286 SOILS. 



term " crawfishy," so commonly applied to white soils in the 

 eastern United States, expresses well the usual condition of 

 the white soils of that region ; which are very commonly in- 

 habited by crayfish, whose holes reach water a few feet below 

 ground, and are surrounded on the outside by piles of white 

 subsoil mixed with " black gravel " or concretions of bog iron 

 ore. It is needless to say why such lands cannot command the 

 favorable consideration of the farmer; they cannot as a rule 

 be cultivated without previous drainage, and even after that 

 will usually prove unthrifty, " raw," and in immediate need of 

 fertilization by greenmanuring, and the use of phosphates. 



In the arid region, lands of this character are of rare occur- 

 rence, while (as has been explained above, chap. 8, p. 135), 

 the light gray or " white " tints are there a very common char- 

 acteristic of even the very best soils. It is true that they are 

 poor in humus and in finely diffused ferric hydrate; but their 

 ' light " texture renders the presence of humus for this pur- 

 pose less needful, and as stated elsewhere (see chap. 8, p. 

 135), the high nitrogen-content of arid humus renders a 

 smaller supply adequate for vegetative purposes. As to iron, 

 its presence being more important as a sign of good drainage 

 and aeration than directly, its absence from soils of great 

 depth and loose texture is of no consequence ; especially when 

 the heat-absorption which it favors is not only not needed, but 

 is usually already in undesirable excess during the hot sum- 

 mers. 



White Alkali Spots. In the valleys of the arid region, how- 

 ever. I'cry white spots commonly indicate the prevalence of 

 alkali salts, and to that extent are an unfavorable indication; 

 especially when coupled with the occurrence of black rings or 

 spots, which indicate the presence of black alkali or carbonate 

 of soda (see chap. 22). 



