(http://esseacourses.strategies.org)
Crops Investigation #9
Goal:
Compare the growth of seedlings in different soil types.
Objectives:
Students will be able to:
- construct and use a data table.
- construct and interpret a line graph.
- explain the parts of an experiment (variables, controls, etc.).
- discuss factors that affect plant growth (such as soil type and moisture).
- discuss the impact that soil type has on plant root growth.
Standards Met:
Overview:
In a previous activity (#1), the students planted seeds. Since then, the students have been caring for the seedlings and making measurements of the seedlings. Students should now analyze their results by constructing and interpreting graphs and by making careful observations of the seedlings.
Materials:
(This experiment was setup weeks ago. The following materials were needed at that time.)
- soil (each student has collected their own)
- small pots or cups (small bathroom cups will work for small seeds, such
as radish, but larger cups will be needed for larger seeds like bean)
- labeling materials (pens and tape)
- seeds (examples): beans (no soybeans due to allergies), grass (only if you
don't let it bloom), corn, sunflower, pea, cucumber, onion, radish, or squash family (pumpkins are fun for the fall)
- area to grow the plants that gets sunlight or in which lights can be set
up
- experimental design worksheet
- rulers
(new materials)
- pans or tubs in which students can rinse soil from the plant roots
- graph paper
Resources:
Actions:
Prior to the lesson:
- The students planted seeds in the soils that they brought from
home. They have also been making measurements and observations of these
seedlings. The easiest measurements are: plant height and number of leaves. Observations might include: appearance of the cotyledons
(like: plump or shriveled or ___ in color), color of the leaves, and overall health of the plant
(like: drooping or erect or turning brown).
During the lesson:
- The first question that the students are trying to answer is:
"How well did the plant grow in this
soil?" Students will use the measurements that they have been making to construct a line graph. Prior to constructing the graph, it might be appropriate to discuss the difference between line graphs and bar graphs.
- After the graph is complete, the students should write conclusions based on their graph in their science notebook.
- The graphs should not be the only data used to answer the question above; all of the student observations that were recorded over the growth period should also be used. Add the conclusions from the observations to the conclusions from the graph in the science notebook.
- Since students used different soil types, the results from different soil types should be compared through a class discussion.
Each student is responsible for being able to discuss their results and
conclusions. Basically, the class is answering the question,
"Does soil type effect the growth of this plant?"
- Once this discussion has been completed, students should write conclusions
about the effect of different soil types on the growth of the seedlings in their science notebooks.
- Similarly, if students used different plant species, there should be a discussion of the effect of soil type on the different plants. Here the question is,
"Does the type of soil affect one plant species differently than another plant species?"
- In addition to the above-ground observations, below-ground observations should also be used as a way to examine the effect of soil type on plant growth. Gently, remove (some of) the plants from the pots and wash the soil away from the
roots by dipping the roots in pans of water. Compare the amount of root growth in the various soil types. Pose the question:
"Does soil type affect the growth of plant roots?"
- During the examination of the roots, a number of different topics can be discussed.
"What is the function of the root system?" Students should be able to come up with at least 3 functions.
- There are two root systems types: tap and fibrous (or adventitious). Students should be able to determine which type of root system their plant has.
- The two types of plant root systems are adapted in different ways. "How is this root system adapted for absorbing water?
...for anchoring the plant? Is this root system well adapted for storing food reserves?"
- If more than one plant species was used, have the students determine the type of root system that
all of the plants have (fibrous vs. tap).
"Does a particular root type grow better in a particular soil type?"
Extensions:
- Soil nutrient test kits can be used to measure the amounts of nutrients at the beginning of the experiment and at the end of the experiment. If materials are readily available, multiple measurements might also be taken at regular intervals during the growth period.
- Soil moisture could be measured if equipment is available. The amount of water added could be kept constant and the moisture level measured. The amount of water added could be varied in order to maintain a set moisture % so that the soil moisture is always kept the same.
- Students could make a scrap book of plants that normally grow in the area from which the soil sample was collected.
Assessment:
All of the data collected and analyzed should be used to write a lab report. Alternatively, the graph and conclusions written in the science notebook can be scored as the assessment for this activity.
Reflection:
Please write a reflection after you teach this lesson to help us make improvements. Reflections should be e-mailed to j.okeefe@moreheadstate.edu and c.wymer@moreheadstate.edu. If you also complete student reflections, please include these as well.