254 



INDEX 



Rocks, losses during soil formation, 15. 



metamorphic, 5. 



sedimentary, 5. 



soil-forming, laboratory exercise, 9. 

 Rolling land, 78. 

 Root crops, fertilizers for, 209. 

 Root systems of different crops, 243. 

 Roots of plants, effect on structure, 



41. 

 Rotation of crops, 242. 



and soil productiveness, 242. 



management of, 246. 



nutrients removed by, 243. 



Sedentary soil, 18. 

 Sedimentary rocks, 5. 

 Separates of soil, 32. 



chemical composition of, 36. 

 examination, 46. 

 properties of, 35. 

 Series, the soil, in soil survey, 44. 

 Soil, as a mechanical support for 

 plants, 1. 

 as a reservoir for water, 2. 

 as a source of plant-food material, 



2. 

 changes during formation from 

 rock, 15. 

 Soil class, in classification for surveys, 

 44. 

 method lor its determination, 47. 

 Soil formation, agencies concerned, 

 11. 

 and transportation, laboratory 

 exercise, 17. 

 Soil formations, 1, 18. 

 Soil-forming minerals, laboratory 



exercise, 8. 

 Soil-forming rocks, laboratory exer- 

 cise, 9. 

 Soil mulch, nature and use, 74. 

 Soil province, in classification for 



surveys, 44. 

 Soil, relation to rock, 15. 

 Soil series, in classification for sur- 

 veys, 44. 

 Soil survey, described, 43. 

 classification of soil for, 43. 

 information furnished by, 44. 

 Soil type, in classification for surveys, 

 44. 



Soils, residual, 18. 



sedentary, 18. 



transported, 18. 

 Specific gravity, apparent, its deter, 

 mination, 48. 



of soil, apparent, 38. 



of soil particles, absolute, 35. 



of soil particles, apparent, 38. 

 Structure, of soil, as affected by freez- 

 ing and thawing, 40. 



as affected by lime, 42. 



as affected by organic matter, 41. 



as affected by plant roots and 

 animals, 41. 



as affected by tillage, 42. 



as affected by wetting and drying, 

 40. 



conditions that affect, 39. 



granular or crumbly, 37. 



defined, 37. 



relation to pore space, 37. 



relation to texture, 39. 



relation to tilth, 39. 



operations that affect, 39. 



separate grain, 37. 

 Subsurface packing, 78. 

 Sulfate of ammonia, action when 

 applied to soils, 160. 



composition, 160. 



sources, 159. 

 Sulfur, as a fertilizer, 182. 



contained in crops, 182. 



contained in drainage water, 183. 



contained in fertilizers, 184. 



contained in soils, 183. 



proportion in earth's crust, 4. 



Temperature, control of, 151. 



demonstration of effect of slope on , 

 154. 



factors that modify, 150. 



of soil and atmosphere, 149. 



of soils, relation to plant growth, 

 148. 

 Texture, of soil, described, 30. 



relation to crops, 32. 



relation to structure, 39. 

 Tile, concrete, 81. 



drains, 81. 



laying, 83. 

 Tillage in relation to structure, 42. 



