442 



INDEX 



Water vapor, increase in tempera- 

 ture by absorption of, 294 

 viscosity of, 187 

 Waves, disintegration by, pressure 



of, 18 



Weathering, advanced, 12 

 chemical agencies of, 19 

 of rock, irregular due to joints 



and stratification, 1 1 

 jointed, 31 



of rocks, chapter on, 11 

 physical agencies, 12 

 Weeder, 340 

 Weeds, controlled bv rotation, 378 



killing of, object of tillage, 326 

 Weight of soil, 176 



strata, 120 

 Wheat belt, winter, rotations for, 



382 



effect of rock phosphate on, 401 

 methods of preparing land for, 



347 



Minidoka project, Idaho, 261 

 production, United States, 1900, 



417 



seed bed for, 346 

 yield, different methods of seed- 

 ing, 254 

 of under varied percolation, 



153 



ten-year average, 409 

 without irrigation, Montana, 



249 

 yields for different depths of 



plowing, 245 



Widtsoe, J. A., drv matter per acre 

 from varied amounts of irri- 

 gation water, 264 

 precipitation on earth's surface, 

 189 



Water, producing power of 30 acre- 

 inches of water applied to 

 varied areas, 265, 266 

 rainfall and evaporation from 



free- water surface, 241 

 suspended matter in river 



waters, 262 

 water in one-foot strata to eight 



feet, 248 



Weir, rectangular, for measuring ir- 

 rigation water, 268 

 trapezoidal or Cippoletti, 269 

 Wild bean, trailing, holds sand, 60 

 Wiley, H. W., odor of soils, 177 

 Wilting coefficient, defined, 212 



from other constants, for- 

 mulae, 213 

 of soils for different plants, 



213 



relation of hygroscopic co- 

 efficient to, 197 

 Wind-carved granite, 18 

 disintegration by, 18 

 movement, factor in aeration, 



313 



ripples on sand, 56 

 Winter wheat acreage, 1909, 416 

 Wisconsin glaciations, 50 

 Wollny, difference in temperature 



due to slope, 304 

 water transpired per pound of 



dry matter, 188 

 Woods, swamp, wet, 30 

 Work, better distributed by rotation, 

 377 



Yarmouth interglacial stage, 46 

 Yields increased by rotations, 378 

 Yoder, P. A., centrifugal elutriator, 

 128 



Zeolites, 4 



