Thatch and Scalping
Two words that I have heard in the same sentence from lawn care professionals in the last week. The operative word here is professionals. Ask one of them what thatch is and wait for the answer. Most of the time I hear, “The leftover grass cuttings from mowing.” Let’s take that one first and save scalping for later.
What is Thatch?
Thatch is indeed a dead layer of organic matter between the top of the soil and the green stuff growing above. It is, typically, not leftovers from mowing. Grass clippings, by and large, are very fine and thin. They break down rapidly into organic matter. Thatch is a layer of rhizomes, stolons and stems from the grass itself. Bermudagrass spread by sending out rhizomes. Rhizomes are technically stems that grow horizontally just below the surface of the soil. Stolons are long stems that run across the surface of the soil and take root at every opportunity from a node on the stem. These make up the majority of what is termed “thatch.”
Another Question about thatch
Look at the picture to the above of the sample taken from a lawn. You can see the tops of the turf and the crowns of the plants just below the green stuff. The material that looks matted is the thatch. Of more interest is the soil. Look at the soil. It is hard and compacted. There is no fluffiness apparent. There are also no worms. I would expect to see at least five earthworms in a shovel full of healthy soil. This is not a healthy lawn.
The guys I talk to agree and then continue with the argument that it doesn’t matter what makes up thatch, it has to be removed mechanically or it will damage the lawn. I ask them how wild bermudagrass plots thrive when there isn’t anyone around to dethatch them. No one seems to have the answer, so I go on to explain that the presence of thatch in a manicured lawn is not a problem with grass cuttings or a lack of maintenance, it is an issue of soil health.
In healthy soil, that huge mass of living organic creatures that we call the microbiome take care of the thatch. As the stolens and rhizomes die, the natural course would be for the chewers and grinders to break those heavy organic pieces into smaller chunks. These smaller chunks are further processed by the digesters (earthworms and the like), and finally, the micro-organisms would have their chance to convert all that organic material into nutrients that would be returned to the turf grasses up above.
Too Much Help
So why doesn’t that occur? Simple. We get in the way. We try to help.
Take fertilizer. Your typical lawn fertilizer is a mixture of synthetic salt-based products that contain a combination of three nutrients, Nitrogen, Phosphorus, and Potassium. All required by plants to grow. Using a basic lawn fertilizer puts a huge amount of these three nutrients into the soil. The plants rush to uptake them and we see a satisfying surge of nice green grass. But what else is really going on beneath the surface? The first thing that happens is you water to get those nutrients into the soil. If your soil is not healthy, the water-soluble fertilizer does what it is supposed to do and dissolves. It then washes away with the runoff from your compacted soil. If by chance, your soil is still healthy enough for the water to infiltrate, a large portion of those nutrients infiltrate right on down to a depth that your plants cant reach. Wasted effort.
When the help is not helping
Now your turf is happy and green. It doesn’t need the micro-organisms that should be in the soil. You see, it is that microbiome that would normally be providing all that N-P-K as well as the 17 or other nutrients that healthy plants require. If the plants are not sending out the chemical signals to the bacteria to provide the nutrients, the bacteria go elsewhere as do the fungi. Without the bacteria, the larger creatures such as protozoa don’t have enough to eat and they leave and so on up the food chain until you don’t have a microbiome left.
Without the fungi and bacteria, your soil cannot form aggregates. Aggregates are the tiny clumps fo sand, clay and organic matter that keep your soil fluffy and light. The aggregates provide the open space in the soil for water and air to infiltrate and for the organisms of the microbiome to live. No aggregates and you get hard compacted soil with no life.
Now, no life means nothing there to break down the thatch, which gets thicker and thicker, further exacerbating the problem in the soil. I think you see where I am going with this.
Feed the Soil, Not the Plant
The solution is not to dethatch the soil. The solution is to bring life back to the soil. I didn’t even mention the use of herbicides and pesticides, all of which contribute to the death of the soil microbiome. If the stuff you spray will kill weeds and pests, it will kill the good bugs and bacteria in the soil.
The picture above shows turf growing in healthy soil. Notice the fluffy look of the soil. It is aggregated into clumps and has a deeper darker color, an indication of the presence of a lot of organic material.
In brief. Stop using chemicals. They are not the solution, they are part of the problem. Don’t feed the plants, feed the soil. Apply a layer of high-quality compost to your lawn twice a year. Use natural herbicides to control the few weeds that may appear. A 10% vinegar solution works well. Water correctly. For more information on a good organic turf system, see our website. Direct links to some of the articles are at the end of this article.
The Real World
I use this same system on my turf. I have added a few pictures of our September lawn. Remember. I don’t use any synthetic fertilizers, herbicides or pesticides.
My front lawn. This is bermudagrass. The picture doesn’t do it justice. It is thick, green, and healthy with no synthetic fertilizers or other toxic chemicals.
Our backyard from the patio. The bermudagrass here lives under the shade of a large pecan tree, the fence on the east side and the house on the west side. Direct sunlight is limited to a few hours a day at most.
With that out of the way, let’s look at the issue of scalping. This is what I hear when I ask that question.
- Fall scalping gives grass a kick start in the spring after going dormant.
- Scalping can eliminate thatch.
- Scalping can protect your lawn against diseases.
- It allows sunlight to get to your soil which is beneficial to lawn growth.
Ok. Here we go.
In the fall, your turfgrass is storing nutrients and carbohydrates in the root system to sustain it when it is dormant during the winter. No, the roots do not quit growing in winter. Only the tops of the grass quit growing. If you scalp your lawn in the fall, you stress the turf when it is working its hardest to prepare for winter. Far from giving it a kickstart in the spring, you may be setting it back.
Scalping won’t eliminate thatch unless you are running the mower so low that it is leaving bare ground behind. See the above discussion about thatch.
Scalping does nothing to prevent disease or pest infestation. In fact, if you stress your turf too much, you weaken it which is like putting out a welcome sign for diseases and pests. Healthy plants have defenses and immunities to most disease and pests. It is when they are stressed that they become easily attacked.
Now this sunlight issue. What happens when sunlight gets to bare soil? The UV portion of sunlight is a natural sterilant. That means that sunlight, hitting unprotected soil, tends to kill all the microorganisms in the top few inches of soil. We also know that nature hates bare soil and has a whole host of plants that it uses to keep soil covered. Most of these we refer to as weeds. Bare soil in your turf is an open invitation to a new crop of winter and spring weeds every year.
The same is true for spring scalping. A healthy lawn with healthy soil beneath should never be scalped. Period.
The Final Word
So there you have it. Healthy soil equals a healthy lawn. Thatch disappears, grass grows, and weeds don’t. Scalping only opens your lawn up to more problems such as stressed turf, more weeds, and more expensive maintenance.
Links and References
For more information on organic systems of turf maintenance, visit our website at West Texas Organic Gardening.
More specific information can be found in these articles. These are only a few of the articles that are relevant to organic soil and turf management.