Lecture 1

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Chapter 1

Why Study Soils?


Few people in the U.S. workforce are soil scientists. However, each year many thousands of students and professionals find that some knowledge of soil is essential for success in their careers. What does one gain from studying soils? Some reasons for studying soil are described in this lesson.

  1. Soil is an integral part of the ecosystem. Air, water and soil comprise the various ecosystems of the earth. A biome is a complex system of soil, climate and organisms. Soil is susceptible to pollution. We pollute soil by exposing it to human sewage, industrial waste products, agricultural and milling wastes, and natural contaminants.

  2. Soil is the domain of Archeology. Soils can reveal information about ancient climates, geology and peoples. Archeologist study ancient habitats, dwellings, and other cultural factors by examining soil. Often a buried topsoil holds a rich archeological find.

  3. Soil properties affect engineering projects. To an engineer soil is earthy material that can be excavated with a shovel. Soil is construction material and typically is the natural foundation that supports the man-made foundation of a building. Soil properties limit engineering uses for a parcel of land. Soils may or may not be suitable for such uses as road beds, septic tank drain fields, dwellings with basements, or recreation facilities.

  4. Soil is the primary resource for food Production. A subsistence diet requires about 400 lb (181 kg) of grain per person per year. This amount of grain production requires about 0.11 acres (0.045 hectares). An affluent, high-meat diet requires at least 4 times more grain (~.44 acres, 0.18 hectares) because the conversion of grain to meat is highly inefficient. Even cattle fed much of their life on pasture are typically fattened up in a feedlot where they are fed about 6 pounds of grain for every pound of weight gain. Of course much of this weight gain is not edible meat, and most of the meat weight is water. This inefficiency is exacerbated by market trends showing that chicken has now surpassed beef consumption. Chickens, of course, are not pastured at all. Trends indicate that within a few years pork will also surpass beef. Again, hogs are rarely pastured. The earth has about 0.62 acres (0.25 hectares) of farmland per person, and about 0.30 acres (0.12 hectares) of grainland per person. As you do the math you realize that the earth does not have enough land for all inhabitants to enjoy an affluent diet. This land shortage will worsen in the future. (Study Table 1-2 in the textbook.)

  5. Soils profoundly affect human history. Farmers in Mesopotamia were irrigating 5500 years ago. Their fields were more productive then than they are now. Irrigated agriculture is rarely sustainable because it tends to raise water tables and increase soil salinity. In Egypt, where farming was successful and sustainable, civilization thrived. The plow was invented there some 6000 years ago. One observer theorized that the pyramids were built because of the large unemployed workforce--unemployed because agriculture was so successful that not all citizens had to be involved in food production. In China the Yellow River is known as China's Sorrow. It floods catastrophically on a regular basis. The Chinese built river dikes about 4000 years ago, and are still building them. The tremendous soil erosion upstream elevates the river bed as suspended sediments settle out of the slow moving water. Artificial levees designed to prevent flooding only exacerbate the problem in the long run because the sediments are forced to remain in the river channel and raise the riverbed closer to the top of the levees. In North America modern settlers caused the erosion of about one-half of our original endowment of topsoil in only about 150 years of myopic farming.

  6. The study of soils is a science of inherent value to mankind. Soil science includes two main divisions: edaphology and pedology. Edaphology is the study of soils as habitat for plants and other organisms. Xenophon, Cato, were early edaphologists. Van Helmont (1577 - 1644) performed a famous willow experiment, concluding that because the only thing he gave a growing willow was water, willows are made of water. He was partly correct but did not realize that the dry matter came mostly from invisible carbon dioxide in the air. Scientific advances accelerated in the 1700s and 1800s. Pedology is the study of soil as a geologic entity. Pedology was born in Russia in the late 1800s. The USDA systematic approach to pedology is based loosely on the Russian approach.

Students are encouraged to look up the following vocabulary words in the textbook glossary and to browse the following web sites.




Web sites

Worldwatch Institute Homepage. This organization provides environmental data and news to individuals and organizations interested in the environment. URL: www.worldwatch.org

Journal of Natural Resources and Life Sciences Education. This is an excellent electronic journal about natural resource education. Abstracts are free, articles are not. URL: www.agronomy.org/journals

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