Compaction: Causes, signs, solutions

Anyone who has thought about their retirement fund understands the long term impact of a slight change in management costs. A fund with an expense ratio of 1.5% sounds small, even compared to a fund with an expense ratio of .2% sounds like only a 1.3% difference. But over time, that difference can add up to thousands of dollars. In much the same way, compaction can cause increased yield loss, over time, resulting in thousands of dollars of lost income and increased challenges.

So just how extensive is the problem of soil compaction? No one knows for certain, because good weather and growing seasons can mask a compaction issue. But anyone driving around the countryside can easily identify many of these symptoms of either surface compaction or subsoil compaction: 

• Tire ruts/lug marks/track depressions
• Surface crusting
• Poor infiltration, standing water
• Soil smearing/ribbons during tillage or planting
• Poor root growth or angular roots (J or L roots)
• Lodged crops
• Slow or uneven plant germination or emergence
• Crops more susceptible to nutrient deficiencies (iron deficiency chlorosis and nitrogen deficiency, for examples) and herbicide injury

As you can see from the list; compaction exhibits itself in many ways, often accentuating or mimicking other agronomic challenges. If you experience any of these issues, you likely have some form of surface and/or subsoil compaction. Generally, fields with short rotations and heavy tillage are significantly more likely to experience compaction. Studies show fields experiencing compaction will experience around a 15% yield loss in the year following, but will continue to experience yield losses for up to 10 years or more. 

So how can we solve past compaction and avoid creating future compaction problems? Generally, farmers have five options: 

1. Tillage
2. Freeze-thaw
3. No-till
4. Cover crops
5. Perennial crops

When considering these options, it is important to consider effectiveness (how well the solution solves existing compaction and/or reduces the chance of future compaction), costs, and side effects. 

Having a farm perform at maximum productivity will require identifying and addressing compaction issues. Tillage may provide a minimal to moderately effective short term benefit, but reaching high profitability and productivity will require building up soil to become compaction resistant. To achieve that level, no-till, cover crops, and for those with the right equipment and markets, perennial crops will be necessary. Luckily, those practices have multiple additional benefits, from improved fertilizer efficiency to reducing nitrogen fertilizer to generating carbon credits. 

By Ryan Stockwell, Grower Engagement Senior Manager and Wisconsin farmer