If the dry weather and drought seen across Iowa this summer continue into the fall, farmers probably won’t have significant problems with soil compaction. But don’t count on that being the case. Harvest is still a few weeks away, and fall weather patterns can quickly bring change. 

No matter how much moisture is in the ground, specialists with Iowa State University Extension say it’s good to review your equipment, check your tire pressure and do everything you can to reduce your footprint on the soil. 

“Starting with dry conditions is good, but some parts of the state have already had a lot of rain,” says Ryan Bergman, program coordinator with ISU Ag & Biosystems Engineering Extension. “Everything hinges on what type of weather we have going into the fall. It can be dry now, and we still end up with a wet harvest.” 

One of the simplest and most important things farmers can do is keep an eye on their tire pressure. Bergman had planned to lead a demonstration on tire pressure and compaction at this year’s now-canceled Farm Progress Show, but he says the concept is simple. 

Proper inflation is important 

Make sure the tires on your tractor and implement are properly inflated for the task at hand. During harvest, when pulling heavy grain carts, a higher tire pressure may be needed to safely support the tongue weight of the load and maintain transport speeds. 

However, when performing tillage or harvesting fodder (tasks that generally have lower tongue weights), lower tire pressures often can be used, which increases the tire-to-ground contact and helps reduce the amount of pressure being transferred to the soil. 

“Every tire manufacturer has a load table, and you have to know your equipment weights,” Bergman says. “Getting the machine weighed with the implement attached to the back and knowing the axle weights of each individual axle is ideal.” 

For equipment such as front-fold planters, it’s important to understand the axle weights in the field and transport positions as large amounts of weight can be shifted to the tractor during this transformation. 

Some equipment manufacturers offer central tire inflation equipment, which allows the operator to adjust tire inflation on the go, but Bergman says it’s still not very common in the U.S.

The best thing is to weigh the machine with the equipment attached, determine the amount of weight on each axle, and adjust the pressure according to the manufacturer specifications for each task. “With all of the equipment technology out there today, it doesn’t replace doing basic setup and maintenance,” Bergman says. 

Compacted soil reduces yield 

When soil becomes compacted, it pushes out the air spaces and reduces the porosity, which results in less water and oxygen infiltration, and also can limit root penetration. 

Mahdi Al-Kaisi, professor and ISU Extension soil management specialist, says a normal, healthy soil usually has about 25% air space, 25% water, 45% solid material and 5% organic matter. Compacted soils can easily cause yield reductions and also can lead to a reduction in healthy soil organisms and the normal biological cycle. 

Although Iowa soils currently aren’t at high risk of compaction, Al-Kaisi says farmers who are doing cleanup from the August windstorms should be cautious traveling in the field.

“While it may be necessary to remove fallen trees debris from fields, especially before harvest, farmers should be creative in how they do this,” he says. “Maybe cut trees in place and haul them away in smaller bunches. And be cautious of the size of equipment and loads being transported across fields.” 

Tips to minimize soil compaction 

ISU Extension soil management specialists offer six basic tips for minimizing soil compaction during and after harvest: 

1. Use dedicated travel lanes. Many combine operators use “on-the-go” unloading into a grain cart to speed harvest. In areas that have received excessive rainfall, farmers may want to consider having dedicated travel lanes for the grain cart. It has been documented that 60% to 80% of soil compaction occurs from the first wheel passes. Subsequent field operations account for a much smaller amount of compaction. 

2. Don’t run at full capacity. Reduce the axle loads of both the combine and grain carts by not loading them to full capacity. This may not be an attractive option in high-yielding cornfields and where harvest already has been delayed. This is much easier to implement in soybeans where the grain volume is much less than corn. A compromise may be to try to keep axle loads lower in the far reaches of fields and achieve the highest axle loads (full capacity) nearest the end rows where grain will be transported out of the field. 

3. Consider tire size and inflation pressure. Use appropriate tire sizes for the conditions and adjust tire air pressure to match the axle load being carried. Larger tires with lower air pressure provide more surface area, allow for better flotation and reduce pressure on the soil surface. 

4. Concentrate nonharvest field activities near the point of exit from the field. While it is tempting to move semitrailers and tractors with wagons along the field edge as harvest continues, this practice increases compaction along the end rows. 

5. Harvest around the wettest areas. The wettest areas are the most at risk for soil compaction, but they also are an accident risk that ultimately could lead to longer harvest delays. Additionally, buried equipment may come with large financial penalties. Come back to these areas later in the fall once the soil conditions are drier or have frozen. 

6. Avoid or minimize tillage. Remember to hold off tillage operations until soil conditions are drier than field capacity. It is important to consider the soil moisture at the depth of tillage. Tillage in wet conditions results in further compaction and smearing of soil instead of the intended fracturing of the soil. If it is absolutely necessary to cosmetically fill in ruts, use a disk unless soil conditions are dry enough for fracturing of the soil through use of more aggressive implements. 

Kick is a communications specialist with ISU Extension.