9 Tips on Managing Soil Compaction
by Greg Stewart, OMAF Corn Specialist

When talking about field operations and the risk of soil compaction, it can be difficult to get specific. Part of the reason is that the vehicle-tire-soil-plant relationship is complex and many factors can impact a ‘specific’ recommendation. And whenever you try to get specific or put numbers to a recommendation, the odds of it being wrong for any one particular farm go up. Nevertheless, here are some points to consider on minimizing soil compaction.

1. Know your axle load. Know your tires. Run the correct inflation pressure!
Very interesting work out of Ohio State in the mid-1990s shows large increases in the amount of air that is squeezed out of the soil when tires are over-inflated. At one time it was difficult to obtain weights and tire specifications in order to get this correct, but this should no longer be the case.
2. Increase tire size and lower inflation pressure.
In many instances, and in particular with tractors and combines, you buy the size of equipment that you feel you must have for the work to be done. This generally locks you into a certain total axle load: the only compaction-reducing option you have is to increase tire size to reduce inflation pressure and hence the contact pressure applied to the ground. Selecting the tallest tire that can possibly fit on the machine is the best starting point.
3. Duals versus singles means lower inflation pressure.
The question about which causes more compaction damage, duals or singles, is still out there. The answer really lies in making sure that your dual tire selection actually involves a larger total air volume carrying the weight of the vehicle and at significantly lower inflation pressures than the single tire option. For example, if you put duals on your tractor and you are still running them at 24 PSI, then something is wrong! You need to look at changing something (e.g., tire type, tire size, weights on the tractor), or check inflation pressure recommendations. If, on the other hand, you can put a single large volume radial on your tractor and operate at 10 PSI, it might be cheaper and more convenient to forget the duals.
4. Plant corn into tire tracks!?
Jack Wiley, former John Deere engineer, spoke at South West Ag Conference in 2003 and made the point that planting corn into tire tracks is not a problem providing your inflation pressure is 16 PSI or less. The growers he has worked with in the Corn Belt all seem to be getting along fine as long as they keep the inflation pressure below this 16 PSI benchmark. Of course what this means is that if your planter tractor gets equipped with big tires that run on low inflation pressure, you don’t worry if a corn row ends up in the track. The higher the clay content of your soils and the wetter you tend to push your planting, the more you should come down below the 16 PSI mark.
5. Deep tillage: solve a problem – create a problem.
If you are doing deep tillage in the range of 6 –14 inches (i.e., disk-ripper), you should be aware of the possibility that those disturbed subsoils may re-compact worse than they were in the first place. This is particularly a risk if you traffic them with high axle loads and/or high inflation pressures while soils are susceptible to compaction (i.e., wet). If you feel your dense subsoils are costing you yield, and you move to a deep tillage operation, make adjustments in equipment, operations and attitude to prevent soil re-consolidation.
6. No-till soys at the mercy of your corn combine.
Growers in a corn-soy-wheat rotation where soys are no-tilled after corn may want to make their first move to low inflation running gear on the combine. Moving from a 30.5 – 32 tire to a 1050 50R 32 tire can mean dropping inflation pressures down into the 15 PSI range and they will still fit behind most 6-row heads. Soil that gets compacted during a wet corn harvest with high inflation pressure tires and high axle loads cannot be expected to recover in time for next year’s no-till beans.
7. High axle loads hold the hammer.
Inflation pressure management is a great tool but what limits your tire options and what puts the sub-soil at risk is total axle load. If you are determined to select grain carts and manure tankers that have axle loads over 15 tonnes, then low inflation pressure options will be more difficult to find. In addition, international research indicates that under some conditions high axle loads and large tires will force compaction deep into the soil profile even in the face of relatively low inflation pressures.
8. Soil conditions matter more than any equipment or tire option.
If you farm soils with relatively low clay contents (less than 15%), you absolutely will not operate equipment on soils that are wet enough to show any rut, and you are in conventional tillage, then save the money you would spend on low compaction tires and go to Florida.
9. Still short on subsoil understanding.
Final comment is that we still have a lack of understanding in regards to our subsoil conditions. How much are our subsoils limiting yields? Is it compaction in these subsoils that is limiting? Which subsoils are already over-consolidated and which are still at risk of further compaction? Researchers, the ag industry and producers will need to continue working together to provide the specifics on these questions.

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