The Effects of Soil Type on Bean Germination
Mr. Spotts
18 December, 2007
6A
C.O.R.E.
ABSTRACT
This experiment was designed to test the idea that bean seeds might sprout better
depending on the type of soil in which they were planted. I hypothesized that the beans
would sprout faster in Soil A, which is browner and contains more organic matter. The
independent variable in the experiment was soil type, and the dependent variable was the
growth of the beans. Variables that were controlled include the amount of light and water
the beans received, the type of seeds and the method in which they were planted.
Each student in class prepared their planting cup by punching five holes in the
bottom and placing a 2 inch by 2 inch piece of paper towel in the inside. One of two
types of soil was filled to the blue line, and five pinto bean seeds were place on that.
Seeds were covered by 0.25 additional inches of soil and then placed water-filled trays
contained in the classroom growth chamber. Results of how many seeds sprouted in each
cup and for each treatment as a whole were recorded in the data table at the beginning of
class for four class periods.
Classroom data was compiled and graphed using Microsoft Excel. The data
showed that while a greater number of seeds planted in Soil A sprouted, the percentage of
seeds that sprouted in each soil type were very similar. Problems that were encountered
included 1) mold growing on the top of the cups that might have prevented additional
seeds from sprouting; and 2) some students not planting seeds according to directions.
Analysis of the limited data we had led me to the conclusion that the bean seeds did not
sprout faster in Soil A compared to Soil B, meaning that my hypothesis was proven
wrong.
QUESTION
The question we attempted to answer by conducting this experiment was “Does
the soil type in which bean seeds are planted determine how fast the beans will sprout?”
HYPOTHESIS
Based on what I knew about soils from the science unit “Solving the Garden
Problem”, I thought that the bean seeds would sprout first in Soil A.
VARIABLES
The independent variable in this experiment was the type of soil used to plant the
seeds. The dependent variable was the sprouting of the bean seeds. Variables that were
controlled include the amount of light and water the beans received, the type of seeds and
the method in which they were planted.
INTRODUCTION
The first unit covered in 6th grade science class dealt with properties of soil. We
examined different soils and learned about soil composition, texture, organic matter and
nutrients. Our textbook was set up so we could examine a school garden and identify
potential problems as to why the garden wouldn’t grow plants. One possible explanation
was that the soil was the wrong type to grown the plants.
In the lessons, we learned that there are different types of soil in different areas of
the country, and I know that certain crops can only be grown well in certain areas of the
country. For example, corn and soybeans are grown in Illinois, while cotton is better
grown in Mississippi. This got me to thinking about how soil type might affect whether
or not plants would germinate or not. I decided to do this experiment in order to test if
one type of soil would be better for growing pinto beans.
MATERIALS
The materials we included in our experiment included the following:
Cup
Soil A
Water
Paper Towel
Soil B
Growth chamber
Pencil or pen
Pinto bean seeds
Data sheet
METHODS
Students followed a precise order of steps in order to test their hypotheses. First,
each student in class prepared his/her planting cup by punching five holes in the bottom
of the cup with a pencil or pen. Next, a 2 inch by 2 inch piece of paper towel was placed
inside the cup to act as a wick to get water up into the soil. Then, students put one of two
types of soil in their cup up to the pre-marked blue line and lightly packed the soil with
their fingers. Five pinto bean seeds were place on the lightly packed soil, and the seeds
were then covered by 0.25 additional inches of the same type of soil. After writing their
names and soil types on the outside of their cups, students placed their seed cups in
water-filled trays contained in the classroom growth chamber. Results of how many
seeds sprouted in each cup and for each treatment as a whole (Soil A and Soil B) were
recorded in the data table at the beginning of class for four class periods.
RESULTS
Data on the bean germination was collected four times after the initial planting.
Results are shown in both table and graph form below.
Class Bean Seed Germination Data Table
Sampling
Total Sprouts
Total Sprouts
Date
in Soil A Cups
in Soil B Cups
19 Nov 07
0
0
22 Nov 07
1
0
23 Nov 07
2
1
27 Nov 07
5
3
29 Nov 07
5
3
Soil Type Vs. Bean Seed Germination
5
4
Soil A
Soil B
3
2
1
Observation Dates
29 Nov
27 Nov
23 Nov
22 Nov
0
19 Nov
Number of Bean Sprouts
6
CONCLUSIONS
The hypothesis in this experiment is that bean seeds will sprout more quickly in
Soil Type A. After four series of classroom observations, the data showed that in fact a
greater number of seeds planted in Soil A sprouted. On the surface, this would lend
support to the hypothesis. However, the percentage of seeds that sprouted in Soil A and
Soil B were both very low and ended up being similar. In Soil A, 5 out of 75 seeds
germinated, which was only 6.7%. In Soil B, 3 out of 55 seeds germinated, which was
only 5.4%. At such low levels of germination, it is impossible to state with confidence
that the soil type had any affect on bean seed germination.
Possible explanations for the low germination rate are centered on two problems.
First, many students noticed a white filamentous mold growing both on bean seeds and
on the top of both types of soil in the cups. This could be due to non-sterile conditions in
the growth chamber or too much moisture in the general area of the growth chamber.
Posters hung to shield the experiment from the other science classes may have acted like
a barrier, preventing moisture from spreading out into the science room. Either the mold
itself or the humid conditions that led to the mold growth may might have kept other
seeds from sprouting.
Secondly, some students did not plant their seeds exactly
according to directions. This could have introduced other variables into the experiment
that kept bean seeds from germinating.
Final analysis of the limited data we had led me to the conclusion that the bean
seeds did not sprout faster in Soil A compared to Soil B, meaning that my hypothesis was
proven wrong. Based on these results, one possible extension of this research would be
to conduct the experiment in a less humid environment. Less water could be kept in the
trays, and a small fan could be used to blow humid air out of the growth chamber.
Additionally, a student could conduct further research on the effects of mold and/or
humidity on the germination of bean seed.
ACKNOWLEDGEMENTS
I would like to extend my appreciation to the sixth grade students at NKO
Middles School, without whom this experiment could not have occurred. Secondly, I
would like to thank Mr. Hudson who fixed the electrical outlet in the science lab, and Mr.
Bly, who provided insight and feedback on the experimental design. Finally, I would like
to thank Michael Anthony Booker, my former student at Greenville-Weston High School
in Greenville, MS, who convinced me that in order for students to learn about science,
they must be involved in doing science.
BIBLIOGRAPHY
1. Science Buddies Topic Selection Wizard, Kenneth Lafferty Hess Family
Charitable Foundation, http://www.sciencebuddies.org/mentoring/tsw_start.shtml
2. University of California at Berkely, Issues and Earth Science. Berkely: Lab Aids
Inc., 2006.