Kennon Forester was the first one I remember calling circle tracks “sacred ground.” Then he added, “We don’t farm that.” He was farming ground that got super slick with just a little rainfall.
Different soil types react to the wheels of irrigation circles in various ways. One of the most exasperating is irregular soil types so that one area, usually the hardest to see or drive to, will develop tracks deep enough to collapse and leave an obstruction adequate to stop one set of wheels. If not caught, this can allow the other wheels to keep moving, usually toppling the circle.
The electronics and software that control the pivots have increasingly robust fail-safes to stop the circle if one set of wheels gets stuck, but fail-safes do fail.
An irrigation circle will have a pivot at the center with a buried pipeline supplying the pressurized water. A series of towers will support a pipe from the pivot to the outside of the circle. Depending on the crop grown, different types of sprinklers dispense the water, with the rate near the center being rather like a heavy mist and those on the perimeter more like a cloudburst.
Evaporation loss can be tempered by dropping the sprinkler heads closer to the crop, with some even dragging on the ground and oozing rather than spraying the water. Either way, the wheels move on the same soil each rotation of the circle and leave a varying track, depending on soil type.
To mitigate the deepening of circle tracks, some changes on the circle itself postpone when the water hits the area of the wheels. When water is delivered closer to ground level, moving the piping back so the tracks are watered after the wheels have passed allows the wheels to run on relatively drier soil.
Dealing with the soil itself in the circle tracks is the other option. I was infuriated to find that one of my best hay growers near Mountain Home, Idaho, was running his swathers to drop the windrow centered on the circle tracks. This allowed the wheels to use that hay as mulch to stabilize the soil in the tracks.
I was infuriated because the first cutting alfalfa hay was the most sought-after cutting.
Various implements are available to move the soil back into the trench made by the circle wheels. But without doing something about the texture of the soil, a few passes of the circle will leave tracks of the same depth.
A grower here on the Royal Slope in Washington, altered a windrow-type gravel trailer to fill the wheel tracks with pea gravel. This was a two-axle “pup” trailer, with a fixed rear axle and a front axle that pivoted to steer. The alterations were to change the air-operated cylinders that opened and closed the emptying gates on the bottom with hydraulic cylinders so it could be operated by a farm tractor’s hydraulics.
With the gates centered on the circle track, the operator would open one gate at a time as the trailer was pulled around the circle, filling it with material that was not easily pushed aside by the wheels. Pea gravel is just that, the larger rocks being about the size of a pea, so the soil in the field isn’t turned into a rock patch. Pea gravel, also called “fines,” is usually the least expensive product from a gravel crusher.
Commercially made implements are also available to meter gravel fill into wheel tracks. Single- and two-axle units designed to be pulled by a farm tractor, with the exit chute visible to the operator, are readily available. Smaller units that mount to the tractor’s three-point hitch round out the smaller end of track fillers.
Most operators size the headers on swathers and mowers to make even cuts in the distance between circle tracks. Generally, only a pair of windrows are made from the outside to the center of a circle. The irrigation circle is then parked within these windrows and the remainder of the field is harvested following the direction of the circle tracks.
It’s one of those maintenance things that can seem to be a real pain, but compared to the cost of righting a fallen circle, it makes sense. Circles never fall where they are quickly noticed nor where they are easily accessible. In addition to the cost of the repair, there is the downtime when the rest of that field isn’t being watered. If this debacle happens three weeks from harvest time in a cornfield almost ready for chopping, there is going to be crop run over and mashed down getting tractors, service trucks and boom trucks to the site, and at least one side of it will be too muddy for normal, easy access.
Kennon said they’re all used to running around the circles in circles. It’s lots of work to get a solid base under those wheels, and they are not plowed or disced.
Yes, it’s sacred ground.
