ORCHARD SOILS 657 



drainage is practically perfect (the water table often being 50 or more 

 feet below the surface) and they are so well aerated that tree roots often 

 penetrate to a depth of 20 feet and ordinarily to depths of 6, 8 or 10. 

 In the Rhine valley grape roots have been traced to a depth of 15 meters. 

 Similar conditions exist in some of the volcanic ash soils of the Pacific 

 Northwest and the alluvial soils and bench lands of many river valleys 

 in Washington, Idaho, Oregon and California. One of the main reasons 

 certain of the arid soils of California have proved so well suited to fruit 

 growing is that the surface soil grades insensibly into the subsoil and 

 that the latter is well drained and thoroughly aerated; hence roots 

 penetrate to great depths and sustain the plant when the surface soil 

 may become too dry.^^ That good drainage and its corollary good 

 aeration are associated with this condition is indicated by Hilgard^^ 

 when he states that with the rise of the water table in such soils through 

 injudicious irrigation trees that had thrived may actually suffer, much 

 as those planted in shallow soil or soil underlaid with an impervious 

 hardpan and from practically the same causes. 



The extent to which the success of the fruit plantation depends on 

 these two factors, drainage and aeration, is not generally realized. In 

 speaking of the soil requirements of the papaya Higgins-^ says: "There 

 are few, if any, soils in which the papaya will not grow if aeration and 

 drainage are adequately supplied. Most of the plantings of this Station 

 are upon soils regarded as unsuitable for other fruit trees, and upon 

 which the avocado is a failure. . . . They are very porous, permitting 

 a perfect drainage and aeration." The same writer goes so far as to 

 say, "There are two essential features of a good banana soil. The 

 first is abundant moisture, the second, good drainage. "^^ In speaking 

 of the soil requirements of forest trees one authority maintains that 

 almost any soil is capable of producing any kind of timber if the moisture 

 requirements are satisfied. ^^ Even the blueberry, which is often classed 

 as a semiaquatic or bog plant, requires a well aerated medium for its 

 roots and does not, contrary to appearances, send them down into the 

 water or into waterlogged soil.^ Obviously, certain shallow rooted 

 species such as the strawberry do not require and could not make full 

 use of a soil of the depth best suited to one of the tree fruits, but even 

 the strawberry will do much better in a soil that is moderately deep 

 (say, two and one half to three feet) and well drained than in one that is 

 shallow or poorly drained and poorlj^ aerated. 



Requirements of Different Crops. — However, there are marked 

 differences between species and even between varieties of the same 

 species in their preferences for soils of unlike textures. The peach 

 and almond flourish only in soils of a comparatively light porous texture, 

 while the pear and quince prefer at least moderately heavy soils and will 

 often do well in extremely heavy soils. The pomegranate is reported as 



