CFS Growing Insights - 10.16.2019

Spring 2019 brought a lot of concerns for potential compaction with spring tillage and planters as conditions weren’t often ideal.

However, compaction issues at harvest time are just as important to manage for the 2020 season and subsequent crops. Damage from soil compaction can significantly impact water infiltration, root development, and ultimately hurt crop yields the following seasons. Most research agrees that yield loss due to soil compaction caused by wheel traffic ranges between 10-20% depending on the extent, so it’s certainly something that deserves attention.

When soils are near 100% saturation, harvest machinery weakens soil structure where water works as a “lubricant, leading to the collapse of soil aggregates. This will cause significant surface compaction, rutting, and deep subsoil compaction. Ruts not only leave the soil surface rough but have severe compaction below them.

There are two types of compaction to be aware of:

1. Surface compaction occurs in the first 12 inches of soil and is caused by high contact pressures from heavy equipment with highly inflated tires.  
   • Road tires inflated to 80-100 psi cause very high contact pressures. Surface compaction can cause very high yield losses the year immediately following but can be managed by using tires with more floatation properties, decreasing tire pressure, or utilizing tracks.
2. Subsoil compaction occurs deeper than 12 inches and is impacted by the weight of the axle load.
   • Most of the research on compaction points towards axle loads that are 10 tons or higher that are operated on ground that is too wet can likely cause subsoil compaction below 20 inches. Subsoil compaction is much harder to recover from since freeze-thaw cycles won’t likely remove this compaction, nor will biological forces such as earthworms, roots, or microbial activity. Deep tillage usually doesn’t go this deep effectively either, so avoidance of heavy axle loads is the best management strategy!      

1. Dedicated travel lanes and controlled traffic:
   • It has been documented that 60-80% of soil compaction occurs from the first wheel passes, subsequent field operations account for a much smaller amount of compaction.
2. Be mindful of the capacity you’re operating at:
   • Try to reduce the axle loads of both the combine and grain carts by not loading them to full capacity. This will be very difficult in a condensed harvest window, but at least avoiding full capacity loads in long stretches across the field may be an effective compromise.
3. Use proper tire size and inflation pressure:
   • Adjusting the tire air pressure to match the axle load being carried can help minimize surface compaction.
4. Keep non-harvest field activities near the field exit: 
   • Designate an area for loading grain trailers near a field exit to limit compaction to the smallest area possible.