Reference no: EM133096990

Exercise - Soil Resources

In this lab you will:
examine the different soil properties and how human activity affects our soil resources.

Background Reading and Needed Supplies
Prior to doing this exercise you should read Chapter 12 in the textbook. With respect to supplies, you will need a calculator, ruler, and colored markers.

Part I - Soil Formation and Properties

1) The photographs in Figure 8.1 on the next page show cross-sectional (profile) views of two different soils-note the meter stick (graduated in centimeters) for scale. The soil profile on the left shows an A-C sequence, and the one on the right is an A-B-C sequence (the C horizon is not visible in the photo).

a) Which soil profile (left or right) is older? Explain how you know.

b) What is causing the reddish color of the B horizon in the right photo?

2) Explain how the color of a B soil horizon can tell you whether a particular site is well-drained or not.

3) Describe why you would want to use soil color to help select a more well-drained site for building a home or installing a septic system.

4) In terms of soil formation, are the two soils in Figure 8.1 still developing or do they represent ancient soils known as paleosols? Explain how you can tell.

5) Take a red marker or pencil and trace the bottom boundary of the A horizon in both photos.

6) What is the non-scientific name commonly used to describe an A horizon?

7) What material gives an A horizon its characteristic blackish color?

8) Describe the basic way in which an A-horizon forms.

9) Explain why A horizons are such a critical resource to society.

Part II - Soil Loss

The photo in Figure 8.2, taken right after a heavy rain event, shows valuable topsoil being lost from an agricultural field. Recall from the textbook that the term soil loss refers to the net loss of soil that occurs when the natural balance between soil formation and erosion is upset.

10) Describe the basic way in which changing the landuse from natural vegetation to agricultural row crops can lead to a dramatic increase in soil erosion, and then soil loss.

11) What types of soil particles are being preferentially lost from the field?

12) Explain how the preferential loss of these soil particles affects soil fertility and crop production.

13) The map in Figure 8.3 shows the estimated amounts of soil loss from U.S. croplands on an annual basis-areas with little to no agricultural activity are shown in white and grey.

a) In terms of the terrain, provide an explanation as to why some areas in the U.S. with the greatest soil loss tend to lie along major river valleys, such as the Mississippi and Ohio.

b) Another noticeable trend on the map is that the wheat-growing region of the Great Plains has far less soil loss than the Midwestern corn-belt states of Iowa and Illinois. Assuming the terrain is similar, provide an explanation as to the differences in soil loss between these two agricultural regions.

14) Using an atlas or the internet, identify the major agricultural region running northwest- southeast through California that provides much of the nation's fresh fruits and vegetables.

15) Similarly, what is the name of the agricultural region in the southern tip of California?

16) The two agricultural regions in California you listed above are extremely productive, but lie in arid to semi-arid climatic zones. What is the source of water for these two regions?

Part III - Mitigation Techniques for Soil Loss and Sediment Pollution

In addition to the loss of valuable topsoil, excessive soil erosion leads to the serious problem known as sediment pollution. Here the excess sediment can fill stream channels, which leads to an increase in the frequency and severity of flooding. Sediment pollution also destroys the habitat for many types of aquatic species, creating a ripple effect through the food chain. Mitigation techniques typically involve: i) keeping the soil from moving off the landscape in the first place; or ii) trapping what does move before it can enter a waterway.

17) In the space provide below each of the following photographs: i) identify the mitigation technique being used to control excessive soil erosion; and ii) provide a brief description of how the technique actually reduces soil loss or sediment pollution.

A) location unknown.
B) Southwest Iowa (Courtesy of USDA-NRCS).
C) Iowa-Minnesota border (Courtesy of USDA-NRCS).
D) Missouri (Courtesy of USDA-NRCS).
E) Story County, Iowa (Courtesy of USDA-NRCS).
F) Statesboro, Georgia.

Part IV - Supplemental Exercise

For this section your instructor will need to provide a soil auger and find two sites for boring a soil profile. One site should be located in a low-lying area, preferably next to a small stream tributary channel, and the other in a topographically high area. While boring a hole, each time the auger bucket becomes full its contents should be carefully removed and laid on the ground in the same order it was removed from the hole. In other words, the upper most material (top of the hole) is laid down first, followed by progressively deeper material.

18) Complete the following tables for the soil profiles you observe in the field. Note that not all of the horizons may be present at a given site.

19) Assuming that one of your sites contains a mixture of sand and clay and a well-developed B
horizon, explain how clay can move vertically through the soil profile but sand can not.

20) At the low-lying site (A), the soil colors below the topsoil should be mostly grey, whereas the colors at the topographically higher site (B) should be yellowish to reddish. Explain why the grey color indicates poor drainage and the yellow and red colors indicate a well-drained area.

21) Compared to the topographically high area, the poorer drainage at your low-lying site should cause it to have a much thicker A horizon, and perhaps even an O horizon. Describe two reasons why the poorer drainage would lead to a thicker accumulation of organic matter.

22) Suppose you were planning to build a house on a piece of property that appears dry, but the soil has a thick A horizon and the underlying profile is completely grey. How might this information affect your building plans?

Attachment:- Soil Resources.rar