EGHS AP Environmental Science 355 Chapter 8 Earth Systems

Soil Texture, Permeability, and Chemical Analysis Lab Objective: * To learn how to use the soil texture pyramid to identify unknown samples of soil * To explore the relationship between soil texture relates to soil permeability. * To learn how to test the chemical parameters related to soil science.

Part 1 Soil Texture & Identification Materials: * 100-ml graduated cylinder * 3 soil samples * Water * 2 rulers Procedure: 1. Fill the graduated cylinder with 25 ml of your soil sample. (each group should investigate a different soil sample and then share

their data) 2. Add 75 ml of water to the graduated cylinder. 3. Cover the graduated cylinder with your hand and invert several times until the soil is thoroughly mixed. 4. Place the cylinder on the table and let it settle for approximately 30 minutes. 5. Once the soil has settled, there should be three distinct layers. Measure the volume of each layer and the total volume of the

sample. 6. Calculate the percentage of each layer and enter your results in the chart that follows. (Do this calculation three times—once for

each layer.) Volume of layer 1, 2, or 3 x 100% = % of sand, silt, or clay

Total volume of soil 7. Use the following Soil Texture Pyramid to identify the type of soil in your sample. Directions for using a Soil Texture Pyramid: * Using a ruler, find the point along the base of the triangle that represents the percent of sand in your sample. Position the ruler on the line that slants in the direction that the numbers are facing for percent sand. * Place the edge of a second ruler at the point along the right side of the pyramid so that the ruler slants in the direction that the numbers are facing for percent silt. * Using a pencil, put a dot where the two rulers intersect. The place where they intersect is the type of soil texture you have. You can check for accuracy by drawing a straight line to the right; that number should be the amount of silt that you have. The three percentages should add up to 100%. 8. Repeat the above procedure for the other soil samples.

Soil Sample % Sand % Silt % Clay Soil texture

Sample 1- Location:

Sample 2- Location:

Sample 3- Location:

9. Now that you have determined the type of soil samples that you have, follow the instructions in the ‘Soil Texture by Feel flow

chart’ that follows. 10. Fill out the following chart with the results of the soil texture by feel test. Did you get the same answers?

Soil Sample 1 2 3 Soil Texture by Feel Analysis

Analysis: 1. Which types of soil can be mixed together to form the best loam? Indicate the percentages of each type of soil. 2. Think about the size of soil particles and how they would be influenced by water. Which ones would be suspended longer and carried further by a moving body of water? 3. The larger the soil particles, the easier it is for water to pass through (permeability). Conversely, the smaller the soil particle, the tighter it will pack to together making it harder for water to penetrate. How do you think this would relate to soil erosion? 4. What can be done about erosion problems? 5. Which soil sample would be more subject to erosion? Part 2: Soil Permeability Materials: 2 plastic cups 3 soil samples 50-ml beaker 50-ml graduated cylinder Background Information: A soil's permeability is a measure of the ability of air and water to move through it. Permeability is influenced by the size, shape, and continuity of the pore spaces, which in turn are dependent on the soil bulk density, structure, and texture. Most soil series are assigned to a single permeability class based on the most restrictive layer in the upper five feet of the soil profile (Table 1). However, soil series with contrasting textures in the soil profile are assigned to more than one permeability class. In most cases, soils with a slow, very slow, rapid, or very rapid permeability classification are considered poor for irrigation. Infiltration is the downward flow of water from the surface through the soil. The infiltration rate (sometimes called intake rate) of a soil is a measure of its ability to absorb an amount of rain or irrigation water over a given time period. It is commonly expressed in inches per hour. The infiltration rate is dependent on the permeability of the surface soil, moisture content of the soil, and surface conditions such as roughness (tillage and plant residue), slope, and plant cover. Coarse-textured soils such as sands and gravel usually have high infiltration rates. The infiltration rates of medium and fine textured soils such as loams, silts, and clays are lower than those of coarse-textured soils and more dependent on the stability of the soil aggregates. Water and plant nutrient losses may be greater in coarse-textured soils, so the timing and quantity of chemical and water applications is particularly critical on these soils.

Procedure: 1. Take one of the plastic cups and poke three holes in the bottom. 2. Fill that cup half way with one of the soil samples. Pack it down lightly to avoid having large air spaces. 3. Have one of the lab partners hold the cup with the soil above an empty cup with no holes so that they can catch the water as it drips

through the soil. 4. The other lab partner should measure out 50 ml of water and slowly pour it on top of the soil. 5. Time for 1 minute and then set the cup with the soil aside. (Be careful where you place the cup. It will continue to drip water, so

put it in a sink or over a cup or beaker.) 6. Pour the water from the second cup into the graduated cylinder to see how much of the 50 ml came through. 7. Record the amount in the following chart; repeat the procedure for the remaining two soil samples. Data:

Soil sample 1 Soil sample 2 Soil sample 3

Volume of water (ml)

Analysis: 1. Based on your data, which soil sample do you think contains the most clay? Which one the most sand? 2. Why would a farmer need to know the soil permeability of his land? 3. Which of the soil samples held more water? Part 3 Soil Test for pH and Nutrients Materials: Soil analysis chemical test reagents (Nitrogen, Phosphorus, Potassium, Background Information: Refer to the supplemental packet. Other parameters that could be tested for that influence soil properties include conductivity and temperature. Procedure: 1. Collect three soil samples from around EGHS (courtyard, forested area near the social studies wing and the soccer field) Make to discard the top 2” of top soil – focus on where the roots are growing! 2. Follow the procedures outlines in the supplemental packet for each parameter. Divide the soil samples around the class so that you are testing four parameters for each soil sample and then sharing your data with other members of the class. 3. What are three key nutrients found in soil are needed by plants? ____________________ ____________________ ____________________

Data:

Soil sample 1 Soil sample 2 Soil sample 3

pH

Nitrates

Phosphorus (P()

Potassium (K)

2. What role does pH play in soil science? 3. What is the role of nitrogen (N) with respect to plant health? 4. What is the role of phosphorus (P) with respect to plant health? 5. What is the role of potassium (K) with respect to plant health? 5. Three nutrients are found in fertilizer. Why add them to agricultural crops or lawns if they are found naturally in soils? 6. Make a labeled sketch showing the stratography of a soil profile (a sketch showing horizons O down to C)