Activity # 3
Hydroponic Systems
Grade Level: 9-12
Module: Hydroponics
Overview
In this activity, students work with different hydroponic systems. Students
set up one or more hydroponic systems and collect data for a four week period
to determine which system resulted in the best plant growth. Students learn
about the role of differe nt environmental factors on plants grown in the
absence of soil. Such factors include pH, light, and aeration.
Key Questions
- Which factors affect hydroponic plant growth?
- Which hydroponic system is best for growing select plants?
Time Frame:
4 weeks
Materials
Depending on which hydroponic systems are selected, different materials
will be needed. In all the methods below, the "nutrient solution" may be
prepared by contacting your local hydroponics supply store (in your local
Yellow Pages) and following instruct ions from the supplier. Another valuable
source of information on hydroponics is the Hydroponic Society of America,
P.O. Box 3075, 2819 Crow Canyon Rd. Suite 218, San Ramon, CA 94583; phone:
510-743-9605; fax: 510-743-9302.
"No Tech" Method
1. Get two yogurt containers (cottage cheese containers, margarine tubs,
and milk cartons also work).
2. Poke a hole the size of a pencil diameter in the bottom of one container
and the lid of the second container.
3. Cut a piece of string about 6 inches long. Rinse the string thoroughly
in water to wash off any materials with which it may have been treated.
4. Tie a knot in one end and slip the string through the top container.
The knot should be against the bottom of the yogurt container to keep
the string from slipping all the way through the hole.
5. Fill the top container with perlite and the bottom container with
nutrient solution.
7. Poke the string through the lid of the second container.
8. Put the lid on the second container and sit the first container on
top.
Germination Tray Method
1. Use a rectangular, food storage-type plastic container.
2. Cut a slit in the middle of the lid lengthwise.
3. Get two pieces of absorbent cloth material, about the height of the
container (black works best to keep light away from the roots).
4. Pull one piece of material through the slit leaving about 2 cm (11/2
inches) at the top of lid. Tape that material to the top of the lid, laying
it flat and away from the center slit.
5. Do this again to the other side of the slit with the second piece
of material, again taping down the 2 cm of material that remain on top
of the lid after you pull the bulk of the material through the slit.
6. Fill the bottom of the container with nutrient solution high enough
so that the hanging material will dip into it and wick up the solution.
7. Place seeds on top of the lid, in the center of the material. Roots
will grow down through the material. Seedlings can be easily transferred
into other systems after germination.
Hydroponics in a Tub Method
1. Get a large plastic tub with a lid.
2. Collect film canisters (one for each student).
3. Cut as many holes as you can fit on the lid (using a sharp utility
knife or hole saw). Each hole should be the size of a film canister. Safety
Note: The teacher may need to cut the holes for younger children.
4. Drill a hole in the bottom of each film canister.
5. Put a string with a knot in one end, inside each film canister.
6. Pull the string through the hole and make it long enough to reach
the nutrient solution. The knot should be tense against the bottom of
the film canister to keep the string from slipping all the way through
the hole.
7. Fill the tub with nutrient solution.
8. Get the lid and put one canister in each hole, then put the lid on
the tub.
9. Fill each canister with perlite.
10. Put a seed or a plant in each canister.
Low Tech Method
1. Get two 2 liter soda bottles.
2. Cut off the top of one soda bottle at the point where the bottle
begins to narrow into a funnel shape.
3. Cut off the bottom of the second soda bottle and invert it to be
used as a top for the first soda bottle.
4. Cut a medium-sized hole in the top of the set-up (approximately 2
centimeters in diameter). Cut a smaller hole near the first hole (approximately
1 centimeter in diameter). Tubing will be fitted into the second hole.
5. Run tubing from an aquarium pump into the small hole for aeration
into the soda bottle.
6. Cut a piece of plastic foam (such as Styrofoam) the size of the medium
hole. Make a slit into the foam half-way; this will be used to support
the plant.
Raft Method
1. Use an inexpensive Styrofoam cooler (one that can hold several liters
of liquid).
2. Create a floating lid using a Styrofoam scrap.
3. Cut cup size holes into lid.
4. Poke holes into bottoms of cups and fill cups with perlite.
5. Place cups in lid and fill cooler with nutrient solution so that
only the bottom centimeter of cup is submerged.
6. Plant seeds in the perlite.
7. Aerate nutrient solution with an aquarium pump. As the roots grow
they will grow through the perlite into the nutrient solution. If the
nutrient solution is not aerated there will not be enough oxygen for healthy
root growth.
Ebb and Flow System
1. Fill cup or bucket with medium (rockwool, perlite, vermiculite).
2. Make a drain outlet in each bucket (see diagram) and connect with
tubing.
3. Plant seeds in rockwool cubes and place in growing medium.
4. Fill bucket with nutrient solution and raise above pot containing
seeds so that solution flows in by gravity feed and fills planted pot
to within 2 centimeters of top.
5. Let solution remain in planted pot for 20 minutes.
6. Place nutrient solution bucket below planted pot and allow nutrient
solution to drain back into its original container.
7. Repeat this ebb and flow 4 to 5 times each day.
Ebb and Flow Table
1. Plants are grown in a tray table top which has drainage holes.
2. A tub or tray is placed below.
3. Four to five times each day the plant tray is flooded for approximately
20 minutes, and the nutrient solution is allowed to drain away into the
tray or bucket.
4. The dimensions and construction of such a system may vary, depending
on the materials available.
High Tech: Method One
1. Get a large PVC pipe (one that is about 5 to 10 centimeters in diameter).
2. Drill holes (with a hole saw) the size of a cup into your pipe.
3. Connect smaller PVC pipes to your large pipe (using plastic adhesives)
to create a design that will fit the space you have. The ends of the PVC
pipe should be capped, depending on where the smaller pipes are attached.
4. Get a bucket filled with nutrient solution and set it below your
PVC set-up. Nutrient solution will drain into the bucket.
5. Put a submersible pump into the bucket.
6. Drill a smaller hole into the top of your large PVC pipe for a hose
from the pump.
7. Run a hose into the top of the pipe to circulate the nutrient solution.
The height and placement of the PVC pipe may need to be adjusted to assure
the pump can deliver the nutrient solution.
High Tech: Method Two Nutrient Film Technique
1. Get a plastic rain gutter and cut into equal sections.
2. Cover tops of rain gutters with plastic and use a knife or punch
to make holes in tops the size of cups.
3. Place a bucket containing nutrient solution under table.
4. Using aquarium tubing, connect pump to one end of gutter. This should
be at the highest point so that gravity can pull the nutrient solution
down each gutter and into the next gutter.
5. In the last gutter, at the lowest point, connect a tube to drain
back into the bucket containing nutrient solution.
6. The nutrient solution should flow continuously through the gutter
at a depth of about 2 mm (just enough to bathe the roots).
Getting Ready
Read through the Materials section to determine what materials, space, and
other items are needed before beginning the activity. The setup will depend
on which hydroponic systems are chosen. Plan on groups of at least 4 or
more members.
Classroom Activity
1. Divide the class into experiment groups and assign each group to build
at least one hydroponic system of their choice or your choice (depending
on materials available). If possible, have groups choose and construct one
or more of the above systems whic h they believe will result in maximum
plant growth. Explain that each group will present their results to the
class at the end of the activity.
2. In each system students should germinate and grow several lettuce
plants for 2 to 4 weeks. They should check plants and record observations
on a daily basis over that time period. Each student should create a data
sheet for daily recording of data. Exa mples of factors to have on a data
sheet include:
- pH of the nutrient solution (use pH paper)
- Plant's general appearance (Does the plant appear a healthy green?
Are there yellow or brown spots?)
- Number of leaves present
- Length of selected leaves since some plants have more of a bushy shape
- Plant height
3. At the end of the four weeks of observation, have students separate the
leaves from the roots. It is best to set the leaves aside and allow them
to dry before weighing. Dry mass is the best indicator of plant growth success.
4. Have the students analyze and graph results to determine which hydroponic
system is the best for lettuce.
Wrap-up Session
Review the results of each hydroponic system with the students. The instructor
can have the students share their results with each other by having them
present the results to the class. Based on their results, can they now answer
the key questions posed a t the beginning of the activity?
- Which factors affect hydroponic plant growth?
- Which hydroponic system is best for growing select plants?
More Activity Ideas
Have the students design an optimal hydroponic system based on the results
they have collected from this activity.
Background for Teachers
Prerequisites:
- Ability to follow detailed instructions
- Ability to keep a lab book, to record observations
- Ability to work in a group
Vocabulary:
- Germination - to sprout from a seed into a seedling
- Vermiculite - material used as heat insulation for starting plant
seeds
- Perlite - small pieces of white volcanic rock used in commercial
potting soils
- Hydroponics - cultivation of plants in water containing dissolved
inorganic nutrients rather than soil
Skills:
- Collecting and recording data
- Constructing a graph from a table of data
Concepts:
- Hydroponics
- Capillary action
- Gravity flow
Keywords: Germination, Vermiculite, Perlite, Hydroponics, Plant Growth,
Nutrients
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