40 MCQs for Quiz 2A - Soils - Fall 2003 | CSES 3114, Quizzes of Soil Physics

Download 40 MCQs for Quiz 2A - Soils - Fall 2003 | CSES 3114 and more Quizzes Soil Physics in PDF only on Docsity! 1 CSES/ENSC/GEOL 3114 - Soils - Fall 2003 – Quiz #2-A Chapters 4, 5 and 7 Name______________________Student#________________________Test #_________ Please choose the best answer for each question. Be sure to read each question and answer set carefully. You must complete the test within the allotted time period of two hours. All answers must be transferred to the Opscan sheet by the end of the test. Be sure to sign your test and turn it in along with your Opscan. Given: Particle Density = 2.65 Mg/m3 or g/cm3 1. A horizons are generally characterized by _____ structures while subsoils tend to be dominated by _____ peds. 1. Single grain; granular 2. Granular and crumb; blocky and prismatic 3. Platy and columnar; massive 4. Single grain or massive; granular or crumb 5. None of the above are correct combinations 2. In well-structured subsoils, the voids between soil pores are primarily ____ while the inter-particle packing voids within the peds are primarily composed of ____. 1. Macropores; micropores 2. Micropores; macropres 3. Eluvial; illuvial 4. Illuvial; eluvial 5. None of the above are correct 3. Platy structure in soils is generally considered to be ____ because it ___________. 1. Beneficial; improves soil strength 2. Beneficial; limits cation leaching 3. Detrimental; limits rooting 4. Inconsequential; disappears in a few weeks 5. None of the above are correct 4. Soil bulk density ______ with decreasing pore space and _______ with increasing mass water content. 1. Increases, decreases 2. Decreases, increases 3. Decreases, stays constant 4. Increases, stays constant 5. Stays constant, increases 5. Plant rooting is usually restricted when soil bulk densities approach ______________ for fine textured and sandy textured soils, respectively. 1. 1.4 to 1.8 2. 0.5 to 1.0 3. 1.0 to 2.0 4. 1.1 to 1.5 5. No “rooting limitation range” exists for bulk density 2 6. In general, as you increase the organic matter content and degree of aggregation in a soil, bulk density will: 1. Decrease 2. Remain constant 3. Increase 4. Increase then decrease 5. None of the above are correct 7. Soil color and color development patterns are commonly employed by soil scientists for: 1. Interpreting the wetness and drainage regime of a soil 2. Correctly specifying the plasticity index 3. Estimating texture and structure in the field 4. All of the above are true 5. None of the above are true 8. Which of the following practices would enhance aggregate stability in an A horizon? 1. Frequent tillage 2. NaSO4 additions 3. Lime additions 4. Routine organic matter additions 5. 3 and 4 above are both correct 9. Soil tilth refers to: 1. The physical condition of the soil in relation to plant growth 2. The compressive resistance of the soil to a tillage implement 3. Tillage practices that maintain mulch cover and minimize disturbance 4. All of the above are true 5. None of the above are true Questions 10-13 refer to the following data: You sample a soil from a carefully measured volume of 150 cm3 in your garden and then dry it down in your oven to final weight of 175 g. The initial wet weight when you sampled it was 225 g. 10. What is the bulk density of this soil? 1. 1.50 2. 1.17 3. 0.33 4. 0.51 5. None of the above are even close (+10%) 11. What is the % porosity of this soil in situ? 1. 44% 2. 56% 3. 100% 4. None of the above are correct (+ 5%) 5. This question cannot be answered with the data given 5 30. Assuming that you set your gravitational reference point below the soil, the matric potential of soil water will always be ___________________, and the gravitational potential will always be ______________________. 1. Negative; negative 2. Negative; positive 3. Positive; negative 4. Positive; positive 5. None of the above are correct answers, water potentials cannot be characterizes in this way. 31. The overall free energy state of soil water at given location and time in a soil is due to: 1. The gravitational potential 2. The matric potential 3. The osmotic potential 4. All of the above contribute to the net free energy state of soil water 5. None of the above are correct answers 32. In soils that are unsaturated, which of the following water potential components usually dominates net soil water potential? 1. The gravitational potential 2. The matric potential 3. The osmotic potential 4. All of the above would substantially contribute to the net soil water potential 5. None of the above are correct answers 33. A soil that was saturated would have a net water potential of approximately ___________ bars while a soil that had been dried down to a point where the only water remaining was that in forms that plant at wilting could not extract would be approximately _____________________ bars net water potential. 1. – 0.1 to –0.3; - 15 2. 1.0; 15 3. 0.0; -31 4. – 1.0; - 15 5. None of the above are correct combinations of water potential values 34. You have four soils of varying texture all with a net water potential of – 0.3 bars. Which soil would hold the most total soil water at this potential? 1. Sand 2. Sandy loam 3. Silt loam 4. Clay 5. None of the above are correct answers because texture has no effect on total soil water holding. 6 35. The rate of saturated water flow in soil is always ____________ than the rate of unsaturated water movement, and also moves at a higher rate in ____________ textured soils. 1. Slower; clay 2. Faster; sandy 3. Faster; clay 4. Slower; sandy 5. None of the above are correct answers 36. A saturated wetting front moving downward through a sandy loam A horizon encounters a poorly structured, high clay Bt horizon. What happens to the rate of downward water movement and why? 1. The rate of water movement accelerates due to the very high matric potential exerted by the clayey subsoil. 2. The rate of water movement accelerates due to the pressure head (hydrostatic load) that builds up at the A-B horizon boundary. 3. The rate of water movement decreases due to the pore size discontinuity and restriction between the two layers. 4. The rate of water movement would not change across the boundary due to offsetting effects of matric potential vs. pore size differential. 5. None of the above are correct answers. 37. You have a soil that holds 60 g of water per 100 g dry soil at 0 bars, 40 g of water at –0.1 bars, 25 g of water at –5 bars, 10 g of water at –15 bars and 5 g of water at –31 bars. What is the plant available water holding capacity of this soil? 1. 0.30 or 30% 2. 0.50 or 50% 3. 0.15 or 15% 4. 0.40 or 40% 5. None of the above are correct; you can’t calculate plant available water like this. 38. You have four soils of varying texture as shown in answers 1-4 below. Which soil would hold the most total plant available water on a mass basis? 1. Sand 2. Sandy loam 3. Silt loam 4. Clay 5. None of the above are correct answers because texture has no effect on plant available water 7 39. The name of the soil structure type shown in the figure to the right is: 1. Angular Blocky 2. Subangular Blocky 3. Coarse Crumb 4. Platy 5. None of the above are correct 40. The best interpretation of the data presented in the figure presented below right is: 1. As soil moisture increases, soil strength and rooting penetration will increase. 2. In low density soils, water content has no effect per se on rooting. 3. The basic relationship between water content and root penetration will vary between low and high bulk density soils 4. Answers 1 and 3 are correct. 5. All of the above (1, 2 and 3) are correct interpretations. Hint: Remember that rooting is inhibited when the penetrometer reading is high.