INDEX. 



5 8l 



PAGE 



Potashes, production of detrimental to agriculture 69 



Potash feldspar, supplies potash to soils 32 



fertilization first in humid, last in arid region 396 



from sea water 69 



limits of adequacy in soils 354 



minerals, orthoclase feldspar 68 



preferential retention of, in soils 272 



Salts, Stassf urt 69 



slightly leached out 24 



sulfate, high-grade 71 t 



Pot-culture tests 336 



Powders, absorption of various gases by, table 277 



Prairie soils, black 53 



Preparation of soils for physical analysis 89 



Productive capacity and duration, forecast of 346 



Progress of humification and formation of coal, table 126, 127 



Pulverulent soils of arid regions 87 



Purifying action of soils 269 



Putrefactive processes, relation to carbonic gas and anaerobic bacteria. . 282 



Putty soils 103 



Pyroxene, augite , 33, 34 



Q. 



Qualifications required for soil study 524 



Quality of irrigation water 246 



Quince, resistance to alkali. ... 479 



Quartz and allied rocks 29 



sand most prominent ingredient of soils 30 



veins, formation of 31 



R. 



Rain belts, temperate and tropical 295 



Rainfall, amount of 215 



distribution in California and Montana 290 



in the United States 215 



most important 290 



on the globe, figure 294 



influence on soil formation 22 



insufficient, forms alkali soils 28 



leaves lime behind 28 



natural disposition of 216 



Rains, beating 221 



cold and warm 3 2 



Reclaimable and irreclaimable alkali lands 534 



Red foothill soils of California 34 



Red or rust-colored soils 34 



advantages of 284 



