INDEX 



763 



Soil-forming minerals, 8. 

 Soil-forming rocks, 6. 

 Soil mulch versus dust mulch, 275. 

 Sour soils, 375. 

 Sources of plant food, 419. 

 Specific gravity, absolute, 112. 

 apparent, 113. 

 of minerals, 112. 

 of soil separates, 113. 

 Specific heat of soil, 294. 

 Spray system of irrigation, 695. 

 Spring, early plowing, 283. 

 Stall manure versus yard manure, 601. 

 Starch, effect of potassium, 551. 

 Stassfurt salts, 522. 

 Storage of water in soil, 279. 

 Straw, effect of nitrogen, 548. 

 effect of phosphorus, 550. 

 relation to denitrification, 456. 

 Stone drains, 638. 

 Stone mulch, 273. 



Structure and capillary movement, 232. 

 and capillary water, 217. 

 and conductivity, 310. 

 defined, 108, 170. 

 effect on diffusion of gases, 483. 

 effect on gravitational movement, 235. 

 modified by tillage, 663. 

 relation to air in soil, 476. 

 temperature relations, 304. 

 Subirrigation, 696. 

 Subsoil and soil defined, 79. 

 Subsoil, composition of, 332. 

 Subsoil plow, 672. 



Subsoiling, relation to dry-farming, 713. 

 Substitution of bases, 355. 

 Substitution of elements by plant, 417. 

 Subsurface packer, 679. 

 Subsurface packing, 714. 

 Sulfates as fertilizer, 526. 

 Sulfate of ammonia as fertilizer, 499. 

 Sulfate of potash, 523. 

 Sulfur, 4, 6. 



Sulfur and acidity, 382. 

 Sulfur as fertilizer, 524. 

 Sulfur bacteria in soil, 439. 

 Sulfur dioxide, from plant decay, 140. 

 Sulfur, free, as fertilizer, 524. 

 Sulfuric acid solution of soil, 329. 

 Superphosphate fertilizer, 514. 

 Surface of roots, 412. 

 Surface of soil particles, 120. 

 Surface tension, 211. 



and capillary movement, 227. 

 and capillary water, 213. 

 Surface water, composition of, 373. 



Swine manure, composition, 584. 

 Symbiosis, nitrogen fixation through, 



457. 

 Syenite, 6, 8. 

 Systems of fertilization, 573. 



Talc, 9. 



Tankage as fertilizer, 507. 

 Temperature changes, affect soil air, 484. 

 Temperature in fermenting manure, 593. 

 Temperature of soil and air, 485. 



annual, 321. 

 • annual range, 322. 



control, 325. 



daily range, 324. 



effect of drainage, 631. 



effect of slope, 317. 



effect of snow, 306. 



evaporation influence, 314. 



factors affecting, 293. 



influence on absorption, 367. 



influence on bacterial activity, 435.' 



influence on efficiency of fertilizer, 

 568. 



influence decay, 129. 



influence on hygroscopicity, 207. 



influence on movement of water, 234. 



influence on organic decay, 315. 

 Tenacity of soil, 174. 

 Terrace, defined, 41. 

 Texture, adaptation of crops to, 105. 



defined, 83. 



effect on capillary movement, 214, 

 229. 



effect on cohesion, 179. 



effect on conductivity, 308. 



effect on hygroscopicity, 204. 



relation to air in soil, 475. 



relation to gravitational movement, 

 235. 



relation to soil classification, 722. 



relation to solubility of soil, 331. 



relation to wilting point, 260. 



rock, and weathering, 23. 



influence on absorption, 355. 



influence on diffusion of gases, 483. 



temperature relations, 304. . 

 Thermal movement of water, 241. 

 Tile, quality, 640. 

 Tile drains, 639. 



carrying capacity, 651. 



cost, 654. 



dangers from roots, 642. 



depth, 646. 



formula for size of tile, 652. 



grade, 645. 



