Turf (Image Comics),

Sod, also known as turf, is the upper layer of soil with the grass growing on it that is often harvested into rolls.

In Australian and British English, sod is more commonly known as ''turf'', and the word "sod" is limited mainly to agricultural senses.

Uses

Sod is generally used for lawns, golf courses, and sports stadiums around the world. In residential construction, it is sold to landscapers, home builders or home owners who use it to establish a lawn quickly and avoid soil erosion. Sod can be used to repair a small area of lawn, golf course, or athletic field that has died and is used as a quicker alternative to re-growing a lawn 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.

Following the passage of the Homestead Act by Congress in 1862, settlers in the Great Plains used sod bricks to build entire sod houses. This was effective because the prairie sod of the Great Plains was so dense and difficult to cut it earned the nickname "Nebraska marble". Blacksmith John Deere made his fortune when he became the first to make a plow that could reliably cut the prairie sod.

Different types of grass are used for sod installation.

Cultivation

Sod is grown on specialist farms. For 2009, the United States Department of Agriculture reported 1,412 farms had of sod in production.

It is usually grown locally (within 100 miles of the target market) to minimize both the cost of transport and also the risk of damage to the product. The farms that produce this grass may have many varieties of grass grown in one location to best suit the consumer's use and preference of appearance.

It is usually harvested 10 to 18 months after planting, depending on the growing climate. On the farm, it undergoes fertilization, frequent mowing, watering, and subsequent vacuuming to remove the clippings. It is harvested using specialized equipment, precision cut to standardized sizes. Sod is typically harvested in small square or rectangular slabs, or large rolls.

The Mississippi State University has developed a hydroponic method of cultivating sod. For the very few sod farms that export turf internationally, this soilless sod may travel both lighter and better than traditional sod. Additionally, since the sod is not grown in soil, it does not need to be washed clean of soil down to the bare roots (or sprigs), so time to export is shortened.

Immediacy

In many applications, such as erosion control and athletic fields, immediacy is a key factor. Seed may be blown about by the 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, and 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 seeding lawn two to three years older. Sod also reduces erosion by stabilizing the soil.

Many prized cultivars (such as Bella Bluegrass) only reproduce vegetatively, not sexually (via seed). Sod cultivation is the only means of producing additional plants. To grow these varieties for sale, turf farms use a technique called sprigging, where recently harvested sod mats are cut into slender rows and replanted in the field.

Cultivars used

Fescue grass

Tall fescue

Tall fescue (''Festuca'' spp.) is a cool-weather group of grasses originating in Europe, commonly used as sod. It is moderately tolerant to both drought and cold, and as such is especially popular in inland temperate environments referred to in the turf and landscaping industries as the " transition zone", where summers are too hot for most cool-weather grasses, yet winters are too cold for most warm-weather grasses. Fescue is well-adapted to clay soils, moderately shade-tolerant, and somewhat resistant to disease, yet vulnerable to the diseases brown patch and Fusarium patch. It grows most actively (and thus provides the most desirable appearance) in spring and fall, and requires frequent watering during summer. Due to its bunch-type growth habit (unique among common sod grasses), it will not spread undesirably or invade adjacent areas once sodded, yet neither will it fill in voids, and periodic maintenance (such as overseeding with Fescue seed) may be required to sustain a homogeneous surface. It has poor wear tolerance compared to Bermuda grass, making it less popular for applications such as athletic fields.

Fine fescues

Fine fescues ('' F. rubra'', '' F. ovina'', '' 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. Otherwise, their characteristics are similar. Fine fescues are generally used in mixtures with other grasses.

Bermuda grass

Bermuda grass is quite commonly used for golf courses and sports fields across the southern portions of the United States. It tolerates a range of climates in the U.S., from hot and humid lagoons, inlets, and bays of the Gulf Coast, to the arid expanses of terrain like plains and deserts in the