Loam soil describes a texture and ratio of soil components, and is valued for its optimal water-holding capacity and drainage that are superior for many plants. Soils generally contain various combinations of sand, clay and silt. Sand particles are the largest and most coarse, while clay particles are small and densely packed. Silt has properties in between. Loam soil describes soil with a balance of these three particle types and is a highly sought type of growing medium.
Texture of Loam
With a mixture of sand, silt and clay, loam exhibits a balanced texture. It is usually soft and breaks into small particles easily, and is both smooth and gritty. Dry loam is smooth when you touch it, but it becomes sticky when wet. Though it includes all types of soil particles, a higher ratio of any one of those particles can change the texture and the usefulness of the soil for various plants. Clay-loam soil has more clay-like properties, becoming plastic when wet and hard when dry. Silt loam contains greater amounts of silt than sand or clay. When dry, it forms clods that are easily broken and made soft. Sandy loams are grittier than other types of loams. Depending on the size of their sand particles, sandy loam may be fine, very fine or coarse.
Properties of Loam
Loam soil should contain 28 to 50 percent silt particles, 7 to 27 percent clay, and 23 to 53 percent sand. Loam soil is often beneficial for plants because it holds moisture but allows oxygen to reach the roots. Heavily compacted soil, on the other hand, tends to contain a higher ratio of clay and is poor-draining, often leading to water-logged soil and rot problems. Soils with too much sand are not proficient at holding water and nutrients or transporting them to the plant roots.
If your garden soil does not drain quickly and appears compacted, add compost, peat moss, bark mulch, perlite or other organic matter to improve it toward a loamy texture. Sand will improve the texture of the soil but contains low levels of nutrients, so it is best to add other amenders as well. Organic matter will improve aeration while boosting the soil's water and nutrient capacity. If you're dealing with sandy soil, adding organic matter will also be beneficial. Add a 2-inch layer of compost or other soil amender to boost the soil's water and nutrient-holding abilities.
Establishing soil with a loam texture is an important first step toward a bountiful garden. Most plants thrive in loamy soil because of the balanced components and properties it provides. Cabbage, Brussels sprouts, peas, mustard and many other vegetables thrive in loam soil. In the wild, sugar maples and ferns are found in loam. Some vegetables, such as carrots and tomatoes, prefer sandy loam soil because the loose texture makes it easier for their roots to extend. In the wild, plants such as wild strawberries and red maples are also found in sandy loam.