LabWorksheet07_GettingtoKnowtheSoils

Name: _____________________________ Lab Worksheet 7: Getting to Know the Soils GEOG 5, Instructor: Joy Fritschle This lab is in three parts: in part 1, you will examine soil horizons, color, and texture; in part 2, you will study several different soil orders from around the world; and in part 3, you will investigate the soils at a specific location in the U.S. Part 1: Soil Properties: Horizons, Color, and Texture In this part of the lab, you will more closely examine the key properties of soils including their horizons, color, and texture. The process of soil formation generally involves the downward movement of clay, water, and dissolved ions. The common result of that is the development of chemically and texturally different layers known as soil horizons . The commonly developed soil horizons are as follows: ➢ O: the layer of organic matter ➢ A: the layer of partially-decayed organic matter mixed with mineral material ➢ E: the eluviated (leached) layer from which some of the clay and iron have been removed to create a pale layer that may be sandier than the other layers ➢ B: the layer of accumulation of clay, iron, and other elements from the overlying soil ➢ C: the layer of incomplete weathering ➢ R: the parent material or bedrock Kim, Lisa

1. Based on the descriptions provided in the table on the next page, label the soil horizons shown on each of the four soil profile diagrams . (remember: not all soils have all the horizons present!) (2 pts) Soil Horizon Labeling Profiles and Descriptions Profiles and Descriptions Soil Profile 1. Few horizons have formed because the parent material was recently exposed to weathering. There is some biological weathering activity initiated by moss growth. Soil Profile 2. This is an arid environment with low rates of weathering. Caliche (calcium carbonate) deposits are found in the B horizon. Soil Profile 3. This is a well-developed soil in a temperate environment. Soil Profile 4. This is a soil in a tropical environment with aluminum oxide deposits (bauxite) in the B and C horizons. O horizon • (soil Profile Develop surface pebble layers called desert pavements/little humus) A horizon • (humus & leached soil) B horizon • (calcium carbonate deposits found) C horizon • (sand stone, shale and limestone) R horizon • (the parent material or the bedrock) O horizon • (the layer of organic matter) A horizon • (The layer of partially- decayed organic matter mixed with mineral material) R horizon • (the parent material or bedrock) O horizon (the • layer of organic matter) A horizon (the layer • of partially- decayed organic matter mixed with mineral material C horizon (the • layer of incomplete weathering) R horizon (bed • rock) O horizon (the layer of • organic matter) A horizon (the layer of • partially-decayed organic matter mixed with mineral material) E horizon (the eluviated • layer from which some of the clay and iron have been removed to create a pale later that may be sandier than the other layers) B horizon (aluminum oxide • deposits are present) C horizon (aluminum oxide • deposits are present) R horizon (bed rock) •

The soil texture triangle provides the names to classify soils with varying percentages of sand (bottom side of triangle), silt (right side of triangle), and clay (left side of triangle. 3. What is the soil name for a soil that has 10% silt, 80% sand, and 10% clay? (0.5 pts) ___________________ What is the soil name for a soil that has 30% silt, 35% sand, and 35% clay? (0.5 pts) ___________________ What is the soil name for a soil that has 75% silt, 10% sand, and 15% clay? (0.5 pts) ___________________ 4. Loam is the ideal soil texture for most vegetable crops. From soil texture triangle, what are the relative amounts of silt, sand, and clay for loam soils? (1 pt) _____% sand _____% silt _____ % clay Each of the three soil textures have different characteristics. The table below summarizes their different properties. Soil Texture and Related Properties Property Sand Silt Clay Soil Fertility: Ability to sustain plant growth Low Moderate-High Moderate-High Porosity: Air spaces (gaps between particles) High Moderate-High Low Permeability: Ability for water to flow through the soil High Moderate-High Low Water Holding Capacity: Ability to hold water against the force of gravity Low Moderate-High High W Loam sand Clay loam Silt loam

5. Based on the table about soil texture and related properties, and your answer to the previous question, describe the characteristics that you would expect to find in loam soils. (0.5 pts) Part 2: Soil Orders In this part of the lab, you will study several different soil orders and their distribution from around the world. You will need to make sure you have first completed Part 1 before doing this section. In the United States, soils are classified into twelve categories called soil orders . This taxonomy is based on the dominant physical and chemical characteristics that make each soil order unique. Like many taxonomies (classification systems) within each category, there are subdivisions. You may be familiar with the taxonomy of living organisms from a biology course: domain, kingdom, phylum, class, order, family, genus, and species. With the soil taxonomy, order is the largest grouping, which can be further divided into suborder, great group, subgroup, family, and soil series. So, soil order is the largest grouping and soil series is the smallest grouping. Before we review the key characteristics of each soil order, let’s analyze the Global Soil Regions map: -Loam soil roughly has 40% sand, 40% silt & 20% clay. It is characterized by right water holding capacity for the growth of plants as well as contains more moisture, nutrients and humus compared to sandy soil.

10. Refer to the global soil regions map. Both aridisols and entisols are found across the Sahara Desert. Why are these two soil orders are commonly found there? (0.5 pts) Alfisols and Spodosols Alfisols and spodosols are common in forest environments. Alfisols are found in humid and temperate climates and spodosols are found in cooler climates with coniferous forests. Alfisols are rich in nutrients and make productive agricultural soils. In contrast, spodosols are more acidic and have low rates of fertility. 11. Which one of the four soil profiles that you labeled best represents an alfisol? (0.5 pts) Soil Profile _____ Which regions of the United States have alfisols? (0.5 pts) Which regions of the world have spodosols? (0.5 pts) Histosols, Mollisols, and Vertisols Histosols are found in wetlands and mollisols are common in grasslands. Vertisols are not associated with a specific landscape—they are distinct from other soil orders because vertisols have large amounts of clays. Key ideas about these three soil orders are as follows: ➢ Given their wetland environment, histosols have high levels of organic content when compared to other soil orders. Little drainage in wetland areas allows for organic materials to accumulate over time. ➢ Mollisols also have higher levels of organic materials due to the activity of plant roots in grassland ecosystems. Mollisols are productive agricultural soils. ➢ Vertisols shrink and swell due to their clay content. When wet, clay absorbs moisture and swells. When dry, clay shrinks and cracks. 12. Peat is partially decayed organic matter. Which soil order would likely be a source of peat? (0.5 pts) ___________________________ Where in the United States are mollisols common? (0.5 pts) Part 3: Getting to Know Your Soils This part of the lab is to be completed in the Lab 7 Discussion board on Canvas. You will need to write a primary post (at least 150 words in length; worth 4pts ) and two secondary posts in response to other students’ primary posts (at least 75 words in length each; worth 1pt each ). The instructions for what you should write about can be found by going to the Discussion menu item in our Canvas course. -Mississippi, Ohio, New York State, Minnesota, Wisconsin Michigan, Indiana -Northen Europe, Russia, northeastern North America, Central & eastern Canada, Indonesia, Florida Histosols -Midwestern States, Iowa, Minnesota, North Dakota, Indiana