The purpose of this project is to determine which group of lettuce will produce the most oxygen. The significance of this project is that we need a renewable supply of oxygen in space that only plants can provide. Hydroponics is the study of growing plants in a substance other than water with nutrients (called a hydroponics nutrient solution). Aquaponics is the study of growing plants in water without nutrients. This project was meant to determine the amount of oxygen produced in percent using aquaponics, hydroponics, and traditional soil. The first hypothesis for this experiment is that the hydroponics group would produce the most amount of oxygen on average. The second hypothesis for this experiment is that the aquaponics group would produce the second most amount of oxygen on average. The third hypothesis for this experiment is that the soil group would produce the least amount of oxygen on average. The independent variable was the growing method. The dependent variable was the amount of oxygen produced. The procedure was to take 24 Bibb lettuce plants and separate them into three groups of eight. Over eight days I measured the amount of oxygen they produced with a BOD meter. The data did not support the first hypothesis. The hypothesis was rejected. The hydroponics group produced 28.7% of oxygen on average. The data did not support the second hypothesis. The hypothesis was rejected. The aquaponics group produced 27.9% of oxygen on average. The data did not support the third hypothesis. The hypothesis was rejected. The soil group produced 30.5% of oxygen on average.
The purpose of this experiment is to compare the oxygen production of plants grown using different methods.
Independent Variable - growth method
Dependent Variable - amount of oxygen produced
H1: The plant grown in rockwool will produce the most oxygen.
H2: The plant grown in water will produce less oxygen than the plant grown in rockwool.
H3: The plant grown in soil will produce the least amount of oxygen.
Photosynthesis
The process in which plants produce oxygen is called photosynthesis. Photosynthesis means "putting together with light". The photosynthesis process takes place in the chlorplasts mainly using chlorophyll, which absorbs sunlight. During this process, the plant produces oxygen and releases it. As long as the plant gets its required amount of light, it should produce plenty of oxygen. The formula for photosynthesis is 6CO2 + 12H2O ---> C6H12O6 + 6H2O + 6O2, which means six water molecules plus six carbon dioxide molecules produce one molecule of sugar plus six molecules of oxygen.
Hydroponics
Hydroponics is the study of growing plants in materials other than soil. Hydroponics means "water works". According to Martin P.N. Gent (1998), the leaves on hydroponically grown plants are more succulent and thicker than those grown in soil. There are seven different medias/cultures: water, aggregate, sand, nutrient film technique (NFT), rockwool, peat/perlite/vermiculite, column, and sawdust. In these cultures, the pH and EC are monitored several times a week.
Water culture
The water culture is the earliest known form of hydroponics. Plants are constrained in a raceway (floating media) or rests on a support that allows the roots to bathe in a nutrient solution.
Aggregate culture
The support media is an aggregate (such as gravel).
Sand culture
The sand culture is similar to the aggregate culture. Sand is the support media.
Nutrient Film Technique (NFT)
The NFT is a variation of the water culture. Must have an adequate spacing in order to produce what it needs to survive. This method is usually used for leafy plants and herbs.
Rockwool culture
This culture is commonly used when growing commercial grops such as melon, peppers, cucumbers, tomatoes, and vine crops. PH and EC monitored several times a week.
Peat, Perlite, and Vermiculite
This culture is similar to the aggregate culture. Used mostly for flowers and houseplants. Uses mixtures of peat, perlite, and vermiculite as the support media. Support media must be discarded after each crop or put into potted plant soil mix.
Column culture
This culture is similar to the above. Mostly used for growing foliage, annuals, flowering plants, strawberries, herbs, spinach, and lettuce. The support media is a mixture of peat and vermiculite.
Sawdust culture
This culture is used mostly to grow vegetables. It is similar to rockwool culture. Sawdust in a bag is the support media.
Title: A Comparison of Hydroponic Oxygen Systems for Space Travel
Hypotheses:
H1: The plant grown in water will produce the most oxygen
H2: The plant grown in rockwool will produce less oxygen than the plant
grown in water
H3: The plant grown in soil will produce the least amount of oxygen
Independent variable (IV): growth method
Dependent variable (DV): amount of oxygen produced
Constants: amount of light, type of light
Safety Considerations
Hazards: chemicals
Precautions: wear safety gear (goggles, aprons) and wash hands after handling the chemicals.
Organism Information
Common Name: Bibb Lettuce
Genus Name: Lactuca sativa
Description: a small, leafy lettuce
Source: South Brevard Nursery
Experimental Methods
Making Hydroponic Solution
Materials
13 1/2 oz sodium nitrate
4 1/2 oz potassium sulfate
10 oz superphosphate
4 oz magnesium sulfate
Trace elements (see below)
100 gal water
To mix less than 100 gallons of water, merely mix and store the larger quantity of powders, then use at the rate of four tsp per gallon or 1/2 lb to 25 gallons. For larger quantities, simply multiply the formula.
Trace element mix
1 oz iron sulfate
1 level tsp manganese sulfate
1 level tsp boric acid powder
1/2 level tsp zinc sulfate
1/2 level tsp copper sulfate
Mix well and store dry. Use 1 gram (about 1/2 tsp) per 100 gallons of nutrient solution. For smaller batches, dissolve 112 tsp of the trace mix into one quart of water, use 1 liquid oz per 3 gallons of nutrient solution. Do not try to save any unused trace mix solution.
Building Systems
All groups
1) Fit plexiglas to each 10 gallon tank.
2) Cut a hole and make a flap in one corner of all the plexiglas tops.
3) Clean out the soil from all the plants.
Hydroponics group
1) Take one plastic tray and put the rockwool in it.
2) Fill the tray with hydroponics solution so that the rockwool is soaking in it.
3) Leave overnight.
4) Place rockwool in another plastic tray
5) Dump out hydroponics solution from the first tray.
6) Place eight lettuce plants in the rockwool (one plant per square).
7) Fill the tray with hydroponics solution halfway up the rockwool squares.
8) Place tray in a ten gallon tank.
Aquaponics group
1) Fill a tray halfway up with water.
2) Place eight lettuce plants in the tray.
3) Place tray in a ten gallon tank.
Soil group
1) Fill about a quarter of the tray with soil.
2) Place eight lettuce plants in the tray.
3) Fill the rest of the way up with soil.
Measuring Oxygen Production
1) Place BOD meter in the hole in the corner of the tank.
2) Make sure you have it on the 'O2 (AIR)' part.
3) Wait about three minutes.
4) Write down the percentage on the screen.
8 blocks of rockwool
RO water
1 bag of soil
3 ten gallon aquariums
24 Bibb lettuce plants
1 BOD meter
plexiglas
4 plastic trays
Sodium nitrate
Aluminum potassium sulfate
Calcium phosphate
Magnesium sulfate
Boric acid powder
Zinc sulfate
Copper sulfate
Botany/lactuca. Retrieved on November 14, 2005 from: http://www.botany.com/lactuca.html
Farabee, Michael J. Photosynthesis. Retrieved on October 6, 2005 from: http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookPS.html#light
Feed Your Hydroponics. Retrieved on December 12, 2005 from: http://www.motherearthnews.com/library/1993_February_March/Feed_Your_Hydroponics
Flinn Scientific. Retrieved on January 18, 2006 from: http://www.flinnsci.com/search_MSDS.asp
Hydroponic Nutrient. Retrieved on December 22, 2005 from: http://www.simplyhydro.com/hydropon.htm
Science Service. (2005). International Rules for Precollege Science Research: for Science and Engineering Fairs/2005-2006. Washington. DC: Science Service.
Smith, Sinjin. Personal communication by email on October 16, 2005.
