Re: How can I build a hydroponics system for a science fair?

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