End Gun Shutoff

By Cale Cloud

With July being Smart Irrigation Month in the state of Georgia, now would be a good time to encourage farmers to take the time to make sure their center pivot’s end gun shutoff controls are properly functioning.  The majority of center pivots in the state of Georgia have a large sprinkler, commonly referred to as an end gun, installed at the very end of the pivot to irrigate field areas beyond the end of the actual pipe structure of the center pivot.  An end gun is a cost-effective option for irrigating an additional 80’ – 100’ of field area, increasing the productivity of a center pivot.  Controls are required to turn the end gun on and off, preventing it from irrigating areas outside of the field boundary or over non-cropped areas. These controls consist of a valve at the end of the machine (connected to the end gun) and mechanical or electronic controls at the center of the pivot machine that control the end gun (via the valve) by pivot angle position.

There are two items you can inspect to make sure your end gun controls are working properly: the end gun valve at the end of the machine and the angle position settings at the center pivot control panel. 

The biggest reason a farmer needs to inspect their pivot’s end gun controls is for malfunctioning control valves.  These control valves can malfunction quite often, causing the end gun to not properly shut off and allowing water to be applied to unwanted areas such as non-cropped areas and public roadways.  Applying water through your pivot’s end gun onto public roadways can create hazardous driving conditions for motorists and can be a major liability issue.  It can also cause serious backlash from the general public and can be negative PR for farmers.  

A farmer can also save substantial amounts of water, and associated pumping expense, with properly functioning end gun shut off controls.  For an example, refer to Figure 1 below.  The center pivot in this image has a total of 8.49 acres of end gun area that can be shut off due to non-cropped areas and public roadways.  If a farmer is growing cotton in this field, for example, they could potentially save 371,000 gallons of water per acre of end gun shutoff area, per season.   

End gun advantages: 

·      Low cost for easily irrigating additional area 

·      Slow, steady and uniform forward and reverse drive action 

·      Pivot end gun / control valve option doesn’t require solenoid when used in conjunction with a booster pump (Courtesy: Nelson Irrigation)

End gun disadvantages:

·      Water application often not as uniform as sprinklers

·      Large droplets with enough energy to displace soil particles

·      Soil impact from large droplets may also compact soil, reducing emergence

·      End gun controls, especially older units, can be prone to malfunction.