Students will discover how soil texture influences the percolation rate of water and the ability of soil to hold minerals.
Part 1: Percolation of Water Through Sand
Review with students the concepts that soils are composed of different sized particles (sand, silt, and clay) and the rate that water moves through a soil is directly related to a soil's particle size. Remind students that that soils of the Pinelands are predominantly sand.
Distribute the "Soil Experiment Part 1 and 2" worksheet to the students.
For the purpose of the following experiment, students may work in pairs or small groups. Distribute dried samples of sand, silt and clay that remain from the soil unit lesson "Sand - The Dominant Ingredient". Every team should also be given filter paper, three funnels, three glass or clear plastic containers on which to place the funnels, and a container of water.
Place filter paper in each funnel. Next, take equal amounts of dry sand, silt, and clay, and place them into separate funnels. Put each funnel over a container.
Ask students to answer question 1 of part 1 on the worksheet, which asks them to predict which type of soil (sand, clay, or silt) will allow water to pass the fastest, second fastest, and slowest and have students write these predictions on a separate piece of paper.
Pour equal amounts of water into each funnel and record the time it takes until the first drop of water appears in the container. Observe and measure the amount of water that passes through the soil and record how long it takes for this to happen. Students should answer questions 2,3, and 4 of part 1 of the worksheet based on this experiment.
Have students share their results and conclusions with the rest of the class.
Discussion questions:
Distribute copies of the "Pinelands Soils Chart" to students to assist them with answering the next five questions on the worksheet. After the students have taken the time to answer questions 5 through 9 of part 1 of the worksheet discuss the questions with the class and have the students share their conclusions.
Part 2: Leaching of Minerals
This portion of the lesson may be done as a teacher demonstration or as a group activity.
In the Pinelands, organic matter lies on the surface of the soil and its decomposition is slow. As water moves rapidly through the humus in the upper layer of this sandy soil, it becomes increasingly acidic and carries soluble minerals, especially iron, with it. "Leaching" is the term used to describe the downward movement of minerals in the soil.
Take a one pound coffee can and remove both ends. Over one end, place a filter or a piece of pantyhose and secure this to the can with a rubber band.
Place a layer of sand in the can, then a layer of colored Jell-O (use red or green colored Jell-O) and continue alternating these layers until the can is full. Then, place the filled container over a sink or large pan and begin to pour water very slowly through the container. To speed up the process, use hot water.
Have students describe what is happening to the containers contents. Ask them to answer questions 1 and 2 of part 2 of the worksheet and record their answers on a separate piece of paper.
After the students have answered these questions, discuss how the experiment illustrated what happens to minerals in Pinelands soil. The sand represents the Pinelands soil while the Jell-O represents the minerals in the upper soil layers.
Percolation of water through the soil's A Horizon washes humus and minerals, including iron, into the B Horizon. Red-yellow coloring of the B Horizon indicates iron has leached into the layer, while humus is represented by the soil's brown coloration.
EVALUATION:
Students may demonstrate an understanding of how soil texture influences the percolation rate of water and the ability of soil to hold minerals in Pinelands soils by successfully completing both parts 1 and 2 of the "Soil Experiment" worksheet.
FOLLOW-UP:
1. Students may take one-pound coffee cans and remove both ends of each can. Push each can into the soil to a depth of at least two inches. Pour one quart of water into each can. Record the amount of time required for all the water to penetrate the soil. This activity should be repeated in different locations like the school yard, a lawn, a garden, or the forest floor. Ask students to predict results, record data, and draw conclusions about the results.
This lesson will introduce the students to the following vocabulary words:(click on the word to see its definition-use your browser's back button to return to this page)
Science standards:
5.1-All students will learn to identify systems of interacting components and understand how their interactions combine to produce the overall behavior of the system.
5.2-All students will develop problem solving, decision making, and inquiry skills, reflected by formulating useable questions and hypotheses, planning experiments, conducting systematic observations, interpreting and analyzing data, drawing conclusions, and communicating results.
5.5-All students will integrate mathematics as a tool for problem-solving in science and as a means of expressing and/or modeling scientific theories.
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