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I usually think of compaction as a spring problem, however, after looking back at past articles I have written, there is a fall compaction press release for 2003, 2004, 2005 and now 2007.

The 2007 cropping season has been very dry for a large portion of the state and harvest started at a rapid pace. From mid September to October 22nd, the state has received an abundance of rainfall, replenishing the soil profile and bringing harvest to a halt. Portions of West Central Minnesota have received over 10 inches of rain in the past 5 weeks, while Southeastern Minnesota has received a devastating 26 inches since August 4th (13 of that in the past 5 weeks).

So what should a producer do? Harvest and risk significant compaction or stay off the field? Easy, harvest the crop.

With that being said, there are three ways to minimize the extent of the compaction you may create. Look at axle loads, properly inflate tires of field equipment, and control the field traffic.

1. Heavy axle loads and wet soil conditions will increase the depth of compaction in the soil profile. As loads become greater than 10 tons an axle there is the potential to compact the soil past the tillage layer. Full combines, slurry tankers, and grain carts can weigh between 20 and 40 tons an axle and whether equipped with tracks or tires, create compaction down to 2-3 feet. Tracks and duals have better floatation than single tires. If you can equip your combine or grain carts with either of these choices it would 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.
2. Before using any equipment in the field make sure to check your tire pressure. 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.
3. The theory behind controlled traffic is that 80% 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 diagonally cross the field. This will create multiple wheel traffic patterns at 80% compaction. If you can’t park the semi trucks on the adjoining road, keep them on the headlands. Semi’s and gravity wagons may have a lower axle load, but the tire inflation is quite high.

Inevitably, there will be some ruts left by fall harvest. How do you manage for these ruts? The first recommendation would be to 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 fill in the ruts. For heavier soils, stay as shallow as you can while filling in the ruts. Even with the best management, producers stated that they have observed yield losses in the rutted area for 3-5 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, timeliness of field operations, decrease the stress on plant roots, and decrease disease potential. 

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