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Tufts OpenCourseware
Authors: Kathleen Merrigan, Ph.D., William Lockeretz, Ph.D.


Out of the Earth: Civilization and the Life of the Soil. Chapter 3. The Fertile Substrate and chapter 4, The Vital Fluid. Daniel Hillel (1991).

Principles of Ecology in Plant Production. Chapter 6. Soil and plant production. E.A. Hanlon and F.M.Rhoads ( 1998)

Key Questions

The Fertile Substrate

  • What are the functions of soils?
  • What are the important processes that lead to soil formation?
  • What are the important components of soils?
  • What are the important properties of sand, silt, clay and organic matter in soils?
  • What is a soil profile?
  • What factors influence soil formation?

The Vital Fluid

  • What is the importance of water for agriculture?
  • What are some of the anomalous properties of water that works to the advantage of agriculture?

Principles of Ecology in Plant Production

  • What is the definition of soil?
  • From the examples referring to different types of soils and crop combinations (page two of the reading), are we looking at the suitability of the soils for growing crops or choice of crops to ensure that soil health is enhanced?
  • What are the functions of soil?
  • What are the uses of crop rotation? Why did farmers reduce this practice over time?
  • How is CEC related to the buffer capacity of soil?
  • How is CEC related to pH of the soil?
  • How does soil texture and structure influence CEC?
  • How is nitrate leaching related to CEC of soil?
  • How is soil texture and structure related to agricultural production and pollution?
  • How can we improve soil structure?
  • What factors influence nutrient uptake by plants?
  • How do soil compaction and plow pans affect agricultural production?
  • What factors are to be considered as one attempts to alter the pH of the soils?
  • What factors influence phytotoxicity?
  • How does soil erosion affect agricultural production and pollution?
  • How do we mitigate soil erosion?
  • Which is an important nutrient which could pollute surface waters because of soil erosion?
  • How do we differentiate between basic (alkaline), saline and sodic soils?

Supplementary Readings

Diagnosing Saline and Sodic Soil Problems. R.M. Waskom, T.A. Bauder, J.G. Davis and G.E. Cardon. CSU Cooperative Extension – Agriculture. Colorado State University

Managing Soil Organic Matter – The Key to Air and Water Quality. NRCS. 2003