Soil Science: Soil Physics and Clay Minerals, Exams of Agricultural engineering

Download Soil Science: Soil Physics and Clay Minerals and more Exams Agricultural engineering in PDF only on Docsity! 1 Soils 201 Exam #2 Name ___________________ 26 February 2008 (118 points total) Section Number __________ I. Single-Answer Multiple Choice (2 points each): Circle the one solution that answers each question or completes each sentence. 1. Water movement by capillary rise from a water table will rise the highest for which texture? a. sand b. clay loam c. silt loam d. loam 2. _____ is the movement of water from the soil surface into the soil profile. a. Infiltration b. Percolation c. Drainage d. Permeability e. Leaching 3. The shrink/swell capacity is likely to be the greatest in which of the following clays? a. Vermiculite b. Kaolinite c. Illite d. Montmorillonite 4. When a magnesium ion is substituted for an aluminum ion in the octahedral sheet of a silicate clay mineral, the change in net charge of that mineral will be a. +1 b. 0 c. -1 d. -2 5. Which of the following clays has the highest degree of ionic substitution? a. Montmorillonite b. Vermiculite c. Chlorite d. Illite e. Kaolinite 6. Compacting a granular-structured silt loam soil will _____ its bulk density, _______ its particle density and ____ its porosity. a. decrease, increase, decrease b. increase, not change, increase c. not change, increase, decrease d. increase, increase, not change e. increase, not change, decrease 2 7. If the same amount of water is applied over the surface to wet different dry soils, the depth of wetting that results will be the deepest if the texture of the soil is _____ . a. silt loam b. sandy loam c. loam d. clay loam 8. Of the following, which silicate clay mineral has the highest nutrient storage capacity? a. montmorillonite b. kaolinite c. illite d. chlorite e. vermiculite 9. Which of the following clays can potentially be a problem for potassium fertility? a. Montmorillonite b. Vermiculite c. Chlorite d. Illite e. Kaolinite 10. Plant available water in soil is between matric potentials of ____ . a. 0 kPa and –1,500 kPa b. 0 kPa and –3,100 kPa c. -10 kPa and –1,500 kPa d. -10 kPa and –3,100 kPa e. -10 kPa and –100 kPa 11. Bluish gray and olive colors in soil result from the ____ . a. oxidation of iron b. accumulation of organic matter c. leaching of iron and aluminum oxides d. reduction of iron 12. The attraction of water molecules to each other is called ____ . a. surface tension b. adhesion c. cohesion d. adsorption 13. The three most abundant chemical elements that make up the Earth's crust are a. O, C, and H. b. Si, Al, and Fe. c. O, Si, and Al. d. Al, Fe, and Ca. e. O, Al, and Fe. 14. With increasing soil pH from 6 to 8, the nutrient storage ability of silicate clay minerals _____ . 5 solution but may have two, three, or four of the answers listed. Mark "T" (for true) for each answer that solves the problem correctly and "F" (for false) for each answer that answers the problem incorrectly. 27-30. Conventional tillage can slow down water movement through a soil because it ____27. buries layers of plant residue in the soil. ____28. can form a tillage pan over time. _T or F___29. causes the cultivated upper layer of soil to have poor tilth. ____30. disrupts earthworm channels. 31-34. In comparing surface fine-textured soils to coarse-textured soils under natural conditions, the coarse-textured soils generally have ____31. greater porosity. ____32. higher bulk density. ____33. a dominance of micropores. ____34. a higher particle density. 35-38. The water molecule is polar which explains why water molecules ____35. are attracted to silicate clay particles. ____36. are attracted to each other. ____37. are attracted to ions. ____38. have one portion that is more negative than positive and an opposite side (with two hydrogens) that is more positive than negative. 39-42. The hydraulic conductivity ____39. is affected by soil organic matter content. ____40. is affected by soil texture and structure. ____41. is the movement of water from higher to lower potential. ____42. is affected by the wetness of the soil pores. 43-46. A soil colloid is ____43. the relative proportion of organic matter and clay in a soil. ____44. an organic or inorganic particle less than 0.001 mm in size. ____45. a chemical compound in which a metallic ion is firmly combined with an organic molecule. ____46. a very small particle with a correspondingly large surface area. 47-50. All clay minerals have a large external surface area; _______ clays have a large internal surface area as well ____47. Kaolinite ____48. Montmorillonite ____49. Illite ____50. Vermiculite 51-54. Water potential can be measured using different equipment including ____51. time domain reflectometry. 6 ____52. a pressure membrane apparatus. ____53. tensiometers. ____54. resistance blocks. 55-58. According to the water movement video shown in class, water will ____55. move into a buried sand layer quickly. ____56. will move quickly through a buried clay layer. ____57. initially move into the micropores of a buried clay loam quicker than it will enter the macropores of a buried sand layer. ____58. will move quickly through a sand layer that is exposed to free water at the soil surface. III. Fill-Ins (2 points each space): Fill-in each space below with the correct answer. 59. The absorption of water by plants occurs when the total water potential inside the root is ________ than the water potential of the soil near the root surface. LESS 60. _____________________ is the driving force for water movement into plants. TRANSPIRATION 61. The two sources of negative charge in silicate clays are from __________________________ and _____________________________. IONIC SUBSITUTION; EXPOSED CRYSTAL EDGES 62. The two basic structures that serve as building blocks for silicate clays are the ___tetrahedron____ (whose central cation is silicon) and the __octahedron____ (whose central cation is aluminum). 63. Silicate clay mineral particles are flat and are made of a series of ____________ , which in turn are made up of ____________ . LAYERS OR PLATES; SHEET 64. __________________ is a 2:1:1 mineral. CHLORITE 65. X-ray diffraction of soil samples, particularly silt- and clay-sized particles, can be used in criminal cases. This is called ________________ mineralogy. FORENSIC 66. ________________ colors are spots of one color on the background of another color. MOTTLED 67. A clay pan in the subsoil can result in the prevention of water movement through the soil profile. With the continued addition of water, a ___perched water table_____ might form. 68. The attraction of water molecules to soil solids is called _________________ . ADHESION 69. ______________ potential is responsible for the lateral movement of water in unsaturated soils. ______________ potential results from the presence of salts and other solutes. MATRIC; OSMOTIC 70. Layers of soil and rock covering a coal seam that are removed prior to surface mining are called ____________________ . OVERBURDEN or SPOIL 71. ____________________ is the restoration of land and environmental values to a surface mine site after the coal is extracted. The process includes restoring the land to its approximate original appearance by replacing topsoil and planting native grasses and ground covers. RECLAMATION