Water in the Soil 73 



50 bushels corn (72 pounds to bushel). . .3,600 pounds 

 Stalks and leaves 3,600 " 



Plant substance 7,200 " 



Approximate quantity of water required 



for each pound of plant substance. . . 300 " 



Water used by crop 2,160,000 " 



A cubic foot of water weighs 62.3 pounds. A rain-fall 

 of one inch would be 5.19 pounds per square foot of 

 soil, or 43,560 X 5.19= 226,175.40 pounds on an acre. 

 Dividing 2,160,000 by 226,175.40, we find that less than 

 ten inches of rainfall would be used by the plants in 

 making fifty bushels of corn per acre. This does not 

 include the water that would evaporate from the soil 

 or be lost by the surface run-off. 



106a. At Stillwater, Oklahoma, the average annual rainfall is 

 about 33 inches. What per cent of this would be required to make 

 50 bushels per acre? What is the average rainfall in your county? 

 See page 74. 



107. Soil Drainage. There are many places in low 

 bottom lands on which water accumulates to an injuri- 

 ous extent, either from seepage from the hills or from 

 the lack of an outlet for the surplus water in very wet 

 spells. Again, there are low "sweeps," "swags," "runs," 

 "sloughs," and the like, in which water stagnates to 

 the detriment of the soil and the crops. Such places 

 may often be greatly improved by making surface 

 ditches or by placing drainage tiles (Fig. 41) to carry off 

 the surplus water. In making open ditches it is better, 

 if circumstances allow, to make them broad with sides 

 sloping up about one foot in three or four. This will 

 permit of the cultivation of the drainage-way, and leave 

 no banks to harbor weeds or interfere with the driving 



