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