72 



Elementary Principles of Agriculture 



311 



I"- 



(b) By adding substances to 

 the soil that increase its water- 

 holding power, such as com- 

 post and green manures 

 (K 101). Increasing the water- 

 storage power of the soil tends 

 to lessen washing. The water 

 "runs" after every little 

 shower in the hard roadway, 

 but in the well-plowed field 

 the rain is soon absorbed and 

 passes to the deeper layers 

 of soil. 



106. Amount of Water Re- 

 quired to Mature a Crop. For 

 every pound of dry matter 

 made by growing corn, cotton, 

 oats, etc., it has been esti- 

 mated from many experi- 

 ments that from two hundred 

 to four hundred pounds of 

 water are required. This in- 

 cludes the entire plant above 

 ground, regardless of that 

 which is harvested. Accept- 

 ing these figures as nearly 

 correct, let us estimate how 

 much of the rainfall is con- 

 sumed in maturing a good 

 crop of corn, cotton, oats, etc. 

 In a field of corn making fifty 

 bushels per acre the figures 

 would be roughly as follows: 



