Students will conduct a basic soil science experiment and re-familiarize themselves with the scientific method.
Students will observe the effects of soil on seed germination and growth. Students will determine the nutrient and pH values of the soils they used for their seeds.
This lesson is ideal as a precursor to the lesson on Succession and Nutrient Cycling in a Temperate Rainforest Ecosystem. It will prepare students for a more extensive encounter with experimental design.
About 2 weeks prior to starting this lesson, prepare 5 bean seeds in 5 cups of good potting soil. Label these plants with the date they were planted. Keep track of appropriate watering schedule to keep the plants healthy. Decide on amount and frequency of watering for students so that this is not a variable.
Review the Scientific Method on Day 1 and for the next 3 weeks allow students 5 minutes each day to observe the growth of their bean and collect data. The second and third 60-minute classroom session will take place approximately 3 weeks after the first and after the bean seeds have grown.
Day 1 Classroom Discussion
Begin Day 1 by reviewing the scientific method with the students. (See additional resources at the end of this lesson for topics of discussion.) Let them know that they will be conducting several scientific investigations over the course of the next 3-4 weeks. Instruct students to fi ll a sandwich bag full of soil from their home and bring it in to school. Any soil is fine and a variety of soils will make for the best experiment. At this time, you should soak enough beans for each student over night.
Days 2 - 22
Divide the class into 6 groups of 3-5 students each. Ask them to examine their soil and their bean seed and make
observations about each. Students will each plant 1 bean seed in their soil and make a hypothesis, such as “My
bean will grow 5 inches tall in 12 days.” Have the students title their experiment. Have the students state their
hypothesis. This experiment will be taking place as the class is preparing for the next 2 activities. Allow students
a few minutes each day to collect data and make observations on their seed’s growth.
Prepare a large graph with each student’s name for this day (the X-axis will have student names; the Y-axis height of bean plant in inches). Within three weeks (judge by the growth of the seeds) students will begin to conclude this experiment. They should have a series of daily observations and a growth chart that shows their hypothesis as well as their actual results. Allow students to meet in their groups and discuss results for about 20 minutes before bringing the whole class together. Students should complete the following Classroom Activity during this time and chart their bean’s growth on the class graph.
Have students each report and mark on a permanent classroom graph the height their bean seed attained and
note any odd characteristics (such as “yellow leaves, brown stem, leaves shriveled”) by their name at the bottom
of the graph. Have a classroom discussion about the results. Include the activity questions in the classroom
Classroom Activity - Drawing Conclusions
Each student should complete these questions while meeting in groups.
1) Why did some of the bean seed grow so fast?
2) What may have kept some from germinating?
3) What was the variable?
4) How does soil affect the growth of plants?
5) What properties need to be present in the soil for good plant growth?
6) Can you make a guess about the soil from the yard where the seed grew the best?
7) What do you think may have happened if we used a fireweed seed instead of a bean seed?
Have students write a conclusion for their experiments in their journal.
Day 24 Classroom Activity
If it does not come up in the classroom conversation, introduce a discussion of nitrogen, phosphorus and potassium. You could direct students by asking if they’ve ever used a fertilizer or by having them check the label of a fertilizer their parents have used.
Bring up the topic of pH and its affects on plants. Ask students to consider what grows in their yards beneath evergreen trees. Give each student a soil testing kit and have them test and chart the results of nitrogen, phosphorus, potassium, and pH for their soil. Have them discuss which factors may have limited or helped their bean seeds to grow. Compare the results with others in their groups and then with the whole class.
Write up a hypothesis, methods, data, observations, and conclusion for the fertilizer and pH portion of the lab. Have student groups compare their results and create one graph for their notebook that represents the group’s results. Ask students to write a conclusion for the entire experiment based on group results, individual results and classroom discussion.
Look for all aspects of the lab to be written up in the journal. There should be a hypothesis, charted data, observations, and a conclusion for both parts of the experiment. There should be an understanding of variables within the lab and there should be some comparisons made between the student’s work and that of the group.
If your class lives near a glacier, you might suggest that the soils they brought from home are like the soils in Kenai Fjords National Park—lots of rock, not much nourishment or water. Ask how long it takes after glacial till is formed for plants to grow? How would you be able to determine this? How would this
quality of soil aff ect a park manager’s decision to build a trail? How does it affect the growth of plants in an area where the glacier has been?
It is likely that no student’s bean seeds will grow as well as the teacher’s since the teacher is using potting soil. Raise this as a question: Why didn’t your seeds do as well? See if anyone can come up with an answer about the origin of the soil. In some areas the soil will be glacial till, largely rock and recently broken down rock. This type of soil does not hold water or nutrients well. Clay soils present another problem by binding nutrients so tightly to the soil molecules and not allowing for drainage. What do the folks who make potting soil need to be sure they are working towards for a good soil?
Carolina Biological Supply sells Rapitest 66-5404 kits that will run 10 soil samples each for nitrogen, phosphorus, potassium, and pH.