Lawn Soil – Understanding Soil Conditions For Growing Healthy Grass and Turf


Summary: Improving lawn soil and the health of any lawn is more than fertilizing grass, watering the lawn and mowing. The health of the grass often depends on what is below the green turf, the makeup and organic composition of the soil the roots of a lawn grow into.

Question: We think our lawn soil is not very healthy. The grass in our lawn does not grow well.

We wanted to know what lawn treatment or soil conditioner we could add to improve the quality of the soil before either laying sod down or seeding the lawn. One neighbor says to add sand and another says to add organic matter. What is the answer to our lawn problems? Clint, Jacksonville, NC

Answer: Clint, it would be helpful for you to gather some basic facts about your lawn soil.

Do this before taking any steps with lawn treatments, adding soil conditioners, dumping sand or working in organic material in the soil.

Most of “lawn knowledge” needed is simple and easy to learn.

Many homeowners under estimate the importance of lawn soil quality and how it relates to the success they will have in growing a beautiful, lush lawn.

Never forget – “All lawn soils can be improved” – none are perfect or measure up to the ideal grass growing standards.

Understanding what soil conditions make for growing healthy grass clippings and a thick lawn, make the task of lawn care much easier.

Soil Comes In Layers

For lawn grasses to achieve their best growth, they should at a minimum have 5 or 6 inches of good, rich and well-drained soil.

Some would say that “lawn soil” goes down as deep as you can imagine. To be more correct what we are talking about is 5 -6 inches of surface soil.


If you look at a soil structure cross section of soil strata, you see basically 3 layers:

  • The bottom layer or porous substratum which is not soil but decomposed rock
  • The middle layer or subsoil is very low in fertility but does hold moisture
  • The top layer or soil surface where organic material, nutrients and biological activity are at the highest. This could be for several inches to several feet deep.

Remember, the deeper grass plant roots grow, the better for the health of the grass clippings. It is very possible, depending on the grass type for the root system to reach downward 24″ – 30″ inches.

The real growth of grass plants occurs in the surface soil. The subsoil is very low in nutrients. Grass roots want food so do not venture much into the subsoil.

However, the subsoil functions as a moisture reservoir for the surface soil as it yields some of its moisture as the surface soil becomes dry. The moisture “released” must be replenished and that is one reason why deep watering a lawn is a good idea.

Good Soil Has Room For Both Air And Water

Regardless of the depth of the surface soil, grass roots must have moisture and air.

Moisture helps break down and dissolve the nutrients the grass and soil needs before the tiny root system can absorb them. The moisture also serves as a water fountain the grass plants require.

However, without air, the root system stays saturated in water, suffocates and rots.

When it rains naturally or through a sprinkler irrigation system the surface soil absorbs and holds the water and the rest of the water drains down through the soil surface into the subsoil.

The subsoil replenishes the water and moisture it needs and passes the rest down into the porous rock. As evaporation and transpiration occur, air replaces where the water was.

Surface soil is a “system” which absorbs moisture, gives up moisture, breathes and repeats.

NOTE: An irrigation specialist advised me to add a lawn surfactant when irrigating my lawn to make sure the water penetrates the soil.

In a perfect scenario everything works to perfection, but as we stated above there are no perfect lawn soils. Soils can become dry with too much air and also water logged starving for air.

If your soil holds too much water and does not drain or too little water, that is where you need to start improving the soil for your lawn.

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