Boak, Robert (rboak@oswego.edu)

Leonard, Thomas (tleonard@oswego.edu)

Oursler, Khristopher (oursler@oswego.edu)

• Nutrients are delivered to the plant in an aqueous solution as opposed to the plant taking them from the soil.
• Expands the scope of gardening; makes it possible to grow a wider variety of plants in a wider variety of climates.

• A hydroponic acre can yield as many as ten thousand plants whereas an acre of dirt can only raise one third of that. (http://archimedes.galilei.com/raiar/histhydr.html)
• Uses 1/30th the amount of water.
• Hydroponics allows for the possibility of the growth of crops outside of their indigenous climate.
• Crop rotation is unnecessary because there is no depletion of nutrients because there is no soil.
• Growing is not regulated by seasonal changes. Hydroponics allows for continual growth throughout the year.
• There is little to no risk of weeds or parasites in controlled systems.
• Has been successfully used to grow crops outside of our atmosphere.

• High cost (i.e. initial capital cost, cost to run)
• High maintenance (i.e.. constant supervision, pH testing, light adjustments, support)
• Requires specialized knowledge and equipment.
• It is a more complicated and involved process than dirt farming.

• There are two types of hydroponics systems for delivering the nutrient solution: Passive and Active.

• Passive systems are basic and easier to set up for the novice hydroponics gardener.
• Passive systems require materials that retain moisture longer such as vermiculite and sand.
• Easily portable, simple and inexpensive.
• Ideal for starting seeds, rooting cuttings and experimental purposes.
• A disadvantage is lower growth rate.
• The common types of passive systems include:
• Wick system
• Drain down system

• A group of wicks anchored in the medium and stretching down to a nutrient solution reservoir draws moisture upward into the growing medium to reach the roots of the plant.
• A disadvantage is that plants do not grow to full maturity because of limited aeration and root zone volume.

• The solution is poured through the system once to three times a day and drained into a container beneath it.
• Roots can clog draining channels.
• Extremely high maintenance.

• Active systems employ pumps and various other devices to pour the solution into the system and uses gravity to drain off the excess in order to be reused.
• Active systems require growing mediums that drain rapidly, such as smooth gravel.
• There are various types of active hydroponics systems that exist:
• Nutrient Film Technique
• Ebb & Flow
• Top Feed
• Aeroponics
• Sub-Aeration

• Nutrient film technique uses little or no medium (which keeps cost down) and works by a continuous flow of nutrient laden solution flowing over the root system.
• This system can produce large-scale crops inexpensively in parts of the world that soil quality is poor.
• Using this system, eight million heads of lettuce could be grown annually on a 2 1/2-acre operation, in comparison with 75,000 produced in the same area by conventional farming techniques. (Resh, 203)
• The greatest problem facing NFT systems has been root dieback caused by inadequate oxygen in the nutrient solution immediately around the roots.
• This problem causes water stress within the plant, which causes wilting and blossom end rot of fruit crops such as tomatoes.
• This system is susceptible to equipment failure and problems arise due to support of the plant.

• This is the most popular hydroponics system due to its low maintenance and low cost.
• Ebb and Flow systems utilize a growing bed full of medium, that is "flooded to a depth of about one inch for about twenty minutes and then allowed to drain back". (Resh p.214)
• These systems are particularly suited for the growing of seedlings, transplants and ornamental potted plants.
• There is little risk of equipment failure due to the fact that there is a growing medium that retains some water. Yet, it drains freely to allow oxygen to get to the root system.
• Ebb and Flow systems allow for uniform fill and complete drainage during the irrigation cycle, thus leading to uniformity in plant growth.
• This type of system can be made fully automatic with the use of computers.

• Top feed systems use pumps to carry the water to the top of the growing medium and gravity drains the solution back to the reservoir.
• These systems are reliable, require low maintenance and can withstand short-term equipment failure because of the growing medium.
• They are suitable for large scale growing of all types of plants.
• A disadvantage of this system is that it is expensive to set up. Also, the nutrient solution is only used once.
• Top feed systems can use a variety of growing mediums, and are available in a wide range of configurations.

• Aeroponics uses pumps and sprayers to bathe the roots, which are suspended in a supporting container, with a nutrient-oxygen mist as opposed to a solution.
• This method is most used in lab studies and not on a large commercial scale. This is due to the expense of setup, possibility of equipment failure and difficulty in plant support.
• This system has proven successful in the propagation of hard to root plants.
• NASA has experimented with the combination of the Aeroponics system and the Nutrient Film Technique, in order to conserve nutrients for the use of hydroponics in space.
• The chief advantage of this type of system, is efficient utilization of greenhouse space by arranging the plants vertically.
• A disadvantage of Aeroponics is regulating the consistency of the sprayers to assure constant nutrient flow.

• In this system an air pump supplies oxygen to the roots of the plants via air stones.
• The solution does not flow to the roots yet they are constantly submerged. The air bubbles supply oxygen to prevent the roots from drowning.
• This system works best with plants that have already rooted.
• The root systems must be totally artificially supported.
• A disadvantage is the lack of overall aeration and root disturbances that restrict plant growth and maturity.
• Since the solution must be periodically changed due to depletion of nutrients, the entire system must be disrupted thus shocking the plants and perhaps causing damage.
• To deter the growth of algae, it is suggested that the water supply be hidden from light.

• The key to success in hydroponics growing is the management of plant nutrition. This is accomplished by managing the nutrient solution properly.
• Contained within this solution are various combinations of nutrients specifically engineered to mimic and/or enhance the nutrient combinations found in soil.
• Contained within the nutrient solution are the following chemicals: Nitrogen, Phosphorous, Potassium, Calcium, Magnesium, Sulphur, Iron, Manganese, Zinc, Boron and Copper.

• Nitrogen- Influential in the production of leaves and the growth of the stem. (Nicholls, 55-56)

• Phosphorus-Vital in the development of flowers, fruits, leaves and stems. Also encourages growth of healthy roots. (Nicholls, 55-56)
• Potassium- Used by the cells of a plant during assimilation of energy produced by photosynthesis. (Nicholls, 55-56)
• Calcium- Spurs root growth. Also facilitates a plant’s absorption of potassium. (Nicholls, 55-56)
• Magnesium- A component of chlorophyll. Also active in the process of distributing phosphorus throughout the plant. (Nicholls, 55-56)
• Sulphur- Joins with phosphorus to heighten the effectiveness of that element. Also used in the production of energy. (Nicholls, 55-56)
• Iron- Important in the production of chlorophyll within a plant. (Nicholls, 55-56)
• Manganese- Aids a plant in the absorption of nitrogen. (Nicholls, 55-56)

• Zinc- Necessary component of the energy transference process in a plant. (Nicholls, 55-56)

• Boron- While it has been established that boron is needed in minute amounts, it is not known precisely how boron is used. (Nicholls, 55-56)
• Copper- Needed in the production of chlorophyll. (Nicholls, 55-56)

• The pH value refers to the acidity or alkalinity of the nutrient solution.
• pH readings run from 0 to 14 (0-6 acidic; 7 neutral; 8-14 alkaline).
• The recommended pH level for a general hydroponic solution is between pH 6 and pH 6.5. (Nicholls, 63)
• Many different variables can effect the pH level.
• Temperature
• Amount of light
• Evaporation
• Tap water refining
• Amount of nutrients
• With this amount of variables, periodically checking the pH level of the solution is vital to maintain a healthy environment for the growth of the plant
• Adjusting the pH level of the nutrient solution can be done simply.
• If a solution is too acidic, add one tablespoon of baking soda to three gallons of solution.
• If a solution is too alkaline, add one tablespoon of white vinegar per four gallons of solution.

• Growing medium is used to lend support to the roots and plant.
• A variety of growing medium are utilized for their individual qualities in various types of hydroponic systems.
• Some popular examples of growing medium are: sand, brick shards, vermiculite, perlite, gravel, rockwool, sawdust, and polyethylene sheeting.
• Sand

• Brick Shards

• Vermiculite/Perlite

• Gravel

• Rockwool (sterile, porous, non-degradable material made from volcanic materials)

• Sawdust

• Polyethylene Sheeting

• The recent developments in plastics have cut hydroponic system costs which has made hydroponics financially feasible the more people.

• The development of pumps has allowed hydroponic systems to evolve to fully automatic systems.
• Presently, advances are being made in the development of highly specialized hydroponic cultures for use in atomic submarines.

• Further development of the application of solar heating in hydroponic greenhouses will reduce cost and economic impact of hydroponics.
• Currently, plans are being drawn for using the techniques of soil-less culture on space stations, and perhaps one day on surfaces of other celestial bodies (planets, moons, etc.) that don’t have soil.
• In the future, developing countries, along with all other nations, will be able to feed many people using less land than current farming techniques.
• Advances in lighting technology will lead to a more widespread use of hydroponics in areas with limited seasonal sunlight.
• In the future, the application of hydroponics in providing food in areas having vast regions of non-arable land, such as deserts and mountainous terrain, will be more heavily used.

Bridwell, Raymond. Hydroponic Gardening. Santa Barbara: Woodbridge Press, 1989.

Nicholls, Richard E. Beginning Hydroponics. Philadelphia: Running Press. 1990.