THE SOILS OF CALIFORNIA 39 



re-cements very slowly. In some cases the hardpan 

 is underlaid by a compact, semi-cemented layer of 

 soil, sand, and gravel that is practically impenetrable 

 to water or to plant roots. With such soils, dyna- 

 miting the hardpan is of little or no value as there 

 is no good soil beneath for the roots to penetrate and 

 no opportunity for drainage or aeration through the 

 substratum. 



"There is another class of hardpan that occurs 

 where variations in the soil-forming activities caused 

 a layer of soil to be deposited, then a layer of ma- 

 terial that cemented to a hardpan, then another 

 layer of soil, another layer of hardpan, and so on. 

 These hardpan layers are hard to handle, as blasting 

 is not satisfactory unless each of the layers is broken. 

 The hardpan layers do not, however, exist as con- 

 tinuous sheets because in the process of formation 

 of the soil, portions were washed away, the space 

 being filled with other soil materials. This, together 

 with the fact that the hardpan is often cracked and 

 sometimes rather soft, gives opportunity for irriga- 

 tion water and plant roots to penetrate to consid- 

 erable depths. 



"Most of the old transported soils have medium 

 textures, with about one-third of a heavy texture and 

 with very few areas of coarse sandy nature. The 

 soils are productive but root and water penetration 

 is retarded by the heavy subsoils or by the hardpans, 

 and their uneven topography makes irrigation diffi- 

 cult and expensive. They give good results with 

 most of the crops of the state, and when their natural 



