Material List: computer and projecting system (optional - individual student computers); soil samples form community/school campus; paper plates (to put soil samples on); gloves; plastic spoons (to probe, dig, and move soil around with); disposable gloves; relief map for classroom display; magnifying lens; local area map; several soil samples from locations in which different plant species grow; trowel; sealable plastic bag; masking tape; markers; red and blue litmus paper (optional-pH probes or Hydrion paper); petri dishes (or small dishes); eye droppers; teaspoons; science learning logs Soil pH and Plants BLM; plant seeds (quick-growing plants such as pea plants, rye grass are ideal); Soil Texture Dichotomous Key BLM (one per student), push pins for map flags; teacher- selected research material for plant growth in environmental conditions of local areas such as forests, marsh, wetlands, coastal plains, etc.; soil cards (see Part C); small paper plates
Part A: The teacher and students are to collect samples of soil from a variety of places in the community and school campus. The teacher could also alert students early in the semester about this activity and have them collect samples as they travel to other parts of the state and country. Have students to look for patterns of a specific characteristic with a specific location. They are to observe closely with a magnifying lens and describe the different particles found. Students should answer the following observation questions:
Is there evidence of organic matter; if so, where would they have come from?
Are there living things in the soil; if so, what are they?
How many different kinds of particles are there; what are the differences?
Students can use the Soil Texture Dichotomous Key BLM to help determine the soil type of their sample. Color comparisons should relate to the chemical composition and provide extensions into what plants/crops grow well in what soils. A county agent or soil specialist can provide information about soil profiles for comparing soils from different areas and determining which types of plants grow best in these areas.
Part B: Small student groups will research and analyze soil pH to determine if their seed plants are compatible with the soil. For this experiment, collect a number of soil samples from locations in which different plant species are growing (i.e., soil samples from under a pine tree, a maple tree, a spruce pine tree, a tomato plant, a watermelon, an azalea bush, clover, or goldenrod). These soil samples can be collected ahead of time or students can collect them on a soil gathering expedition around the school (this could be incorporated into a plant identification hike). Students could also bring in soil samples from home (encourage them to only gather soil from under plants that they can positively identify).
To collect the soil samples, use a trowel to dig down 10-15 cm into the soil (harming the root system of the plant as little as possible in the process). Place a soil sample into a sealable small plastic bag. Label the container with the name of the plant using masking tape and a marker. Fill in the hole dug as best as possible.
Provide each group with one soil sample, several pieces of red and blue litmus paper (optional-pH probes or pH paper), an eyedropper, and two petri dishes (or small dishes). Review what litmus paper is for and how to read the results from this pH indicator. Instruct the students to place a piece of blue litmus paper in one petri dish and a piece of red litmus paper in the other petri dish. The students should then place approximately a teaspoon of their soil sample on top of each strip. Using the eyedropper, the students should then moisten the soil until the strips of litmus paper become wet. Finally, instruct the students to brush the soil away with their hands and determine if it is acidic or alkaline, as indicated by the color of the litmus/pH paper or reading on the probe. Direct the students to construct a table in their science learning logs (view literacy strategy descriptions) consisting of two columns titled ďAcidic SoilĒ and ďAlkaline Soil.Ē In the appropriate column, the students should record the name of the plant species under which their soil was found.
Instruct each student group to display their soil sample on a small paper plate (with the plant species name clearly visible) and the results of the pH tests in their work area.
Allow the students to circulate throughout the room, recording the findings for each soil sample. After all data is recorded, students will use the data to answer the Soil pH and Plants BLM. Design and conduct an experiment to test the growth of a variety of plant species in different soil pH. Design and conduct an experiment to test the effect of soil nutrients on plant growth.
Part C: Prior to this part of the activity, download Discovery Channelís Soil Safari to a computer desktop that can be used with a projector for whole class viewing or download to individual student computers. Print the soil cards for each student.
Display a soil sample and a rock sample and ask students if they know of a process that would allow the rock sample to become the soil sample. Guide studentsí responses to weathering, connecting to studentsí prior learning. Ask students how long they think it would take for the rock sample to weather into the soil sample. Accept all and display them on overhead, chart paper, or board. Inform students that geologists have estimated that it takes approximately 12,000 years for rocks to weather into soil. Explain that this time varies with certain conditions, such as parent material (sediment type), climate (and weathering), organisms (flat vs. rugged land), topography, and time (rate of soil formation, which is dependent upon all of the above). The biological activity imparts organic debris (litter), and installs decomposer bacteria and other life forms (e.g., worms, millipedes, ants). This added organic matter is called humus. Thus, we could sum up soil formation as Solid products of weathering (sediments) + Humus = Soil.
Students will focus on the biological factors in soil formation using the Discovery Channelís Soil Safari. This virtual field guide profiles species selected from each major type of soil organism, ranging from the largest animals to live underground to the smallest micro-organisms. Each profile provides information on the organism's size and ecological role in creating and maintaining soil health. Pass out soil cards to students. Begin with a brief discussion on how animals contribute to its environment. Pass out the soil cards with the instructions that students use in Soil Safari. (Soil cards)
Students are to note the contribution an animal provides to the soil, along with basic information (its size, its food source) and any facts of particular interest to the student. After they complete the activity, students should refer back to their soil cards. These cards can then be used to evaluate students reading comprehension, understanding of how a variety of animals make important contributions to soil and their environment.