134 Irrigation and Drainage 



ground is illustrated in Fig. 24, where all losses by 

 surface evaporation were prevented by placing an air- 

 tight cover over the areas under experiment. In order 

 that the extreme influence of subsoiling might be 

 ascertained, 8 inches of the surface soil was completely 

 removed from an area 6x6 feet on a side., and when 

 the subsoil had been spaded to a depth of 13 inches 

 more it was returned to its place without firming in any 

 way, except to smooth the surface with a plank pressed 

 down by the weight of a man. After samples of soil 

 had been taken from this and the adjacent area, to give 

 the existing water content, water was slowly sprinkled 

 over the two surfaces until 254.41 pounds, or 1.36 

 inches, had been added to each, and then they were 

 covered, as shown in the figure, and allowed to stand 

 from June 11 until June 15, when the covers were 

 removed and samples of soil again taken, to demon- 

 strate what changes had occurred. 



When this was done it was found that the water 

 added had effected the changes which are recorded in 

 the table which follows : 



Subsoiled Not subsoiled Difference 



LBS. LBS. LBS. 



The first foot gained 124.6 102.1 +22.5 



The second foot gained 72.57 10.34 +62.23 



The third foot gained 38.22 12.05 +26.17 



The fourth foot gained 33.26 3.82 +29.43 



The fifth foot lost 2.29 19.5 17.21 



Total water gained 268.65 128.31 



Total water added 254.41 254.41 



Difference +14.24 126.1 



