A nutrient-rich soil with the right balance is critical for a healthy lawn. It is probably the most significant factor for growing beautifully lush turf. Almost any problem associated with your lawn, be it a disease, weak growth, weeds, or pests, can usually be narrowed down to your soil. To achieve healthy soil, it is vital to understand the basics of soil composition.
Ideal Soil Composition
The most suitable soil for growing grass is called loam soil. It is a combination of silt, sand, and clay that has both water and nutrient retaining properties while providing enough air-flow and drainage to allow excess water to run off without washing away essential nutrients. Good loam soil conditions are comprised of 40% silt, 40% sand, and 20% clay. If it has a larger quantity of sand, it is called sandy loam. More silt is called silty loam, and more clay is known as clay loam. Clay is the smallest of particles contained in loam. It feels sticky and can often stain the fingers. Silt, on the other hand, feels smooth and slick. Sand is the largest particle found in loam and feels gritty.
The components of loam and their concentrations will determine how soil will handle how it holds onto and drains water. Clay loam will retain a lot of water, but it will drain poorly. On the flip side, sandy loam allows for good air flow to the roots and good drainage, but it can drain too quickly, leaving water unavailable for thirsty plants.
Layers of Soil
Soil is actually made up of four distinct layers. The top layer is comprised of organic matter. Dead leaves, insects, grass clippings, plants, and dead insects make up this uppermost layer of soil. Below the layer of organic material is topsoil. This is the layer where most plant growth occurs. Plants take root in topsoil, which is composed of air, water, organic material, gases, and minerals. The second layer can range in thickness from 6″ to 20″ in depth. Subsoil is the third layer and is made up of mostly sand or clay, and there is very little organic material in this layer. The final layer is bedrock, which is solid rock. Between the third and fourth layers of soil, there are typically smaller pieces of rocks that have broken off of the larger piece. These smaller pieces of rock are often referred to as parent material because most of the soil’s composition originates from the bedrock.
When we talk about soil and soil composition, most of the time, we are referring to the second layer of soil, which is what we call topsoil. As already mentioned, topsoil contains a mix of air, water, organic material, gases, liquids, and minerals. Each of these components can occur in varying levels throughout the same property. One section of your yard can have topsoil rich in organic material and minerals, whereas other areas of your yard can be significantly lacking many resources necessary for plant growth.
Air – Even compact soil has some air within it. Over three-quarters of air is made up of nitrogen, which also happens to be a critical element for healthy turf. Oxygen is the second most abundant element of air making up around 20% of its composition and is a by-product of photosynthesis in plants. Argon and carbon dioxide are both found in quantities of less than 1% each with carbon dioxide being a necessary compound for photosynthesis.
Water – It should come as no surprise that water molecules are an essential component of topsoil. Water present in the topsoil layer is what helps to feed thirsty plants. Water-soluble nitrogen is soaked up through a plant’s roots and is part of a chemical reaction in the plants during photosynthesis.
Organic Material – Organic material refers to carbon-based compounds. These come from the detritus of organisms such as plants and animals as well as their waste. Organic material supplies nutrition to living organisms and acts as a buffer in water solutions to help maintain a neutral pH (or close to it). Things like stems, leaves, insects, and manure are all examples of organic materials that may be found in topsoil.
Gases – Gases can form in topsoil as a result of decomposition and are often a by-product of aerobic metabolism. Methane, carbon dioxide, and nitrous oxide are all examples of gases that can be found in some quantity in topsoil.
Living Organisms – This includes anything from fungi to earthworms to bacteria. Many organisms are living in topsoil and help to create a healthy ecosystem and contribute to the organic material that helps to make up good quality topsoil.
To achieve the best results from your soil, it helps to know what you’re working with so you can correct any issues. You can test your soil yourself by picking up a kit from a home improvement store. Soil test kits are relatively inexpensive and are relatively simple to use. If you are going to test your soil, it is important to take many samples from different areas of your yard. As previously mentioned, different areas of your yard can have vastly different soil properties and composition. You will want to take as many as 20 core samples to get an overall better picture of your soil health. If you are not comfortable taking your own soil samples, many professional lawn care companies will take soil samples and analyze the results to determine the best course of action.
Make Adjustments for Healthy Soil
Once the results of your soil testing have been determined, you can analyze the results and make necessary adjustments to your soil to achieve the healthiest possible turf.
Soil Composition – This will tell you what amounts of your soil are sand, silt, and clay. If your analysis shows that you have a predominantly clay soil, you can remedy this by adding coarse sand, bark, or even sawdust to the clay to help with drainage. If your soil tests show you have predominantly sandy soil, you can add organic material such as compost or manure to help hold in some moisture for thirsty plants. Silty soil is often considered the most fertile. However, the fine particles of silty soil can be easily compacted, which makes it drain poorly. If your soil testing indicates silty loam, you can add compost or dried and ground pine bark to bulk up silty loam and provide good drainage.
Soil pH – The soil’s pH is an indicator of how acidic or alkaline your soil is. A pH between 0 and 7 indicates acidic soil, whereas a pH between 7 and 14 is considered alkaline with 7 being neutral. Ideally, soil pH should be slightly acidic, falling between 6 and 7. Soil that is either too acidic or too alkaline can affect the solubility of nutrients available to plants. Correcting soil pH to provide the perfect environment for healthy turf is relatively easy. For acidic soils, lime treatments can help correct the pH and bring it to a more neutral number suitable for turf growth. To balance alkaline soils, common sulfur is typically the least expensive option though ferrous sulfate or aluminum sulfate may be better options. To lower the alkalinity of soil over time, regularly applying compost or manure can help maintain a more neutral pH. If you need to alter your soil’s pH by more than one point in either direction, it is best to hire a professional lawn care company to make the proper adjustments for you.
Soil Nutrients – These are essentially what is going to feed your lawn. The three primary nutrients found in healthy soil are nitrogen, phosphorus, and potassium. Nitrogen is the key element in plant growth and is found in all plant cells. Nitrogen is easily leached out of soil by over-irrigating or heavy rainfall. Phosphorus is important because it helps transfer energy from sunlight to plants. It also helps to stimulate root growth and also is what helps speed up the maturity of plants. Finally, potassium is what helps a plant remain resistant to diseases and increases durability. Other important elements in soil include calcium, magnesium, and sulfur. Calcium does for plants what it does for human bones–helps add strength during growth. Magnesium is important to aid in photosynthesis. Sulfur is involved in the energy processes of plants. The remaining minerals of iron, manganese, copper, zinc, boron, and molybdenum are found in trace amounts in soil, but all play roles in maintaining a plant’s overall health and vigor. Soil that is low on certain minerals or lacking altogether can be corrected by applying the right fertilizers to boost the appropriate mineral levels.
In some cases, soil can become polluted, which makes it unhealthy or unable to sustain healthy turf. This can occur as a result of atmospheric pollutants or through direct contact from materials spills. The most common form of land degradation that results in soil contamination is human-made chemicals. Petroleum-based hydrocarbons, solvents, pesticides, and lead are just a few examples of contaminants that can disrupt the delicate ecosystem. Cleaning up contaminated soil is not as simple as making adjustments for soil composition. In many cases, complete excavation is required to eliminate toxins from the environment. Depending on the type of contamination and severity, some environmental mitigation can include soil aeration, thermal remediation, or bioremediation may be used to restore healthy conditions.
Achieving healthy soil is often one of the most important factors to achieving a healthy lawn. The soil can be thought of as the birthplace of plants. Its contents help to nourish the life that emerges from it. Good quality soil will usually result in a healthy lawn. The perfect loamy soil will allow grass to absorb water while maintaining good airflow and drain away excess water. Many issues with turf growth stem directly from soil issues. Fungal infections, weeds, and drought can typically be managed by establishing proper soil conditions. Since most fungal issues in turf stem from over-irrigating, it is easy to understand why a good loam soil will help prevent disease from getting established. Weeds are frequently found in turf where grass is thinning. Thinning grass is often a symptom of disease or drought conditions–both of which can be managed by a healthy balance of sand, silt, and clay. What it comes down to is simple: healthy soil = healthy turf.