164 SOILS. 



in which the depth of the surface soil-sample to be taken is 

 prescribed as nine inches by the rules of the Association of Am. 

 Official Chemists (in the writer's experience it is more nearly 

 six inches as a rule). Alongside of the Eastern soil thus 

 characterized is placed a typical " adobe " soil from the grounds 

 of the California Experiment station, of which a sample show- 

 ing uniform blackness to three feet depth was exhibited at the 

 World's Fair at Chicago in 1893. At the right is a profile of 

 the noted hop soil on the bench lands of the Russian river, Cal., 

 in which the humus-content was determined down to twelve 

 feet, the humus-percentage being .44% at that depth against 

 1.21% in the surface foot (see chapt. 8, p. 139). In this and 

 similar soils the roots of hops reach down to as much as 

 fourteen feet without much lateral expansion ; as shown in plate 

 No. 31 of this chapter. Similar conditions prevail in the sandy 

 uplands, as, e. g., in the wheat lands of Stanislaus county, Cal., 

 mentioned above. 



Taking the clay soils as a fair type for comparison, it would 

 seem that the farmer in the arid region owns from three to four 

 farms, one above another, as compared with the same acreage 

 in the Eastern states. 



Subsoils and Deep-plowing in the Arid Region. Up to the 

 present time this advantage is but little appreciated and acted 

 upon by the farmers of the arid region. They still instinctively 

 cling to the practice taught them by their fathers, and which is 

 still promulgated as the only correct practice, in most books on 

 agriculture. There are of course in the arid as well as in the 

 humid region, cases in which deep plowing is inadvisable ; viz, 

 that of marsh or swamp lands, as well as sometimes in very 

 sandy, porous soils, the cultural value of which often depends 

 essentially upon the presence of a somewhat consolidated, and 

 more retentive subsoil, which should not be broken up. But in 

 most soils not of extreme physical character, it is in the arid 

 region not only permissible, but eminently advisable to plow, 

 for preparation, as deeply as circumstances permit, in order to 

 facilitate the penetration of the roots beyond the reach of harm 

 from the summer's drought ; while for the same reason, subse- 

 quent cultivation should be to a moderate depth only, for the 

 better conservation of moisture, and the formation of a pro- 

 tective surface mulch (see chapter 13). 



