MadSci Network: Botany

Re: Which plants are best suited for hydroponics and w

Date: Sun Mar 11 22:51:28 2001
Posted By: David Hershey, Faculty, Botany, NA
Area of science: Botany
ID: 984343902.Bt

Complete question:

I am about to be doing a project for my AP Biology class evaluating the 
effectiveness of hydroponic growing methods.  I am planning on using 
both soilless culture and water culture setups, as well as a setup in 
potting soil as a control.  I have read that beans are often used in 
hydroponics experiments, but I have not been able to find out why this is 
so.  Also, I am concerned that bean plants will grow too large for my 
project; I am planning on growing them inside with plant lights for a 
minimum of 3 weeks, possibly longer.  For this procedure, what plants 
would be best to use, and what are their optimum pH and other growing 
conditions?  Also, I know that there are commercial nutrient solutions 
available for hydroponics, but I would like to know if it is possible to make 
your own.  I found a recipe online, but it was incomplete; it simply lumped 
all the micronutrients as "trace elements."  Thanks!


Three weeks is a rather short timeframe for a plant growth experiment. Beans 
are readily available and germinate rapidly so are often used in school 
experiments. The drawbacks are that they need a lot of light, get tall, and 
often need staking. I often use houseplants because they root readily in 
solution culture and grow well under indoor light conditions. I particularly 
like piggyback plant (Tolmiea menziesii) because it roots readily via foliar 
plantlets. Devil's backbone (Kalanchoe daigremontianum) also produces foliar 
plantlets and works well. Wandering jews also root very easily and grow 
rapidly. If you want a crop, a leaf lettuce would be a good choice because it 
stays short, grows rapidly, does not need to flower before harvest, and is 
produced commercially in hydroponics. 

For most rapid growth, give your plants as much electric light as possible for 
18 hours per day. A standard system for school experiments uses three, 4-foot 
shop fixtures side by side, each with two 40-watt cool white fluorescent tubes. 
Keep the plants within a couple cm of the tubes. 

It is often easier to buy a mixture of salts to make a hydroponic solution than 
to make up your own from individual salts because it requires balances, lab 
glassware, etc. One of that standard research nutrient solutions for 
hydroponics is Hoagland solution. Hoagland had two solutions, #1 has all 
nitrate; #2 had some ammonium, which kept the pH lower. Most people now use a 
modified Hoagland solution because the originals used iron tartrate instead of 
a chelate. I have never seen Hoagland solution sold commercially but have seen 
other research-type solutions offered by scientific supply companies at hefty 
prices ($7 per liter). Many hydroponic companies offer salt mixtures that can 
be used to prepare a hydroponic solution that will grow fine plants. They are 
relatively inexpensive with names such as Eco-Grow and Dyna-Gro. Try Worm's way 
(1-800-274-9676), Eco Enterprises (1-800-426-6937), or other hydroponic 
company. Miracle-Gro is not formulated for hydroponics so will kill plants if 
used in solution culture. 

Hoagland solution #1 (per liter of nutrient solution): 
5 ml of 1 M potassium nitrate 
5 ml of 1 M calcium nitrate 
1 ml of 1 M monopotassium phosphate 
2 ml of 1 M magnesium sulfate 
1 ml of micronutrient stock solution (see recipe below) 
1 to 5 ml of 1000 mg/liter iron from iron chelate (Fe-EDTA, Fe-DTPA, 
or Fe-EDDHA) 

Hoagland Solution #2: 
6 ml of 1 M potassium nitrate 
4 ml of 1 M calcium nitrate 
1 ml of 1 M monoammonium phosphate 
2 ml of 1 M magnesium sulfate 
1 ml of micronutrient stock solution 
1 to 5 ml of iron chelate stock solution as for #1 

Micronutrient stock solution per liter: 
2.86 g boric acid 
1.81 g manganese chloride - 4 hydrate 
0.22 g zinc sulfate - 7 hydrate 
0.08 g copper sulfate - 5 hydrate 
0.02 g 85% molybdic acid 

When diluted 1:1000 the micronutrient stock solution provides the 
following in mg/liter: 
Boron 0.5 
Manganese 0.5 
Zinc 0.05 
Copper 0.02 
Molybdenum 0.01 


Hershey, D.R. 1995. Plant Biology Science Projects. New York: Wiley.

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