276 SOILS AND FERTILIZERS 



To what extent does the color of soils influence the temperature ? 

 44. What is the specific heat of soils ? 45. To what extent does 

 drainage influence soil temperature? 46. How do manured and 

 unmanured land compare as to temperature ? 47. VVhat 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. W T hat effect does a weak current of electricity have upon crop 

 growth ? 52. Do all soils possess the same power to absorb gases ? 

 Why? 



CHAPTER II. 



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. Explain 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 following rocks and minerals 

 and state the quality of soil which each produces : Granite, mica, 

 hornblende, zeolites, kaolin, apatite, and limestone. 



CHAPTER III. 



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. W T hat 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 



