Hydroponics - Wikiparency

# Hydroponics **Hydroponics** is a method of growing plants without soil.[^umn-ext] Instead of drawing water and minerals from the ground, the roots sit in water that carries the nutrients dissolved in it, either bare or anchored in an inert material such as perlite, gravel or rockwool. The grower supplies what soil would otherwise provide. Water brings the major nutrients [[Nitrogen|nitrogen]], [[Phosphorus|phosphorus]] and [[Potassium|potassium]], along with smaller amounts of elements such as [[Calcium|calcium]], [[Magnesium|magnesium]], [[Sulfur|sulfur]] and [[Iron|iron]]. Air or moving water brings [[Oxygen|oxygen]] to the roots, and lamps can stand in for the sun. On the Thury spine, hydroponics is water put to work as the delivery system for agriculture. The same questions of flow, pressure and exchange that run a turbine decide whether a root gets enough oxygen and nutrient, and the practice links the Compendium to the agricultural centers of excellence. ## History The science is older than the word. In 1860 the German botanist Julius von Sachs published experiments showing, in his words, "that land plants are capable of absorbing their nutritive matters out of watery solutions, without the aid of soil."[^hoagland] For decades the water-culture method stayed a laboratory tool. In the 1920s and 1930s William F. Gericke of the University of California, Berkeley, set out to adapt it to commercial crop production. He grew tomatoes and other crops in tanks, coined the term *hydroponics*, and described the method in *Science* in 1937.[^osu-em9453][^gericke1937] Dennis Hoagland and Daniel Arnon, also at Berkeley, published *The Water-Culture Method for Growing Plants Without Soil* in 1938. It noted that the method was "also described under such names as 'tray agriculture,' 'tank farming,' and the recently coined term, 'hydroponics.'" Their nutrient recipes, revised in 1950, became standard laboratory solutions.[^hoagland][^hoagland1950] An early practical use was on Wake Island in the Pacific, where Pan American Airways refueled its trans-Pacific Clippers. In 1938 *Time* reported that tank gardens there would provide fresh beans, tomatoes and other vegetables for the resident staff and for the Clippers' crews and passengers.[^time1938][^nps-panam] ## Techniques University of Minnesota Extension describes the systems most used at small scale. In **deep water culture**, plants float above a container of nutrient solution with their roots hanging into it. In the **nutrient film technique**, a thin film of solution flows down shallow sloping channels past the roots. In **ebb and flow** systems a tray is flooded and then drained back into a reservoir. **Drip systems** feed each plant through an emitter.[^umn-ext] The difference between them is how water and air reach the root: submerged, as a moving film, or in alternating floods and drains. ## Advantages The University of Minnesota reports that controlled-environment agriculture, including hydroponic growing, uses only about 10% of the water needed in conventional farming.[^umn-cea] Growing indoors also allows year-round production and close control of light, temperature and nutrients.[^shelford] ## Substrates (growing support materials) Where roots need support, growers use inert substrates. UMN Extension lists perlite, expanded clay (hydroton), pumice, gravel, coconut coir and rockwool. Rockwool holds oxygen well but does not biodegrade; coir holds water well; expanded clay drains freely but holds little water; perlite holds oxygen but can clog pumps; gravel drains well but is heavy.[^umn-ext] ## Nutrient solutions A hydroponic solution must supply every element the plant would otherwise take from soil. Hoagland and Arnon's standard solutions combine potassium phosphate, potassium nitrate, calcium nitrate and magnesium sulfate, with trace amounts of micronutrients such as [[Boron|boron]], [[Manganese|manganese]], [[Zinc|zinc]], [[Copper|copper]] and [[Molybdenum|molybdenum]].[^hoagland] Growers track two numbers. The first is pH: plants do best in water with a pH of 5.4–7.0. The second is electrical conductivity, which measures how much fertilizer is dissolved. As plants mature they tolerate less of it.[^umn-ext] ## Additional improvements In fully indoor facilities, light becomes the controlled input. A chapter on controlled-environment plant production in *Introduction to Biosystems Engineering* gives the daily light integral, the total photosynthetic light a crop receives in a day, as the main target. For hydroponic lettuce, staying within 3 mol m⁻² d⁻¹ of the target is acceptable if any surplus or deficit is made up over the next two days.[^shelford] ## Crops grown Leafy crops do best. UMN Extension recommends lettuce, herbs and brassicas such as mustards and kale for year-round indoor growing, and tomatoes, cucumbers and strawberries outdoors in summer.[^umn-ext] ## Urban hydroponics Controlled-environment growing now ranges from growth chambers and plant factories to shipping containers and vertical farms.[^shelford] Plant growth in closed systems is also studied for spaceflight. [[NASA|NASA]]'s Veggie unit on the International Space Station, which grows plants in "pillows" of calcined clay rather than in open solution, began its first lettuce crop in May 2014; in August 2015 the crew harvested leaves to eat.[^nasa-veggie] ## Minnesota *This section is specific to Wikitube.* University of Minnesota Extension publishes guidance for home and small-scale hydroponic growers, and the university runs research in controlled-environment agriculture with 145 plant growth chambers.[^umn-ext][^umn-cea] Its aquaponics program studies the year-round growing of fish and plants together.[^umn-aquaponics] In Faribault, Living Greens Farm grows greens aeroponically, with nutrient-rich mist, on 32 racks each 56 feet long.[^startribune2021] ## See also - [[Agricultural_engineering]] - [[Water]] - [[Hydrology]] ## References [^umn-ext]: Hoidal, Natalie; Reardon, Amanda; Worth, Leah; Rogers, Mary (reviewed 2022). "Small-scale hydroponics." University of Minnesota Extension. https://extension.umn.edu/gardening-minnesota/small-scale-hydroponics [^hoagland]: Hoagland, D. R.; Arnon, D. I. (1938). *The Water-Culture Method for Growing Plants Without Soil*. California Agricultural Experiment Station Circular 347. University of California College of Agriculture, Berkeley. https://archive.org/download/waterculturemeth347hoag/waterculturemeth347hoag.pdf [^hoagland1950]: Hoagland, D. R.; Arnon, D. I. (1950). *The Water-Culture Method for Growing Plants Without Soil*, revised edition. Circular 347. https://openlibrary.org/books/OL25240089M [^gericke1937]: Gericke, W. F. (1937). "Hydroponics—crop production in liquid culture media." *Science* 85 (2198): 177–178. https://doi.org/10.1126/science.85.2198.177 [^osu-em9453]: Nelson, M.; Langellotto, G.; Nackley, L. (2025). "Hydro hints: What is hydroponics?" Oregon State University Extension, EM 9453. https://extension.oregonstate.edu/catalog/em-9453-hydro-hints-what-hydroponics [^time1938]: "Science: Hydroponics to Wake." *Time*, May 23, 1938. https://time.com/archive/6820208/science-hydroponics-to-wake/ [^nps-panam]: National Park Service. "Pan American Airways on the Home Front in the Pacific." https://www.nps.gov/articles/000/pan-american-airways-on-the-wwii-home-front-in-the-pacific.htm [^umn-cea]: University of Minnesota Twin Cities. "Controlled environment agriculture at the University of Minnesota." https://twin-cities.umn.edu/news-events/inside-track-increased-food-production [^shelford]: Shelford, T. J.; Both, A. J. (2020). "Plant Production in Controlled Environments." In Holden, N. M.; Wolfe, M. L.; Ogejo, J. A.; Cummins, E. J. (eds.), *Introduction to Biosystems Engineering*. https://doi.org/10.21061/IntroBiosystemsEngineering/Plant_Controlled_Environment [^nasa-veggie]: NASA (2020). "Veggie." NASA Facts FS-2020-01-007-KSC. https://www.nasa.gov/wp-content/uploads/2019/04/veggie_fact_sheet_508.pdf [^umn-aquaponics]: University of Minnesota. "Aquaponics." https://aquaponics.umn.edu/ [^startribune2021]: Condon, P. (November 13, 2021). "Minnesota's Living Greens Farm has ambitious indoor produce plans." *Star Tribune*. https://www.startribune.com/minnesotas-living-greens-farm-has-ambitious-indoor-produce-plans/600116250 ## Sources - Holden, N. M.; Wolfe, M. L.; Ogejo, J. A.; Cummins, E. J., eds. (2021). *Introduction to Biosystems Engineering*. Virginia Tech Publishing — on the [[PORTAL_Centers_of_Excellence]] book shelf and the Compendium's Northern Agriculture shelf. ## External links - [Small-scale hydroponics](https://extension.umn.edu/gardening-minnesota/small-scale-hydroponics), University of Minnesota Extension - [UMN Aquaponics](https://aquaponics.umn.edu/)  **Part of the [[WT!Thury_Hydrodynamics_Compendium|Thury Hydrodynamics Compendium]]** — main article for section 17, *Hydroponics*. Related sections: [[Properties_of_water]] · [[Hydrology]].   **Microsim — three.js (Wikitube framework):** *Hydroponics* <div class="wt-sim" data-src="https://wikitube-3d-microsims.netlify.app/thury/Hydroponics.html" data-title="Hydroponics"></div> *Built from `MICROSIM_GUIDE/specs/sims/Hydroponics.json`; part of the [[WT!Thury_Hydrodynamics_Compendium|Thury Hydrodynamics Compendium]] set.*  ## Wikipedia : Wikitube **Strict pair:** [Wikipedia](https://en.wikipedia.org/wiki/Hydroponics) : [Wikitube](https://en.wikitube.io/wiki/Hydroponics) · pinned revision [1373202384](https://en.wikipedia.org/w/index.php?oldid=1373202384) · 2026-09-10 ## Previous hub tags Hubs: `Life_Physics`, `Systems`. Portals: [[PORTAL_Thury_Hydrodynamics_Apex_Spine]], [[PORTAL_Centers_of_Excellence]]. --- *Thury main articles, wave 2 · 2026-09-10 · drafted · Compendium section 17 · sim pending THY-077.*