Summary: The best soil for a lawn is a loam soil, a soil that drains well and contains – clay, sand and humus – in the right proportions
Question: We want to improve our lawn soil, it is a very clay soil lawn, what is the best soil for our lawn? What can we add as soil conditioners? Nathan, Columbia, SC
Answer: Nathan, soil poorly or well drained boils down to the space in the soil, the size of the pore spaces, the little spaces and cavities that exist between the separate soil particles. These spaces in the soil all depend on the elements which make up the soil media and in what ratios they are all put together.
From a working perspective the overall makeup of soil comes from 3 different ingredients:
Mud, we’ve all seen it, wore it or got it on our cars – that is clay. Most people know what sand is, somewhere along the line people have seen a beach in person or through pictures. However, not everyone knows what humus is.
Humus is the end result of organic matter that has decayed, or dead animals and dead plant material. When living things die they over time become soil, as micro-organisms feed on, breakdown and convert the animal or plant in what we call humus. This is the substance which gives soil on the surface its black or dark brown.
For a healthy lawn the soil needs to drain well, be rich in nutrients, breathe and grow a vibrant root system. For the lawn soil to drain well it needs – sand, clay and humus – all in the right ratios. Since you describe your soil as very clay, this means the pores spaces are very tight, does not drain well and holds too much water.
For those who have more of a sandy lawn soil, the soil has pore spaces which are large and do not hold enough water. When sand, clay and humus all come together in the right amounts, the humus acts as a “glue” to bind all the materials to create a soil that has large and small pores that holds both moisture and air.
Lawn Soil Like Post-it Notes
This is the type of soil which can very loosely be described as loam. It is sort of strange, people know it almost by instinct when the come in contact with this type of “perfect soil”. It is sort of like “post-it notes”, they stick to some things but not like tape. A good loam soil cannot make a mud pie when it is wet, but it also does not fall apart when it is dry. All the soil particles, sand, clay and humus hold together in small clusters made up of smaller granular structures.
This it the best type of soil for a lawn – the surface soil. A soil which allows the root system to grow and stretch its roots, breathe and hold a rich reservoir of nutrients to create a lush carpet of grass, inviting the kids to play and calling for the lawn mower to give it a trim.