Index. 



601 



Soil, temperature low when wet, 29 ; i 

 cooled by evaporation. 32 : pntn-o r* 

 40 ; compared with subsoils, 49, 72, 74, 

 75 ; clayey types, 49, 71, 74, 75 ; uses 

 of, 50 ; micro-organisms in, 50 ; forma- 

 tion of, 51 ; rock texture in formation, 

 51 ; conversion of limestone into, 52 ; 

 Influence of rock fissures on soil forma- 

 tion, 53 ; removal of, 53 ; produced by 

 running water, 54, originating through 

 glaciers, 57, 58, 59, 60, formation of 

 humus type, 61, 62, 63 ; formed by 

 wind action, 63 ; loess, 64 ; produced 

 by animals, 64 ; convection, 65, ac- 

 tion of earth worms, 66, 67 : chemical 

 nature of, 69, 71 ; chemical composi- 

 tion, 69, 71, 74, 75, 78, 81; constitu- 

 ents of essential to fertility, 69 ; com- 

 parison of kinds, 72, 74, 75; of arid 

 and humid regions, 73, 76 ; chemical 

 nature compared with parent rock, 77 ; 

 plant food removed from by crops, 79, 



Riant food in acre foot, 79 ; nitrogen 

 i, 82 ; forrrs in which nitrogen oc- 

 curs in, 83 ; distribution of nitrogen in, 

 83 ; amount of nitric acid in, 84 : 

 sources of nitrogen in, 85 ; soluble 

 salts in field, 92 ; physical nature of, 

 108 ; texture of, 108 ; number of 

 grains per cubic inch, 109 ; pore 

 space of, 111; surface of per gram, 

 118, per pound, 118, per cubic foot, 

 124 ; movement of air through. 125 : 

 heavy and light, 128 ; weight per 

 cubic foot, 127 ; capacity of for water, 

 131, 134 ; kinds yielding moisture to 

 crops most completely, 136 ; advance 

 of roots through, 148 ; rate of percola- 

 tion from, 159, 160 ; capillary rise of 

 water in, 163 ; mulches, 185 : 

 changes in temperature of, 207 ; im- 

 portance of right temperature of, 212 ; 

 observed temperatures, 213 ; specific 

 heat of. 21 ">. 21 H: temperature In 

 fluenced by color, 217, by texture, 218. 

 by topography, 218, by tillage, 219, 

 by chemical changes, 219; by rain, 

 219, by evaporation, 32. 212 ; best 

 condition of for plowing, 251. 



Soil grains, number per cubic inch, 

 109, per gram, 118, per pound, 117; 

 specific gravity of, 110 ; effective diam- 

 eter, 121, 124; method of determining 

 effective diameter, 121 : computed sur- 

 face of, 124 ; relation of water capacity 

 to, 124 ; relation of root hairs to. 147 ; 

 relation of diameter of to flow, 266. 



Soil kernp's, size. 110: relation to tpx- 

 ture, 231 ; destruction of In puddled 

 soil. 2:w : lustration of. 2'U. 



Soil moisture. 129 ; movements of Influ- 

 enced by soluble salts. ]o<; : ] ( ,<* of. 

 lessened by soluble salts. 107 ; relation 

 of per cent, of to thickness of water 

 lilm. 137 : amount of, affected by 

 jointed, structure, 138 ; amount in- 

 creased by open texture. 138 ; amount 



available Increased by drainage, 139, 

 by subsolhng, 200 ; types of move- 

 ment, 158: percolation of, 1f>8; grav- 

 itational movements of, 158 ; capil- 

 lary movements of, 161 ; observed 

 night of capillary rise of, 165, influ- 

 enced by rain, 170, 190, by farm 

 yard manure, 172, by mulches, 173, 

 by firming the soil, 174 ; thermal 

 movements of, 175 ; hygroscopic, 175 ; 

 conserved by early fall plowing, 182, 

 early spring plowing, 183 ; by sub- 

 soiling, 195, by early seeding, 200, 

 by wind breaks, 202 ; possible waste 

 through untimely cultivation, 189 ; 

 movement of, affected by subsoiling, 

 197 ; danger of loss of through green 

 manuring, 201 ; loss through action 

 of weeds, 224 ; Influence of on draft of 

 plows, -44. 



Soil mulches, effectiveness of, 185 ; 

 method of demonstrating influence of, 

 187. 



Soil surface, Influence of, on chemi- 

 cal analyses, 72: amount por gram, 

 118, per pound, 118, per cubic foot, 

 124; difficulty of determination, 11. 

 Soil temperature, 212 ; importance of to 

 life forms, 212; at which growth be- 

 gins, 212; best for germination, 212; 

 influence of on rate of germination, 

 214; effect of on root pressure, 215; 

 influence of color on, 217, of to- 

 pography on, 218, of uneven n oss of 

 surface on. 218, of looseness of sur- 

 face on, 219, of tillage on, 219, of 

 physical and chemical changes on, 219, 

 - ot raiiis on, 219, of evaporation, 

 220, of rolling on, 221, of prepara- 

 tion of seed bed on, 222, of under 

 draining on, 222, 287 ; means for con- 

 trolling, 221. 

 ^oil-tube, 116. 



Soil water, viscosity of modified by salts, 

 106 ; proportion of available to 

 crops, 161 ; internal evaporation of, 

 179; conservation of, 181; modes of 

 controlling, 181, late fall plowing to 

 conserve, 181. 

 Solar energy, 20 ; rate of transmission, 



22. amount of, 22. 



Soluble salts, amount In field soils, 02 ; 

 amount of limiting plant growth, 93, 

 in Yellowstone Park, 93; in Algeria, 

 93 ; why injurious to plants, 93 : con- 

 centration of in zones, 94; origin of, 

 94 ; removal of by leaching, i>. : in 

 marsh soils, 95 ; change in amount of 

 with season, 98 : variation of with elf- 

 ferent crops. 99 ; influence of on move- 

 ments of soil moisture. 106 : modifica- 

 tion of surface tension by. 100 -. lessen 

 the loss of soil moisture. 107 ; Influence 

 in cementing soil granules. 233 ; drain- 

 age of to remove excess, 286. 

 solution. 38: Influence of temperature 

 on, 39 : saturated. 39. 



