INDEX 



441 



critical element, 292 ; apparent 

 increase under dry-farming, 283 ; 

 accumulation in upper layers, 

 287 ; stubble and, 228 ; reasons 

 for dry-farm fertility, 286-292; 

 effect of continuous cropping, 

 282 ; maintaining soil fertility, 

 281-300 ; possible equilibrium of, 

 293 ; coming great question, 300; 

 and amount to sow, 222 ; and 

 transpiration, 183-186; effect on 

 transpiration, 182, 191 ; evapora- 

 tion decreases with, 138 ; prob- 

 lem in California, 383 ; problem 

 in Great Basin, 387. 

 Soil-water, see also Water, Capillary 

 Water; for loss of, see also Trans- 

 piration; in virgin soils, 112; 

 why desert soils contain moisture, 

 148 ; how rain-water is changed 

 into, 108-110; total water capac- 

 ity, 104 ; hygroscopic moisture, 

 102, 137; capillary, 106; field 

 capacity for capillary, 107 ; grav- 

 itational, 104 ; downward move- 

 ment, 111—115; dependent on 

 pore-space, 102 ; sinks deeper 

 with cultivation, 116 ; possible 

 amount stored in soils, 119 

 storage by fallowing, 122-125 

 thickness of film in per cents, 108 

 effect of thinning the film, 147 

 at harvesting, 117; danger of 

 dry soil, 117; importance of 

 moist subsoil, 116; demonstra- 

 tion that it may mature crops, 

 95; necessary to mature crops, 

 118; stored in Great Plains soils, 

 122; amount stored in Utah 

 experiments, 121 ; methods of 

 loss, 165; manner of upward 

 movement, 152 ; how it reaches 

 surface, 141 ; causes of evapora- 

 tion of, 160 ; conditions of evap- 

 oration from, 136 ; evaporation 

 proportioned to, 138; dissipated 

 by winds, 135 ; evaporation of 



capillary, 137 ; cfTect of rapid 

 top drying of soils, 147-152 ; 

 makes independent of rain distri- 

 bution, 130 ; in spring and mid- 

 summer, 143; effect on absorp- 

 tion, 168; movement through 

 plants, 170 ; effect on transpira- 

 tion, 180 ; and amount to sow, 

 222 ; germination and, insuffi- 

 cient, 218 ; effect on germination, 

 209. 

 Soils, dry-farm, 50-80 ; importance 

 in dry-farming, 50 ; formation of, 

 physical agencies, 52 ; chemical 

 agencies, 54 ; physical constit- 

 uents of, 56 ; sizes of particles, 

 99 ; composition of humid and 

 arid, 67, 68 ; characteristics of 

 arid soils, 56, 71 ; definition and 

 characteristics of topsoil, 59 ; 

 characteristic structure of arid, 

 61 ; structure of, 99-101 ; humus 

 in arid, 58 ; depth of, in arid 

 countries, 61 ; depth of dry- 

 farming, 62, 78 ; favorable for 

 dry-farming, 77 ; pore-space of, ■* 

 101; alkali, 66; blowing of soils 

 in Great Plains, 198 ; breaking 

 soil crust in spring, 227 ; arid 

 soil deficient in clay, 58 ; native 

 vegetation of arid, 79 ; effect of 

 kind, on transpiration, 187, 188 ; 

 for dry-farm, 413 ; deep soil 

 needed, 140 ; weak and strong, 

 58 ; physical classification of, 

 57; judging of, 78; divisions of 

 the United States, 74 ; depth in 

 soil-water studies, 1 19 ; field 

 capacity for water, 107-110; 

 danger of cracks, 141 ; danger of 

 low soil-water, 117; dry surface 

 soil to prevent evaporation, 150 ; 

 effect of rapid top drying, 147- 

 152; natural mulch on different, 

 149; calcareous soils form good 

 mulch, 157 ; civilization and arid, 

 73. 



