Without even knowing it, you could be hindering the yield potential of your forages by causing soil compaction with normal field activity.

Soil compaction, or loss of soil structure, is caused by multiple passes of heavy equipment or continuous shallow tillage. Compaction prevents crops from developing a full root system, essential for taking in water and nutrients.

In a well-structured soil column, a plant’s roots can grow deep into the soil via old root systems and earthworm burrows. But when soil is compacted, roots attempting to grow downward run into dense soil layers and are forced to grow laterally. Late in the season, if plants become water-deficient, roots may be unable to reach water deep in the soil column.

Impact of compaction
Though often overlooked, some level of soil compaction is inevitable in any crop production system. All soils are susceptible to soil compaction, but clay soils are typically the most prone due to poor drainage and smaller pore space between soil particles.

The layers formed by soil compaction prevent water from flowing down through the soil column, leading to soil saturation and erosion caused by water runoff. In addition, soil compaction suffocates plants by trapping carbon dioxide and preventing oxygen from reaching the plant through the soil structure.

It does not take much soil compaction to have a negative impact on the yield potential of corn silage and alfalfa. And once a field is compacted, reversing the problem is difficult.

Rotating from alfalfa to corn silage
Though alfalfa is a sod-forming crop, land coming out of alfalfa often has more compaction issues due to the increased traffic associated with multiple cuttings. High-traffic areas need special attention before the field is ready for silage production.

The best way to prevent compaction in an alfalfa field is to vary equipment paths, therefore spreading the weight of each load across the field. Before rotating to corn, consider deep tillage or v-ripping twice instead of once to ensure the previous crop is torn out properly and the compaction layers are shattered. Also, keep out of the field when it is too wet to avoid making the compaction even worse.

Preventing compaction
It is much simpler to prevent compaction than to rebuild soil structure. Consider the following methods to help reduce the potential for soil compaction:

1. Moisture. Most compaction is caused by field operation in the spring when the soil is still wet. It can be tempting to start tillage early in the spring, but even if the surface is dry, tillage on a wet subsurface can lead to compaction. When the soil is wet, pressure from large equipment or tillage forces soil particles together, creating a dense soil layer and destroying the soil structure.

2. Tillage. Proper tillage practices also can help prevent soil compaction. Continual shallow tillage in a conventional tillage system will cause more compaction than deep tillage. It is important to utilize both shallow tillage and a subsoil tillage method to break up layers in the soil.

3. Equipment. Choosing the right equipment, such as dual tires or wider equipment, helps to distribute the load evenly over more ground to prevent deep compaction. Wider equipment also allows you to reduce the number of passes over a field. Do not overinflate tires – tires should bulge out slightly when sitting on a hard surface.

4. Traffic. In alfalfa production, it is especially critical to minimize high-traffic areas as much as possible. Have multiple access points to a field so not all equipment travels over the same ground at every cutting.

Coping with compaction
Once in place, soil compaction is difficult to remove and its effects can last up to four years or longer. Some compaction of the soil is often unavoidable, but it is possible to manage compaction and the risk of compaction on your operation.

• If you have fields with high clay content that are more prone to compaction, shorten alfalfa rotation on that ground.

• When planting corn silage, do not start field work early in the spring when the ground is still wet.

• Producers who irrigate should cut off moisture early enough in the season to allow plenty of drying time before harvest.

• Ensure fertility levels are adequate to help get a compacted field back to its full production capacity.

If soil compaction is already an issue, certain cultivation practices can be implemented to help break up dense soil layers. Deep tillage – greater than 18 inches – helps break deep compaction. Varying the tillage depth also helps prevent the buildup of compaction layers.

Patience
Whether it is waiting an extra week for fields to dry before making a pass with the chisel plow or allowing the natural freezing and thawing of the soil to rebuild its structure, managing soil compaction requires a lot of patience. However, it is important to minimize soil compaction to optimize forage root growth and yield potential. Remember: Rescuing a field from soil compaction can take several years – a better practice is to implement good field management techniques now to help avoid compaction altogether.  FG