HYDROPONICS: GROWING PLANTS WITHOUT SOIL
Plants need sunlight, carbon dioxide (from the air), and mineral nutrients such as nitrogen and phosphorus. Traditionally, farmers have obtained these nutrients from soil. Hydroponics involves growing plants by exposing their roots to a nutrient-rich water solution instead of soil, usually inside of a greenhouse. Indoor hydroponic farming has a number of advantages over conventional outdoor growing systems: Crops can be grown indoors under controlled conditions almost anywhere. Yields and availability are increased because crops are grown year round, regardless of weather conditions. In dense urban areas, crops can be grown on rooftops, underground with artificial lighting (as is now done in Tokyo, Japan), and on floating barges, thus requiring much less land. Fertilizer and water use are reduced through the recycling of nutrient and water solutions. There is no runoff of excess fertilizer into streams or other waterways. In the controlled greenhouse environment, there is little or