32 



FIELD OPERATIOXS OF THE BUREAU OF SOILS, 1910. 



This is a better soil as letrards its present utilization than the other 

 types of the same -ories. It will be found to surpass them in its 

 capacity for irrigation development and in its adaptation to general 

 farm crops as well as grapes, the stone fruits, and alfalfa. In com- 

 mon with the other plains soils of the west side, extensive irrigation 

 can only be had by a comprehensive gravity system, supplied by 

 storage of the flood waters of the west-side tributaries or by diversion 

 from the main river at some point at a distance from the area. 

 Tuderground water for pumping is not available in sufficient quan- 

 tities or at a cost commensurate with the supply, anii the elevation of 

 the areas does not ai)pear to allow extensive watering by pumping 

 from the Sacramento Kivcr, 



The following table gives the average results of mechanical analyses 

 of the soil and subsoil of this type: 



Mechanical anali/.'ics of Tehama silt loam. 



TEHAMA CLAY. 



The Tehama clay constitutes the heaviest and most refractory mem- 

 ber of the Tehama series. Typically it consists of a compact clay 

 ranging from a light grayish brown to yellowish brown in color and 

 extending to a depth of HO to 48 inches. When wet this soil is very 

 .-sticky. I'xhiljiting the tendency of the adobes to adhere to vehicles 

 or implements. Upon drying it soon acquires a hard, impenetrable 

 .structure, cracks and checks. It is of poor tilth througliout. In 

 nearly all cases below this mantle of soil will be found a hard, im- 

 jjenetrable layer of varying character, but in all cases defined as a 

 i-(Miinant of the undei'lyiiig material of the Redding or Corning series. 

 In >ome cases the dei)osition of the Tehama clay has occurred directly 

 iij)()ii the true hardpan of these series, but usually the older series 

 iiave Ix'cn siiflicieiitly ei'oded to bring the less solidly cemented sands 

 and gravels of their underlying strata next to the clay. 



This type occurs in .several elongated and slightly depressed bodies, 

 usually wheie the Tehama silt loam joins the Redding or Corning 

 series. It ^-ometimes occupies small areas between remnants of Red- 

 ding loam bodies, is always poorly drained during the rainy season, 

 ii-regiilarly defined, and of small importance. The surface is tree- 

 les.■^ and gently slojiing to flat. ex(ej)t for an occasional meandering 

 depression, usually subject to the accumulation of drainage water 



