42 CALIFORNIA VEGETABLES 



of account the heavy adobe, which is little used for these crops 

 except by gardeners who radically change its physical character. 



Prevailing Character of California Soils. In his interesting 

 contrast of the soils of arid and humid regions, Dr. Hilgard makes 

 some generalizations, which we collate to serve our present purpose. 



The character of the soils of the arid regions is predominantly 

 sandy or silty, with but a small portion of clay unless derived 

 directly or indirectly from pre-existing formations of clay or clay 

 shales. 



The idea of inherent fertility has been associated so generally 

 with sorts of a more or less clayey character, that the newcomer 

 will frequently be suspicious of the productiveness and desirabilty 

 of the sandy or silty soils of the arid region that experience has 

 shown to be of the highest type in both respects. 



Another point of great importance is that the difference be- 

 tween soil and subsoil, which is so striking and important in regions 

 of abundant rainfall, is largely obliterated in arid climates. Very 

 commonly hardly a perceptible change of tint or texture is found 

 for depths of several feet and material from such depths, when 

 thrown on the surface, is nearly or quite as fertile as the original 

 surface soil. In the case of a cellar dug near Nevada City, the 

 red soil mass excavated from a depth of seven to ten feet was 

 spread over part of a vegetable garden near by and tomatoes, 

 beans and watermelons were planted on it. The growth was even 

 better than on the parts of the old surface not covered, which had 

 apparently become somewhat exhausted by years of use. 



Examination has shown that the percentage of humus or veg- 

 etable mold is less in the soils of the arid region, but their humus 

 contains more nitrogen. Thus, probably, on the average not only 

 is the aggregate supply of nitrogen in the soils of the arid region 

 approximately equal to that of humid soils, but its absorption by 

 plants is exceptionally favored by climatic conditions. 



As to the minerals which constitute fertility, the soils of the 

 arid region contain nearly fifteen times as much lime, five times 

 as much magnesia, three times as much potash, and about the 

 same amount of phosphoric acid as the soils of the humid regions. 



Significance of These Facts. These leading characteristics 

 of California's horticulture soils are of the highest significance 

 to the vegetable grower because they show that California is rich 

 in soils of ideal excellence for his purposes. They are light soils 



