Loamy soil is a type of soil that is composed mostly of sand, silt, and a smaller amount of clay. By weight, its mineral composition is about 40–40–20% concentration of sand–silt–clay, respectively. Loam soils generally contain more nutrients, moisture, and humus than sandy soils, have better drainage and infiltration of water and air than silt- and clay-rich soils, and are easier to till than clay soils. Loamy soil is ideal for most garden plants because it holds plenty of moisture but also drains well so that sufficient air can reach the roots. Loam soils can be classified into subgroups: sandy loam, silt loam, clay loam, and silty clay loam. The sand particles are the largest among loams three components—sand, silt, and clay. Sand does not hold moisture, but it lends good aeration and drainage as a component of loamy soil. Loamy soil is created by blending all three soil components, and it has the ability to retain enough moisture (as well as an abundance of nutrients) to keep plants healthy. Gardeners can improve heavy, compacted soil by adding organic matter, such as compost, animal manure, cover crops, or organic mulch materials, each year as the soil is worked. Highly sandy soils can be a problem since they do not hold much water and few nutrients, as well. Adding organic materials to a sandy soil will improve its ability to hold water and nutrients.