Center pivots are designed to be a very efficient way to apply water to crops, but, like every piece of machinery on the farm, top performance requires good maintenance and skilled operation. While the maintenance schedule in the operation manual is a good start, Lindsay Applications Engineer Steve Melvin has a few additional recommendations.
The pressure is the single most important indicator that the system, from pump to sprinklers, is functioning properly. The pressure should be monitored frequently during the season and compared to the average of the normal operating pressure. FieldNET™ by Lindsay, gives you the ability to continuously monitor the pressure at the pivot point as well as at the out end of the pivot, sending an alert if it finds a problem. A new pressure gauge or pressure transducer should be used if there is any concern with the old one.
The minimum design pressure, when the pivot is operating on level ground and the end gun is on, can be found in the sprinkler chart (if you can’t find the sprinkler chart, your dealer can get a copy for you).
If the pivot is operating up a hill, the pressure point will need to be higher to compensate for the increased elevation (1 psi for each 2.3 feet of elevation increase). You can also install a gauge on the out end of the pivot, just before one of the last regulators, and then check the pressure when the end of the pivot is at the highest elevation. The reading should be at least five pounds higher than the rater pressure of the regulator.
If the pump is no longer able to supply the same quantity of water at the same pressure, then you should run a new sprinkler chart to reflect the lower flow rates and change the sprinkler nozzle size accordingly.
If a flow meter is available, the flow should also be monitored regularly. Leaks, missing sprinklers, worn out sprinkler orifices or regulators can cause the flow rate to go up, while plugged nozzles can cause the flow rate to decrease. And, a combination of leaks and plugged nozzles can make the pressure and flow look about right. That’s why it’s important to look the system over when it’s operating.
When the crop is small, look at the water coming out of the sprinklers from a distance and with the sunlight reflecting off the water. The pattern should look even with higher amounts coming out the farther you look out from the pivot point.
If the check is done when you can see bare soil, set the pivot to move at 100 percent and look at the soil wetting pattern. It should be fairly uniform after the pivot has passed. A best management practice is to get into the habit of quickly looking at the water pattern each time you pass by one of your pivots.
Keep Pivots in Top Working Condition
Because the pivot applies extra water to the area during shut down and start-up, water application efficiency can be greatly reduced if the pivot continually shuts down or gets stuck because of poor track management.
Unreliable pivots also affect a grower’s peace of mind – causing them to worry about a shut down that could happen at any time. That worry often prompts them to keep the field extra wet, just in case – a strategy that almost always results in overwatering. To optimize efficiency, repair and/or replace pivots as needed, so you are confident that they will run reliably when irrigation is needed.