LAB 10: SOIL GEOGRAPHY
In this module, you will identify and explain the geographic distribution, patterns, and processes associated with Earth’s soils.
Note: Please refer to the GETTING STARTED lab module to learn tips on how to set up and maneuver through the Google Earth () component of this lab.
The following is a list of important words and concepts used in this lab module:
|Cation-exchange capacity (CEC)||Particle size –sand, silt, clay||Soil profile|
|CLORPT||Pedogenic processes||Soil structure|
|Diagnostic horizon||Pore space||Soil solution|
|Eluviation||Soil color – hue, value, chroma||Soil Taxonomy|
|Humus||Soil consistence||Soil texture|
|Illuviation||Soil horizons – O, A, E, B, C, R||Transpiration|
|Inorganic material (matter)||Soil moisture|
|Organic material (matter)||Soil pH|
LAB MODULES LEARNING OBJECTIVES
After successfully completing this module, you should be able to:
· Identify the fundamental components of soil
· Explain the factors that influence the development of soil (CLORPT)
· Identify soil orders and soil series by diagnostic characteristics and location
· Explain soil profiles and soil horizons
· Recognize soils by texture and color
· Describe the geography of soils at various taxonomic levels
This module examines the geography of soil. Topics include soil classifications, soil horizons, soil moisture, pH and color. While these topics may appear to be disparate, you will learn how they are inherently related.
The modules start with five opening topics, or vignettes, which are found in the accompanying Google Earth file. These vignettes introduce basic concepts of the geography of soil. Some of the vignettes have animations, videos, or short articles that will provide another perspective or visual explanation for the topic at hand. After reading the vignette and associated links, answer the following questions. Please note that some components of this lab may take a while to download or open, especially if you have a slow internet connection.
Expand SOIL GEOGRAPHY and then expand the INTRODUCTION folder.
Read Topic 1: The Earth’s Soils.
Question 1: Looking at the map, what is the soil moisture terminology used for regions with relatively humid climates and well-distributed rainfall, where water moves down through the soil via soil pores, like that of eastern USA, the United Kingdom, Norway, and eastern China?
Read Topic 2: Soil Forming Factors
Question 2: Which factor – climate, organisms, relief, parent material, or time – would affect most universally the soils in mountainous areas?
d. parent material
Read Topic 3: Soil Characteristics
Question 3: How are colloids beneficial to plants (Hint: What can they do that helps plants)?
a. Colloids dissolve soil water for plant use
b. Colloids contain acid ions that leach nutrients from soil
c. Colloids harbor positively charged surfaces to attract nutrients
d. Colloids hold soil nutrients for plant use
Read Topic 4: Soil Horizons
Question 4: The photo image shows a massive horizon of accumulated clays, oxides, and organics. Does this soil profile show a massive O horizon, A horizon, E horizon, B horizon, or C horizon?
a. 0 horizon
b. A horizon
c. E horizon
d. B horizon
e. C horizon
Read Topic 5: Soil Degradation
Question 5: Reading the map, what is the global status of soil in South Africa, the internal region of Madagascar, and the majority of eastern China?
a. Very high severity
b. High severity
c. Moderate severity
d. Low severity
Collapse and uncheck INTRODUCTION
In this section, you will identify how soils are distributed at a global scale. Remember, scale is an important concept in geography, because some patterns can be seen only at the global (coarse) scale and not at the local (fine) scale.
Expand GLOBAL PERSPECTIVE and then click and select, Soil Taxonomy Map.
Soils are generally classified using their soil profiles and other physical, chemical, and biological characteristics. How they are classified, or grouped into categories, depends on the classification system used. There are many recognized soil classification systems in the world, including classification systems from Canada, Russia, China, Germany, Australia, the United States, and the internationally recognized FAO World Reference Base for Soil Resources (WRB). For this section, the soil order nomenclature (how soils are named) is based on the United States classification system known as the USDA Soil Taxonomy. The resultant map overlay shows particular geographic patterns of soil with climate and relief that are evident at the global scale.
Doubleclick and select Atlanta. When you arrive at your destination, choose the dominant soil order for the city. Repeat this for the remaining questions in this section.
Question 6: What is the predominant soil order for Atlanta, Georgia, USA and the surrounding region?
Doubleclick and select Bhopal
Question 7: What is the predominant soil order for Bhopal, India and the surrounding region?
Doubleclick and select Hamar
Question 8: What is the predominant soil order for Hamar, Norway and the surrounding region?
Doubleclick and select Yaounde
Question 9: What is the predominant soil order for Yaounde, Cameroon and the surrounding region?
Doubleclick and select Sarawak
Question 10: Sarawak is a Malaysian state located on the Island of Borneo. The predominant soil order for most of Sarawak is the same as which of the following locations?
a. Yaounde, Cameroon
b. Hamar, Norway
c. Bhopal, India
d. Atlanta, Georgia
Collapse and uncheck GLOBAL PERSPECTIVE
Physical, chemical, and other unique properties help classify soils at all levels of taxonomy. Soils are classified from the highest level, the soil order, down to the lowest level, the soil series. The levels between soil order and soil series are soil suborder, great group, subgroup, and families. The USDA Soil Taxonomy recognizes 12 soil orders, 64 suborders, over 300 great groups, and over 20,000 soil series.
The soil order level is important at the macro (global) scale, or when general descriptions of soil are needed. The soil series level is important at the micro (local) scale, or when specific soil descriptions are needed. At the local scale, soils are very complex and can vary significantly within a relatively small area due to various environmental factors. These factors can include the steepness of the terrain, the size and speed of streams, the native plants or crops that grow on it, the type of parent material (rocks) below it, the age of the soil, and soil disturbance (for example, fire).
Continue practicing your identification of soil orders at a global scale.
Expand SOIL ORDER and then click and select Identification. If you need help with identification, click and select Information. This link takes you to The Twelve Soil Orders of Soil Taxonomy web page hosted by the USDA Natural Resources Conservation Service. You can use this to help you identify soils 1 through 12.
Question 11: Soil 1:
Question 12: Soil 2:
Question 13: Soil 3:
Question 14: Soil 4:
Question 15: Soil 5:
Question 16: Soil 6:
Question 17: Soil 7:
Question 18: Soil 8:
Question 19: Soil 9:
Question 20: Soil 10:
Question 21: Soil 11:
Question 22: Soil 12:
<Question 11-22: Pull from the following list>
The USDA Soil Taxonomy uses color, texture, structure, and other soil properties of a soil profile, measured from the surface down to two meters depth (NCRS). Within the soil profile, soil horizons are important in the identification of the soil order and lower taxonomic levels. Soil horizons at the surface are sometimes known as epipedons. Many soils have a diagnostic horizon or other soil characteristics that are unique to that soil and help to differentiate them from other soil types.
Expand SOIL PROFILE, and then doubleclick and select Soil Taxonomy Map. Next, double-click and select Soil 1. In this section, you will look at six different soil profiles. To identify each soil order, an image along with CLORPT (CLimate, Organisms, Relief, Parent material, Time) information and diagnostic characteristics are provided. After you identify the soil order, expand the folder and select and click Location A and Location B to determine the most likely location.
Question 23: What is Soil 1? _____________________
Question 24: This soil order is most likely to be found at or around Location A, B, C or D?
a. Location A
b. Location B
c. Location C
d. Location D
Question 25: What is Soil 2? _____________________
Question 26: This soil order is most likely to be found at or around Location E, F, G, or H?
a. Location E
b. Location F
c. Location G
d. Location H
Question 27: What is Soil 3? _____________________
Question 28: This soil order is most likely to be found at or around Location I, J, K, or L
a. Location I
b. Location J
c. Location K
d. Location L
Question 29: What is Soil 4? _____________________
Question 30: This soil order is most likely to be found at or around Location M, N, O, or P?
a. Location M
b. Location N
c. Location O
d. Location P
Question 31: What is Soil 5? _____________________
Question 32: This soil order is most likely to be found at or around Location Q, R, S, or T?
a. Location Q
b. Location R
c. Location S
d. Location T
One common physical soil property that helps to classify soils is soil texture. Soil texture is one of the first things determined for a given soil or soil horizon, and equates to the size of the particles for a given soil. The three relative sizes of soil particles include sand (largest/coarse), silt (medium), and clay (smallest/fine). Most soils contain a percentage of each of these particle sizes. Figure 1 shows the USDA Soil Texture Triangle which determines soil texture classes by percent sand, silt, and clay.
|Figure 1. USDA Soil Texture Triangle (NCRS).|
Use the Soil Texture Triangle to determine the soil texture class for each of the following examples. Note that the numbers for each separate (sand, silt, clay) on the Soil Texture Triangle are directionally aligned with the associated lines.
Question 33: What is the soil texture class for a soil that is 50 percent clay, 30 percent silt, and 20 percent sand?
a. Silty clay loam
d. Sandy loam
e. Sandy clay loam
Question 34: What is the soil texture class for a soil that is 15 percent clay, 45 percent silt, and 40 percent sand?
a. Silty clay loam
d. Sandy loam
e. Sandy clay loam
Soil texture can be identified in the field using a texture-by-feel method, a relatively accurate finger identification technique in which the combination of sand (gritty), silt (smooth and flexible), and clay (sticky) are estimated using a series of yesno questions. Surprising to some, this mechanical-analysis procedure to identify soils can be highly accurate among trained soil scientists.
Expand SOIL TEXTURE and then click and select Soil Texture by Feel to view a video of how this soil texture identification method is determined in the field.
Texture is important because it relates to weathering and parent material. It also plays a role in water movement, and nutrient availability. Finer textures like clay have smaller pore spaces lending to slower water movement through the soil, and a propensity for a higher CEC and therefore better nutrient availability for plants.
Question 35: After wetting and kneading the soil, determine the steps in soil texture by feel for a clay soil, by moving the four answers below to place in the correct order.
a. Determine the length of the ribbon
b. Determine if soil can form a ball
c. Determine if the soil is smooth or gritty, or neither smooth nor gritty
d. Determine if soil can form a ribbon
Question 36: You have a 3cm ribbon that is very gritty. What type of soil is it?
a. Sandy loam
b. Sandy clay loam
c. Clay loam
d. Silty clay loam
Doubleclick and select California Texture Map. To close the citation, click the X in the top right corner of the window.
Doubleclick and select Location U. Repeat for Location V and W.
Based on the Soil Texture Triangle provided, and referring back to Figure 1, determine the approximate soil texture for each of the following locations.
Question 37: Soil Texture at Location U is ______________.
b. Loamy sand
c. Silty loam
Question 38: Soil Texture at Location V is ______________.
c. Silt clay
Question 39: Soil Texture at Location W is ______________.
b. Sandy clay
c. Silt loam
d. Clay loam
Question 40: In what location (U, V or W) would soils have the largest pore space, fastest water movement, lowest cation exchange capacity (CEC), and limited nutrient availability for plants?
a. Location U
b. Location V
c. Location W
You have just completed Lab Module 11.