INDEX 



429 



ililgard, E. W., fertility in Russian 



soils, 392 



force exerted by roots in pene- 

 trating soil, 1!) 

 grades of soil particles, system 



of, 124 

 highest amount of alkali with 



plants unaffected, 284 

 hygroscopic capacity of soils, 



194 



nitrogen content of humus, 1!)4 

 on use of hygroscopic moisture, 



198 

 roots and humus in Russian 



soils, 144 

 vertical distribution of alkali, 



281 

 Hopkins, C. (1., grades of particles, 



system of, 124 

 production of sweet clover per 



'acre, 173 



Humid and arid subsoils, 70 

 regions, alkali of, 290 

 soils, 75 



nitrogen in humus of, 147' 

 Humidity, affecting hygroscopic 



moisture, 190 



Humilication, progress of, 140 

 Hummocks, called lx>gs, 30 

 Humus, defined, 142 



determination of, 15(5 

 in Chernozem soils, 144 

 nitrogen content of, 147 

 llydration, 21 

 Hydrochloric acid, decomposition 



\v, 20 



Hygroscopic capacity of soils. 1!)4 

 coeflicient from other constants, 



formula-, 1!)7 

 of soils, 10(i 

 relation to wilting coefficient, 



107 

 moisture, affected by colloids, 



195 



by humidity, 190 

 by organic matter, 190 

 by si/e of particles, 194 

 by temperature, 195 

 chapter on, 194 

 use of, 107 



Ice-laid deposits, chapter on. 41 

 Igneous rocks, ti 

 Ignition, loss on, 154 

 Implements of tillage, compactors, 

 335 



Implements of tillage, cultivators, 



337 



harrows, 332 

 listers, 332 

 plows, 327 

 seeders, 337 

 Insects, controlled by rotation, 377 



mix soil, 315 



Interglacial stages, Aftonian, 40 

 1'eorian, 48 

 Sangamon, 47 

 Yarmouth, 40 



Internal area or surface, 181 

 Intrusive rocks, 

 lowan glaciation, 48 



important loess deposit con- 

 nected with, 02 



Irrigated land, crops for, alfalfa, 275 

 cereals, 273 

 forage crops, 275 

 fruits, 275 

 sugar beets, 275 

 vegetables, 275 

 Irrigation, chapter on, 257 



bv overhead sprav or sprink- 



" ling. 272 



canals lined with concrete, 25,'; 

 cultivation after, 27-'! 

 efl'ect of, on rise of alkali, 2>Sl 

 in humid climates. 275 

 methods of, Hooding, 270 

 furrow, 271 

 sprinkling or overhead spravs, 



272 



sub-irrigation, 272 

 potatoes by furrows. 271 

 preparation of land for. 250 

 projects in I'nited States. 257 

 in varied quantities, yield of 



dry matter, 204 

 sources of, diversion of 



streams, 258 

 pumping from streams or 



canals. 250 

 reservoirs. 259 

 subterranean supply. 250 

 water, character of, '201 

 time of. _'<;:! 



Illinois soil survey. 112 

 Illinoisan glacial ion. 47 



lardinc. \V. M., yiejd of milo mai/e. 



Texas. 25.'5 

 Jersevan or Nehraskan glaciation, 



40 ' 

 Johnson. S. W., carbon dioxide in 



soil air, 20 



