40 



FIELD OPERATIONS OF THE BUREAU OF SOILS, 1910. 



condition sometimes prevails for short periods, owino; to the diffi- 

 culty with which water percolates through the soil. 



The Kirkwood silty clay adobe is quite different in texture and 

 structure from the numerous types derived from the Red Bluff for- 

 mation. It is probable, however, that it is derived from the same or 

 kindred materials, its elevation and location bearing out such a con- 

 clusion. It is treeless, but supports a heavy growth of wild oats and 

 other grasses. 



The tj'pe is partly devoted to grain farming, good yields being 

 secured. Fruit culture is hardly possible without irrigation. All of 

 this inextensive type is capable of development where irrigation 

 water is provided. Underground water is not available, and it must 

 be irrigated by the same methods as the surrounding types. It is 

 believed that pears, alfalfa, and a variety of fruit crops will be well 

 adapted to this type. Its poor tilth will be much improved under 

 cultivation. 



The following table gives the average results of mechanical analy- 

 ses of the soil of this type : 



Mechanicul analyses of Kirkwood silti/ clan adohr. 



The followin;; sample contained more than one-half of i per cent calcium carbonate 

 {CaCOs) : No. 2411:], .5.13 per cent. 



TU.SCAN STONY SANDY I.OAM. 



The surface soil of the Tuscan stony sandy loam consists of from 

 3 to 12 inches of reddish or reddish-brown sandy loam, slightly 

 sticky and rather compact. Everywhere over the surface are quanti- 

 ties of rounded bowlders, occurring as an irregular, scattered cover- 

 ing or as numerous meandering strips, occupying the bottoms of 

 .shallow depressions. These loose stones, all of volcanic origin, range 

 ill size from 8 to 14 inches in diameter. In their disintegration they 

 fill the soil material with quantities of small-sized subangular frag- 

 ments. This shallow mantle of stony loam, usually of a sandy na- 

 ture. iej)re.sents the total depth available for agriculture. It is 

 immediately underlain by masses of cemented waterworn gravel, 

 sometimes roughly assorted and interstratified with beds of fine-tex- 

 lured gray material, some of them Ijeing tufaceous, but most of them 

 being gray sand derived from volcanic rocks of various kinds. Nu- 

 merous exposures bear out the great depth and uniformity of this 

 material. The soil is often eroded over considerable areas, exposing 

 these indurated beds with but a thin irregular covering. 



