Everything you need to know about Soil Compaction

What is soil Compaction?

Compacted soil is soil that has been compressed causing it to lose its natural structure, resulting in an inability to absorb water and air. Soil's inorganic matter is made up of different-sized particles, sand, silt, and clay. These particles are found in soils across the world with different ratios resulting in very diverse soil types. Soil is further mixed with organic matter, microorganisms, and plant roots which assist in creating soil structure. The soil's structure is critical to its ability to infiltrate water and allow oxygen diffusion deep into the soil which is key for plants. What soil structure requires is pores spaces that allow water, air, and microorganisms to travel through soil. This provides the necessary conditions for healthy plant growth.

When soil compacts the spaces between the soil particles collapse, reducing the amount of air and water that can penetrate the soil. Compacted soil can be identified by a hard pan which has increased resistance to penetration. This causes a barrier which prevents water and oxygen from passing through. The issue is that the compaction layer might be hiding just below the soil at depths anywhere from 10 cm to 1.5 meters The consequences of this can cause a range of knock-on effects.

It's important to address soil compaction as soon as possible to prevent further damage to the soil and plant health. First understanding what leads to soil compaction can help prevent further damage.

So, what causes soil compaction?

1. Heavy foot traffic: Frequent walking or driving over the same area of soil can lead to soil compaction, especially in high-traffic areas like paths, driveways, and around garden beds. Avoid walking in your beds to prevent compacting the soil.

2. Rain: believe it or not hard rainfall is a leading cause of compaction. Low-growing cover crops and grasses protect the soil from the compacting effect of rainfall.

3. Heavy equipment and machinery: The use of heavy equipment or machinery, such as tractors or construction vehicles contributes to soil compaction. These vehicles' weight cause soil particles to become more tightly packed, especially if the soil is wet or moist.

4. Tillage: While conventionally thought to open up the soil, long-term tillage has the opposite effect. Over-tilling the soil breaks up soil structure and before it can regenerate the soil creates a hardpan layer. This dense, compacted layer of soil forms below the surface and leads to plant stress responses.

5. High clay content: Soils with a high clay content are prone to compaction, as clay particles are small and tend to pack tightly forming a very heavy soil. When clay soil compacts the clay platelets stack onto each other bound together with an ionic charge. Addressing this requires you to flocculate the clay with the correct solution, test this beforehand.

6. Poor soil management: Poor soil management practices, such as excessive fertiliser usage, improper watering, or lack of organic matter, can also contribute to soil compaction. Overuse of chemical fertilizers can increase salt accumulation in the soil leading to soil salination. This makes it extremely difficult for plants to absorb water and nutrients.

What issues are caused by Soil Compaction?

One of the primary issues soil compaction causes for plant growth is reduced water infiltration and drainage. Compacted soil has fewer pore spaces which mean that water cannot penetrate the soil as easily. This poor drainage leads to waterlogging which suffocates plant roots and causes them to rot. During rainy weather, if you are noticing rapid pooling of water in certain areas there is likely a drainage issue.

Soil compaction reduces the amount of oxygen available to plant roots. Oxygen is critical for root growth and function, as it is essential for plants to perform their biological functions, When soil is compacted, there is less oxygen in the soil, which can lead to poor root growth and reduced nutrient uptake.

Compacted soil is denser and harder than healthy soil, which makes it more difficult for plant roots to penetrate the soil and support their above-ground growth. This can lead to stunted growth and reduced yields, as well as increased susceptibility to wind, pests and diseases.

Due to compacted soil reduced water infiltration, another threat is erosion. Especially problematic in elevated areas, this surface runoff can cut deep into the soil and transport it away from your fields. Holding onto top soil and reducing erosion is critical to land management which is worsened by your soil compaction layer.

Another issue soil compaction causes for plant growth is increased susceptibility to drought stress. Compacted soil has a reduced capacity to store water, which means that plants grown in compacted soil are more vulnerable to drought conditions. This can lead to reduced plant growth, wilting, and in severe cases, plant death.

Testing for Soil Compaction

When a compaction layer is formed a hard crust is created somewhere in the depth of the soil. To figure out what depth a soil compaction layer is a Soil Penetrometer is used. This tool is a long probe used to pierce the ground and test the resistance it faces as it penetrates the soil. When a compaction layer is met the penetrometer will register the increased resistance. Once a resistance threshold is met you know where your compaction layer begins and the level of compaction. This allows you to check the depth of the penetrometer and determine where your compaction layer is.

If you would like onsite testing for your soil contact us to book a Soil Compaction Assessment.

How can you deal with Soil Compaction?

By identifying soil compaction with our soil penetrometer, SoilScopes can provide recommendations for how to address the issue. Some potential solutions include:

1. Reduce compaction: Address the practices causing the compaction and prevent them from happening. As mentioned above consider ways to minimise the compaction-causing events before beginning a remediation plan.

2. Soil amendments: Adding organic matter to the soil can help improve soil structure and reduce compaction. Organic matter especially already decomposed compost, leaf litter, and manure can help break up clay soils. This is due to the microbial activity stimulated by applying those inputs. Microbes will assist in creating soil structure thanks to their biological glues which create the critical aggregates in soil.

3. Aeration: One of the most effective methods for dealing with soil compaction is to aerate the soil. Aeration involves perforating the soil with small holes to allow air and water to penetrate more easily. This can be done using a garden fork or a mechanical aerator. Once these holes are created inoculations of the correct microorganisms can rapidly reduce compaction layers.

4. Cover crops: Planting cover crops is the most cost-effective solution for dealing with widespread compacting. Cover crop blends can be designed with the goal of reducing compaction in mind, the sees selected will be aimed at managing this. Species with deep tap roots and strong advantageous roots are used to reduce compaction. These crops can also help hold soil in place and add organic matter to the soil, which can improve soil structure and reduce compaction.

5. Contact us: Getting your soil tested for compaction is the first step to creating an action plan to deal with the issue. We will assist with mapping the soil compaction and creating a solution to help you manage this. Click here to contact us for assistance.

In conclusion, soil compaction is a common problem that can have significant negative impacts on plant growth and health. However, by identifying soil compaction with a soil penetrometer and implementing appropriate solutions gardeners and farmers can improve their soil health and ultimately produce healthier plants. At SoilScopes, we're excited to offer our new soil compaction assessment service to help our customers achieve their gardening goals.