28 CALIFORNIA FRUITS: HOW TO GROW THEM 



which includes the results of his long study of California soils and 

 climates. It is the purpose of the writer to set forth a few general 

 characters of California fruit soils, with notes of their local 

 occurrence, referring the reader to Prof. Hilgard's treatise for fuller 

 exposition. 



Very extensive studies of California soils have been recently 

 made under the direction of Dr. Milton Whitney, Chief of the 

 Bureau of Soils of the United States Department of Agriculture, 

 and a new classification and nomenclature of them, from his points 

 of view, with extended maps of their occurrence, are to be found in 

 the special reports of the Bureau. 



DISTINCTIVE CHARACTERS OF CALIFORNIA SOILS 



One of the most interesting and important recent achievements 

 in soil investigation consists in demonstrating distinctive differ- 

 ences between soils formed under arid and under humid climatic 

 conditions. In the development of this subject certain distinctive 

 characters of California soils clearly appear, and they are of direct 

 relation to the thrift, productiveness, treatment and longevity of 

 fruit trees. These characters are : (a) lightness and consequent 

 permeability and ease of cultivation; (b) depth, admitting excep- 

 tional root extension and penetration ; and (c) richness, containing 

 some kinds of plant food in considerably greater amounts than are 

 found in the soils of humid regions. These characteristics, as 

 demonstrated by Prof. Hilgard, may be outlined in this way with 

 special reference to their relations to fruit growing. 



Lightness. California soils predominantly exhibit the sandy, 

 silty or pulverulent nature of all soils formed under arid conditions, 

 save in case of pre-existing clay formations of former geological 

 epochs, as well as slack-water deposits of the present epoch, all of 

 which are substantially independent of climate. While "sand" in 

 the humid regions means virtually quartz grains only, in the arid 

 country it means very largely grains and powder of the other soil- 

 forming minerals as well. While, therefore, in the humid region, 

 sandy land as a rule means poor land, in the arid, on the contrary, 

 sandy lands are at least as desirable as heavier ones, both on the 

 score of high productiveness, durability, and ease of cultivation, 

 together with ready resistance to drouth. 



Depth. Another point of great importance is that the difference 

 between 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 what is more important, 

 material from such depths, when thrown on the surface oftentimes 

 subserves the agricultural uses of a soil nearly or quite as well 



