Location, Exposure, Soils, and Windbreaks 21 



ently applied. It often requires more time, however, and 

 as the "settling" is very uneven, much leveling is required 

 in order to fit the land for cultivation. The tendency to 

 settle appears to be due to the porous condition of the 



subsoil. 



Seepage 



The presence of an underlying stratum of shale within 

 six feet of the surface should always be looked on with 

 suspicion, and as a rule, such land should be avoided for 

 orchard purposes. Wet or " seeped" places are bound to 

 occur as irrigation increases, for the reason that the water 

 cannot escape except by evaporation. Consequently, the 

 level of the water in the soil gradually rises until it comes 

 to the surface. This may occur only in small spots which 

 do no great amount of harm, but usually these areas grad- 

 ually spread until from a few to many acres are involved. 

 Large tracts of valuable orchards have been ruined in this 

 way. 



An impervious layer of clay is also sometimes found 

 which has the same effect as shale. There are other pecul- 

 iar formations which tend to hold water. One which is 

 more or less common occurs in soils that are rather deep 

 and porous but not stratified. Water moves easily among 

 the particles of such soils, but not to any extent laterally, 

 as is the case where strata occur. Such soils are very 

 likely to become seepy, especially when they occur at the 

 lower levels, and when irrigation is practiced on the higher 

 lands adjacent. 



According to surveys made by the Bureau of Soils of the 

 United States Department of Agriculture, however, by far 

 the greatest amount of damage by seepage in the fruit 



