266 SOILS AND FERTILIZERS 



perature ? 44. What is the specific heat of soils ? 45. To what ex- 

 tent does drainage influence soil temperature ? 46. How do 

 manured and unmanured land compare as to temperature ? 47. 

 What relation does heat bear to crop growth ? 48. What materials 

 impart color to soils? 49. What is the effect of loss of organic 

 matter upon the color of soils ? 50. What materials impart taste to 

 soils ? Odor ? 51. What effect does a weak current of electricity 

 have upon crop growth ? 52. Do all soils possess the same power 

 to absorb gases? Why? 53. What is agricultural geology? 54. 

 What agencies have taken part in soil formation? 55. How does 

 the action of heat and cold aid in soil formation ? 56. Explain the 

 action of water in soil formation. 57. What is glacial action, and 

 how has it been an important factor in soil formation ? 58. Ex- 

 plain the action of vegetation upon soils. 59. How has the action 

 of micro-organisms aided in soil formation ? 60. Explain the 

 terms : Sedentary, transported, alluvial, colluvial, volcanic, and 

 windformed soils. 61. What is feldspar and what kind of soil 

 does it produce ? 62. Give the general composition of the follow- 

 ing rocks and minerals and state the quality of soil which each 

 produces: Granite, mica, hornblende, zeolites, kaolin, apatite, and 

 limestone. 63. What elements are liable to be the most deficient 

 in soils ? 64. Name the acid- and base-forming elements present 

 in soils. 65. What are the elements most essential for crop growth ? 

 66. State some of the different ways in which the elements present 

 in soils combine. 67. Why is it customary to speak of the oxides of 

 the elements and to deal with them rather than with the elements ? 

 68. Do the elements exist in the soil in the form of oxides? 69. 

 What are double silicates? 70. In what forms does carbon occur 

 in soils? 71. Is the soil carbon the source of the plant carbon ? 

 72. What can you say regarding the occurrence and importance of 

 the sulphur compounds ? 73. What influence would o. 10 per cent, 

 chlorine have upon the soil ? 74. In what forms does phosphorus 

 occur in soils? 75. What is the principal form in which the nitro- 

 gen occurs in soils ? 76. What can be said regarding the hydrogen 

 and oxygen of the soil? 77. State the principal forms and the 

 value as plant food of the following elements : Aluminum, potas- 

 sium, calcium, sodium, and iron. 78. For plant food purposes, 

 what three divisions are made of the soil compounds ? 79. Why 

 are the complex silicates of no value as plant food ? 80. Give the 

 relative amounts of plant food in the three classes. 81. How is a 

 soil analysis made ? 82. What can be said regarding the economic 

 value of a soil analysis ? 83. What are some of the important facts 

 to observe in interpreting results of soil analysis ? 84. Under what 

 conditions are the results most valuable ? 85. Do the terms volatile 

 matter and organic matter mean the same ? 86. How may organic 



