The thriving ecosystem in your lawn’s soil and why it matters

Grass is the most cultivated plant in the U.S., but we neglect the ecosystem in the soil underneath which filters rain, absorbs CO2, and keeps your lawn well-fed.

We don’t think of the grass growing in our lawn like we do the plants growing in our gardens. One is to walk on and play on, the other to cultivate for ornamental purposes or for food. Yet, grass is a plant like any other and requires a functioning, thriving soil ecosystem just as our garden plants do.

lawn soil

We take great pains to not walk on our gardens, but we trample our yards into bare patches which become compacted as hard as cement. We cut our lawns weekly, frequently too low to the ground and don’t think of them as plants the way we do our hydrangeas or our tomatoes. Yet left untended our grass will flower and set seed just as most of our garden flowers and vegetables will. In fact, let your grass grow all summer and it will seed itself. Your lawn will fill in quickly without any help from you.

In a perfect lawn, rainwater filters quickly through the grass and the topsoil, and on its way down, carries nutrients to plant roots. The water continues down through the subsoil and eventually replenishes the local aquifier. This is an extremely important process, especially as we enter an era of more frequent droughts. But when the topsoil is hard packed and the density of cement, water simply runs off as it does on a street or pavement. Water winds its way across lawn after lawn and what doesn’t get absorbed by healthy soil is lost to storm sewers.

Unless and until that water hits a low point in your yard . There the water sits…and sits..until it evaporates. The grass is submerged underwater and starves to death, because the roots can’t absorb air and the blades can’t perform photosynthesis. The water also encourages the establishment of molds and anaerobic bacteria, which easily infect the already starving grass, setting up a cascade effect of disease and pest infestation. Proper grading of your property is part of the solution, but most important is to slow the runoff and allow the water to be absorbed by your lawn.

Forget about lawn chemistry and focus on lawn biology

Compost and organic materials like mulches serve a number of purposes, whether applied to your lawn or garden: they insulate plant roots and soil from harsh weather, help to hold moisture in soil, and aid in building and supporting insect life and microorganisms. It’s the insects and earthworms that create the majority of paths and tunnels in the soil through which water passes.

Your lawn, like all plants, are fed by humic acids which derive from humus, mature compost. Humic acids are produced by the biodegredation of dead organic matter. Those egg shells you throw into your compost pile eventually break down into their most basic chemical components and when mixed with the chemical components of other organic material, create a complex plant food.

In the 19th century Justus von Leibig recognized this principle. Leibig, a German chemist, was the first to suggest that nitrogen could be supplied to plants in the form of ammonia and substituted for natural fertilizers like animal manures. Hence the birth of the chemical fertilizer industry and the slow destruction of soil. Leibig wasn’t wrong in principle – nitrogen is most definitely a key component in plant nutrition. But he missed the fact that the soil the plants grow in requires multiple organic compounds to support the plants and protect them from disease and pests . Only now are scientists beginning to accept the importance of restoring intensively farmed soils with organic materials in between crops. It’s clear that chemical fertilizers acidify topsoil, discouraging insects, bacteria, fungi, and earthworm activity. Dig a block of soil from a yard that’s been chemically treated for years and you’ll see that it’s virtually lifeless.

When your lawn is supported by soil teeming with microbes and insects, passageways for water and air will be plentiful, rainwater will quickly filter through topsoil, roots will be fed, the grass will remain healthy and the need for nourishment beyond mulched grass clippings will be unnecessary. A high performing lawn will absorb more than its fair share of torrential rains, reducing runoff into the public storm sewers and watershed. It will also remain amazingly resistant to compaction and the effects of drought, as the grass’ roots will plunge deep into the soil where they will stay cool. Plus, when you create conditions for grass to thrive, weeds become irrelevant, as they have nowhere to grow inside dense, thick clusters of grass.

How to get your lawn in shape

  • Mulch tree leaves every fall with your lawn mower – autumn tree leaves are the ultimate source of nutrition for your lawn
  • Aerate your lawn in spring for three successive years and apply finished compost. You can also use mushroom compost, corn gluten meal, or bagged manure
  • Make sure the blade on your mower is a mulching blade and keep it sharp so it will grind grass clippings and leaves into a fine mulch
  • Do a little detective work: Dig up a 12×12 square of your lawn and examine it: How deep do the roots penetrate? How dark is the soil? How many inches deep is the darkest soil? Dark is good – it means your soil has good tilth.

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About Todd Heft

Todd Heft is an organic gardener and freelance garden writer who lives in the Lehigh Valley, PA and has gardened for most of his life. When he isn't writing or reading about organic gardening, he's gardening. His first book, "Homegrown Tomatoes: The Step-By-Step Guide to Growing Delicious Organic Tomatoes In Your Garden" is available on Amazon now. Google

3 Responses to The thriving ecosystem in your lawn’s soil and why it matters

  1. Nice to see this written on the internet. I’ve told folks on occasion that they should spread or have compost blown on their lawns.

    Also, I think aerating is so good, is should probably be done to lawn in the landscaping twice or three times over.

    Some services sell the service prematurely when soil is mushy, and home owners need to watch out for that, and wait until they can poke a hole in the ground, step on it, and the opening not squash shut.

  2. Kris Lord says:

    Great tips from a slightly different angle, which is great to see.

    Aeration is the single most beneficial thing you can do to any lawn, as keeping the soil from becoming compacted will allow the grass to thrive and the organisms in the soil to do their work properly.

    If your lawn is becoming thin and lifeless, you don’t need to throw chemicals on it, just Aerate it to bring it back to life!

  3. Qa Program says:

    Thanks for your nice post. You put a nice twist to it. Nice work Todd.