INDEX 



253 



Organic matter, examination of soil 

 for, 58. 



extraction of, 59. 



influence on rate of percolation, 59. 



influence on water held by soils, 60. 



injurious effect, 55. 



in soil, description, 51. 



in soil management, 55. 



kinds of, 51. 



porosity of, 53. 



sources of, 57. 

 Oxygen, proportion in earth's crust, 4. 



Packing, subsurface, 78. 

 Particles of soil, examination, 46. 



number per gram, 30. 



relative sizes, 31. 



shape of, 30. 



space occupied by, 30. 

 Peat, origin, 21. 

 Percolation, test for rate of, 86. 

 Plant constituents, obtained from air 

 or water, 3. 



obtained from soil, 3. 

 Plant-food materials, available and 

 unavailable, 94. 



essential to growth, 3. 



absorption by plants, 105. 



in apatite, 7. 



in calcite, 7. 



in drainage water, 102. 



in dolomite, 7. 



in farm manure, 222. 



in green manures, 236. 



in gypsum, 7. 



in hematite, 7. 



in liquid excreta, 222. 



in minerals, 7. 



in soils, 90. 



in solid excreta, 222. 



laboratory exercise, 9. 



liberation by lime, 190. 



movement of, 93. 



obtained from air or water, 3. 



obtained from soil, 3. 



possible exhaustion, 109. 



proportion in soils, 93. 



quantities in earth's crust, 4. 



removed by crops, 108. 



total supply in soils, 92. 



variations in soils, 90. 



Plan* growth, conditions of, labora- 

 tory exercise, 9. 

 Plant nutrients, laboratory exercise, 



9. 

 Plant roots, aid in solution of soil 

 constituents, 106. 

 solvent action, 107. 

 Plants, effect on rock disintegration, 

 14. 

 substances essential to growth, 3. 

 uses of water by, 2. 

 Phosphate, bone, 171. 



mineral, 171. 

 Phosphoric acid, effect on plant 



growth, 175. 

 Phosphoric acid, plants benefited by, 

 176. 

 proportion in earth's crust, 4. 

 reverted, 173. 

 Phosphoric acid fertilizers, 171. 



availability of, 174. 

 Pore space, its determination, 49. 



relation to structure, 37. 

 Potash, effect on plant growth, 181. 



proportion in earth's crust, 4. 

 Potash fertilizers, sources, 179. 



wood ashes, 180. 

 Province, the soil, in soil survey, 44. 



Quartz, substance of which composed, 



7. 



Residual soils, composition, 20. 

 described, 18. 

 distribution of, 20. 

 loss during formation, 19. 

 Rock, changes in soil formation, 15. 

 disintegration by heat and cold, 12. 

 disintegration, effect of gases on, 



14. 

 disintegration, effect of glaciers on, 



13. 

 disintegration, effect of ice on, 13. 

 disintegration, effect of plants on, 



14. 

 erosion by wind, 14. 

 expansion by heat, 12. 

 relation to soil, 15. 

 Rocks, from which soil has been 

 formed, 5. 

 igneous, 5. 



