Physical and Chemical Characteristics of Soil APES 8

Your typed lab report should include the following parts from below: Your name, Lab title, Objective, Purpose, Hypothesis, the formula after procedure step 6, data table 1, data table 2, data table 3, and both sets of Analysis Questions and Answers, and a conclusion which includes restating your hypothesis, whether you support or do not support your hypothesis, concrete data to back up your acceptance on non-acceptance of your hypothesis and at least 3 sources of error. You will use both the physical and chemical characteristics of soil labs to do this.

Objectives: Students will learn how to use the soil texture pyramid to identify unknown samples of

soil and to help them discover how soil texture relates to permeability. Students will become proficient in determining soil texture and judging the cohesive

and adhesive properties of a soil sample. To use a rapitest © 1601 soil test kit to determine the quantities of Nitrogen, Phosphorus, pH,

and Potash (potassium) within a soil sample.Purpose:

How does soil texture affect the soil permeability?Hypothesis:

If ______then_____ because________.Materials:

Part one:o 100mL graduated cylindero 3 soil samples (collected and dried over several weeks.)o Watero 2 rulers (optional)o Alum

Part two:o 2 plastic cupso 3 soil samples (same as part one)o 50 mL beakero 50 mL graduated cylinder

Physical Characteristics Procedure: Part 11. Fill the graduated cylinder with 25 ml of your soil sample.

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. Add one pinch of alum.

4. Place the cylinder on the table and let it settle for approximately 24 hours. (set up step 9 of this procedure during the rest of the class (wait time)).

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 which may have changed due to settling.

Physical and Chemical Characteristics of Soil APES 8

6. Calculate the percentage of each layer and enter your results in the chart that follows. (Do this calculation 3 times—once for each layer.)

Volume of layer 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.

Physical and Chemical Characteristics of Soil APES 8

Table 1

Soil Sample % Sand % Silt % Clay Soil texture

1

2

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.

Physical and Chemical Characteristics of Soil APES 8

Definition of Ribbon: Can you make it into a “worm” shape?

Physical and Chemical Characteristics of Soil APES 8

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

Table 2

Soil sample Soil texture by feel analysis

1

2

Analysis Part 1:

1. What is the relationship between soil texture and permeability?2. Which types of soil can be mixed together to form the best loam (for farming)? Indicate the percentages of each type of soil.4. What can be done about erosion problems? 5. Which soil sample (1 or 2) would be more subject to erosion? Why?

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.

Physical and Chemical Characteristics of Soil APES 8

Physical Characteristics Procedure: Part 21. Take one of the plastic cups and poke three holes in the bottom.2. Fill that cup halfway 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.Table 3

Soil sample 1 Soil sample 2

Volume of water (ml)

Physical and Chemical Characteristics of Soil APES 8

Materials: Rapitest kit 1601 Soil samples (2-3) Water (preferably distilled) Pipettes

Chemical characteristics Procedure:For pH

1. Remove the cap from the green comparator and take out the package of capsules. Make sure the color chart (film) is in place.

2. Fill the chamber to soil fill line with soil sample.3. Holding the capsule horizontally over the test chamber, carefully separate the two halves of the

green capsule and pour into the test chamber.4. Using the dropper provided, add water to the test chamber to the water fill line.5. Fit the cap onto the comparator, making sure it is properly sealed. Shake thoroughly.6. Allow soil to settle and color to develop for about a minute.7. Compare color of solution against pH chart. For best results allow daylight to illuminate the

solution.For N, P, K tests

8. Fill a clean container with 1 C of soil and 5 C of water. (already done for you)9. Thoroughly shake or stir the soil and water together for at least 1 minute. Allow the solution to

settle for 24 hours. (already done for you)10. Select the appropriate comparator for the test you wish to perform.

a. P=Blueb. N=mauve c. K=Orange

Comparator color matches capsule color. Make sure you use the correct comparator with the correct capsule.

11. Using the dropper provided, fill the test and reference chambers to the fill mark on the chart with the solution from your soil sample. Be careful not to disturb the soil. Transfer only liquid.

12. Remove one of the appropriate colored capsules from its poly bag. Holding the capsule horizontally over the test chamber, carefully separate the two halves and pour the powder into the test chamber.

13. Fit the cap onto the comparator, making sure it is properly sealed. Shake thoroughly.14. Allow color to develop for 10 minutes.15. Compare color of solution against pH chart. For best results allow daylight to illuminate the

solution.