Heavy machinery on wet soils is a sure prescription for compaction. But there are three ways to minimize the compaction: Look at axle loads, properly inflate tires of field equipment, and control field traffic.
Heavy axle loads and wet soil conditions will increase the depth of compaction in the soil profile. Tracks and duals have better floatation than single tires. If you can equip your combine or grain carts with either of these choices it will increase floatation and allow the combine a few extra passes before it gets stuck. To help minimize the compaction due to the weight of the combine, unload the combine on the headlands or unload the combine more frequently.
Check your tire pressure before using any equipment in the field. Not only does this help reduce soil compaction, it also improves tractor efficiency. Studies have shown that given the same axle load, inflation of the tires (psi) will determine the depth and severity of the compaction. Check with your tire manufacturer or search the web for proper tire size and inflation rate for the carrying capacity of your equipment.
The theory behind controlled traffic is that 80 percent of the compaction happens on the first pass, so use this to your advantage. While it may take awhile to replace equipment that will use the same wheel tracks, there is one piece of equipment that should receive special attention: the grain cart. The grain cart has the highest potential to compact the soil due to the large carrying capacity (up past 1,000 bushels) and a single axle on which to carry that weight.
When using a grain cart, try to use the same paths across the field. When unloading the combine, use the combine's previous wheel tracks. After loading, follow those tracks down the field and take the headlands back to the semi or field entrance. Never cross the field diagonally. If you can't park the semi trucks on the adjoining road, keep them on the headlands.
To manage ruts left by fall harvest, wait as long as you can before getting into the field for tillage. Let the soil dry out as much as possible. For sandier soils, try going 6-8 inches deep and filling in the ruts. For heavier soils, stay as shallow as you can while filling in the ruts. Even with the best management, producers say they have observed yield losses in the rutted area for three to five years.
Instinct would lead you to believe that you should till as deep as possible to shatter any smeared soil or compacted layers that were created. However, your soil's best natural defense against compaction is soil structure. The deeper you till and the more aggressive your operations, the more structure you will damage, leaving your soil susceptible to further compaction.
Your soil is one of the most important factors when growing a healthy crop. Preventing soil compaction or decreasing the affected depth will increase water infiltration and storage capacity, and timeliness of field operations. It will also decrease the stress on plant roots, and decrease disease potential.
- Jodi DeJong-Hughes is a crops educator with University of Minnesota Extension.