526 



INDEX 



PAGE 



Rainfall, United States, map of . . 137 



Effect on structure 119 



Relation to irrigation practice . . 222 

 When small, may cause loss of 



water 198 



Rains, gentle, best 216 



Raw phosphates and organic mat- 

 ter.. 361 



Reclamation of alkali soil by drain- 

 age 247 



Reduction of nitrates to nitrites. .420 



Nitrates to ammonia 420 



Nitrites to free nitrogen 420 



Relation of lime to magnesium .... 350 



Residual soils 31 



Characteristics of section 40 



Proportionate loss of elements 



in formation, table 34 



Texture of 41 



Reverted phosphoric acid 338 



Ridge culture.effect on evaporation 216 



Ries, on plasticity 97 



Rise of alkali 314 



Roberts, plow sole 474 



Rodents effect on the soil 388 



Rocks, as source of soil 2 



Aggregates of minerals 10 



And its products 2 



Aqueous 11, 12 



Classification of 10 



Decay, agencies of 14 



Decay, atmospheric 16 



Decay, by solution 22 



Decay, ice as agency 27 



Decay, type of and composition 



of soil 36 



Decay, type of and texture of 



soil 36 



Expansion due to heat 20 



Igneous 11, 12 



Important soil-forming 9 



Porosity of 21 



Roller, conditions where effective .487 



And packers, types of 486 



Effect on soil temperature 459 



Relation to percolation 194 



When used to mulch soil 487 



Roots, absorbing system 292 



Absorption of mineral matter. . . 277 

 As related to crop rotations. . . .505 

 Crops, absorption of nutrients. .296 

 Conditions where enter drains 

 253,261 



PAGE 



Roots, effect on composition of soil 



air 437 



Excretion of acids 290 



Hairs, relation to soil particles. .287 

 j Of plants, strike deep in drained 



soil 245 



Osmotic activity 292 



Osmotic equilibrium in 287 



Plants, effect on the soil 391, 113 



Rotation of crops 503 



Rotation of crops, principles of. . .504 



Effect on soil structure 506 



Nutrients removed by 504 



Part in soil management 465 



Place of manure in 383 



Relation to diseases and in- 

 sects 508 



Relation to loss of plant food . . . 509 

 Relation to toxic substances. . .509 



Relation to weed growth 508- 



Root systems of different crops . 505 

 Some crops prepare food for 



others 505 



Rothamsted, figures on evapora- 

 tion 196 



Tables of percolations 192 



Rubbish, covering by plow 476 



Salisbury, and Chamberlin, char- 

 acter of minerals 8 



Sachs, experiments on solvent ac- 

 tion of roots 288 



Salt, effect on soil 354 



Sand-dunes, damage by 497 



Naturally mulched 206 



Sandstone soils 39 



Sandy soil 74 



Sandy soil, organic matter in 12 



Sanitary conditions, effect of drain- 

 age on 247 



Saturation, total water for 161 



And gravitational water 



Wave of in soil, useful 194 



Sawdust as litter in manure 368 



Schubler, figures on effect of color 



on temperature 457 



On soil shrinkage 98 



Season, length of increased by 



drainage 243 



Secondary minerals 5 



Sedimentary rocks 11,12 



Sedentary soils 30 



Sedentary soils, divisions of 31 



