Reducing Soil Compaction during Spring Field Operations

Soil compaction is called the 'silent thief' because it quietly robs you of production potential and reduces infiltration and aeration. Due to the weight involved, manure spreading and silage harvesting are operations that can cause significant compaction. But how to avoid soil compaction when soil conditions are marginal for field traffic? Here are a few tips to follow :

• Stay off of soil that is too wet. When you can make a ball out of the soil, it is in the 'plastic' state and most compactible (this is called the 'ball test'). If soil acts as a fluid, it is in the 'liquid' state, and you will cause deep ruts. Both conditions are too wet to be on it. You may evaluate fields based on drainage class and avoid those lying wet. You can also look at their exposure to the sun. North-facing slopes tend to stay wet longer than south-facing slopes. But there are other things you can do to avoid compaction.
• Limit traffic across the whole field as much as possible and limit tracking areas more than once. Because most compaction is caused in the first trip, it is important to limit those second and third passes. Organize traffic lanes and don’t randomly drive over the field. Traffic lanes can be evaluated later and, if needed, loosened with a deep tillage tool without having to address the whole field.
• Use flotation tires or tracks on tractor and equipment tires. Surface compaction is primarily due to contact pressure, and this is closely related to the inflation pressure of tires. Road tires are typically inflated to 95-120 psi, causing severe surface compaction. Use flotation tires instead and run them at much lower pressures. Tracks reduce contact stress by spreading out the load over a large footprint.
• Adjust tire inflation pressure to the lowest allowable pressure. Research has shown that the same tire inflated to a high pressure will cause a lot more compaction compared to when it is inflated to a low pressure. Therefore, use the lowest allowable pressure (but don't underinflate the tire either). Check with your tire dealer to determine the right inflation pressure. Tire pressure in the field should be less than 35 psi, and preferably less than 20 psi.
• Reduce axle load. Axle load is the determining cause of deep compaction, which leaves long-lasting effects. More axles help reduce deep compaction. Typically, a 10-ton axle load should be the limit to avoid compaction below 12 inches.
• Avoid tillage. No-till soil has been shown to resist compaction better. The soil will have a more stable structure, with a firm matrix to carry weight, interspersed with macropores. There is more biological activity in no-till soil that helps alleviate any compaction that is caused.
• Maintain living roots 24/7/365. The tremendous root systems of some cover crops like rye or triticale will keep the equipment up and maintain porosity in the soil. Tap-rooted species create larger pores that will stay open after the cover crop dies and the root decomposes. Subsequent crop roots will then follow these channels.
• Build organic matter. Soil with high organic matter content is less compactable. But building organic matter is a long-term process. Proven practices to build organic matter are to use crop diversity and cover crops, have continuously living root systems in the soil, return crop residues to the soil, add manure with high-solid content, use compost, and use no-tillage.