Agronomists say that for all the plant growth you see above ground, there is an equivalent root mass found underneath the soil's surface supplying plants with life-giving nutrients. This living, breathable soil environment is critical to crop health. And just like a human's crushed rib cage following an auto accident, extreme wheel traffic can impair the soil's ability to live, breathe and nourish future crops.

Tilth is an all-encompassing term for soil's physical condition. It describes the soil particles, moisture level, drainage, air pockets and, to some extent, the biological activity. When these attributes are working in harmony with one another, soil has the greatest potential to support high yields. When one of the factors becomes impaired, the entire system can suffer. In the case of soil health, more often than not, the problem is surface or subsoil compaction.

Surface soil compaction occurs to some extent nearly every year as the ground becomes slightly compressed due to wheel traffic. In some instances, we can see this extensive damage by observing plants that don't do well in severely compressed wheel tracks. Since surface compaction significantly reduces crop yields, it is one of the reasons agronomists recommend travel lanes in fields to minimize its effects.

Meanwhile, subsoil compaction impacts crop yields to a lesser degree than its surface-crushing counterpart. While that's the good news, once sandwiched, subsoil can be damaged for generations. Even in colder climates, freeze-thaw cycles have little impact beyond 20 inches or below the earth's surface (except for northern regions this year). Deep tillage or subsoiling can help in some instances, but it also raises the likelihood of even further compaction down the road. Deep-rooted cover crops such as alfalfa can help restore subsoil. Still, the soil structure is never quite the same.

Like most advice you'll receive from your doctor, prevention is the best course of action. That starts with simply staying off of wet soils. That can be easier said than done as doing fieldwork and hauling manure often top our to-do lists. Proper tire inflation also minimizes the squeeze on soil particles.

While medical science has helped many auto accident victims recover from their injuries, the impaired bodies are never quite the same. The same holds true for soil health. While intervention can minimize the injury, once compressed, compacted soils never quite return to their former growing potential.

This editorial appears on page 252 of the April 10, 2014 issue of Hoard's Dairyman.

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