After unseasonably wet, cold weather this spring, farmers are eager to get their seed in the ground but they must be conscientious of soil compaction. We understand their sense of urgency, but we also know they’ll have better results if they wait for more suitable field conditions.
The best rule of thumb is to let the field dry before doing fieldwork. Use a quick field test to check the soil moisture: mold a length of soil between your index finger and thumb, or roll it into a ball in your hand. Observe whether the soil breaks apart as you work it. If you toss the ball of soil into the air and it shatters or cracks upon falling to the ground, then conditions are likely suitable for tillage or planting.
Working soils that are too wet this spring could have negative impacts on your crops during the growing season including: stunted plant growth; slow infiltration of water and/or ponding; high surface runoff and soil erosion under normal or light rainfall; poor root system establishment; and nutrient deficiency.
To reduce or minimize soil compaction:
- Avoid working wet soil. Soil is most susceptible to compaction when it’s saturated and cannot absorb any more water. Use the quick field test method above to access the soil conditions, and begin planting or working the soil only if the proper conditions exist.
- Reduce tillage. Crop residue can intercept raindrops and prevent the soil surface from sealing and compacting.
- Use the right implements. The degree of compaction is determined by the moisture content of the soil, as well as the weight of the equipment in the field. Reduce the weight on each axle, choose wider tires and adjust air pressure to reduce the load on the soil surface. Iowa State University research shows that using equipment with 6 pounds per square inch (psi) of surface pressure yielded 9 bushels per acre more than equipment with 16 psi.
Soil compaction can be avoided with better management. For more information, click here to download Iowa State University Extension’s publication, Understanding & Managing Soil Compaction.