Now is the time to dig your crops. No, we are not talking about root crops, nor is this some 1960s hippie newsletter. It is something I have uncovered over 50 years of studying forage crops, and why they grow or don’t grow.

This came about as I was doing considerable work on no-till. The No. 1 factor limiting no-till success and growth was that the roots were not going below 6 to 8 inches. That ground was like a roadbed underneath.

This layer is at the base of the moldboard plow. It looks great from the tractor seat; the surface looks nice and fluffy. But it leaves an impenetrable roadbed underneath, and most farmers do not get off the tractor to look at what is happening.

I convinced a farmer one morning to take five minutes and check his field next to the house. He reluctantly agreed, thinking it was a waste of time. At 5 p.m., I said I had to go home. He kept saying “one more field.” He then said he learned more about his fields and cropping in that one day of digging holes than at all our seminars.

I have seen these root-limiting layers in all soils — sand, gravel, silt and clay. Beginning research here in Tennessee, we requested deep tillage before planting our plots. We were assured there was no compaction in the silty clay soils worked by an offset disk. That view changed quickly once they dropped the deep tillage unit into the field. Both moldboard and disks really compact this soil.

Multiple shallow vertical tillage trips can do the same thing, as I found in one of my New York research trials. When farmers switch to no-till in these conditions without removing the compaction, the result is a crop that has little or no roots. They blame no-till when the problem was actually previous tillage.

With today’s modern tractors, farmers are pushing the envelope with wet soils. Wet spots continually get bigger, and it only takes seconds to compact. The problem is it can take years to repair the damage.

ROOT OF THE MATTER: Roots should be round and have many small feeder roots coming off. Rectangle and flattened roots with few feeders emerging is indicative of compacted soil.

Despite old farmer tales in the North, frost does not remove compaction. In an area with heavy freezes, we had a 15-year alfalfa timothy hayfield that clearly showed compaction from the moldboard when it was originally plowed for seeding. The individual plow share marks could still be seen. No roots went below 7 inches. This was plowed with a smaller tractor when the soil was still plastic at the plow shear layer.

Massive equipment today puts compaction even deeper. At a compaction seminar in Canada, equipment with 100 psi tires and more than 10-tons-per-axle load broke the compaction sensor down 20 inches. Multiple trips in all kinds of conditions can leave your soil with the consistency of a large block of concrete. The worst was in soils the farmers thought would not compact.

Get ready to dig

The take-home message here is that you must go out and look in your fields. It takes effort and time to dig holes and to carefully excavate roots. But teasing the soil away from the roots will reveal the history of what these roots were dealing with from the moment they emerged from the seed.

Horizontal roots are an indication of a compacted layer. We even saw this on sand soil that was deep-tilled and then moldboard-plowed the next spring. No roots went below the 7-inch plow pan, even though the soil underneath the pan I could put my arm in up to my elbow.

Roots should be round and have many small feeder roots coming off. Rectangle and flattened roots with few feeders emerging is indicative of compacted soil.

This raises the question: Is the 2 inches over and 2 inches down fertilizer placement a result of normal root growth, or a result of plowed and disked field compacted layers causing the corn to grow that way?

Giant monster-ripping machines with disks and choppers are impressive, but they are not the best way to remove compaction. They pulverize the soil structure, which then consolidates into a giant lump. The deep wings leave a severely compacted layer at the bottom. Roots will never penetrate it, nor will water and oxygen. Curved shanks will ensure any rocks and lumps are brought to the surface.

Finally, deep tillage without changing the rest of the cropping system is a waste of time. Adding insult to injury, it ensures the deeper layers along with the surface are also severely compacted.

Try this approach

A holistic approach is to remove the deep compaction with a narrow (three-quarter-inch) vertical shank with a small foot at the bottom (no wings). Narrow vertical shanks with a pointed lead edge slip around the rocks and leave them in the soil as long as tractor speed is kept reasonable.

Keep in mind that it may take a couple of passes over several years to completely remove the deeper compaction. Ironically, removing compaction and then implementing year-round cropping systems based on no-till has a tremendous beneficial effect on the soil.

Shattering the compaction in a pass and then growing winter forage, followed next season by summer energy crops, has worked. Many farmers report that the soil is getting noticeably softer and easier to plant.

They also report a tremendous increase in earthworm populations. This is an underestimated factor in the switch to no-till after compaction is removed. The benefit is from both the small worms and the large “night crawlers,” the latter of which will bore holes 4 feet into the soil profile. Each worm leaves a macro hole in the soil that is stabilized by organic matter and worm casting.

When it pours, the rain is captured and moved deep into the soil profile to be recovered by feeding crops. When it pours, these macropores enable critical oxygen to move into the soil to keep the roots growing and healthy. Multiple farmers have commented on the visible increase in worms in their now healthy, uncompacted soil. Tillage destroys worms either directly or by destroying soil structure, so there is no oxygen, which is critical to their survival.

And remember to dig

All this is useless, though, unless you go out and look in your fields by digging holes. You need to accurately determine at what layers the compaction occurs.

In that 15-year alfalfa field I mentioned up top, we ran the deep tillage at 14 inches. All it did was cut a groove in the compacted soil. Digging a hole revealed this. We lowered the shank 2 inches, the tractor shifted down two gears to pull it, and we shattered the entire plow pan.

Compaction is caused by tillage operations; wheel traffic with axle loads and high tire pressure; heavy raindrops on tilled soils (surface compaction); and using the same old cropping system in the field without rotation.

You need to correct this by doing something different.