Run-off, ponding and mud related wheel track issues are problems most growers try to deal with after they occur.
“Because of the properties of a circle, the outer spans need to put out a significant amount more water than the first spans to balance the application depth,” said Tim Wilson, irrigation engineering manager at Lindsay Corporation. “This means that the hourly application rate (peak rate) is very high on the last few spans on longer machines. If you combine this with tight clay soils and slopes, you might have a mess on your hands out at the end of your pivots.”
Wilson says there are several proactive steps growers can take to limit or prevent tracking problems. He suggests:
- Using offsets on the last few spans. This involves using boombacks alternating in each direction from the span pipe (this works on both full- and part-circle machines). This spreads out the water and lowers the peak application rate.
- Using truss rod clips. This also spreads out the water and lowers the peak application rate – just not as much as offsets.
- On full-circle machines, using boombacks at the towers with 180-degree sprinklers directed away from the tower to keep water out of the wheel track
- Using larger water throw diameter sprinklers. This lowers the peak hourly application rate.
- Taking the time to calculate an irrigation schedule that gives you top yield but does not over water. Just because you can pump 1200 gpm, doesn’t mean you should.
- Speeding up the machine - maybe. Under the right conditions, it can be a good option, but be careful, because it may cause other problems. Growers might see double the evaporation losses. You might also not be pushing the water down into the root zone deep enough.