18 Fruit-growing in Arid Regions 



ceedingly fine; some of them are of considerable depth. 

 The supposition is that their origin was from some vol- 

 cano, probably in our region from Mt. Hood, which is 

 almost an extinct volcano, though not quite, since at the 

 present time considerable fumes of sulfur and steam 

 are given out from the old crater. I might also add that 

 this soil is exceedingly rich in mineral plant-food, es- 

 pecially in potash and phosphoric acid, and seems to be 

 almost inexhaustible when the supply of humus and 

 nitrogen is kept up in it. 



"I believe some think that some of this soil was thrown 

 out as a dust from the volcano, others that it is disinte- 

 grated lava. This may give you some idea as to what 

 we term volcanic ash soil." 



Such soils, in common with others of the region, are de- 

 ficient in vegetable matter, and consequently the nitrogen 

 content is low. This feature may be corrected by the 

 judicious use of shade-crops in the orchards and by grow- 

 ing alfalfa before the land is planted to trees. 



Some instances occur where it is difficult to grow trees 

 successfully because of excessive drainage. The soil is 

 so loose in its make-up that water rapidly sinks and is 

 soon lost. This character might be corrected, to some 

 extent at least, by the addition of organic matter, which 

 may be best supplied by plowing under green-manure. 



The Subsoil 



The subsoil is as important as the surface soil; this is 

 a feature that is often overlooked and on which the uniniti- 

 ated are often deceived. Mesa lands are often shallow, 

 being underlaid with a layer of marl, gypsum, or shale. 



