Soil Compaction Threat is High

Sep 14, 2018

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By Sjoerd Willem Duiker
After another prolonged period of rainfall, the soils across most of the commonwealth are again saturated.
Soil compaction threat during silage harvest is high this year.
At this crucial time for corn silage harvest, what can you do to avoid destroying your soils by compaction? The soil is highly sensitive to rut formation when it is saturated, and it is highly compactable when it is in the plastic state, when you can form a ball by kneading the soil. If you can wait until the soil dries out more, that would be preferable, but that may not be an option if you need to harvest a crop like corn silage that loses quality as it matures.
Some other principles and actions can help you manage soil compaction. First, avoid subsoil compaction at all costs by keeping axle loads below 10 tons, because the effects of deep soil compaction can be long-lasting. In a long-term multi-national project, soil compaction by heavy farm machinery (axle loads > 10 tons) was found to reduce corn yields for more than 10 years afterwards.
Causing some surface compaction may be unavoidable if you need to harvest corn silage this year. Fortunately, the effects of surface compaction are typically not as long-lasting, but they are usually more severe. In one study, crop yields were reduced 95% when the entire surface of a long-term no-till soil was compacted severely by back-and-forth traffic. However, yields bounced back quickly the year afterwards without doing any tillage, showing the resiliency of long-term no-tillage. Surface contact pressure determines to a large extent the surface compaction that is caused. So, keeping surface contact pressure low is key at this time – this can be achieved by using special flotation tires inflated to low tire pressure, or using tracks. If you see significant rut formation (greater than 2 inches deep) you should check your tires and inflation pressure. Road tires inflated to 80 or 90 psi really shouldn’t be used in farm fields, but especially not in high soil moisture conditions.
Building soil health will be an important ally to manage compaction. If you have used no-tillage for the long haul, you will notice that the soil supports the weight better due to higher aggregate stability. At the same time, no-till soil maintains much of its macroporosity. Also, the high soil organic matter content near the soil surface makes soil resist compaction better. Keeping living roots in the soil is another important practice. The roots act as a geotextile. At the same time, living roots help repair soil from compaction, and it is therefore important to have the drill in the field at silage harvest time to plant the cover crop that will help heal your land. Non-inversion subsoiling may be an option if you determine your soil has been compacted to the extent that it would not be possible to repair it with biological means. Make sure you do subsoiling only when the soil has dried out sufficiently. This may be impossible this year. Make sure you put soil health building practices in place immediately after any tillage. Although some compaction may be expected this year during silage harvest, you can do what it takes to limit its effects by using practices that improve your soil health.