756 



INDEX 



Growing season, effect of drainage, 631. 



Growth, effects of nitrogen, 547. 



Guano, as fertilizer, 507. 



Guarantee, fertilizer, 558. 



Gypsum, 9, 542. 



Gypsum, correction for alkali, 400. 



Gypsum, lime fertilizer, 539. 



Gypsum, solvent action of roots on, 



406. 

 Gypsum to reinforce manure, 609. 



Handling manure, 602. 



Hardpan, alkali, effect on drainage, 659. 



Harrow as cultivator, 676. 



Heat, absorption of, 300. 



and cold, mechanical action, 16. 



chemical and physical changes due 

 to, 291. 



condensation, 209. 



convection in soil, 307. 



functions of, in soil, 289. 



effect on soil, 466. 



unit denned, 314. 



sources in soil, 292. 



specific heat of soil, 294. 

 Head of water, denned, 706 

 Head of water for irrigation, 702. 

 Heaving of soil indicates wetness, 628, 



632. 

 Heiden's formula for manure production, 



588. 

 Helminthosporium, disease organism, 



426. 



Hematite, 9. 



Hematite, hydration of, 21. 

 Herring-bone system of drainage, 645. 

 High-grade fertilizer, 562. 

 Hillside plow, 670. 

 Histidine, plant-food, 497. 

 Home-mixing fertilizer, 563. 

 Home-mixing fertilizer, method, 567. 

 Hoof meal as fertilizer, 507. 

 Hornblende, 9. 



Hornblende in soil separates, 101. 

 Horse manure, composition, 584. 

 Humid and arid soils, 71. 

 Humid climates, irrigation in, 689. 



soils, composition of, 72. 



soils, organic matter of, 146, 147. 

 Humidity, effect on hygroscopicity, 207. 

 Humus, absorption by, 365. 

 Humus ash composition, 145. 



and conductivity, 310. 



and capillarity, 219. 



and efficiency of fertilizer, 569. 



and roots of plants, 127. 



Humus and run-off, 269. 



and specific heat, 297. 



as plant-food, 495. 



composition of, 131. 



content of soils, 147. 



effect of drainage on formation, 632. 



effect on hygroscopicity, 204. 



effect on granulation, 190. 



effect on cohesion, 170. 



effects on soil, 150. 



estimation of, 142, 144. 



in glacial soil, 54. 



nature of, in soil, 130. 



specific gravity of, 113. 

 Humus, defined, 130. 

 Hydration as weathering agent, 20. 

 Hydrochloric acid used in soil survey, 



728. 



Hydrochloric acid solution of soil, 329. 

 Hydrochloric acid test for carbonates, 



388. 



Hydrogen, 4, 6. 



Hydrogen, from plant decay, 140. 

 Hygroscopic coefficient, 257. 

 Hygroscopic moisture, 201, 202. 

 Hygroscopic moisture and plasticity, 

 171. 



relation to colloids, 168. 



relation to plants, 256. 

 Hygroscopicity, determination of, 208. 



Ice, as erosive agent, 16. 



Ice-formed soils, 52. 



Ice sheet, 47. 



Igneous soil-forming rocks, 6. 



Implements, tillage, 664. 



Infection by soil fungi, 425. 



Inoculation of soil for legumes, 460. 



Inorganic colloids, 158, 162. 



Insects in soil, 423. 



Inspection of fertilizers, 556. 



Interception losses in fftrests, 287. 



Iodine in ash of sea weed, 404. 



Iron, 4, 6. 



Iron a catalytic fertilizer, 529. 



Iron as a soil color, 75. 



Iron phosphate available, 337. 



Iron in soil separates, 102. 



Irrigation, amount of water applied, 708 . 



amount of water to apply, 710. 



and alkali, 397. 



application of water and yield, 208. 



canals, 693. 



canals, linings, 694. 



conditions that warrant, 683. 



development in the United States, 686. 



