26 CALIFORNIA FRUITS: HOW TO GROW THEM 



fuller understanding of the distinctive character of California soils 

 and their intelligent utilization. 



Veny 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. 



In 1913 a systematic and comprehensive study of California soils 

 preliminary to their mapping and an exposition of their suitabilities was 

 begun by Professor C. F. Shaw of the University of California. 



DISTINCTIVE CHARACTERS OF CALIFORNIA SOILS 



One of the most interesting and important recent achievements in 

 soil investigation consists in demonstrating distinctive differences be- 

 tween 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 exceptional 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 predominately 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 deposts 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 productive- 

 ness, 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 com- 

 monly 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 agricul- 

 tural uses of a soil nearly or quite as well as the original surface soil. 

 The unconcern with which irrigators proceed to level or otherwise 

 grade their land, even though this may involve covering up large 

 areas of surface soil with subsoil from several feet depth ; the rapidity 



