tailieunhanh - Encyclopedia of Global Resources part 65

Encyclopedia of Global Resources part 65 provides a wide variety of perspectives on both traditional and more recent views of Earth's resources. It serves as a bridge connecting the domains of resource exploitation, environmentalism, geology, and biology, and it explains their interrelationships in terms that students and other nonspecialists can understand. The articles in this set are extremely diverse, with articles covering soil, fisheries, forests, aluminum, the Industrial Revolution, the . Department of the Interior, the hydrologic cycle, glass, and placer mineral deposits. . | 588 Hydroponics Global Resources . Geological Survey Water Science for Schools What Is Hydrology and What Do Hydrologists Do http edu See also Aquifers Atmosphere Biodiversity Geochemical cycles Glaciation Groundwater Lakes Oceans Streams and rivers Water pollution and water pollution control Water rights. Hydroponics Categories Scientific disciplines environment conservation and resource management The term hydroponics literally means water culture and originally referred to the growth of plants in a liquid medium. It later applied to all systems used to grow plants in nutrient solutions with or without the addition of inert material synthetic soil for mechanical support. Background The ability to produce food and fiber for an evergrowing population is the most fundamental of all resources and hydroponics has become an important method of crop production. The increase in the number of commercial greenhouse operations has resulted in a tremendous increase in the use of hydroponic systems. Greenhouses are utilized in the production of a wide array of bedding plants flowers trees and shrubs for commercial as well as for home and garden use. Cash receipts from greenhouse and nurser y crops total billions of dollars annually. In some arid regions the vast majority of vegetable crops are produced in greenhouses. Types of Hydroponic Systems The four most commonly used hydroponic systems are sand-culture systems aggregate systems nutrient film techniques and floating systems. While these systems are similar in their use of nutrient solutions they vary in both the presence and type of supporting medium and in the frequency of nutrient application. In sand culture coarse sand is used in containers or spread over an entire greenhouse floor or bed on top of a recirculating drain system. A drip irrigation system is used to apply nutrient solution periodically and a drainage system is used to collect the excess solution as it drains through .