How to Firm up Soft Soil (6 Proven Methods)

If you can’t walk across your lawn without your feet sinking into the ground, it’s time take to take action. But before you do so, it’s important to learn what’s caused the soil to become soft in the first place.

Soft soil is caused by a number of issues, which include waterlogging from insufficient drainage, lack of aeration, lack of decomposing matter, and lack of stones, gravel, and rocks in the soil. An analysis of your soil can help you to address these issues. You can further harden the soil using a lime or bitumen stabilizer.

What Is Your Ground Made up of?

There are few places on earth with perfect soil conditions, and it is like winning a scratch card if your soil ticks all the boxes. Soils come in a range of densities, nutrient levels, and drainage rates, which can give you either hard or spongy soil.

The hard soils that offer excellent drainage are often dry and lack the nutrients that vegetation needs to thrive. Soft soils will give you perfect levels of pH, but they may have problems draining excess water and can go boggy in rains.

These are the most common soil types:

Clay Soil

The fine particles of silts that make up clay are an excellent source of nutrients for grass, tree, and other plants. Clay sits within a pH of 5.5 to 7.0, which is perfect for grass, delicate flowers, and fruit-bearing plants.

The biggest problem with clay is that it is so compact and muddy when wet that it forces most of the air out, depriving the roots of oxygen. And when clay dries out in the summer, it can be so dense that roots struggle to break through and get enough nutrients and water.

Sandy Soil

The roots of plants tend to prefer soil with good drainage, but this can mean supplying a lot more water. Sandy soil is a mix of small- to medium-sized grains of rock and mulch, which creates plenty of air cavities for the roots.

The loose structure of sandy soil makes it easy for roots of both large and small plants to grow through. Irrigation will wash nutrients straight through sandy soils, so you will need to keep adding fertilizer. And sandy soils tend to sink after heavy rainfall and can develop dips.

Peat Soil

Peat is a natural product, dug up from beneath growing moss, with few developing microorganisms. Compost is decomposing organic matter that anyone can manufacture to whatever pH level is necessary using a dual chamber tumbling composter.

Peat and compost have low densities and feel squishy in texture. They will crumble apart in your hands and feel spongy underfoot. Peat and compost soils have trouble holding on to water and dry out in the summer, making the ground even softer and less stable.

Stoney Soil

Many gardeners will add stones to the soil to improve drainage. Stones prevent compaction and help hold in pockets of air for the benefit of root systems. Porous stones will also soak up water and slow-release it, rather than letting it all drain away, which is good for sandy and peat soils.

Limestone will neutralize soil acidity, which can be a good thing in clay soils with high pH levels. The main issue with stones is the appearance, and if you are trying to cultivate a flower bed, small stones and rocks can make it look untidy.

What Causes Soft Soil?

You need to start by looking at what the issue is and then consider if it is bad enough to call for action. Drainage and aeration are semi-linked and simple to remedy.

Fertilization can be a more involved process if the soil is dry and solid. You may also need to take the plunge and use an electric tiller/cultivator.

Drainage

Soft and squishy soils after often the result of waterlogging, where the soil is so dense that it refuses to let water drain through. This can create pockets of mud beneath the soil or turf, which makes the ground feel unstable and mushy.

Aeration

The roots of plants prefer soils that offer them consistent access to oxygen but with a decent amount of nitrogen and water. Aerated soils can drain water away faster than dense soils, and allow roots to grow deeper, which will also help firm up the ground.

Compost

A lack of decomposing organic matter in sandy soils will make it feel soft. Roots will grow to wherever the food is. If the food is at the surface of the soil, the roots will grow horizontally, not downwards, which is what you need to firm up the soil.

Stones

All compost, sandy, and clay soils lack the solid material to stop them from moving around while you walk over them. Small stones, gravel, and rocks all stabilize the soil and prevent erosion from the wind and rain.

How to Firm up Soft Soil

Most soils enjoy some form of texture blending, whether it is soft sandy soil that needs more compost or adding stone chips to clay soil for better drainage.

Here are a few more things you can do to improve the hardness of your soft soil:

Stone Chips

This is an inexpensive but labor-intensive solution, where you can mix gravel or small stones into the soil. This works well in muddy clay-type soils where you want to improve drainage and aeration. The stones will also make voids for the roots of your plants to grow between.

Compost

Compost or wood mulch mixed into the soil will help improve drainage and the soil to dry out. Though it is a type of fertilizer, mulch can even help when mixed into clay soils and prevent compaction in the summer when it dries.

Aeration

If you have problems with the soil going solid in the summer and mushy in the winter, try aeration shoes. This will help the soil dry faster after heavy rain without compacting the soil further.

Aerating will allow nutrients to work further into the soil and encourage the roots of plants to grow deeper and spread out more, firming up the soil.

Drains

Depending on your climate zone, your biggest issue may be that you get too much annual rainfall. Even sandy soil can become waterlogged, creating mushy soil if it does not have time to let the water soak away.

For localized muddy spots, you can install storm drain covers into the ground, which you can open during flooding. This involves drilling down for the water to seep far below the topsoil. Or installing a drainpipe and connecting to your main drain system.

You can also install a French drain, which is a porous pipe that you bury a few inches beneath the topsoil. You will then need to dig channels around your garden to lay the pipe in and cover it with gravel and topsoil.

Lime Stabilization

Both lime and cement can help with unstable soils. You can work either powder into the soil without extra water. Lime is better for clay soils that are always muddy. Cement will cure and harden up the soil and give it more structure.

Bitumen Stabilization

Bitumen is a waterproof compound like that of road tar. The idea is that less water can make its way into the soil, stopping it from getting muddy. Bitumen will also bind the soil together, but this is more of a radical final solution for stabilizing soil.