INDEX 



251 



Fertilizers, phosphoric acid, tests for, 

 177. 

 potash, 179. 

 potash, tests for, 185. 

 response of soil to, 218. 

 tests for nitrogenous fertilizers, 169. 

 that should not be mixed, 203. 

 the limiting factor, 215. 

 the purchase and mixing of, 196. 

 use of, 207. 

 Fertilizing the rotation, 213. 

 Formation of soil, agencies concerned, 



11. 

 Formations of soil, 18. 

 Freezing and thawing of soil, effect 



on structure, 40. 

 Frost, effect on rock disintegration, 

 12. 



Gases, diffusion of, 144. 



effect on rock disintegration, 14. 

 Germs, injurious to crops, 125. 



in soil, kinds of, 125. 



not directly injurious to crops, 126. 

 Glacial soils, composition of, 26. 



described, 25. 



distribution of, 26. 



formation of, 25. 

 Glaciers, effect on rock disintegra- 

 tion, 13. 

 Grains, fertilizers for, 207. 

 Granite, losses during soil formation, 



15. 

 Grasses, fertilizers for, 208. 

 Gravitational water, 67. 

 Green manures, crops used for, 238. 



effect on soil acidity, 115. 



handling, 240. 



materials supplied by, 236. 



nature of, 235. 



protective action of, 235. 



when to use, 235. 

 Guano, 165. 

 Gypsum, plant-food material in, 7. 



use on land, 192. 



Heat and cold, effect on rock disin- 

 tegration, 12. 



Heat of soil, sources of, 149. 



"Heavy" soil, and absolute specific 

 gravity, 35. 



"Heavy" soil, and apparent specific 



gravity, 38. 

 Hematite, plant-food material in, 7. 

 Hygroscopic water, 61. 



Ice, effect on rock disintegration, 13. 

 Igneous rocks, 5. 



Inoculation of soil for legumes, 138. 

 Iron, proportion in earth's crust, 4. 

 Irrigation for removal of alkali, 120. 



Lacustrine soils, described, 25. 



formation of, 25. 

 Law of diminishing returns, 215. 

 Legumes, fertilizers for, 208. 

 Leguminous plants as nitrogen fixers, 



137. 

 "Light" soil, and absolute specific 

 gravity, 35. 



and apparent specific gravity, 38. 

 Lime, absorption by soils, 188. 



as a soil amendment, 187. 



caustic vs. ground limestone, 191. 



demonstration of flocculation by, 

 194.. 



effect on bacterial action, 189. 



effect on plant diseases, 190. 



effect on tilth, 189. 



fineness of grinding limestone, 191. 



forms of, 189. 



in relation to structure, 42. 



liberation of plant-food materials, 

 190. 



magnesium, 190. 



proportion in earth's crust, 4. 



requirements of soils, 188. 



tests for, 193. 

 Limestone, effect of fineness of grind- 

 ing, 191. 



ground vs. caustic lime, 191. 



losses during soil formation, 15. 

 Limiting factors in plant growth, 215. 

 Loess, composition, 27. 



distribution, 26. 



Magnesia, proportion in earth's crust, 



4. 

 Manure, cow, partial composition of, 



222. 

 effect of food on composition of, 



224. 



