INDEX OF SUBJECT MATTER 



575 



Green manures, importance of, 537. 



influence of decay of, 543. 



influence of decay on lime and phos- 

 phorus, 545. 



influence of decay on nitrate accu- 

 mulation, 544. 



influence on crops, 552. 



influence on nitrate reduction, 426. 



manner of turning under, 549. 



practical utilization of, 552. 



relation of to the rotation, 552. 



relation to humus formation, 543. 



relative value of different crops for, 

 547. 



time for plowing under, 548. 



to maintain organic matter, 123. 



use of, 548. 



use of lime with, 550. 

 Ground limestone, 365. 

 Guano, nature of, 445. 

 Guarantees on fertilizers, statement of, 



481. 

 Gullying and its control, 206. 

 Gypsum as a soil amendment, 379. 



effect of on soils, 379. 



reinforcement of manure with, 527 



use of in alkali control, 342. 



Haber -method of fixing nitrogen, 453. 

 Handling of manure, covered yards, 523. 



hauling directly to field, 521. 



influence on composition, 507. 



manure pits, 523. 



piles outside, 522. 



care of in stalls, 520. 

 Hematite, as a soil color, 37. 



change of to limonite, 27. 



formation of in soil, 25. 



source of in soil, 7. 

 Heat, conduction of, 240. 



conduction of in soil, 234. 



conductivity of various soils for, 235. 



convection transfer of, 238. 



cycle between soil and atmosphere, 

 225. 



factors affecting conduction of, 235, 



evaporation loss by, 241. 

 importance in soil formation, 

 loss of from soil, 240. 

 movement in soil, 234. 

 radiation of, 240. 



21. 



Heat of wetting of soils, amount of, 153. 

 data of, 154. 

 effect of texture on, 154. 

 significance of, 153. 

 High grade fertilizers, importance of, 



4£3. 

 Higher plants, influence on nitrification, 



422. 

 Home-mixing of fertilizers, calculation 

 of, 487. 

 advantages, 485. 

 good mixtures for, 487. 

 how performed, 486. 

 Hoof meal, composition of, 446. 

 Humid soil, biological activity in, 32. 

 chemical analysis of, 31. 

 humus content of, 120. 

 Humidity, influence of on the hygro- 

 scopic coefficient, 158. 

 Humus, amount in California soils, 120. 

 amount in Nebraska loess, 120. 

 defined, 115. 



determination of, 115, 312. 

 formation of from green manures, 

 543. 

 Hydration, influence of in soil formation, 



26. 

 Hydrogen-ion concentration, a measure 

 of soil acidity, 356. 

 method of expression, 350. 

 relation to soil acidity, 346. 

 Hydrolysis, explanation of, 348. 



production of by enzymes, 390. 

 Hygroscopic capacity of soils, data on, 



156. 

 Hygroscopic coefficient, data as to spe- 

 cific soils, 157. 

 defined, 152. 

 determination of, 154. 

 factors affecting, 157. 

 range of in soils, 158. 

 Hygroscopic water of soils, specific char- 

 acter of, 153. 



Ice, disintegration of rocks by, 23. 

 glacial, in soil formation, 18. 



Ice action, glaciation, 53. 



Ice age, 53. 



Ignition method for determining soil or- 

 ganic matter, 112. 



Influence of alkali, condition affecting, 

 338. 



