Do any of you recall learning about "The Dust Bowl", a period of drought, dust storms, and poor agricultural practices that decimated portions of the American Midwest and Plains during the Great Depression? Explain

Soil Taxonomy

Pedon
As we learned in Weeks 1 & 2, the USDA System of soil classification is the standard used for most environmental and agricultural purposes here in the United States. The basic unit of measurement is called the pedon (USDA-NRCS 1999). The USDA-NRCS (1999) defines it thus,

“A pedon has the smallest volume for which one should
describe and sample the soil to represent the nature and
arrangement of its horizons and variability in the properties that
are preserved in samples. A pedon is comparable in some ways
to the unit cell of a crystal. It has three dimensions. Its lower
limit is the somewhat vague limit between the soil and non soil
below. Its lateral dimensions are large enough to represent the
nature of any horizons and variability that may be present. A
horizon may vary in thickness or in composition, or it may be
discontinuous. The minimal horizontal area of a pedon is
arbitrarily set at 1 m2, but it ranges to 10 m2, depending on the
variability in the soil.”

Naming of Soils

Much like the naming of plants and animals, the naming of soils and classifying into particular taxa follows a particular set of rules. The reason for this is to be sure that someone recording a soil survey in California and someone else doing one in North Carolina can have a common language. The USDA System uses a multi-categorical classification based on real, observed soils (rather than theoretical ones) and measurable properties (USDA-NRCS, 1999).

Mineral vs. Organic Soils
A soil can be considered mineral under two distinct conditions. Either it is infrequently saturated by water AND contains less than 20% organic carbon, OR it is frequently saturated but has a specific ratio of organic carbon to clay (USDA-NRCS, 1999). Everything else is considered organic soil (USDA-NRCS, 1999). These are the most basic versions of the definition, see your textbook or the USDA-NRCS definitions for specifics (USDA-NRCS, 1999, pp 19 & 20).

References:

USDA-NRCS. (1999). Soil Taxonomy: A basic system of soil classification for making and interpreting soil surveys – Second Edition. Agriculture Handbook Number 436. 871pp. Retrieved at: http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_051232.pdf

Soils in Agriculture

Fertilizer
Amending the soil to increase crop yields is the cornerstone of modern corporate farming. The cycle of growing – amending – harvesting – amending – growing, etc. goes on and on. We are starting to be concerned about this cycle because of the impacts of excessive fertilization on the soil. Remember our lesson on nutrient cycling? As you read this week ask yourself continuously if we can feed the world’s huge, growing population and still alter some of the more common, negative practices.

Erosion

Soil erosion (loss of topsoil) is a catastrophic problem in some parts of the world. It has been so here in the US as well. Do any of you recall learning about “The Dust Bowl”, a period of drought, dust storms, and poor agricultural practices that decimated portions of the American Midwest and Plains during the Great Depression? We have learned from that experience in some ways, but the droughts that some of you highlighted in our forum about moisture have led some folks to predict that it could happen again.

Current Research
In this week’s quiz you are asked to locate a peer-reviewed, primary scientific research article that you select from a provided list. Just as a reminder, peer-reviewed means that it is in a scientific journal where it has been sent to a number of scientists who do similar work to accept, deny, or suggest revisions in order to improve the science or the communication of it. Primary research means that the people who wrote the paper are the ones who did the work. Examples of journals that would fall into this category are: Ecology, Science, Nature, Journal of Applied Ecology. There are many more. Sources that would NOT qualify would be things such as: National Geographic, The New York Times, Newsweek, Mother Earth News. Again, there are many more.