Soil is the foundation on which everything else is built. Life and the experience of life need soil to grow, prosper, and create. Soil is responsible for growing food, nutrients, and shelter while it provides a foundation for homes, roads, and buildings. When soil is stable and of excellent quality, air and water circulate for maximum plant growth, erosion is minimal, and insects and microbes make their homes where they are most beneficial. Soil compaction has both positive and negative implications depending on how and why the soil was compacted. While compaction might aid construction, it doesn’t bode well for crops and harvests.
Soil compaction is most often seen on farmland and areas where land is cultivated as heavy machinery passing over land presses soil into itself. When people use heavy machinery, 70 to 80% of soil compaction takes place on the first pass. Yet the compression of soil has its benefits when used to the right advantage.
What is Soil Compaction?
When soil aggregates or particles are pressed together constantly and over time, soil compaction takes place. Soil compaction and its resulting issues must be considered when planting new crops, building roadways, or during restoration.
To illustrate soil compaction, consider a slice of bread. This slice of bread is probably full of varying sizes of holes that allow air and liquid to pass through. If the slice is squeezed until it gets doughy, the result is a lump that’s been smashed and pressed together to make it smaller and denser. This makes it much more difficult for air and liquid to penetrate. Compacted soil reacts the same way — heavy, dense, and less likely to absorb water or nutrients, which will starve roots.
Soil compaction presses soil particles together to reduce pore size. As soil pores are reduced, soil volume is affected and much less likely to drain, just as water rolls off the mushed slice of bread. When soil’s density is increased, infiltration slows and gas exchange is reduced, causing a reduction in soil nutrients and fertility.
Soil compaction also compromises soil strength. When the soil is dense and of low porosity, roots have a harder time digging down through compacted layers to take hold.
Effects of Soil Compaction
Soil compaction has far-reaching implications as it affects all stages of soil life. Burrowing animals may have difficulty creating a habitat from compacted soil which will impact soil formation. Compacted soil increases the likelihood of aeration problems that impacts rooting plants. The flow of nutrients may drastically slow and impact crop and harvest schedules.
Plants and animals aren’t the only ones who need nutrition; soil does as well. If the soil isn’t fed properly, it cannot feed roots properly. When a root tries to make its way through soil and reaches a depth it can no longer push through, it will grow in horizontally resulting in a pancake effect. This stunts the growth of the plant and minimizes its ability to draw water and nutrition from the soil. As one plant is affected, so are all. Crop yields may be drastically reduced due to soil compaction.
The structure of the soil is another essential factor in the effects of compaction. When soil structure is destabilized, compaction from external pressure is easier to achieve. Soils subject to heavy traffic are slower to warm when compared with less compacted soils.
Try reshaping the slice of bread from earlier. Although the slice might be formed back into a square shape, its integrity has forever been altered and it is no longer what it once was.
Causes of Soil Compaction
Soil compaction is most often seen when machinery or automobiles pass over the surface. Soil types also have an influence on compaction depending on their moisture level and the contents of the soil’s organic matter. Organic matter works with other elements to bind soil particles together. Areas of land susceptible to compaction might contain wet soil that is much more likely to bind and compact.
When is Soil Compaction Desired?
Soil compaction is sometimes an end result. Take for instance the case of infrastructures like roadways and bridges. Considering that compacted soil is often strengthened by making it heavier due to the force of pressing soil particles together, this makes it desirable as a base for something like a highway.
The soil under man-made structures must be stable and less likely to erode or otherwise be carried away. Housing is also where soil compaction is necessary and welcomed for a solid foundation where there will be less settling or disturbance of the underlying soil structure.
Machines such as vibrating rollers or compactors are designed for just this purpose. Proof rolling, or test rolling, is a method used to determine if the soil will bear the long-term impacts of compaction and construction.
Since wet soil is more easily compacted than dry, it is best to stay off saturated lands to avoid compressing the soil with machinery. Increasing water infiltration and storage ability by incorporating natural coir geotextiles to help soil drain and aerate efficiently. Create more efficient practices around planting and harvest to stay off the land as much as possible and allow for nature to work unobstructed.
Compaction can be tested with a simple test. Drive a stake into the ground where there is little to no machinery or heavy traffic. Note how far the stake can be driven and the number of strikes to drive it to that depth. Now do the same in areas where compaction is suspected. Note the number of strikes to drive the stake as well as its corresponding depth. Although it’s not foolproof, this method gives a rudimentary assessment of soil compaction.
Soil compaction can have its upside if it is part of the underlying foundation of concrete, asphalt, etc., to build homes and roadways, but when compaction takes place and interferes with growth and production, it becomes a problem. The good news is that soil compaction takes place primarily from human activity and human interventions can minimize its impact.