Soil Science Exam Questions PDF
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This document consists of exam questions related to soil science. Topics covered include the Dokuchaev function, soil horizons, weathering, soil functions, and soil properties. It explores various aspects of soil formation and the physicochemical properties of soil.
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xercises for the examination Introduction to Soil Science, WS 23/24, Prof. Bigalke Soil E formation and soil function . Explain the Dokuchaev function for soil formation? 1 The Dokuchaev function states that soil formation depends on five factors: climate, organisms, parent material,...
xercises for the examination Introduction to Soil Science, WS 23/24, Prof. Bigalke Soil E formation and soil function . Explain the Dokuchaev function for soil formation? 1 The Dokuchaev function states that soil formation depends on five factors: climate, organisms, parent material, relief, and time. These factors interact to develop distinct soil profiles. 2. Name four types of physical and chemical weathering? hysical: Freeze-thaw action, exfoliation, thermal expansion, abrasion. P Chemical: Hydrolysis, oxidation, carbonation, dissolution. . Name the five soil-forming processes and give an example of where and why they can be 3 seen in a soil profile? Draw the processes in the photo? Podsolization: Occurs in acidic, high rainfall areas(e.g., boreal forests). Laterization: Found in tropical regions due to intenseleaching. Calcification: Seen in dry climates, causing calciumcarbonate accumulation. Gleization: Common in waterlogged soils, leading toblue-grey coloration. Humification: Organic matter decomposition forminghumus. . What is a soil horizon? 4 A distinct layer within a soil profile, such as O (organic), A (topsoil), B (subsoil), C (parent material), and R (bedrock). 5. Under which climatic conditions does physical weathering predominate and under which onditions does chemical weathering predominate? Where is chemical weathering particularly c pronounced? P hysical weathering: Cold/dry climates. Chemical weathering: Warm/humid climates (e.g., tropical rainforests). . How does the soil type and soil color change in the course of soil formation? What do you call 6 these processes? Soils develop from initial parent material to well-formed profiles, darkening with organic accumulation (humification) or lightening with leaching (eluviation). . What is the difference between soil type and soil type? 7 Soiltyperefers to classification (e.g., sandy soil,clay soil). Soiltexturedescribes particle sizes (sand, silt,clay). . Name 5 soil functions and give a short description of each function (1-3 sentences). 8 Water filtration: Soils filter pollutants. Nutrient cycling: Releases essential nutrients. Carbon storage: Stores organic carbon. abitat provision: Supports biodiversity. H Food production: Essential for agriculture. 9. Which physicochemical soil properties are important for the soil function "food production"? oil constituents S Texture, structure, nutrient content, water-holding capacity, and pH. 0. Why are clay minerals negatively charged? 1 Clay minerals are negatively chargeddue to isomorphoussubstitution, where lower valency cations replace higher valency ones. 1. Give an example for one three layer clay mineral and for one two layer clay mineral? How do 1 the two minerals form and what are their properties (charge, swelling)? T hree-layer: Montmorillonite (high swelling). Two-layer: Kaolinite (low swelling). 2. What components does soil humus consist of? What consequences does this have for the 1 turnover of the carbon pool in the soil? Consists of humic substances, fulvic acids, and organic residues. 3. Which minerals accumulate in the soil in the course of soil formation? Name three 1 examples. Iron oxides (hematite), Aluminum oxides (gibbsite), Silicates (quartz). 4. What is the dominant iron oxide in Central European soils, and which is formed in tropical 1 soils? How do the colors and chemical formulas differ? Central Europe:Goethite (FeO(OH))(yellow-brown). Tropics:Hematite (Fe₂O₃)(red). 5. Why are highly weathered tropical soils rich in iron but poor in silicates? 1 Tropical soils are iron-rich but silicate-poordueto intense weathering, which removes silica. 6. You are in a spruce forest in the foothills of the Alps on acidic metamorphic rock. What type 1 and structure of organic layer do you expect? Thick mor humus due to slow decomposition. 7. Give (at least) one example each of soil micro-, meso- and macro-fauna. 1 Microfauna: Bacteria. esofauna: Nematodes. M Macrofauna: Earthworms. 8. What is the difference between the soil air and the normal athmosphere? 1 Soil air hashigher CO₂, lower O₂, due to respiration. 19. 0. What happens to the water that reaches the soil with the precipitation? Describe at least 2 three processes and three ways in which water can occur in soil? Infiltration, percolation, capillary rise. 1. What types of water exist in the soil? 2 Gravitational water, capillary water, hygroscopic water. 2. What is the total potential of water in the soil? What is it important for and what potentials 2 does it consist of? Sum of matric, osmotic, and gravitational potentials. 3. What is the usable field capacity and why is it important in agriculture? 2 Water available for plants after drainage. 4. How does the oxygen mixing ratio in the soil air change after a heavy rain event and why? 2 Oxygen mixing after rain: Decreases due to water saturation. Chemistry & Physics 5. Name three soil processes that you can recognize by the soil color? 2 Oxidation (red/yellow soils), Reduction (grey/blue soils), Organic accumulation (dark soils). 26. Which system is used to describe soil color in a comparable way? unsell color chart M 27. Briefly describe the formation of the soil structure. ggregation of soil particles due to organic matter and clay. A 8. What is shear resistance? 2 Soil’s resistance to deformation. 9. What are colloids? 2 Fine particles with high surface charge, affecting nutrient retention. 0. On which parameters does the stability of a colloidal suspension depend? 3 Depends on pH, ionic strength, and organic matter. 1. Which pH ranges occur most frequently in soil and why? 3 4-8, influenced by climate and mineral content. 2. Why does soil humus carry variable charges? Sketch the relationship between variable 3 charges and the pH value. (2 points) Due to pH-dependent functional groups. 3. Name 2 soil components that are important for cation exchange and one soil component 3 that is important for anion exchange? C ation: Clay, organic matter. Anion: Oxides. 4. Name three processes that lead to soil acidification? 3 Leaching, organic matter decomposition, acid rain. 5. What is the redox potential and why is it important in soil? 3 Indicates oxidation/reduction status. 6. What causes low redox potentials in the soil and what are the effects? 3 Caused by waterlogging. Leads to iron/manganese reduction. 7. How can a partially low redox potential in the soil be recognized? 3 Gleying (bluish-grey soils). 8. Name three parameters on which the speciation of elements in the soil solution depends? 3 pH, redox potential, organic matter. 9. Name two types of sorption in soil? 3 Adsorption, absorption. 0. Define the cation exchange capacity (CEC) and explain which soil components contribute 4 to the CEC. Soil’s ability to hold nutrients. 1. What is meant by "bases" in soil science? Name the primary sources of "bases". How are 4 plant-available bases bound in the soil. (3 points) Ca²⁺, Mg²⁺, K⁺, Na⁺. Derived from weathering. 42. Which forms of nitrogen in the soil are available to plants? Nitrate (NO₃⁻), ammonium (NH₄⁺). 3. Where does the nitrogen in the soil come from (without fertilization) and why is nitrogen 4 often a limiting nutrient? Organic matter, nitrogen fixation. 4. Where does the phosphorus in the soil come from (without fertilization) and why is 4 phosphorus often a limiting nutrient? Soil classification Weathering of minerals like apatite. 5. Name two different classification systems for soils? 4 USDA Soil Taxonomy, WRB (World Reference Base). 6. Why are soils classified? 4 Organizes soils by properties for agricultural, environmental use. 7. What type of soil forms in Central Europe from a brown earth on a marly parent rock and 4 why? Luvisol, due to clay accumulation. 8. Explain the process of lessivation. Which soil type does lessivation lead to? How can you 4 recognize lessivation in the field? Give a typical horizon sequence. (4 points) Process: Clay eluviation. Soil type: Luvisol. Horizon sequence: A-E-Bt-C. 9. Explain the process of podsolization. What type of soil does podsolization lead to? How can 4 you recognize podzolization in the field? Give a typical horizon sequence. (4 points) Soil functions S ○ oil type: Podzol. ○ Recognizable by bleaching in E horizon. ○ Horizon sequence: O-A-E-Bs-C. 0. Name two soil functions and one soil component, one soil property and one process that are 5 important for these functions? Briefly explain the reason for your choice for each point? Water retention: Clay, organic matter. Nutrient cycling: Microorganisms, minerals. 1. Name two soil functions for which the clay content of a soil is important and briefly explain 5 why? W ater retention. Cation exchange capacity. 2. Name two soil components and two (physical or chemical) soil properties which are 5 important for agricultural production and explain why they are important? pH, organic matter, texture, structure. 3. Name one soil type which is well suited for agricultural production and explain why? Answer 5 the questions based on your notes and documents and also consult soil science Loam (balanced sand, silt, clay), rich in nutrients.
