Your Guide to Different Types of Soil Amendments
We've said it before, and we'll say it again: healthy soil is the foundation of a healthy lawn. However, not all homeowners are fortunate to have ideal soil—nutrient-rich, well-draining, and moisture-retaining enough for optimal plant growth. Even for those who are, it's important to understand that soil is dynamic. Over time, various factors like nutrient uptake, leaching, runoff, and different lawn activities can deplete its nutrients or lead to compacted soil, ultimately leading to a decline in overall health.
In Florida, many homeowners face challenges growing healthy grass due to the varying soil conditions. Myakkah (pronounced My-yakah) is a unique type of sandy soil prevalent in the North and Central regions of the state. It has a gray, fine texture with marine origins.
Meanwhile, the panhandle soils often contain high amounts of clay, which compact easily and drain more slowly than sandy soils. In South Florida, soils tend to be peaty and fertile, requiring fewer amendments. But, further south, soils are shallow and have high pH levels due to the limestone bedrock.
What Are Soil Amendments?
Soil amendments aid in improving soil conditions by addressing physical soil properties, such as texture, pH levels, and nutrient content. Some amendments help relieve soil compaction, improve drainage, and allow for better nutrient absorption, while others enrich the soil with essential nutrients, increase moisture retention, or balance pH levels.
While not always necessary, a soil test is valuable for determining the necessary amendments for your lawn. You can perform a basic soil test using a kit available at local garden stores, providing immediate pH level results. However, consider sending a soil sample to a specialized testing laboratory for more comprehensive and accurate data. It can provide recommendations tailored to your soil's composition and the type of grass you plan to grow.
Soil Amendments and What They are Used For
It's easy to confuse lawn fertilizers with soil amendments, as both are designed to facilitate healthy plant growth. Whereas fertilizers are designed to add nutrients to the soil, soil amendments are materials that alter physical soil conditions. However, some soil amendments can also provide nutrients to the soil, blurring the lines between the two.
Continue reading as we discuss the common soil amendments for texture and drainage and their functions in more detail.
Soil Amendments Based on the Soil Type
Soil comprises rock particles and organic matter known as humus. It has varying clay, sand, and silt proportions and is categorized by the dominant particle size or percentage. The composition of your soil influences its various functions, such as water retention, nutrient-holding capacity, and erosion resistance.
Loam is the preferred soil type for most lawns, with a balanced clay-to-silt-to-sand ratio of 20-40-40. However, your soil may not be ideal initially, and soil amendments can help improve its quality, creating a better environment conducive to growth.
Clay Soil
Clay soil is characterized by having over 40 percent clay content. It is composed of fine rock particles that are talc-like when dry but heavy and sticky when wet. This type of soil forms dense, poor-draining soil that absorbs water slowly and retains moisture for extended periods, leading to waterlogging that can damage plants. Additionally, clay soil is prone to compaction, which prevents water, air, and nutrients from penetrating and reaching the plant roots. Compacted soil also limits root growth.
Correcting clay soil involves adding materials to break up its dense structure, improving water absorption, drainage, and airflow. Contrary to common belief, adding sand to clay soils can exacerbate its issues by creating a concrete-like structure. Instead, you can use organic matter like compost or the following soil amendments to improve the soil texture:
Organic Amendments - These include compost, well-rotted manure, and fibrous organic materials like composted wood chips, straw, shredded bark, peat moss, and sawdust.
Perlite - A lightweight, white granular material used to loosen the soil structure and improve permeability.
Gypsum - A soft sulfate mineral that clumps fine clay particles together to create space for air and water.
Sandy Soil
Sandy soil consists of larger, coarser particles that feel gritty and don't hold together well. This type of soil drains quickly, often leaving plants without enough moisture. It also struggles to retain nutrients, which means nutrients leach away before reaching the roots.
The best materials for correcting sandy soils should increase their mass and ability to hold water and nutrients, creating a more favorable environment for plant growth. These include:
Organic Amendments - Some examples are compost, worm castings, peat moss, and composted manure.
Vermiculite - An absorbent mineral that allows soil to retain moisture better and absorb more nutrients like magnesium, calcium, and potassium without altering soil pH.
Biochar - A porous carbon-like organic matter that helps soil absorb and store more moisture and nutrients.
Silty Soil
Silt has smaller particles than sand, giving it a silky texture that feels slippery underfoot when wet. But, despite its finer texture, it also struggles with water retention, like sandy soils. Soil that is predominantly silt—about 80 percent—is particularly prone to erosion, as wind and rain can easily wash away the nutrient-rich topsoil.
If you have silty soil, you can address erosion concerns by adding materials that bind the soil together. These include organic matter like compost, aged manure, composted wood chips, decayed sawdust, and wood shavings. You can also use the same soil amendments as working with sandy soil.
Other Types of Soil Amendments
In addition to improving soil texture and drainage, you can add soil amendments to adjust soil pH, creating a more conducive environment for the plants you prefer to grow.
Soil pH determines the acidity or alkalinity of your soil, measured on a scale from 0 to 14, with 7 being neutral. The type of soil amendment you need depends on the existing pH levels of your soil and the ideal pH range for your grass. For example, most warm-season grasses that thrive in Florida require slightly acidic soils, averaging 5.5 to 6.0 or higher.
Agricultural lime and wood ash are common soil amendments used to raise the pH in acidic soils. Meanwhile, materials like elemental sulfur and aluminum sulfate lower the pH in alkaline soils. We have previously published an in-depth guide on adjusting soil pH when planting grass plugs.
How and When to Apply Soil Amendments
Ideally, soil amendments should be worked into the soil before starting a new lawn, whether you're installing sod or transplanting grass plugs. It ensures that the amendments are well integrated, creating an optimal environment for the roots to access nutrients from the soil.
Similarly, soil amendments should be applied before fertilizers. Amendments like lime or sulfur for adjusting pH levels or compost for improving soil structure should be mixed into the soil first. Once incorporated, you can then apply fertilizer for grass as necessary. Work the materials into the ground when the soil is moist enough to form a ball but dry
- When existing grass shows signs of decline
In established lawns, when you observe slow growth, thinning grass, or soil that either dries too quickly or too slowly, it may also be time for amending. Soil testing is crucial to determine its specific needs, avoiding the risks of using the wrong materials or incorrect amounts that can damage your lawn.
Because you cannot work the amendments into an established lawn, apply them evenly across the surface as a top dressing and water it at least 6 inches deep. Deep watering ensures the amendments reach the root zone effectively. For clay or dense soil, consider using the cycle and soak method, breaking up watering times into multiple cycles with intervals to allow for better absorption.
You can also improve soil exposure by aerating and dethatching the lawn before amending, which helps the materials penetrate the soil surface more effectively.
Takeaway
You can maximize nutrient absorption in your soil by amending it properly. It means lawn fertilizers go hand in hand with soil amendments to create an environment that supports healthy grass growth. By enriching your soil with the right nutrients and correcting its texture, you can ensure that your grass has everything to develop into a healthy, dense green lawn.
If you're starting a new lawn with grass plugs, supplementing your soil with NutriPod® can help accelerate growth and support establishment. Each pod is designed to be worked directly into the root zone before placing each plug, making them easily accessible to the roots for optimal growth.
Visit our website today to shop NutriPod® grass plug fertilizer and give your lawn the nutrients it needs to thrive!
