Do you have an area of your lawn where personnel are constantly walking? Maybe not just personnel, but you also have equipment going through that area all the time? Are there all sorts of personnel walking in the same areas…personnel coming in and out of the house, in and out of automobiles, delivery personnel or postal personnel? Does your mower or other equipment have to go a certain route on your turfgrass every time? This is what I call a “high traffic” area.
For example, at the gate to my backyard, there is an area that has a difficult time growing turf. Any person or piece of equipment (mostly my lawn tractor) that has to go in to or out of my backyard has to pass through that gate. That turf is always beaten down. And, it looks even worse in the summer, especially during times of drought stress or heat stress. And, that area happens to be under a great deal of shade. So, I’m out of luck on many counts.
When your turf is being trampled, there are basically two things going on. First, there is direct, physical damage being done to the turf plants. Second, the turf may suffer the consequences of soil compaction. The kinetic effects on the turf leaves are self explanatory. The soil compaction may not be so self explanatory. Compacted soil hinders root growth, water penetration and the take up of necessary nutrients. Compaction occurs when soil particles are pressed together. That pressing together of the soil particles eliminates the pore spaces in the soil that are required for air and water. As many of us know, soils high in clay content are more susceptible to compaction than soils higher in sand or silt.
What causes soil compaction? In agriculture, it is usually rain, improper tillage, minimal crop rotation and wheel traffic. Those all contribute to compacted soil on the farm. In your yard, it is usually foot or wheel traffic. Real hardcore pedologists (Like me!) use the term “bulk density”…the bulk density of soil. Bulk density is a measure of a soil’s mass per unit volume of soil. It is used as a measure of soil wetness, volumetric water content, and porosity. Factors that influence the measurement include organic matter content, the porosity of the soil, and the soil structure. A soil that has a well developed structure will become less dense as porosity increases; as a result the bulk density of the soil will decrease. Soils which show massive structures and less porosity will show higher bulk densities. This blog post will go full circle. More on soil density later.
As I’ve said several times throughout this blog, species selection should be the first consideration if you want to take on this problem. Different types of turfs vary in their ability to tolerate wear. Now, I’m here to tell you, if an area has real excessive (and I mean a whole lot) of foot and/or wheel traffic, no turf is going to stand up to it. What is real excessive? Well, I’d say that would be constant movement over an area. Not a turf on this planet can handle huge amounts of traffic.
Yet, if there is a moderate amount of traffic, there are some species that are better than others. The most tolerant warm season grasses are zoysiagrass and bermudagrass. Of the cool season grasses, perennial ryegrass and tall fescue are pretty tough. Kentucky bluegrass is fairly tough but rough bluegrass and colonial bentgrass are terrible.
Here’s a quick, final thought on species selection. My lawn is primarily tall fescue. In fact, you could call my lawn a “cool season blend”. Remember – a mix is comprised of more than one species of turfgrass; a blend is when there is more than one cultivar within a species. One of my goals for my lawn is consistency. I would not want to plant, say, zoysia in that area on each side of my backyard gate. It would look different. It would ruin my lawn’s consistency, and possibly spread. So, planting a patch of a different species in that area is not really desirable for me.
There are some management practices one can do to enhance your turf’s tolerance to traffic. One thing I say all the time – for many reasons, now this one - mow your turf high. We know that longer turf leaves have more leaf surface exposed to the process of photosynthesis. And, mowing higher encourages deeper roots. Also, mowing is always a stress. Perhaps mowing that area less goes hand in hand with allowing the grass to be longer and will help it deal with traffic better.
Small amounts of thatch are acceptable. If you read my blog post titled “Thatch”, you know I have said you should not have more than half an inch of thatch. That still holds true. But, having a small (less than 0.5 inch) layer of thatch can provide a cushioning barrier. It keeps the turf leaves from actually getting crushed.
From a fertilizer perspective, another thought is to reduce your nitrogen application. An excessively thick and lush stand of turf is more susceptible to damage. Increasing your potassium application will also increase the wear tolerance of your turfgrass.
The only way to alleviate soil compaction is to core aerate. Like many golf courses, core aerating more than once a year is an excellent thing to do, even if you don’t have compacted soil. Those compacted cores are removed and replaced with holes that allow greater air and water movement. Turfgrass roots grow into those holes and are exposed to air, nutrients and water. If I could, I’d aerate my lawn at least twice a year – once in the fall and again in the spring. Although most compaction is found in the top two inches of the soil, the deeper the cores, the better the results. Read my blog post on “Aeration”.
Finally, some (other) experts say a light topdressing of sand after the aeration will change the soil texture. I’m not a big fan of that. Why? Because most homeowners don’t do that correctly. Golf course superintendents get it right…most of the time. It must be a VERY LIGHT topdressing. And it should only be done in certain circumstances and in certain locations. Messing up your soil texture is very difficult and very expensive to reverse. As I said in my “Establishment” blog post, just putting down 1 to 2 inches of sand can cause “layering” of the soil. When soils have these layers, the layers can become impermeable. When you have impermeable layers in your soil, that is another different set of problems. Having compacted soil pales in comparison to the problems posed by layered soil. If you have layered soil, might as well rent that bulldozer with the huge soil ripper attached to it. You want to add something to your soil after aeration? Add organic matter like humus, peat or other soil conditioners or soil amendments like that.
While I’m thinking about it; let me say this. Gypsum will not break up compacted soil. It will increase the calcium content of your soil and the salt content of your soil. The use of sulfur has also been incorrectly acclaimed to break up compacted soils. Sulfur has an acidifying effect on a soil. Adding sulfur to a calcareous soil (soil mostly or partly composed of calcium carbonate) only creates gypsum (calcium sulfate). All of this will mess with your pH level. Don’t use any of these things for compacted soil. Really, the basic solution for compacted soils is to physically manipulate the soil. There are no short cuts when dealing with compacted soil. There is nothing you can just pour out of a bottle or dump out of a bag to fix it.
I guess I’ve said enough about dealing with high traffic areas in your turfgrass. This sort of turned in to a block of instruction on compacted soil.
If what I’ve laid out here doesn’t really apply or does not work, well, perhaps this is one of those battles you should withdraw from and live to fight another day. I hate to say it. Maybe you should do something to manage traffic flow. Raising your garden beds, establishing a walk way, installing a fence or garden wall (like a "hard scape" solution), mulching…these can all be alternatives to having a hard soil bare patch in your beautiful lawn.