question: how does hydroponics work if overwatering plants kills them?
comment: It's all about the oxygen. In wet soil, the roots become oxygen starved and rotten. Same thing happens in stagnant water. Hydroponic systems use air blowers to fill the intake water with bubbles and oxygenate it. If you stop the blowers, then the root zone gets stagnant and rotten just like in over watered soil.
passages: The hydroponic method of plant production by means of suspending the plant roots in a solution of nutrient-rich, oxygenated water. Traditional methods favor the use of plastic buckets and large containers with the plant contained in a net pot suspended from the centre of the lid and the roots suspended in the nutrient solution.
   Section::::In Hydroponics.:Principles of Operation.
  
  The fundamental principle of hydroponics relies on fertilized and aerated water which provides both nutrition and oxygen to a plant's 
  
  root zone. It often involves relatively sophisticated mechanization processes which can be daunting to casual hobbyists. Nutrient solutions must usually be below the temperature at which pathogen growth can begin, yet not so cool that root activity is suppressed. Active aeration of the fertilizer solution is common, since root systems themselves remove oxygen, creating conditions which also can promote pathogenic bacteria and water-borne molds.
   Section::::Techniques.:Continuous-flow solution culture.
   In the hydroponic system, nutrient-spiked water is pumped up from a reservoir at the base of the system and trickles down from bottle to bottle, bathing the plants’ roots along the way. Water and nutrients that are not absorbed collect in the reservoir and will be pumped through again at the next interval. Plants grown in soil have roots that extend far and wide, but hydroponically grown plants roots are hairy and dense. Because the roots are so compact, a hydroponic system is a much more efficient use of space.
  
  Section::::About.:Partners.
   BULLET::::- Selective absorption of nutrients by plants often imbalances the amount of counterions in solution. This imbalance can rapidly affect solution pH and the ability of plants to absorb nutrients of similar ionic charge (see article membrane potential). For instance, nitrate anions are often consumed rapidly by plants to form proteins, leaving an excess of cations in solution. This cation imbalance can lead to deficiency symptoms in other cation based nutrients (e.g. Mg) even when an ideal quantity of those nutrients are dissolved in the solution.
   The biggest advantage of top-fed deep water culture over standard deep water culture is increased growth during the first few weeks. With deep water culture, there is a time when the roots have not reached the water yet. With top-fed deep water culture, the roots get easy access to water from the beginning and will grow to the reservoir below much more quickly than with a deep water culture system. Once the roots have reached the reservoir below, there is not a huge advantage with top-fed deep water culture over standard deep water culture. However, due to the quicker growth in the beginning, grow time can be reduced by a few weeks.
   Two other plant nutritionists, Dennis R. Hoagland and Daniel I. Arnon, at the University of California were asked to research Gericke's claims. The two wrote a classic 1938 agricultural bulletin, "The Water Culture Method for Growing Plants Without Soil," which made the claim that hydroponic crop yields were no better than crop yields with good-quality soils. Crop yields were ultimately limited by factors other than mineral nutrients, especially light. This research, however, overlooked the fact that hydroponics has other advantages including the fact that the roots of the plant have constant access to oxygen and that the plants have access to as much or as little water as they need. This is important as one of the most common errors when growing is over- and under- watering; and hydroponics prevents this from occurring as large amounts of water can be made available to the plant and any water not used, drained away, recirculated, or actively aerated, eliminating anoxic conditions, which drown root systems in soil. In soil, a grower needs to be very experienced to know exactly how much water to feed the plant. Too much and the plant will be unable to access oxygen; too little and the plant will lose the ability to transport nutrients, which are typically moved into the roots while in solution. These two researchers developed several formulas for mineral nutrient solutions, known as Hoagland solution. Modified Hoagland solutions are still in use.
   Breeding for drought stress tolerance
  
  Breeding for drought resistance is the process of breeding plants with the goal of reducing the impact of dehydration on plant growth.
  
  Section::::Dehydration stress in crop plants.
  
  In nature or crop fields, water is often the most limiting factor for plant growth. If plants do not receive adequate rainfall or irrigation, the resulting dehydration stress can reduce growth more than all other environmental stresses combined.
   The solution is oxygen saturated by an air pump combined with porous stones. With this method, the plants grow much faster because of the high amount of oxygen that the roots receive. The Kratky Method is similar to deep water culture, but uses a non-circulating water reservoir.
  
  Section::::Techniques.:Deep water culture.:Top-fed deep water culture.
   Section::::Techniques.:Aeroponics.
  
  Aeroponics is a system wherein roots are continuously or discontinuously kept in an environment saturated with fine drops (a mist or aerosol) of nutrient solution. The method requires no substrate and entails growing plants with their roots suspended in a deep air or growth chamber with the roots periodically wetted with a fine mist of atomized nutrients. Excellent aeration is the main advantage of aeroponics.
   The concept of water deficit, as developed by Stocker in the 1920s, is a useful index of the balance in the plant between uptake and loss of water. Slight water deficits are normal and do not impair the functioning of the plant, while greater deficits disrupt normal plant processes.
   BULLET::::- Other systems use towers that are trickle-fed from the top, horizontal PVC pipes with holes for the pots, plastic barrels cut in half with gravel or rafts in them. Each approach has its own benefits.
  
  Since plants at different growth stages require different amounts of minerals and nutrients, plant harvesting is staggered with seedlings growing at the same time as mature plants. This ensures stable nutrient content in the water because of continuous symbiotic cleansing of toxins from the water.
  
  Section::::Biofilter.
   BULLET::::- Drainage: In soils of bad drainage the water delivered through rain or irrigation may pool and stagnate. As a result, prevail anaerobic conditions and plant roots suffocate. Stagnant water also favors plant-attacking water molds. In soils of excess drainage, on the other hand, plants don't get to absorb adequate water and nutrients are washed from the porous medium to end up in groundwater reserves.
   Most plants have the ability to close their stomata at the start of water stress, at least partially, to restrict rates of transpiration. They use signals or hormones sent up from the roots and through the transpiration stream. Since roots are the parts responsible for water searching and uptake, they can detect the condition of dry soil. The signals sent are an early warning system - before the water stress gets too severe, the plant will go into water-economy mode.
   BULLET::::- Depending on the pH and/or on the presence of water contaminants, nutrients such as iron can precipitate from the solution and become unavailable to plants. Routine adjustments to pH, buffering the solution, and/or the use of chelating agents is often necessary.
   Hydrozoning
  
  Hydrozoning is the practice of clustering together plants with similar water requirements in an effort to conserve water. Grouping plants into hydrozones is an approach to irrigation and garden design where plants with similar water needs are grouped together. Through the practice of hydrozoning, it is possible to customize irrigation schedules for each area’s needs, improving efficiency and avoiding overwatering and underwatering certain plants and grasses. 
   Section::::Nutrient solutions.:Mixing solutions.
   BULLET::::- Laboratory glassware, such as burettes and pipettes, for performing titrations.
  
  BULLET::::- Colorimeters for solution tests which apply the Beer–Lambert law.
  
  Using chemical equipment for hydroponic solutions can be beneficial to growers of any background because nutrient solutions are often reusable. Because nutrient solutions are virtually never completely depleted, and should never be due to the unacceptably low osmotic pressure that would result, re-fortification of old solutions with new nutrients can save growers money and can control point source pollution, a common source for the eutrophication of nearby lakes and streams.
  
  Section::::Nutrient solutions.:Tools.:Software.
   After the biofilter, the water is transported to the hydroponic component where the plants are located, and where they will absorb the nutrients, cleaning the water before it returns to the biofilter. Almost all techniques used in hydroponics and aquaponics are also applicable to anthroponics. These include: Deep water culture, Nutrient film technique, and Media beds.
  
  Section::::Advantages.
   Section::::Substrates (growing support materials).:Rice husks.
  
  Parboiled rice husks (PBH) are an agricultural byproduct that would otherwise have little use. They decay over time, and allow drainage, and even retain less water than growstones. A study showed that rice husks did not affect the effects of plant growth regulators.
  
  Section::::Substrates (growing support materials).:Perlite.
   Some researchers have used aeroponics to study the effects of root zone gas composition on plant performance. Soffer and Burger [Soffer et al., 1988] studied the effects of dissolved oxygen concentrations on the formation of adventitious roots in what they termed “aero-hydroponics.” They utilized a 3-tier hydro and aero system, in which three separate zones were formed within the root area. The ends of the roots were submerged in the nutrient reservoir, while the middle of the root section received nutrient mist and the upper portion was above the mist. Their results showed that dissolved O is essential to root formation, but went on to show that for the three O concentrations tested, the number of roots and root length were always greater in the central misted section than either the submersed section or the un-misted section. Even at the lowest concentration, the misted section rooted successfully.
   In continuous-flow solution culture, the nutrient solution constantly flows past the roots. It is much easier to automate than the static solution culture because sampling and adjustments to the temperature and nutrient concentrations can be made in a large storage tank that has potential to serve thousands of plants. A popular variation is the nutrient film technique or NFT, whereby a very shallow stream of water containing all the dissolved nutrients required for plant growth is recirculated past the bare roots of plants in a watertight thick root mat, which develops in the bottom of the channel and has an upper surface that, although moist, is in the air. Subsequent to this, an abundant supply of oxygen is provided to the roots of the plants. A properly designed NFT system is based on using the right channel slope, the right flow rate, and the right channel length. The main advantage of the NFT system over other forms of hydroponics is that the plant roots are exposed to adequate supplies of water, oxygen, and nutrients. In all other forms of production, there is a conflict between the supply of these requirements, since excessive or deficient amounts of one results in an imbalance of one or both of the others. NFT, because of its design, provides a system where all three requirements for healthy plant growth can be met at the same time, provided that the simple concept of NFT is always remembered and practised. The result of these advantages is that higher yields of high-quality produce are obtained over an extended period of cropping. A downside of NFT is that it has very little buffering against interruptions in the flow (e.g., power outages). But, overall, it is probably one of the more productive techniques.
   Hydroculture compared to traditional farming in terms of crops yield per area in a controlled environment was roughly 10 times more efficient than traditional farming, uses 13 times less water in one crop cycle than traditional farming, but on average uses 100 times more kilojoules per kilogram of energy than traditional farming.
  
  Section::::Techniques.:Ebb and flow (flood and drain) sub-irrigation.
   Brown and Pezeshki devised an experiment in which many "S. alterniflora" individuals were put under situations of increased salinity, increased water stress, and then a combined treatment. They found that those plants that experienced the combined treatment exhibited an increase in water stress, where plants are unable to get a sufficient amount of water from the soil, a decrease in photosynthetic activity, and ultimately death (Brown & Pezeshki 2007).
   Section::::Plant nutrition in agricultural systems.
  
  Section::::Plant nutrition in agricultural systems.:Hydroponics.
  
presuppositions: Hydroponics should not be able to successfully grow plants if over watering is known to kill plants. Hydroponics should not efficiently be able to grow plants due to them overwatering plants which is known to kill plants. Because hydroponics overwater plants, and overwatering plants are known to kill them. They should not be able to effectively grow plants without killing them.  Hydroponics should not be effective because they overwatered plants which is known to kill them.  Hydroponic systems shouldn't work on plants because they over water plans.  Hydroponics shouldn't be a effecient technique due to plants dying from overwatering. 
corrections: Overwatered plants only harms plants when there is not enough oxygen, Hydroponics use air blowing systems to ensure that plants receive enough oxygen.  Overwatered plants only die from too little oxygen, and hydroponics use air blowing systems to keep plants oxygenated.  Overwatered plants only die when they have too little oxygen, however hydroponics provide plants with oxygen via the use of an air blower, which prevents them from being harmed.  Overwatered plants only die when there is not enough oxygen, and hydroponic systems use air blowers to prevent overwatered plants.  Overwatered plants only die when there is not enough oxygen and hydroponic machines prevent this by using air blowing systems on the plants.  Overwatered plants only die when there is not enough oxygen provided, hydroponic systems use air blowers to oxygenated plants. 
raw_presuppositions: Hydroponics should not be able to successfully grow plants if over watering is known to kill plants. Hydroponics should not efficiently be able to grow plants due to them overwatering plants which is known to kill plants. Because hydroponics overwater plants, and overwatering plants are known to kill them. They should not be able to effectively grow plants without killing them.  Hydroponics should not be effective because they overwatered plants which is known to kill them.  Hydroponic systems shouldn't work on plants because they over water plans.  Hydroponics shouldn't be a effecient technique due to plants dying from overwatering.  Overwatered plants die from too much water
raw_corrections: Overwatered plants only harms plants when there is not enough oxygen, Hydroponics use air blowing systems to ensure that plants receive enough oxygen.  Overwatered plants only die from too little oxygen, and hydroponics use air blowing systems to keep plants oxygenated.  Overwatered plants only die when they have too little oxygen, however hydroponics provide plants with oxygen via the use of an air blower, which prevents them from being harmed.  Overwatered plants only die when there is not enough oxygen, and hydroponic systems use air blowers to prevent overwatered plants.  Overwatered plants only die when there is not enough oxygen and hydroponic machines prevent this by using air blowing systems on the plants.  Overwatered plants only die when there is not enough oxygen provided, hydroponic systems use air blowers to oxygenated plants.  Overwatered plants die from too little oxygen.