Discussion & Explanation:
Offer an explanation for the class results and explain why it is either consistent or inconsistent with your original prediction.
What did you find out after completing your experiment? Would you recommend adding biochar to fields of mung plants? Use
data and evidence from the class experiment and from the results of other experiments by other scientists to support your
Claim: What is your claim about biochar? Under what conditions (e.g., in what types of soils) is biochar an effective soil additive to increase plant biomass?
Biochar is not a good way to increase plant growth in topsoil. The mung beans did not grow larger when they were in topsoil with biochar compared with topsoil without biochar.
Evidence: What evidence (data) do you have to support your claim about biochar? Provide evidence from your class data in the
form of a graph or table.
The plants were shorter when grown with biochar compared to without biochar in all the different soil types. The amounts of shoots and
roots was almost the same in soils with biochar and without biochar.
Reasoning: Provide a biochar recommendation (whether to use it or not) to your neighbor who also farms mung beans. The
neighbor asks, “Why do you make this claim about biochar?” Explain the reasons why you made this suggestion to your neighbor. Why is biochar effective in the conditions you identified and less effective in other conditions?
Based on my experiment, I would not recommend adding biochar to your soil because it did not make the plants grow any bigger. In the soils we tested, biochar did not increase plant growth. I think that the soils we used are already fertile and support
good plant growth, so adding biochar didn’t help. We learned that biochar can help keep soils moist. If your soils are dry, then
adding biochar might be useful for keeping water in the soil so the plant can get the water it needs. We also learned that biochar
doesn’t affect all plants the same way. If you are growing a different plant than mung beans, biochar might help plant growth
• What variables that you did not test or control for might have influenced your results?
We did not test the fertility and amount of nutrients in the soil types.
• Describe two things you would do differently if you repeated the experiment.
I would try to measure or control some things about the soil types, like the amount of nutrients in the different soil types.
6 8 10 12 14 16 18 20
Day of growth
control (n = 13)
biochar (n = 14)
Figure A2. Plant height data for potting soil treatment collected by students during plant growth experiment.
Points represent means. Error bars represent one standard deviation from the mean. Numbers in legend are
number of student replicates within each treatment.