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Ways to prevent soil compaction during harvest

Maintaining healthy soil is important. The Minnesota Department of Agriculture asserts that “protecting soil is critical to protecting our ecosystems and our ability to raise crops or maintain a backyard garden.” One threat to the health and function of agricultural soils is compaction.

Soil compaction is an especially important issue because it has compounding effects. Even if an agricultural soil has sufficient nutrients, plants will grow poorly if they cannot reach nutrients, water, and air. As a result, yields are lower and input costs may be higher.

We often think of avoiding compaction in our wet soils during planting. However, soil compaction is not just a spring issue. Minnesota often has wet soil conditions during harvest, and there are three major ways to prevent compaction while harvesting. You can manage axle loads, properly inflate field equipment tires, and control field traffic.

The weight of our field equipment can increase the severity of compaction in wet soils. Heavy axle loads lead to deeper compaction in the soil profile. As loads increase beyond 10 tons per axle, the potential to compact the soil past the tillage layer increases. Full combines, slurry tankers, and grain carts can weigh between 18 and 40 tons per axle and can create compaction 2 to 3 feet deep. Equipping machinery with tracks or duals can help cause less compaction due to increased flotation. Additionally, combines should be unloaded more frequently to decrease the weight of the combine.

Before using any equipment in the field, check tire pressure. Proper inflation helps reduce soil compaction and improves tractor efficiency. Studies have shown that tire inflation (psi) will determine the depth and severity of compaction even when axle loads are held constant. Producers should check with their tire manufacturer or search the web for proper tire size and inflation rate for their equipment.

The reasoning behind controlled traffic is that the majority of soil compaction (about 80 percent) occurs on the first pass through the field. As far as equipment goes, the grain cart has the greatest potential to compact the soil due its large carrying capacity (>1,500 bushels) and its single axle on which to carry that weight.

Jodi Dejong-Hughes, soils educator, has compiled these tips to follow when using a grain cart:

1. Try to use the same paths across the field.
2. Use the combine's previous wheel tracks when unloading the combine.
3. After loading the grain cart, follow those tracks down the field and take the headlands back to the semi or field entrance.
4. Never diagonally cross the field. This will create multiple wheel track patterns at 80 percent compaction.
5. If semis cannot be parked on the road, they should be kept on the headlands. Semis and gravity wagons may have a lower axle load, but the tire inflation is quite high.

Preventing soil compaction will enhance water infiltration and storage capacity, decrease plant root stress, and should help with efficiency and timeliness of operations in the spring.