|MadSci Network: Botany|
Hydroponics has been broadly defined as any kind of soilless plant culture including growing plants in solution, sand, gravel, rockwool, perlite and other inert media. However, the best kind of hydroponics for science fair projects is solution culture because the roots are visible, and it is the kind most often used in scientific research. Three main things are needed for a hydroponic system: 1) a reservoir, 2) a means for aeration, and 3) a nutrient solution. The reservoir can be any kind of plastic food container. My book has a design for a reservoir built from 2-liter soda bottles. Having a wide opening is important of you intend to remove the intact plant for examination or to place in a new solution. On a small scale, black plastic film cans work well. If the container walls are transparent to light then cover them with aluminum foil or other opaque material to exclude light and prevent algae growth. Aeration of the solution is most easily provided by gently bubbling air through the solution. Aquarium air pumps, plastic aquarium tubing, and aquarium valves works well. One small pump with enough valves can aerate ten or more hydroponic reservoirs. A plastic soda straw can be slipped over the aquarium tubing to keep the end in the solution straight. Hydroponic companies sell salt mixtures that can be dissolved in water to make a hydroponic nutrient solution. House plant fertilizers, such as Miracle-Gro, will not work for hydroponics. You can also mix your own nutrient solutions but it requires about ten chemicals, balances, and lab glassware. I recently posted a recipe for a Hoagland solution wich you can search for in the Mad Scientist archive. I usually recommend growing plants that do not grow tall and need staking because staking is a pain in solution culture hydroponics. Many houseplants work well including wandering jews, piggyback plant (Tolmiea menziesii), devil's backbone (Kalanchoe daigremontiana) and spider plant. Those four houseplants all root readily in solution culture reservoir. Lettuce is a good vegetable crop that is easily grown from seed. Wisconsin fast plants also are easily grown from seed. A variety of dwarf flowers can also be grown from seed, such as coleus, French marigold, impatiens, zinnia, and polka dot plant. Even with hydroponics, give your plants adequate light and temperature if you want rapid growth. A bank of four foot fluorescent shop fixtures, each with two cool white tubes, works well. See my book or the Wisconsin Fast Plant website for light bank construction plans. Reference Hershey, D.R. 1995. Plant Biology Science Projects. New York: Wiley. Wisconsin Fast Plants
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