With fall harvest underway across Nebraska, recent rains have left fields soft, with harvest equipment cutting ruts into the soil in some areas. These ruts leave the soil surface uneven and can indicate significant compaction below the surface. That compaction can restrict root growth for several growing seasons and increase runoff by reducing water infiltration. Heavy grain carts and the tractors pulling them can worsen compaction in wet fields.
12 Tips to Avoid Compaction on Wet Soils
- Wait until the soil dries enough to support the combine.
- Don't use grain tank extensions or fill the combine to capacity.
- Use the lowest tire inflation pressure recommended by the manufacturer for the equipment's load and operating speed.
- Use wider tires that can operate at lower inflation pressures.
- Consider increased-flexion (IF) or very-high-flexion (VF) radial tires, which can carry the same load at lower inflation pressures.
- Keep grain trucks out of the field. Consider unloading at the ends of the field rather than on the go.
- Keep grain carts in the same wheel tracks as the combine whenever possible.
- Avoid turning equipment around in the middle of the field.
- Reduce grain cart loads and unload more frequently.
- Establish designated grain cart paths and stay on them.
- Avoid tilling wet soils, which are especially susceptible to compaction.
- Use cover crops to help build soil structure over time.
If combines and grain carts aren't leaving visible ruts, there may be less concern about severe compaction from wheel traffic. However, the absence of ruts doesn't rule out compaction. Compaction occurs when pressure reduces the pore space between soil particles. Wheel traffic on wet soil can leave obvious ruts, while compaction from tilling wet soil may be less visible because it occurs across the tilled area, particularly below the tillage depth.
According to Kendall Kirk with Clemson Cooperative Extension Service, soil compaction is often greatest on end-rows or turn-rows, where machines turn around at the end of a pass, but some degree of compaction occurs wherever equipment travels in the field. Reducing tire inflation pressure within the manufacturer's recommended range can help limit surface compaction. Lower pressure increases the tire's footprint — the area in contact with the soil — distributing the same weight over a larger area and reducing pressure on the soil.
If ruts formed during harvest, tillage can help break up compaction, but the soil must be dry enough to fracture rather than smear. If the soil was wet enough to form ruts, it's likely too wet for tillage. Tilling wet soil can cause additional compaction because soil particles slide more easily under the weight of the tractor and tillage equipment. This compaction can be harder to detect because it occurs across the tilled area, even though the surface appears loosened. Deep tillage in wet conditions often cuts slots and smears the soil rather than fracturing compacted layers.
Tillage is a major contributor to soil compaction because it breaks down existing soil structure and can compact soil below the tillage depth. Ruts may extend through the loosened soil to the compacted layer beneath it. With less soil structure in the tilled layer, subsequent equipment passes can compact the soil more easily, either across the width of the tillage implement or in wheel tracks.
Controlling Traffic, Controlling Compaction
Producers should practice controlled traffic to limit the areas of a field affected by wheel traffic compaction. Approximately 80% to 85% of wheel traffic compaction can occur during the first pass. Subsequent passes along the same tracks generally cause less additional compaction because the soil has already been compressed. By using the same traffic lanes year after year, producers can protect soil structure and improve water infiltration in areas that remain free of equipment traffic.
Controlled traffic lanes can improve traction, soil load-bearing capacity and the timeliness of planting and harvest while minimizing potential yield losses from compaction. The goal is to manage compaction rather than eliminate it by concentrating equipment traffic in designated lanes and separating traffic zones from crop root zones. This keeps compaction in areas where it is less detrimental to root growth and the uptake of water and nutrients. Fertilizer placement and furrow irrigation practices can also be adjusted as traffic lanes become established.
To minimize wheel compaction during harvest, grain carts should follow the same wheel tracks as the combine whenever possible. Moving a few rows over to spread out compaction instead affects a larger area of the field. Grain trucks should also stay out of fields because their heavy axle loads and higher tire inflation pressures can increase soil compaction.
If ruts formed during harvest, wait until the soil is dry enough to smooth them without causing additional compaction. Light tillage before planting next spring may be sufficient to level the surface. Avoid deep tillage when spring soils are still wet, as it can worsen compaction and further disrupt soil structure.
To fracture compaction caused by this year's harvest traffic, producers may need to wait until next fall, when soils are dry enough for effective tillage. However, compaction beneath deep ruts may extend beyond the reach of most tillage equipment. In these cases, prevention is far more effective than attempting to repair the damage. Building soil structure and avoiding equipment traffic on wet soils whenever possible are the best long-term strategies. Controlled traffic, reduced tillage and cover crops can all help improve soil structure and reduce future compaction.
Resources
- Clemson, Michelin Study Impact of Tire Pressure on Soil Compaction in South Carolina, Clemson University, Aug. 28, 2023
