Soil Compaction Management - Be Wise Rather Than Clever
Posted: November 6, 2012
The recent rainfall has saturated the soil and cool conditions maintain the soil at or near field capacity, when soil is most sensitive to compaction. Considering this is not the first nor the last time we will be faced with this situation, it is worth to have a thorough understanding of the basics of soil compaction and to make the investment to address it to maintain the productivity of your soil and improve your ability to be in the field under sub-optimal conditions.
The basics of soil compaction management are in order of importance: (1) help your soil resist and bounce back from compaction; (2) avoid causing compaction; (3) remediate compaction only if needed. You can make soil resist compaction by practicing continuous no-tillage and using cover crops. No-till soil has firm aggregates giving you good support for traffic, yet they are interspersed with macropores providing aeration and percolation. Cover crops, even if established after harvest, help soil resist and cure the effects of compaction.
Of course these practices are no cure-all so it is also important to avoid compaction as much as possible. To avoid compaction is like the wise man who plans to avoid getting in trouble instead of the clever man who knows how to get out of a situation he got into. Avoid driving on wet soil and keeping cattle out of the field when the soil is wet is number one. If the topsoil is frozen or if the soil is very dry little compaction is caused. So if temperatures cause the top 2 inches to be frozen that may be a good opportunity to get into the field. With our increasing equipment size it also becomes important to use tires or tracks to increase your footprint. It is important to use the minimum allowable tire pressure in your flotation tires or you won't have the large footprint that helps reduce the sinkage and high contact pressure that cause surface compaction. Using low-inflation tires on tractors also helps to reduce slippage and increases horse-power output of your tractor. Further, the axle load is important, too. It is recommended to keep axle load below 10 tons - to help avoid causing subsoil compaction.
Finally, what to do if, despite all your best efforts, you still have compaction in the field? Before doing any tillage you have to remember its negative effects: therefore it makes sense to limit tillage as much as possible and only use it sparingly. In my experience, no tillage is usually necessary except if deep ruts have been created. If ruts are limited to lower, wet-laying parts of the field, it may be possible to use a backhoe, or chisel plow or disk to smoothen the ruts. On the other hand, if ruts are distributed across the field, it is probably necessary to smoothen the whole field. If the soil in the bottom of the ruts is severely compacted it may be necessary to do deep tillage to remediate that. New sub-soilers don't do a lot of surface disturbance, which keeps residue cover in place. This is important because the mulch helps provide soil erosion protection and reduce drought stress in the summer. The best time to do sub-soiling is when the soil is dry to cause maximum shattering. Unfortunately it may be difficult to find this condition this fall. Using a field cultivator to smoothen the ruts is recommended above a disk to keep more residue at the soil surface. The tillage destroys soil structure - so now it is important to help nature to build soil structure back up - primarily by planting your crop or cover crop soon after the tillage is done. Building organic matter content with manure or compost applications is also helpful to restore your soils to productivity and resist compaction.
- Associate Professor of Soil Management and Applied Soil Physics