using blocks of sprinklers may limit the number of effective management zones within a field.

The second approach is to control each individual sprinkler along the lateral independently.