29 



given to any soil which on drying shrinks markedly and breaks into 

 blocks with wide cracks between. (See Fig. 6.) An adobe structure 

 is undesirable because the soils dry out, not only from the surface but 

 also from the sides of the wide cracks. In irrigating, the water must 

 first fill the cracks and then slowly soak into the hard baked block. 



On wetting, the blocks swell up and close the cracks, which reopen 

 again on drying. Considerable injury to plants may occur through 

 the breaking of roots that cross the lines of the cracks and through 

 the drying of many of the feeding roots. 



The soils of California are exceedingly productive. They may be 

 compared to the rich bottom lands of the humid regions. The un- 

 favorable conditions that may exist, such as hardpan, alkali, poor 

 drainage, poor structure, etc., can be readily recognized. The presence 

 of alkali can be determined by chemical means or by noting the 

 character of the vegetation and the condition of the surface soil. 

 Drainage conditions, texture and structure, and the presence of hard- 

 pan can be determined by examining the soil, boring in it ,with a soil 

 auger (Fig. 7). The prospective settler should not be content with the 

 examination of the surface soil, but should bore frequently, examining 

 the soil to a depth of at least six feet and carefully noting conditions, 

 bearing in mind that plants that would in a humid region send their 

 roots two or three feet into the soil, will here have a root penetration 

 of six to twelve or more feet.* 



IKKIGATIONf 



As a general rule, irrigation is either a valuable aid to agriculture 

 or a necessity throughout California, so that the settler should look 

 carefully into everything that pertains to the extent, reliability, per- 

 manency, and cost of an irrigation water supply for his farm. 



* Dr. E. W. Hilgard writes: "While much detail cannot of course be given within its 

 scope, I think the part dealing with the selection of land should be somewhat enlarged, as 

 being of prime importance, and in some respects most likely to give the newcomer from the 

 humid region trouble. 



"First, I think it should be told him somewhat more definitely that the light sandy and 

 silty nature of our soils is not, as would be the case in the East, a sign of poverty, but that 

 these are among our most substantial lands. And as he will naturally be looking for a 

 'substantial subsoil,' he should be told that the surface soil here is not from three to nine 

 inches deep, but that it counts by feet, usually three or more, and the absence of a subsoil 

 does not mean that the land will be 'leachy,' but is a distinct advantage for root penetration. 

 He should also be told that a gray soil in California is not necessarily poor in humus, and 

 that the surface foot very frequently contains less humus than the second and third foot, 

 where the development of the roots, from the decay of which the humus is usually derived. 

 is most copious. 



"The somewhat elaborate discussion of hardpan may lead the newcomer to believe that 

 hardpans are the most prominent features of California soils ; whereas the great depth and 

 uniformity of soil masses is certainly the most characteristic feature of the bulk of California 

 lands." 



t By FRANK ADAMS, Irrigation Manager, Office of Experiment Stations, U. S. Department 

 of Agriculture. 



