Gardening can be likened to cooking. Your plants need the right ingredients in order to achieve success. Your garden soil is the foundation of your plant's health and success, so it's essential to get it just right. One of the key aspects of soil is its texture and composition. Soil composition refers to all of the components of soil (air, water, minerals, and organic matter). Soil texture refers to the proportions of the solid mineral components (sand, silt, and clay) that make up 45% of the soil and, therefore, determine much of how it interacts with pressure, water, nutrients, and developing plant roots. If your soil contains too much of any one soil component, it can hinder plant growth by creating unfavorable conditions. Luckily, soil amending can help balance these issues, creating a welcoming environment for your garden to thrive.

The Basics of Soil Texture

Before we can amend the soil, we need to understand what’s wrong so we know what it needs. As I mentioned above, soil texture refers to the distribution of the mineral particles in your soil: sand (large particles), silt (medium particles), and clay (small particles). Loam, a balanced mixture of these particles, is often considered the ideal texture for most plants because it supports good drainage, water retention, and nutrient delivery. Each mineral particle comes with its own beneficial qualities. However, when imbalanced, you are likely to experience problems in your garden. Want to learn more about the big picture of how soil is structured? Check out our article about soil composition.

Sand

Sand has a coarse, gritty texture, and measures from 2 to 0.05 mm in size. Its particles are large, allowing space for air and water within the soil. However, too much sand can lead to too much pore space that does not hold onto nutrients well enough to support healthy plant growth. A handful of plants can benefit from such an environment, but most prefer something more balanced.

Silt

Silt has a fine, flour-like texture and measures from 0.002 to 0.05 mm in size. This is small enough that individual particles are not typically viewable without a visual aid. It is known to hold onto nutrients well while also retaining moisture necessary for plant growth. However, it is susceptible to erosion, compaction, poor drainage and aeration.

Clay

Clay is the finest soil particle measuring less than 0.002 mm in size. Being smaller than silt, clay requires an electron microscope to view individual particles. The fineness allows for clay to hold onto nutrients and water well. However, it is also highly susceptible to compaction, poor drainage and aeration, and is slow to thaw.

Clay-heavy soil is often the culprit of compaction not only because of its size, but its shape. Clay can often be found in a plated shape, allowing them to stack on top of each other with little pore space. This not only makes it difficult for water to drain and air to travel, but also for roots to access nutrients locked onto the clay particles. While clay is a valuable component of soil texture, it is best balanced out with sand and silt to enable drainage and nutrient accessibility.

Testing and Analyzing Your Soil Texture

One great way to get in tune with your soil is to complete a soil analysis test. There are many options for purchasing test kits that can give you a whole host of information that can be helpful in knowing how to amend your soil. The best value for a complete analysis is usually found with your local extension office, but there are also a few ways to know what type of soil texture you have from home! The jar test and the ribbon test are the most common options. They are free and easy to do. Check out these simple instructions from the United States Botanic Garden for identifying your soil texture from home.

Common Soil Problems

Once you know your soil texture, you can make decisions to improve the growing conditions for your plants. Sandy soil drains water well but does not hold onto nutrients. Silt soils are highly susceptible to erosion but are great for making nutrients accessible. Clay soils drain poorly and become waterlogged easily but can retain nutrients. Clay and silty soils can become compacted when heavy equipment or foot traffic passes over the area. Compacted soil results in poor aeration, which makes it difficult for roots to grow and access nutrients. Poor drainage, compaction, and nutrient accessibility can all be improved by amending the soil and using sustainable growing practices to improve soil texture and composition.

Improving Soil Compaction

Soil compaction is when soil particles are pressed together, reducing pore space and making it difficult for water, air, and roots to penetrate. This can lead to poor plant growth and increased susceptibility to disease. To improve soil compaction, you want to combine some short and long-term solutions. To quickly improve compacted soils, you can amend the soil with sand. This is usually more practical for a small growing area. Compaction can also be improved from year to year by increasing the organic matter contents of the soil. Materials rich in organic matter include compost, manure, worm castings, coco coir, and peat, among others.

Improving Soil Drainage

You will often see growing instructions indicate that you should plant into well-draining soil. This means that the soil should become hydrated when watered, while allowing excess to drain away from the root area. When water does not adequately drain, plants become more susceptible to root rot and fungal diseases. To improve soil texture for improved drainage, amend with sand and organic matter. Below, you will find several ideas for increasing the organic matter contents of your soil.

Improving Water Retention

If your soil is quickly drying out, or you live in a region that experiences drought conditions, you may want to amend your soil texture to better retain water to reduce the effects of heat stress on your plants. If your soil has a sandy texture, you may want to consider tilling in topsoil from a local green waste facility or garden center. This will increase the amount of silt and clay. However it will highly increase the amount of soil you are working with. If your soil texture is not necessarily sandy, but you want to improve water retention, increase the organic matter contents. This will need to be done each year to continue improving your soil conditions from year to year. The organic matter will allow more water to be held in the growing zone while continuing to allow excess to drain away. For small spaces or containers, consider adding Retain water retention crystals. These will expand to act as temporary water reserves until needed in the soil.

Organic Matter

Organic matter is oftentimes the magic bullet when it comes to fixing soil issues of various kinds. What is it? It is the dark portion of soil where nutrients are easily accessible to plants. In the wild, you will find the greatest proportions of organic matter naturally found in places where there is a lot of plant matter forming and decomposing with microbe and insect activity, such as the Pacific Northwest. Organic matter can be any plant or animal substance that is partially or fully decomposed. This typically takes the form of compost, manure, worm castings, leaf mold, cover crops, etc. All of these options improve soil structure, water retention, and nutrient retention and accessibility.

Cover Crops

While not strictly a soil amendment, cover crops do wonders to improve compacted soil, especially once they are tilled back into the soil. Plants like clover, alfalfa, and rye are frequently grown to be tilled back into the soil, adding organic matter and improving structure. Legumes such as peas and vetch raise nitrogen levels, while grasses like rye and barley add organic matter and prevent erosion. Root crops like radishes and turnips are great for loosening compacted soils and creating pore space for improved drainage. Cover crops are grown for the purpose of being killed and turned into the soil rather than harvesting. To terminate a cover crop, you can cut or mow it, till it back into the soil, spray with an herbicide (not recommended), push the stems down (crimping), and solarize by covering it with a tarp. A combination of these methods is commonly recommended.

Other Amendments to Improve Garden Soils

Options like perlite, vermiculite, sand, and gypsum can be easily purchased online or at garden centers. The soil composition of home garden spaces and containers can be improved when these are incorporated into the soil. Use perlite for heavy soils that need help draining. Use vermiculite for soils that have a hard time holding onto moisture for long enough to let the plants use it. Use coarse sand to improve drainage in heavy clay soils. Use gypsum to break up compacted soils and improve drainage.

Lara Wadsworth, True Leaf Market Writer

I am a native of Southwestern Michigan, where I also reside, and I love all things plants! I got a Bachelor's Degree in Horticulture and found the first work-from-home job I could get. Now, I spend my days writing for TLM, playing with my dog, eating delicious food with my husband, and plotting my next landscape or gardening move. I believe everyone should get down and dirty in the soil now and then. Happy Gardening!