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 our lawns which filters rain, absorbs CO2, and keeps the grass 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 and food. Yet, grass is a plant like any other and requires a functioning, thriving soil ecosystem just as our gardens do.

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 many 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.

Water needs to flow through your lawn’s soil

In a healthy 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 aquifer. This is an extremely important process, especially as we enter an era of more frequent droughts. But when the topsoil is hard-packed and becomes 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 and local waterways, along with everything it picks up en route.

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 for a time and effectively drowns. It starves to death because the roots can’t absorb air and the plant 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.

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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 the soil, and aid in building and supporting insect life, microorganisms, and soil tilth. 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, is fed by humic acids which derive from humus, mature compost. Humic acids are produced by the biodegradation of dead organic matter. Those eggshells 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 this complex plant food.

Justus von Leibig invents fertilizer

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 synthetic fertilizer industry and some would argue, the slow destruction of soil. Leibig wasn’t wrong in principle – nitrogen is most definitely a key component in plant nutrition and can definitely be synthesized from ammonia. 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 the 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 and helping to prevent or slow flooding. 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 lawnmower – autumn tree leaves are a great 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.