ESPM 120 Homework 2: 2005

Assigned: Sept. 16

Due: Sept. 23, 5 pm (Amundson mailbox, 137 Mulford; Assignment Envelope outside Amundson office, 317 Hilgard).

Please show all work for calculations

State Factors, Texture, Bulk Density, and Soil Horizons

1. In class, we went through the derivation of Stokes law, and the Box in Chapter 4 also provides a detailed insight as to how this law can be used to separate different soil particle sizes.

  1. If you set up a cylinder of water with some loose soil added, how long (after thoroughly mixing the suspension) would you need to wait until all the finest sand passed a depth of 10 cm?
  1. How long would you wait until all coarse clay (>0.001 mm) passed a 10 cm depth?

2. In class, we went over the ways to determine bulk density – especially the method whereby a ped is coated with paraffin, and immersed in water. If an air-dried ped of soil weighs 175 g, but only 40 g when immersed in water,

  1. what is its bulk density?
  2. What is its porosity (assume a particle density of 2.65 g/cm3)?

3. On the accompanying picture at the end of the homework is a picture of a soil profile exposed here on campus on the south side of Haviland Hall as part of the Asian Library project. I have identified where the key horizon boundaries are. The soil formed on a gentle hillslope grading down toward a tributary of Strawberry Creek. The landscape was formerly a grassland with a few coastal live oaks (as well as shrubs of various types). The underlying parent material is the sandstone that crops out in several places on campus (north side of Giannini Hall for example). The soil has likely had many thousands of years to develop given the gentle slope and its height above the present stream. Go ahead and look at it yourself if it is still open.

a. Name the horizons using our upper and lower case nomenclature. The key is to think about how these horizons differ from the parent material, and the main things that have occurred. Note the colors of the surface. Note the orange/yellow colors in the middle of the profile (and since you can’t get access to the profile, (hint) the higher clay in this zone). Note the exposed fractured rock at the base.

4. A soil has a profile with the following horizons: O, E, Bhs, Bs, C. (see also the picture in the lecture illustrations of this soil from the NE USA.) The parent material is a sandy glacial outwash deposit found in upstate New York.

  1. What processes have affected each of these horizons and changed them from the parent material.

5. Soil profile information for some of the United States is now available on the web. Here, we want you to simply link to this important data base and learn something about the soils near you home. Go to the NRCS (Natural Resource Conservation Service, a branch of the USDA) web site at http://ssldata.nrcs.usda.gov/querypage.asp. Search by State and County. Click “Execute Query.” Pick a soil series name that either sounds familiar (name of a town, etc) or just one that you are curious in. Then click “generate report.” The “Primary Characterization Report” will have all the lab data, while the “NASIS Pedon Description” will contain the field description of the soil (a more detailed version of what we will do on the field trip). At the bottom of the NASIS report is the actual description, with horizon names on left and color, structure, etc. data following the name.

  1. Attach the printout of the soil profile description, and describe the processes that affect each horizon of this soil.
  2. What characteristic(s) about the soil were a surprise or unexpected finding for you?