Dry weather is widespread across the state of Pennsylvania this fall. This means even many of those perpetual wet spots have dried up, opening an opportunity to alleviate soil compaction.

Soil compaction affects soil physical, chemical and biological properties negatively for crop growth.

It leads to increased bulk density, reduced porosity, increased penetration resistance, and reduced water infiltration and percolation.

Soil compaction also increases the potential for denitrification and ammonia volatilization due to reduced aeration and water infiltration.

Uptake of potassium and phosphorus is reduced due to root growth inhibition and reduction in soil biological activity.

So it is important to minimize compaction. But common field activities using heavy equipment, especially when soil is wet, trampling by livestock and soil tillage may have caused soil compaction in the past. 



To identify problem soil compaction use both soil and crop observations. The soil compaction tester, or penetrometer is one means of compaction detection, but it is not useful when soil conditions are too dry.

Instead, in very dry soils, take a shovel and dig a hole with a vertical face perpendicular to the crop rows. Push a knife horizontally into the soil profile for about 1 inch starting from the top. You may be able to feel a distinct layer with higher resistance just below common tillage depth.

If roots are clearly restricted at a certain depth this may call for action.

Also evaluate the soil structure. Compacted soil structure is massive and does not fall apart in small aggregates whereas root growth is restricted to the cracks between clods.



It is important to evaluate the soil to determine if subsoiling will be beneficial. Our research has shown that our most common agricultural soils do not benefit from sub-soiling unless they are severely compacted.

We are now evaluating subsoiling on soils with naturally compacted sub-soils called fragipans, but still need more years to evaluate the practice. The recommendation is therefore not to use a subsoiler unless the soil is severely compacted.

If you decide that subsoiling is justified, it is time to decide which subsoiler to use, and how to set it. 

There are different types of subsoilers. With the recognized benefits of surface residue preservation, modern subsoilers do not turn surface soil over.