Top Dressing With Compost - Austin - Top Choice Lawn Care

Austin area soils are famous for their poor quality. Ask any avid local gardener, and they will give you a list of their soil woes. Ultimately it comes down to the fact that we have very little soil, the soil we do have is rocky, and it’s full of clay. 

This poor soil is hard on lawns. There is a huge list of things lawns need to be happy, but several of the big items are sunlight, air, water, and nutrients. Soil quality can have a big impact on three of these four items. Plants absorb water, nutrients, and even air through their roots.  As a consequence, soil quality can have the biggest impact on the health of your lawn.

A good soil will have a lot of organic matter in it to provide nutrients, will have the capacity to hold water, and will also be able to drain well so the soil can dry out.  A soil’s ability to do those three things is impacted by the type of soil and the soil structure.

Central Texas Soil Types:

There are three main types of inorganic material that all soils are made of. These particles are called clay, silt, and sand. Clay is the smallest particle size, and is “sticky” — the chemicals that form clay bond to things easily. Silt is only slightly larger than clay but doesn’t bind to things like clay does. Sand is the largest particle of the three, and drains very well and resists compaction.  An ideal mix is called loam, and is a mixture of all three in roughly equal proportions. Combining loam with organic material creates the perfect soil. 

Because our soil consists of mostly clay, with very little organic material, it doesn’t drain very well and has very few nutrients. The clay binds with water as soon as your irrigation kicks on. The top layer of soil will saturate quickly, preventing water from soaking deep into the soil. If you continue to add water, it will run off the soil rather than soak in. This is one reason we are so prone to flooding in our area.

The clay also binds to nutrients like fertilizers, but it binds in such a way that those nutrients aren’t available for plants to use (clay is a bit greedy). Clay also binds to itself to create a compacted layer of soil that excludes air and is difficult for roots to grow through. On a hot summer day in Austin the soil can often feel harder than concrete.

Fixing Clay soil:

Unfortunately, there is no quick fix to change clay into perfect soil. What we focus on is changing the soil structure, rather than try to change the type of soil. You improve the soil structure by breaking up the compacted clay and adding organic material. This gives the clay something useful to bind to, and it is a material that combats every problem that clay causes. The organic material will improve drainage, resist compaction, and both holds and releases nutrients and water. 

Clay soil mixed with a lot of organic material is transformed and behaves more like an ideal loam soil. Water can seep deeper into the soil, it resists compaction, and plants love it.

In nature, organic material is added to the soil slowly over decades. Plants grow and die, leaves fall, and other organic materials fall into the soil. As this natural organic material decomposes, it is incorporated into the soil by worms, insects, fungus and bacteria. The same is true in our yards.  Grass clippings, leaves, and other debris are typically mulched by our mowers and the organic material gradually becomes a part of the soil.

This is where top dressing steps in. It is the best way to add organic material to a lawn. Top dressing is a shortcut, where we spread that thin layer of compost-rich soil over the lawn.  Our compost soil blend is a mix of 50 percent compost and 50 percent loam — basically perfect soil. 

What is compost?

Compost can consist of many things, but it is a general term for organic material that has already started the road to decomposition and incorporation into soil. It is not a raw material. It has been processed by bacteria and fungus (100% natural process) into a form that is immediately useful and beneficial. 

Compost and other organic materials are used up over time. It’s basically what the plants live on, but bacteria and fungus also continue to break down the organic material. At the end of the process, we end up with a material generally called humates. Humates are amazing for plants and soil. Water-soluble humates are often included in fertilization programs (including ours!), but it takes tons of compost to produce a small amount of humates. 

What this means is that organic materials and compost need to be added to the soil regularly. People generally add tons of organic material to their planting beds without even thinking about it. In beds we call it mulch, and it adds a lot of organic material. Ever wonder why your grass seems to grow better in your planting bed than your lawn? Now you know.

Top dressing with compost adds those same much needed organic materials directly to the lawn.  We don’t mix them into the soil, mostly because it would damage the lawn. But, generally the grass will grow up through the top dressing and the compost is incorporated directly into the lawn. Over time, worms and insects will help mix this thin layer in with the existing soil.