764 



INDEX 



Tile drains, interval, 647. 



laying, 649. 



outlets, 656. 



silt basins, 656. 



size, 650, 654. 



surface intakes, 656. 



trenches, construction, 648. 

 Tile drainage in alkali land, 659. 

 Tile drainage in muck and peat soil, 658. 

 Till, glacial soil, 53. 

 Tillage, objects, 663. 



relation to colloids, 166. 



relation on granulation, 194. 



relation to means of soil infection, 

 425. 



relation to run-off, 269. 



relation to soil ventilation, 487. 



implenaents, 664. 



practices, 663. 

 Tillering and moisture, 253. 

 Tilth, effect of lime, 534. 

 Tilth of soil, 184. 



Toxic material and drainage, 262, 632. 

 Toxic material in soil, 136. 

 Toxic substances, effect of lime, 536. 

 Toxicity and loss of bases, 378. 

 Trade values of fertilizer, 559. 

 Transpiration ratio, 244. 

 Transpiration and fertility, 250. 

 Transported soils, 31, 46. 

 Type of soil, named, 725. 

 Type of soil, the unit, 720. 



Unavailable soil water, 256. 

 Underdrains, advantages, 635. 

 XJnderdrains, tile, 639. 

 Units in water measurement, 706. 

 Urea, derived from cyanamide, 504. 

 Urea, product of decay, 130. 

 Urine in manures, 584, 586. 



Value of fertilizer, trade, 559, 562. 



Value of manure, commercial, 602. 



Vegetables, feeding power, 415. 



Vegetation as means of soil classifica- 

 tion, 720. 



Vegetative growth, favored by nitrogen, 

 547. 



Ventilation of soil, effect of drainage, 

 487, 630. 



Vertical drainage, 660. 



Volcanic dust, 63. 



Water, amount to apply in irrigation, 710. 

 available to plants, 261. 

 application, time, 709. 



Water, as solvent m soil analysis, 340. 



as weathering agent, 14. 



carrying power, 40. 



content, maximum, 262. 



control of, 264. 



capillary form, 210. 



effect of movement on soil air, 483. 



equivalents of soil, 220. 



expansive power in freezing, 17. 



forms in soil, 200. 



functions of, in plant growth, 243. 



gravitational form, 233. 



hygroscopic form, 202. 



interception losses, 287. 



losses from evaporation, 270. 



losses from run-off, 265. 



relation of application to yield, 708. 



requirements of plants, 244. 



saved by mulch, 279. 



sources for irrigation, 693. 



specific heat, relation to, 298, 



storage in soil, 713. 



surfaces in soil, 212. 



unavailable in soil, 256. 

 Water-logged land, 659. 

 Water-slaked lime, 539, 

 Weathering, conditions affecting, 22. 



forces of, 14. 



in arid and humid regions, 23. 



of rocks, 13. 



special cases, 27. 

 Weeder, cultivator, 676. 

 Weeds and crop growth, 280. 

 Weight of soil, 115. 

 Weir, for measurement of water, 707. 

 Wetting and drying, effect on granula- 

 tion, 187. 

 White alkali, 392. 

 Wilt of crops, a soil organism, 425. 

 Wilting coefficient, 257, 258. 

 Wilting point, calculation of, 260. 

 Wilting point, relation to texture, 261. 

 Wilting, when it occurs, 257. 

 Wind, effect of suction on soil air, 486, 

 Wind, erosion by, 15. 

 Wind, soils formed by, 58. 

 Wind-breaks and moisture control, 285. 

 Wood ashes, as fertilizer, 523. 

 Wool waste, as fertilizer, 507. 

 Worms in soil, 422. 



Yard manure, 578. 



Zeolites, 9, 355. 



Zinc sulfide test for acidity, 387. 



Zircon, 9. 



Printed in the United States of America. 



