Soil Labs

(20 points)

Background Information:

Part 1 Soil permeability:

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 5 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.

Table 1. Soil Permeability Classes.

------

Infiltration Rate

Classification (inches/hour)

------

Very Slow Less than 0.06

Slow 0.06 to 0.2

Moderately Slow 0.2 to 0.6

Moderate 0.6 to 2.0

Moderately Rapid 2.0 to 6.0

Rapid 6.0 to 20.0

Very Rapid Greater than 20.0

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. It 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 on coarse textured soils, so the timing and quantity of chemical and water applications is particularly critical on these soils.

Materials:

2 Plastic cups

1 Soil sample

50 ml beaker

50 ml graduated cylinder

Procedure:

1. Take one of the plastic cups and poke three holes in the bottom.

2. Fill the plastic cup with the holes half way with one of the soil samples. Pack it down lightly so that there are not large air spaces.

3. One of the lab partners will hold the cup with the soil above the cup that has no holes and is empty so that they can catch the water as it drips through the soil.

4. The other lab partner will measure out 50 mls of water and slowly pour it on top of the soil.

5. Time for 2 minute and then set the cup with the soil aside. (Be careful, it will still drip water, so put it in a sink or over a cup or beaker).

6. Pour the water from the cup into the graduated cylinder to see how much of the 50 mls came through. Record it.

Analysis:

1. Could the size of the soil particles affect life of microorganisms living in the soil?

2. Based on infiltration how much sand and clay do you think there was?

3. Why would a farmer need to know the soil permeability on his land?

4. What is waterlogged? Which sample would be most likely to become waterlogged? What would this do to crops grown in this soil type?

5. Calculate the flow rate (mL/sec or minute) for the sample.

Part 2: Soil texture by feel

Once you have followed the flow chart for each of your soil samples, fill out the chart below with the results of the soil by texture test.

Soil Sample / Soil Texture By Feel Analysis
1

Analysis:

1. What is the relationship between soil texture and water?

2. Which types of soil can be mixed together to form the best loam?

3. What are the causes of erosion?

4. What can be done about erosion problems?

Part 3 Soil Texture Lab


Materials: 100 mL graduated cylinder

Soil sample

Water

2 Rulers

Procedure:

1. Place 10 ml of water in the graduated cylinder.

2. Fill the graduated cylinder with 25 ml of your soil sample.

3. Add 65 ml of water to the graduated cylinder.

4. Cover the graduated cylinder with your hand and invert several times until the soil is thoroughly mixed. Add one scoop of alum.

5. Place the cylinder on the table and let it settle for approximately 30 minutes.

6. Once the soil has settled, there should be 3 distinct layers. Measure the volume of each layer and the total volume of the sample.

7. Calculate the percentage of each layer. (You will do this calculation 3 times- one for each layer)

Volume of layer 1___ X 100% = % of sand, silt or clay Repeat using volume of Layer 2 and 3

Total volume of soil

8. Use the 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. You can check for accuracy by drawing a straight line to the right and that number should be the amount of silt that you have. The three percentages should add up to 100%.

Copy and fill in table:

Soil Sample / % Sand / % Silt / % Clay / Soil Texture

Questions:

  1. Now that you have determined the type of soil samples that you have, compare them to your soil texture by feel. Did you get the same answers?
  2. Describe the different types of erosion. Determine the ecological effect of each type.
  3. Describe the different types of irrigation. How do they decrease erosion?
  4. Describe the different types of agriculture. Hoe does each increase or decrease erosion?
  5. The irrigation of farmland is vital to the production of the world’s food supply. In China, 87 percent of the water withdrawn is used for irrigation. In the United States, this figure approaches 41 percent. Most of the water is applied to the land in a process called gravity irrigation, in which the water is simply allowed to flow, via the force of gravity, into the fields.
  1. Describe one positive and one negative impact of gravity irrigation.
  2. Describe one alternative to gravity irrigation. Give one positive and one negative effect of that practice.
  3. Massive irrigation programs can also impact underground water supplies. Describe one negative impact that irrigation might have on those supplies.
  4. Dams are often used to create irrigation water reservoirs. Describe two positive and two negative impacts that a large dam would have on immediate area around it.
  1. As the world’s population increases and availability of new arable land decreases, providing sufficient food for the world’s human population is becoming increasingly difficult. The table below shows the area of land needed to feed the world’s population for 1900 projected to the year 2060.

Year / 1900 / 1940 / 1980 / 2020 / 2060
Land Area Needed (billion hectares) / 0.40 / 0.60 / 1.25 / 2.50 / 4.75
  1. On the graph below, plot the data from the table above and draw a smooth curve.
  1. Assume that the maximum arable land area on Earth is 4.00 billion hectares. Using the smooth curve that you created above, determine the year in which the human population is likely to run out or arable land for agriculture.
  2. Soil quality is a critical factor in agriculture. Identify TWO physical and/or chemical properties of soils and describe the role of each property in determining soil quality.
  3. Describe TWO viable strategies for reducing the amount of land need for agriculture.
  4. One problem that can result from agriculture is soil salinization.

(i)Describe how salinization occurs.

(ii)Describe one method to prevent or remediate soil salinization.

Part 4 Soil Nutrient Lab

Purpose: To find the levels of nitrogen, phosphorous, potash and pH in the students soil sample.

Materials: Order from a supply catalog or purchase from a garden store several Rapitest soil test kits.

Procedure:

1. Use the soil sample for the nutrient testing.

2. Using a small beaker or plastic cup, have the student make a five parts water to one part soil mixture.

3. Fill each of the plastic soil test vials (from the rapidest kit) to the dotted line with the soil/water mixture.

4. The vials have color-coordinated capsules that go with each soil test. Find the blue capsule and carefully separate it so that you can pour the powder into the blue vial. Cap and shake until the white powder is completely dissolved. (Be careful not to have the vial explode!) Repeat with the other three colored capsules.

5. Wait until a color develops. (This usually takes about 5 minutes).

6. Record the results in the table below. For fertilizer decide from the following choices:

10-0-0 or 10-5-10 or 5-10-10 or 5-10-5 or 10-10-10 or 5-5-10 or 10-5-5 (the numbers represent the percentage of nitrogen-phosphorous-potassium in the fertilizer)

SOIL

/

NITROGEN

/

PHOSPHOROUS

/

POTASSIUM

/

pH

/

FERTILIZER

Analysis:

1. What do you think gardeners and farmers could do to minimize contamination of groundwater from certain compounds in fertilizers?

2. Do you think the plants in this soil sample are getting the essential nutrients that they need?

3. Is there a relationship between the elements found in your soil sample and the pH?

4. How would precipitation or irrigation affect the elements in the soil?

5. What environmental effects does adding the wrong type of fertilizer have?

6. Suppose you have just started a summer internship working for a cooperative extension service, where you will collect soil samples, conduct laboratory and field tests, and make recommendations on soil conservation and agricultural practices.

A. Identify and describe one chemical and one physical soil test that could be performed and explain how the results of these tests will allow the cooperative extension service to make specific recommendations for sustainable agriculture.

B. Explain one advantage and one disadvantage to using inorganic commercial fertilizers.

C. Describe TWO soil conservation practices that are designed to decrease soil erosion.

D. Identify one biome that is characterized by soil that is rich in humus. Describe how humus originated in the soils of this biome and TWO ways that humus improves soil conditions for plant growth.