64 AGRICULTURE ON THE PACIFIC SLOPE 



" black alkali." The compacting of the soil by the 

 winter rains thus compels us to plow, or at least culti- 

 vate deeply, every year. 



Crush some hard, dry soil by pounding, then put it 

 in a tumbler and mark how high it reaches. Then 

 dampen the soil by dropping on water gently while 

 working it with your fingers. It will become loose and 

 crumbly, and when put back into the tumbler it will 

 be a finger's width or more above the first mark. 



FIG. 35. A diagram to show the effect of plowing. 



How deep shall we plow and spade? That depends 

 on the earth of the surface soil, the layer containing 

 humus or vegetable mold, which has been fully 

 weathered (see page 30). We have seen already that 

 the thickness of this layer may vary greatly; from a 

 few inches in the humid region, to several feet in the 

 arid states, such as most of California, eastern Oregon 

 and Washington, Idaho, Montana, Utah, etc. There- 

 fore, in the Eastern states, the rule is that with the 

 turning plow you should not plow deeper than from 

 six to nine inches; as, if you go deeper, you turn up the 

 raw, yellow subsoil, and spoil the seed bed. But in 

 the arid region you may, as a rule, plow just as deep as 



