VERTICAL FARMING 57 



green manure should be grown and plowed under deeply. The 

 chief feature in conserving moisture is, of course, to get the 

 moisture in hand. This can only be done by leading it down 

 into the soil to great depths. If the soil is of such a nature that 

 this takes place of its own accord, all well and good, but many 

 soils are not that way. They are stubborn, and need a real first- 

 class shooting with an explosive to subdue them. Then the 

 maintenance of the organic matter and surface mulch can reach 

 their desired effects. 



QUESTIONS 



1 . What soil conditions cause water to be held on the surface of 



fields? 



2. Will oil rise faster in a moist or dry lamp wick? Will the 



same principle always hold true of soils? 



3. Why does a dry layer of soil stop the capillary rise of 



moisture ? 



4. When should a dust mulch be renewed? 



5. W r hat effect would a few inches of loose straw on the surface 



have on the soil moisture during a rain ? During hot, dry 

 weather? 



6. Why is it beneficial to fall plow and deep till thin, hard 



lands and cover the surface with trash? 



7. Which will you find at greater depths, wheat or clover 



roots ? 



