Sod is the upper layer of turf that is harvested for transplanting. Turf consists of a variable thickness of a soil medium that supports a community of turfgrasses. Sod is typically made with grasses that spread laterally through the soil and form a dense mat. In British and Australian English, sod is more commonly known as turf and the term "sod" is mainly used in agriculture. Sod is used to establish lawns or other greenways in spaces like golf courses or sports stadiums. Typically, after construction or other landscape disruption, builders, owners, and landscape specialists place sod to establish a grass cover. Sod is grown on specialized farms; the grass is grown for 12 to 18 months before the sod is cut from the top layer of the soil and prepared for transportation. Sod is often cut in either squares or rolls, making it easier to transport and distribute. Different species of grass are grown in different geographic regions because of the differing climatic conditions. More recently, some producers have developed turf mixes that include wildflowers and other native plants.
Uses Sod is used around the world for lawns, golf courses, and sports stadiums. In residential construction, it is sold to landscapers, home builders, and home owners, who use it to quickly establish a lawn and avoid soil erosion. Sod can be used to repair small, dead or damaged areas of lawn, golf course, or athletic field, and is used as a quicker alternative to re-growing from seed. Sod is also effective in increasing cooling, improving air and water quality, and assisting in flood prevention by draining water.
Scandinavia has a long history of employing sod roofing, and a traditional house type is the Icelandic turf house. In the United States, following the passage of the Homestead Act by Congress in 1862, settlers in the Great Plains used sod bricks to build sod houses. This was effective because prairie sod of the Great Plains was dense and difficult to cut, and was nicknamed "Nebraska marble". Blacksmith John Deere made his fortune when he became the first to make a plow that could reliably cut prairie sod. Different types of grass are used for sod installation.
Cultivation
Sod is grown on specialist farms, usually within 100 miles (160 km) of the target market. This minimizes both the cost of transportation and the risk of damage to the product. Sod-producing farms may have many varieties of grass growing in one location to best suit the consumer's use and preference. Sod is usually harvested 10 to 18 months after planting, depending on the growing climate. During cultivation, it undergoes fertilization, frequent mowing, watering, and in some cases, vacuuming to remove the clippings. It is harvested using specialized equipment that precisely cuts it to standardized sizes. Sod is typically harvested in small, square or rolled rectangular slabs, or 4-foot (1.2 m) wide rolls. Prior to commercial sod cultivation, prospective consumers would pay farmers to cut and harvest their pastures.
Mississippi State University developed a hydroponic method of cultivating sod in 2006. For the limited number of sod-exporting farms, this soilless sod may ship more efficiently and with less weight than traditional sod. Additionally, because it is not grown in soil, it does not need to be washed down to bare roots or sprigs, shortening the time and cost of exporting it.
Impact on soils A study of sod farms in Turkey found harvesting sod causes a significant loss of topsoil and key nutrients, more than that of other kinds of agriculture in the region.
Immediacy Immediacy is a key factor in many applications, such as erosion control and athletic fields. Seed may be blown about by wind, eaten by birds, or fail because of drought. It takes some weeks to form a visually appealing lawn and further time before it is robust enough for use. Sod largely avoids these problems; with proper care, newly laid sod is usually fully functional within 30 days of installation, and its root system is comparable to that of a two-to-three-years-older seeding lawn. Sod reduces erosion by stabilizing the soil. Many cultivars and some species can only be reproduced vegetatively rather than sexually via seed. For these, sod cultivation is the only means of producing additional plants. To grow these varieties, turf farms use a technique called sprigging; recently harvested sod mats are cut into slender rows and replanted in the field.
Species used
Fescue grass
Tall fescue Tall fescue (Lolium arundinaceum), which is commonly used for sod, is a cool-season grass originating in Europe. It is moderately tolerant to drought and temperature extremes, and is especially popular in many temperate environments; it is known in the turf and landscaping industries as the "transition zone". In these areas, summers are too hot for most cool-season grasses, while winters are too cold for most warm-season grasses. Tall fescue is well adapted to various soils, moderately shade tolerant, and somewhat resistant to most diseases. It is vulnerable to Brown patch and Pythium blight. It grows most actively, and thus provides the most desirable appearance, in spring and fall, and requires moderate watering during summer. Due to its bunch-type growth habit, which is unique among common sod grasses, it does not spread aggressively or invade adjacent areas once established. Tall fescue does not actively fill in bare spots, and periodic maintenance such as overseeding may be required to maintain a uniform surface. This bunch-type growing habit contributes to a somewhat-lower wear tolerance compared to Kentucky Bluegrass or Bermuda grass, making it less commonly used for purposes such as athletic fields.
Fine fescues Fine fescues (F. rubra, F. rubra subsp. commutata, F. trichophylla) are less popular as sod than the tall fescues. As their names suggest, they exhibit much thinner leaf blades and tolerate lower mowing heights than the tall fescues. They may be somewhat more resistant to common diseases and most generally prefer cool, shadier climates. Otherwise, their characteristics are similar, except for Creeping Red fescues (F. rubra), which spread via rhizomes and can form a dense sod. Fine fescues are generally used in mixtures with other grasses for shade and soil quality tolerance.
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