Let cover crops do your tillage with roots
If you were going to build a road, how would you do it? Hans Kok says most road builders start with a sandy loam soil if possible, wet it down, then disk it many times. You’ve got a soil at its most vulnerable time, and a tool that compacts soil.
Since you don’t want a road in your field, Kok says there are things you can do to help the soil. Kok is co-director of the Indiana Conservation Cropping Initiative.
The easiest soil to compact is sandy loam, he notes. However, that doesn’t mean that silt loams and clay loams won’t compact.
• Mud doesn’t compact as much as “tacky” soil.
• The first pass with a disk can do maximum damage on tacky soils.
• Experts suggest letting cover crops do your tillage instead.
“The big factor is if the soil is susceptible,” he says. “That depends upon soil moisture level. You won’t compact a soil if it’s very dry, and you don’t compact it if it’s extremely wet. The soil simply squishes sideways. You do maximum soil compaction damage when soil is at the ‘it’s a bit tacky, but I’ll run anyway’ phase.”
Types of compaction
Some soils are naturally dense, either with a fragipan or just very dense subsoil. There may not be a lot you can do about these situations, other than to grow cover crops to get as much rooting depth as possible.
You’re also likely going to get surface crusting in almost any soil if conditions are right for it, Kok notes. The one factor you can control most is vehicle traffic. As noted, the disk is the worst possible tool for creating tillage pans. A chunk of soil from the top 6 inches may have so many compacted layers that it looks like philo baking dough, used to make thin-layered specialty pastries, he adds.
If you have tillage pans, determine the depth at which they occur. Roots won’t go through them without some help. That’s where cover crops and rebuilding organic matter come in.
The first step is to know you have these layers. “A penetrometer is basically a moisture tester,” he says. “It’s really not my tool of choice for finding compacted layers. I use a shovel and expose the layers.”
Deep soil compaction
In some cases, you may deal with deeper soil compaction. That’s often created by tractor and implement tracks on those “it’s tacky, but I’ll go” soil conditions. “About 80% of the soil gets traffic in a conventional system, and most of the soil compaction damage happens on the first pass,” Kok notes.
If you can control the traffic on most of the field, such as in a no-till or strip-till system, then the majority of the soil doesn’t see a track.
“Our preference for fixing and preventing problems is cover crops in no-till,” he says. “Let the cover crop roots do the tilling for you. They can run several feet deep and loosen the soil.”
Proof is in clear water: Hans Kok operates a rain simulator to show that rain hitting protected soil produces less runoff water, and the water that does run off is clearer.
This article published in the September, 2011 edition of INDIANA PRAIRIE FARMER.
All rights reserved. Copyright Farm Progress Cos. 2011.