Killing Radishes E Fair Projects

Name: Thomas
Grade Level 7th
Awards: Mid-Columbia Science Fair. Distinction for Scientific Thought. Washington Apple. Washington State Science and Engineering Fair. 1st place ribbon and trophy.

PURPOSE

The purpose of this experiment was to determine the toxicity threshold concentration of herbicide on radishes.

I became interested in this idea when I read an article showing that if you use a low enough concentration of herbicide it can actually have a beneficial effect on the plant.

The information gained from this experiment would help farmers know the largest possible amount of herbicide you could use in an area where they are growing radishes and still not kill the radish with 2,4-D.

HYPOTHESIS

My first hypothesis was that if there were a small enough amount of herbicide it would not harm or kill the radishes.

My second hypothesis was that too much herbicide would harm or kill the plants.

I based my first hypothesis on the fact that a man named Edward Calabrese had seen a beneficial effect when he poisoned peppermint plants with the herbicide Phosfon. I based both of my hypotheses on the statement by a scientist of the 1600’s, Paracelsus, “All things are poison and nothing is without poison” and another statement by the same person, “It is the dose that makes it a poison”.  

EXPERIMENT DESIGN

The constants in this study were: 

•  Type of plant
•  Seed age and storage
•  Soil moisture
•  Temperature
•  Amount of light
•  Pot size and shape
•  Amount of soil
•  Soil type 
•  Testing procedure
•  Planting depth
•  The type of herbicide I used and how much I used for all plants of a specific test group

The responding variable was the amount of radishes left alive per group over a period of weeks.

To measure the responding variable I counted how many radishes were left alive per group out of 10.

MATERIALS

QUANTITY   ITEM DESCRIPTION

PROCEDURES

1. Plant seeds:
a) Poke a pencil through the bottom side of 120 Styrofoam cups.
b) Fill each cup with the potting soil to within 2 cm of the rim.
c) Put the cups into 8 cardboard trays with 15 cups in each tray.
d) Fill each cup with 50 ml of water.  
e) Place 2 radish seeds in each cup.
f) Next cover the seeds with a large pinch of potting soil.
2. Build the growing enclosure by:
a) Take one of the A-frames and 4 screws.
b) Then carefully hold one of the grow lights up onto the bottom of the A-frame and put the screws into their holes.
c) Repeat with the other A-frame.
d) Place the A-frames structures put them relatively close to each other.
3. Germinate seeds, grow seedlings:
a) Next put 4 trays under one A-frame and 4 under the other.
b) Drape the curtain over the two A-frames.
c) Maintain temperature between 16 degrees Celsius and 19 degrees Celsius.  
d) Cover cups with plastic to assist germination.  
e) Wait about 2 days for the radishes to germinate.
f) After the radishes have germinated turn on the grow lights.
g) After 4 more days add 16 ml of water to each cup.
h) Now add some topsoil to each cup so the plants don’t fall out.
i) 6 days later drench the soil with approximately 32 ml of water per cup.
j) Sort the 120 Styrofoam plant cups into 12 groups and label the groups 1-12.
4. Prepare herbicide concentrations: 
a) Take the twelve 8. 5 ounce Styrofoam herbicide cups and label them #’s 1-12.
b) Fill herbicide cup #1 with 160 ml of water and add NO Weedar.   This is the control.
c) Fill herbicide cup #2 with 160 ml of water and add 1 ml of Weedar using the syringe. ( Equals 6250 ppm)
d) Fill herbicide cup #3 with 160 ml of water and add 0. 1 ml of Weedar with the syringe. ( Equals 625 ppm)
e) Fill herbicide cup #4 with 160 ml of water and apply 0. 01 ml of Weedar using syringe. ( Equals 62. 5 ppm)
f) Fill a flask with 320 ml of H2O and apply 0. 01 ml of 2,4-D. Pour 160 ml into cup #5. ( Equals 31. 3 ppm)
g) Dilute 160 ml in flask with additional 160 ml of water. Pour 160 ml into cup #6. (Equals 15. 6 ppm)
h) Repeat last step, except pour into cup #7 (Equals 7. 8 ppm)
i) Repeat last step 5 more times, pouring dilutions into cups #8 - #12, having 3. 9 ppm, 2. 0 ppm, 1. 0 ppm, 0. 5 ppm, and 0. 2 ppm respectively)
5. Stir the mixture in herbicide cup #2 and apply 16 ml to each cup in group #2.
6. Repeat step 5 for all other herbicide groups, being sure to use each on the respective plant group (for example, herbicide #6 goes only on plant group 6. )

RESULTS

The original purpose of this experiment was to determine the toxicity threshold concentration of herbicide on radishes.

The results of the experiment were that the toxicity threshold was between groups 6 and 7 because this was the point where 40% of the plants died (in group 7) and 90% of the plants died (group 6). After group 7 then the number of deaths decreased to 10% in group 8 and then 9-12 were all 100% except for group 10 having 90%. Also groups 2-4 had 100% death and group 5 had 90% death. This claims the threshold to be between groups 6 and 7.

CONCLUSION

My first hypothesis was that if I gave the radishes a small enough dose of herbicide it would not kill it them.

The results indicate that this hypothesis should be accepted, because the plants with the recommended dose of herbicide or higher all died.  

My second hypothesis was that too much herbicide would harm or kill the radishes.

My hypothesis should be accepted because the plants with lower than the recommended dose mostly lived except for the two groups right after the recommended dose, which had 90% and 40% die.
 

My second hypothesis should also be accepted, because the plants with less than the given dose had 60% or more of the plants surviving.  

Because of the results of this experiment I wonder if I used a different plant or a different herbicide would I get the same effect that I did with radishes and 2, 4-D. I also wonder if there is a certain amount of herbicide that would actually have a beneficial effect.

If I were to conduct this project again I would check my plants more, make a better curtain to make sure the light is somewhat contained, water the plants more accurately, have the project run for at least an additional week, and I would use at least 20 plants in each group. Abstract