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Soils Exams
| Question | Answer |
|---|---|
| On what size fraction are the USDA-NRCS soil texture classes are determined? | Over 2mm in size |
| You observe a forest soil with the following horizon sequence: Ap, E, Bt, C. The ______ contains the largest concentrations of organic matter, while the ______ contains the largest amounts of clay. Hint: looking for Ap, E, Bt, or C for each blank. | Ap Bt |
| If you looked at the various minerals in an igneous or metamorphic rock, which type of mineral would weather the slowest? | Light colored quartz |
| After a heavy rain, you observe a substantial amount of water running off the surface of a cornfield that is tilled every year. Which service is the soil not providing? | Regulating water supply and quantity |
| Which of the following weathering mechanisms is considered to be a physical weathering process? | Which of the following weathering mechanisms is considered to be a physical weathering process? |
| Which of the following materials would not qualify as “soil” based on the definition we used during week 1 in lecture? | Which of the following materials would not qualify as “soil” based on the definition we used during week 1 in lecture? |
| Soil microbes digest leaf litter and release CO2 to the atmosphere. This is an example of which service provided by the soil: | Modifies the composition of the atmosphere |
| The ____ horizon is characterized by being most affected (leached and altered) by net losses of soluble and mobile material. The ____ horizon is characterized by a zone of accumulation. Hint: looking for A, E, B, or C for each blank. | E B |
| What are the five soil forming factors? | Organisms, parent material, climate, topography, time |
| The soil profile formed from which parent material has no distinct layering, no rock fragments, and no saprolite, but high silt content? | Eolian |
| The soil profile formed from this parent material has no distinguishing layers or rock fragments in the upper horizons, but saprolite is identifiable in the C horizon | Residuum |
| The soil profile formed from this parent material has lots of jumbled, jagged rocks throughout the profile. | Colluvium |
| The soil profile formed from which parent material has distinct layering with multiple buried A horizons and smooth rocks that lay flat throughout the profile? | Alluvium |
| In general, soils formed under grasslands contain thicker A horizons, while soils formed under forests contain better developed B horizons. Hint: looking for A, E, B, or C for each blank. | A B |
| You run a particle size analysis in the laboratory and you determine that your soil is 10% coarse fragments > 2mm, 40% clay sized particles and 20% silt sized particles. What is the percent sand in your sample? | 40% |
| Illuviation and eluviation are two examples of which soil forming process? | Translocations |
| Web Soil Survey tells you the textural class of the soil in your Ap horizon is a “Loam”. Which of the following statements are true of a “loam” soil? | Loams are equally influenced by sand, silt, and clay |
| Which is the most general level of soil taxonomy? | Soil Order |
| Your house is located on the summit of a hill slope. You want to have a garden with deep, fertile soils. What position would be the WORST place to have the garden? | Shoulder and Slope |
| Match the letter to the special property it signifies. | T = Accumulation of clay H = Humic material I = Fibric organic matter |
| Study 22 from test 1 | study 22 from test 1 |
| What is flocculation? | Flocculation is the coming together of soil colloids when their negative charges are neutralized by positively charged cations. |
| Which of the following processes does not promote the formation of aggregates? | Tillage |
| You have a soil core that is exact 10 cm3 and has an oven dry weight of 12.5 g. What is the bulk density? | 1.25 g/cm3 |
| When soil is saturated, flow of water through soil is primarily driven by ________; however, when the soil is unsaturated, the flow of water is primarily driven by_______. | Gravitational potential/Matric Potential |
| Your friend asks what kind of surface soil structure would be best for plant growth. You tell him: | Granular |
| Your favorite potted plant is dying. Because you are now soil savvy, you do some soil analysis and find that: bulk density = 1.1 g/cm3, volumetric water content = 99%, and organic matter content = 55%. You instantly: | Drain the soil, because the roots might not be getting enough air |
| Total soil water potential is a combination of which three potentials? | Matric potential, osmotic potential, and gravitational potential |
| Which soil has the lowest bulk density? | A well aggregated loam |
| Which soil is likely to have the most pore space? | A well aggregated loam |
| You have two soils (A and B) directly adjacent and in contact with each other. In soil A, the total water potential is -500 kPa, while in soil B the total water potential is -25 kPa. Which direction and what type of water movement would occur? | Water would move from B to A via unsaturated flow. |
| Q 13, 14, 15, 16 test 2 | Q 13 test 2 |
| Which of the following soil orders would most likely exhibit substantial anion exchange capacity (AEC) under its native/normal pH and mineralogy? | Oxisols |
| Which cations are common acid cations in soils? | H+ Al3+ |
| Q 5,6 test 3 | Q 5,6 test 3 |
| The hydrolysis of one mole of Al3+ generates how many moles of H+? | 3 |
| Which are common base cations in soils? | K+ Na+ Mg2+ Ca2+ |
| What are the sources of pH dependent charge in soil? | Fe and Al Oxides Broken Clay Sheets Functional Groups of organic matter |
| You perform the single wash method to determine the CEC of a soil sample from your lawn. Using the data below, calculate the CEC . Ion Amount (cmolc kg-1) Mg2+ 4 Ca2+ 6 H+ 10 K+ 8 Na+ 3 Al3+ | 32 |
| In a soil comprised of mostly kaolinite and iron oxides, liming raises the pH from pH = 4 to pH = 7. What happens to pH dependent charge on the clays and total CEC? Correct! | pH dependent charges on the colloids changes from positive to negative and CEC is increasing. |
| Q 12,13 test 3 | Q 12,13 test 3 |
| What would cause the MOST shrinking and swelling in a clay? | isomorphous substitution is in the octahedral layer. |
| The major soil colloids are: | Iron Oxides, organic matter, clays. |
| Which of the following best describes cation exchange? | The continual substitution of adsorbed cations at colloid surfaces |
| A soil sample was found to have a CEC of 12.0 cmolc kg-1. How many cmolc kg-1 of K1+ would be required to satisfy this negative charge? | 12 |
| A soil sample was found to have a CEC of 12.0 cmolc kg-1. How many cmol kg-1 of Al3+ would be required to satisfy this negative charge? | 4 |
| A soil sample was found to have a CEC of 12.0 cmolc kg-1. How many cmolc kg-1 of Mg2+ would be required to satisfy this negative charge? | 12 |
| A soil sample was found to have a CEC of 12.0 cmolc kg-1. How many cmol kg-1 of Na+ would be required to satisfy this negative charge? | 12 |
| The majority of oxygen is transported through soil by.... | Diffusion |
| The concentration of carbon dioxide: | Is higher in the soil air compared to the atmosphere |
| In order for a soil to form redoximorphic features like mottles of Fe-depletions and concentrations, which of the following conditions are required? | Absence of oxygen Presence of terminal electron acceptors |
| In normal soils, ________ buffers pH in acid soils (pH = 4), but ___________ buffers pH in alkaline soils (pH = 8)? | Al, CO3 |
| In saturated soils with no oxygen, which list of elements are all potential electron acceptors? | Fe, Mn, N, S |
| The source of electrons in soil redox reactions is ____________. The reactions are controlled by________ . | Organic C, microbes |
| Given the following redox reaction: Fe+3 + C-2 → Fe+2 + C-1. Which element is being oxidized and which is being reduced? | Fe is reduced and C is oxidized |
| Q 28, 29 Test 3 | Q 28,29 Test 3 |
Created by:
jackscarbs